JP7541463B2 - Improved vent pipe structure with double pipes in the upward flow section - Google Patents

Description

The present invention relates to a sewage inverted structure that passes under obstacles such as rivers and underground passages, and in particular to an inverted structure that prevents the adhesion or accumulation of impurities in the passage of a separate sewer vent pipe and reduces maintenance and construction costs.

Wastewater such as domestic wastewater from homes and wastewater from industrial facilities is treated through separate sewer pipes, but when there are obstacles such as rivers or underground passages in the middle of the flow path, an inverted structure with a vent pipe that passes under the obstacle is used. Figure 14 shows a conventional inverted sewer structure. As shown in the figure, an upstream sewer pipe 305 and a downstream sewer pipe 306, which are sandwiched between them by a vent pipe 301 that passes under the river. The vent pipe 301 has, in order from the inlet side, a downwardly inclined downward flow section 311, a horizontal flow section or lateral flow section 312 that communicates with the downward flow section and passes under the obstacle almost horizontally, and an upward flow section 313 that communicates with the horizontal flow section 312 and is inclined upward. Then, between the bottom of the cross section of the upstream sewer pipe and the bottom of the cross section of the downstream sewer pipe, there is an overflow head ΔH, which corresponds to the head loss in the overflow path, and the sewage is caused to flow down into the vent pipe 301 by the hydrostatic pressure of the sewage based on this head.

When the water flow in the thus configured inverted overpass structure enters the vent pipe (inverted overpass section) 301, which passes under obstacles such as rivers and underground passages, it flows in a full pipe state inside the vent pipe, so the flow rate is slower than in the upstream sewer pipe, which has a free water surface. This decrease in flow rate leads to the accumulation of solids and other impurities, so it is common to make the pipe diameter of the inverted overpass section 301 smaller than the pipe diameter of the upstream sewer pipe 305 to ensure the flow rate, i.e., the sweeping force, required to sweep the impurities.

However, sewage, which is domestic wastewater, contains a large amount of floating impurities such as oil and settling impurities such as soil and sand. For this reason, the sweeping force of the conventional vent pipe overflow is not sufficient, and settling impurities are likely to remain in this part and settle and accumulate at the joint between the horizontal flow section 312 and the upward flow section 313. In other words, gravel with high settling tendency that cannot run up the upward flow section to the downstream sewer pipe 306 by the flow force of sewage alone accumulates in this part. Then, at night, when the flow rate of sewage is low, fine clayey soil enters and infiltrates into the gaps between the settled gravel, solidifying and forming a sedimentary layer. If this sedimentary layer is left for a long period of time, it will form a stronger sedimentary layer, which may also clog the vent pipe 301.

On the other hand, the sewer system is designed to always have twice the flow capacity of the planned sewage volume. Therefore, when the sewage volume is small, the sewage does not fill the downflow section 311, the water level in this downflow section becomes low, and the above-mentioned head difference ΔH cannot be secured. This reduces the hydrostatic pressure that pushes the sewage away, and combined with the small sewage volume, causes floating impurities such as oil mixed in the sewage to float and accumulate on the water surface of the downflow section 311 and remain there for a long time. Therefore, when a large amount of floating impurities such as oil is mixed in the sewage, these floating impurities swell and solidify near the water surface of the downflow section 311, forming a sediment layer. Furthermore, this, combined with the fact that the flow force of the sewage is reduced by the sediment layer, eventually causes the sediment layer to clog the vent pipe 301.

In response to this, the applicant previously proposed in JP 2011-220106 A a method of removing impurities by supplying compressed air into the vent pipe. The proposed measure against floating impurities was to supply compressed air for a specified time at specified intervals through an opening in the pipe wall of the downstream vent pipe 311 to break up floating impurities that have accumulated and solidified near the water surface of the downstream vent pipe and allow them to flow down and be removed. Furthermore, as a measure against settling impurities, the applicant disclosed a technique in which compressed air is supplied for a specified time at specified intervals into the flow path of the upstream vent pipe 313 to float up settling impurities that have adhered or accumulated near the bottom surface of the upstream vent pipe 313, allowing them to flow down and be removed.

JP 2011-220106 A

Fujiro Narihara, "Reducing costs with elegant sewer pipe designs" Sankaido, 2005 "2019 Sewerage Construction Planning and Design Guidelines and Commentary" Japan Sewage Works Association "Model Experiments on the Tracing Characteristics of Sediments in Sewers 1," May 2006, Journal of the Japan Sewage Works Association, Vol. 43, No. 523, Japan Sewage Works Association, Public Interest Incorporated Association

However, the settleable impurities countermeasure disclosed in Patent Document 1 had the following problems associated with supplying air into the upflow vent pipe. That is, the settleable impurities countermeasure disclosed in Patent Document 1 supplies compressed air from an opening in the lower half of the flow path cross section of the vent pipe (bottom side) toward the center of the flow path, so the supplied air moves toward the upper half of the flow path cross section of the vent pipe (top side) due to its buoyancy, and moves upward along the top side of the pipe inside the pipe. For this reason, the sweeping force that flows down and removes the settleable impurities accumulated at the bottom of the vent pipe (lower half of the flow path cross section) is weak, and some of the settleable impurities tend to remain settled at the bottom of the vent pipe. This phenomenon is particularly likely to occur when the gradient of the upflow vent pipe is large or the inner diameter is 250 mm or more.

Furthermore, the floating debris countermeasures disclosed in Patent Document 1 could cause the following problems in some cases: The floating debris that accumulates and deposits in the downward flow vent pipe when the vent pipe is overflowed is formed when insoluble plastics, paper, fibers, etc. are infiltrated and solidified by adhesion of oils and gels in the sewage, and accumulates and deposits near the water surface when the water flow is stopped in the vent pipe.
The floating debris countermeasure disclosed in Patent Document 1 is to eject compressed air toward the floating debris to separate oils, glue, etc. from the debris. The oils, glue, etc. are separated by the action of compressed air, and the debris is de-solidified. However, since the buoyancy of the debris is greater, it is difficult to remove the floating debris by the action of compressed air alone. Therefore, the floating debris continues to float on the water surface in a de-solidified state, and will be solidified again by the oils, glue, etc. in the sewage. Therefore, the floating debris countermeasure disclosed in Patent Document 1 has a problem that compressed air must be supplied frequently, which increases the amount of work and costs.

Furthermore, when the upward flow vent pipe is a thin pipe with an inner diameter of 200 mm or less, which is the minimum pipe diameter of a sewer pipe (see Non-Patent Document 2), there is also a problem of an airlock state occurring as described below.
That is, the air supplied into the vent pipe rises toward the top of the pipe and collides with the inner wall of the pipe, where some of the air with greater buoyancy rises downstream, but some of the air moves upstream against the flow of the sewage. In this case, the air moving upstream enters the lateral flow vent pipe and advances to the equilibrium point with the hydrostatic pressure due to the required head loss H. At this time, the hydrostatic pressure only acts to compress the air, so the air remains there, creating a so-called airlock state and impeding the flow inside the vent pipe.

In addition, some sewer pipes have adopted a reserve pipe system in consideration of pipe blockage accidents and cleaning. The reserve pipe system is a system in which a reserve pipe is installed in parallel with the main pipe to be used only in the event of an accident or cleaning, and the entire flow path of the vent pipe underpass structure is configured as a double pipe, and by switching the flow path to the reserve pipe during cleaning, work can be done without stopping the flow of sewage. This reserve pipe is often made of the same diameter, inclination angle, and length as the main pipe. While the provision of a reserve pipe has the advantage that cleaning can be done without sewage flowing in the main pipe, the condition in which sewage does not flow in the reserve pipe continues for a long period of time, so that the sewage (polluted water) remaining in the reserve pipe decays over time and generates hydrogen sulfide gas, which not only causes bad odors but also promotes corrosion with the concrete and promotes the deterioration of the entire underpass facility. In addition, there is a cost disadvantage in that the construction cost of the underpass must be more than doubled by providing a reserve pipe. Furthermore, the reserve pipe switching gate has a statutory service life of 15 years at most, so there is also the drawback that renewal work is required after a certain period of time. In this way, the reserve pipe system is prone to various problems due to the reserve pipe not being used under normal circumstances.

In view of the above problems, there was a need for an underground vent pipe structure that would ensure that both floating and sinking impurities could be removed using only the force of the everyday sewage flow, and that would be able to deal with accidents and cleaning while keeping a single vent pipe in operation, even in the unlikely event that an unexpectedly large amount of impurities were to flow into the sewer pipe.

The object of the present invention is to provide a vent pipe underpass structure that does not require a spare pipe for cleaning, can reliably remove these impurities using only the force of everyday sewage flow, and can remove the impurities with just a simple operation even in an emergency where a large amount of impurities flow into the sewer pipe.

After extensive research, the inventors have discovered a vent pipe structure that makes it difficult for settling impurities to accumulate on a daily basis and that allows easy removal of settling impurities that flow down when more settling impurities than expected flow in due to unforeseen circumstances, by configuring the upflow vent pipe with a double-pipe configuration and providing a means for ejecting compressed air using a supply method different from that used in the past. Furthermore, by providing a specified straightening section in the upstream sewer pipe, setting the downflow vent pipe at a specified inclination, and ejecting pressurized water instead of compressed air to a specified location using a specified method, the inventors have discovered a vent pipe structure that makes it difficult for floating impurities to accumulate on a daily basis and that allows easy removal of floating impurities that flow down when more settling impurities than expected flow in due to unforeseen circumstances, and have completed the present invention.

In order to solve the above problems, the vent pipe underpass structure of the present invention is as follows:
A vent pipe that passes under obstacles such as rivers and underground passages,
and a sedimentation impurity removing means for removing impurities adhering to or accumulating inside the vent pipe.
The vent pipe is
A downflow vent pipe extending from a downstream end of the upstream sewer pipe at an incline downward in the downstream direction;
a lateral upflow section vent pipe extending downstream from a lower end of the downflow section vent pipe through under the obstacle;
and an upflow section vent pipe extending from the downstream end of the horizontal upflow section vent pipe to the upstream end of the downstream sewer pipe at an incline upward in the downstream direction, the upflow section vent pipe comprising a first upflow section vent pipe and at least one second upflow section vent pipe having the same inclination;
The second upflow section vent pipe is disposed along an inner wall or an outer wall, or along both the inner and outer walls, of the first upflow section vent pipe,
Moreover, it is characterized in that the diameter is smaller than the diameter of the first upward flow section vent pipe.

The sedimentable impurities removing means includes:
At least two air discharge holes opening toward the downstream direction at positions spaced apart from each other by a predetermined distance from the upstream end of the upflow section vent pipe;
an air pipe communicating with each of the air discharge holes,
The air discharge hole includes a low-stage air discharge hole that opens into the first upward flow section vent pipe;
a high-stage air discharge hole that opens into the second upflow section vent pipe at a position downstream of the low-stage air discharge hole,
The low stage air pipe communicating with the low stage air discharge hole is
a diameter of the high stage air pipe communicating with the high stage air discharge hole is smaller than the diameter of the high stage air pipe,
Compressed air is supplied downstream through air pipes respectively communicating with the low stage air discharge hole and the high stage air discharge hole for a predetermined period of time as appropriate.

The inclination angle of the downward flow vent pipe is 30 degrees or less,
A straightening section is provided in a predetermined section of the upstream sewer pipe,
The pipe diameter of this flow straightening section is desirably equal to or smaller than the pipe diameter of the downward flow section vent pipe.

The downward flow section vent pipe is provided with a floating impurity removal means,
The floating contaminant removing means includes:
At least one pressure water discharge hole that opens near the water surface when the water is stopped in the downward flow section vent pipe;
a pressure water injection pipe communicating with the pressure water discharge hole,
From the pressure water discharge hole through the pressure water injection pipe,
When the water is stopped in the downward flow vent pipe, toward the water surface,
Pressurized water is supplied for a predetermined period of time at predetermined time intervals as appropriate.

Furthermore, the plurality of pressure water discharge holes provided in the downward flow section vent pipe are
Near the water surface when the water is stopped in the downward flow vent pipe,
It is desirable that the nozzle be provided at a position spaced a predetermined distance upstream or downstream.

The vent pipe underpass structure of the present invention allows impurities that have flowed into the sewer to be removed by simply using the sweeping force of the daily sewage, making the risk of pipe blockage extremely low even without frequent cleaning, and eliminating the need to install a spare pipe for cleaning. Even in the event of a situation in which the amount of impurities flowing into the sewer temporarily increases during an emergency such as a flood or earthquake, the impurities removal means provided by the present invention can be operated to remove such impurities with just a simple operation.

FIG. 1 is a schematic cross-sectional view of a vent pipe recessed structure. FIG. 1A is a schematic cross-sectional view showing one embodiment of the structure of an upward flow vent pipe in the vent pipe under-passing structure of the present invention, and FIG. 1B is an enlarged cross-sectional view taken along line X-X of FIG. 1A is a schematic cross-sectional view showing another embodiment of the structure of the upward flow vent pipe in the vent pipe underpass structure of the present invention, and FIG. 1B is an enlarged cross-sectional view taken along line YY in FIG. 1 is an enlarged cross-sectional view showing one embodiment of the structure of an upward flow vent pipe in the vent pipe underpass structure of the present invention. FIG. An enlarged cross-sectional view showing another embodiment of the structure of the upward flow vent pipe in the vent pipe underpass structure of the present invention. FIG. 1 is an enlarged cross-sectional view showing the connection between the upstream sewer pipe and the straightening section in the vent pipe underpass structure of the present invention, in which (a) shows the connection state before improvement, and (b) shows the connection state of one embodiment after improvement. 1A and 1B are diagrams showing the connection between the upstream sewer pipe and the straightening section in the vent pipe underpass structure of the present invention, where (a) is an enlarged plan view and (b) is an enlarged cross-sectional view along line Z-Z in (a). 1 is a schematic diagram showing one embodiment of the vent pipe underpass structure of the present invention, in which another sewer pipe merges into the straightening section. FIG. 1 is a schematic cross-sectional view showing one embodiment of the structure of a downward flow vent pipe in the vent pipe recessed structure of the present invention. FIG. 1 is a schematic cross-sectional view showing the connection state of a downflow vent pipe and a lateral upflow vent pipe in one embodiment of the vent pipe buried structure of the present invention. FIG. 1 is a schematic diagram showing another embodiment of the vent pipe recessed structure of the present invention. FIG. 1 is a schematic diagram showing yet another embodiment of the vent pipe recess structure of the present invention. FIG. 1 is a schematic cross-sectional view showing one embodiment of a floating impurity removal means provided in a downward flow vent pipe in the vent pipe underpass structure of the present invention. FIG. FIG. 1 is a schematic cross-sectional view of a conventional sewer pipe inverted structure.

Next, an embodiment of the present invention will be described with reference to the drawings.

As shown in Figure 1, the basic structure of the vent pipe underpass of the present invention includes a vent pipe underpass structure 1 that passes under obstacles such as rivers and underground passages, a settling impurity removal means 8 that removes impurities that accumulate in the vent pipe of the vent pipe underpass structure 1, and, if necessary, a floating impurity removal means 7 that removes impurities that adhere to the vent pipe. The vent pipe underpass structure 1 includes a downflow section vent pipe 2 that extends from the downstream end of the upstream sewer pipe 5 at an incline downward in the downstream direction, a horizontal upflow section vent pipe 3 that extends from the lower end of the downflow section vent pipe 2 downstream, passing under the obstacle, and an upflow section vent pipe 4 that extends from the downstream end of the horizontal upflow section vent pipe 3 to the upstream end of the downstream sewer pipe 6 at an incline upward in the downstream direction. A straightening section 51 may also be provided in a predetermined section of the upstream sewer pipe 5 that is connected to the upstream side of the downflow vent pipe 2.

As mentioned above, in general, in a vent pipe underpass structure, floating impurities such as wood chips, fallen leaves, plastic, paper, oil, etc. tend to accumulate in layers near the water surface when the water is stopped in the downward flow vent pipe 2, and sedimentary impurities such as sand tend to accumulate near the connection between the horizontal flow vent pipe 3 and the upward flow vent pipe 4. If these are left for a long period of time, the floating impurities may mix with oil and adhere to the inside of the vent pipe, or the sedimentary impurities may become solidified and harden, causing the vent pipe to become clogged. Therefore, the vent pipe underpass structure of the present invention has the following configuration as a measure against these impurities.

First, as a countermeasure against settling impurities, in the vent pipe underpass structure of the present invention, the upflow section vent pipe 4, which is usually a single pipe, is composed of at least two upflow section vent pipes 41, 42 having the same gradient. The upflow section vent pipe 4 is provided with air outlet holes 81a, 82a that supply compressed air to the at least two upflow section vent pipes 41, 42, respectively, and air pipes 81, 82 that communicate with these air outlet holes, respectively, as a settling impurities removal means 8. As a countermeasure against floating impurities, the inclination angle θ1 of the downflow section vent pipe 2 is 30 degrees or less, and a straightening section 51 is provided in a predetermined section of the upstream sewer pipe 5 connected to the upstream side of the downflow section vent pipe 2, and the pipe diameter of this straightening section 51 is less than the pipe diameter of the downflow section vent pipe 2. Furthermore, in the vent pipe underpass structure 1 of the present invention, in preparation for emergencies such as heavy rain disasters in which the amount of impurities flowing into the vent pipe underpass increases, a floating impurities removal means 7 that removes floating impurities by supplying pressurized water can be provided, which includes a pressurized water discharge hole that opens near the water surface when the water is stopped in the downward flow section vent pipe 2, and a pressurized water injection pipe that communicates with this pressurized water discharge hole.

Next, we will explain in more detail the preferred structure and operation of each of these configurations that are unique to the vent pipe overpass structure of the present invention.

First, as a measure against sedimentary impurities that tend to accumulate near the connecting portion between the horizontal upflow section vent pipe 3 and the upflow section vent pipe 4, the upflow section vent pipe 4, which is a double pipe or a double pipe, of the vent pipe underpass structure 1 of the present invention will be described with reference to Figures 2 to 5. The upflow section vent pipe 4 of the present invention is a pipe that is usually a single pipe, but is made into at least two (two in the illustrated case) upflow section vent pipes 41 and 42 with the same gradient. The two upflow section vent pipes are each composed of vent pipes with different pipe diameters, and for convenience of explanation, the upflow section vent pipe with the larger pipe diameter will be referred to as the first upflow section vent pipe 41, and the upflow section vent pipe with the smaller pipe diameter will be referred to as the second upflow section vent pipe 42. Therefore, the first upflow section vent pipe 41 is the so-called main pipe. These can be either a so-called double pipe structure in which the second upflow section vent pipe 42 that amplifies the flow path cross section is arranged along the outer wall of the first upflow section vent pipe 41 as shown in Figure 2, or a so-called double pipe structure in which the second upflow section vent pipe 42 that divides the flow path cross section is arranged along the inner wall of the first upflow section vent pipe 41 as shown in Figure 3, or a combination of both. In this way, the vent pipe underpass structure 1 of the present invention has the downflow section vent pipe 2 and the lateral upflow section vent pipe 3 as single-strand pipes, and only the upflow section vent pipe 4 has a double-strand pipe structure 41, 42 with the same gradient.

Specifically, the second upflow section vent pipe 42 is preferably set to have an inner diameter of approximately 100 mm or less, regardless of the inner diameter of the first upflow section vent pipe 41. By attaching the second upflow section vent pipe 42 having an inner diameter of approximately 100 mm or less to the outer or inner wall of the first upflow section vent pipe 41 to form a two-pipe configuration in which the upflow section vent pipe is a double pipe or a double pipe, even if the inner diameter of the first upflow section vent pipe 41 is large, the second upflow section vent pipe 42 can efficiently scoop up sediments such as soil and sand and flow them downstream. In particular, even when the sewage flow rate is low at night, the second upflow section vent pipe 42 has a narrow inner diameter of 100 mm or less, so that an appropriate sewage flow is generated, making it possible to continuously prevent settling of sedimentary impurities and adhesion to the vent pipe. This makes it possible to create a so-called maintenance-free state in which accumulation and retention of sedimentary impurities is prevented on a daily basis without relying on mechanical force.
This structure is effective in easily preventing the accumulation of sediment, etc., even in the case of an inverted overpass where the sewage flow rate is low for a long period of time due to a small amount of sewage flow, or in the case of an inverted overpass where the upstream sewer is still in the process of being constructed. In addition, since the first upflow section vent pipe 41 and the second upflow section vent pipe 42 are provided with the same gradient, the excavation range during construction of the inverted overpass structure does not change significantly from that of a single-pipe inverted overpass structure, making it economical.

Depending on the inner diameter of the first upflow section vent pipe 41, the second upflow section vent pipe 42 can be either a double-pipe structure or a double-pipe structure, or a combination of both. In either the double-pipe structure or the double-pipe structure, the second upflow section vent pipe 42 can be a plurality of pipes as necessary. For example, when the inner diameter of the first upflow section vent pipe 41 is 250 to 350 mm, the second upflow section vent pipe 42 can be a double-pipe structure with one pipe, and the inner diameter of the second upflow section vent pipe 42 can be set to 80 mm. When the inner diameter of the first upflow section vent pipe 41 is 400 mm or more, a double-pipe structure can be used. Furthermore, when the inner diameter of the first upflow section vent pipe 41 is 1300 mm or more, a structure combining a double-pipe structure and a double-pipe structure can be used. In addition, when the inner diameter of the first upflow section vent pipe 41 is about 20 times or more than the inner diameter of the second upflow section vent pipe 42, such as when the inner diameter of the first upflow section vent pipe 41 is 2000 mm compared to the inner diameter of the second upflow section vent pipe 42 of 100 mm, it is possible to use two or three second upflow section vent pipes 42, each of which is attached to the outer wall of the first upflow section vent pipe 41 to form a triple- or quadruple-pipe structure. By configuring the second upflow section vent pipe 42 as described above in accordance with the inner diameter of the first upflow section vent pipe 41, it becomes possible to scoop up and flow down to the downstream sewer pipe 6 even sand or the like having a particle size of 5 mm or less due to the potential energy due to the required head loss H of the inverted structure. In other words, the first upflow vent pipe, which is the main pipe, is primarily responsible for ensuring the flow capacity of the sewage flow, and the second upflow vent pipe is primarily responsible for removing settleable impurities.

In addition, by configuring the second upward flow section vent pipe 42 as described above, it is possible to fully respond to the expected future spread of disposers to ordinary households. In other words, crushed eggshells, shells, etc., which are expected to flow into the sewer pipe due to the introduction of a disposer, can be removed without retention in the upward flow section vent pipe structure of the present invention with a two-row pipe configuration. According to Non-Patent Document 3, eggshells and shells, which require particular attention among the sedimentary impurities crushed by a disposer, are reported to be concentrated in the particle size range of 0.85 to 4.75 mm, with a specific gravity of eggshells: 2.65 and shells: 2.84. This is smaller in both particle size and specific gravity than sand, etc. of 5 mm or less that can be removed by the upward flow section vent pipe structure of the present invention with a two-row pipe configuration, so it is judged that it will be removed without any problems. Also, considering that the disposer is a structure that "grinds" food waste, fibrous materials are expected to remain as they are. For this reason, there is concern that as disposers become more widespread, onion skins, bamboo shoot skins, banana stems, soybean pods, and other materials that can cause drainage blockages will increasingly end up in the sewer system. However, considering that these fibers have a lighter specific gravity than sand, it is believed that no problems will arise with the vent pipe structure 1 of the present invention, which has the ability to remove sand and other materials with a particle size of 5 mm or less.

The pipe used as the second upward flow section vent pipe 42 in the present invention may be a rigid polyvinyl chloride pipe with an inner diameter of approximately 100 mm or less, a rigid polyvinyl chloride pipe, a reinforced plastic composite pipe for insertion into a sewer system, or the like.

When the upflow section vent pipe 4 is a double-pipe structure, the second upflow section vent pipe 42 is preferably attached to the outer wall of the first upflow section vent pipe 41. Specific methods of attachment include, taking into consideration the length of the second upflow section vent pipe 42 and the ground conditions of the installation site, adhesively joining the second upflow section vent pipe 42 to the outer wall in the bottom direction of the first upflow section vent pipe 41, filling the gap between the first upflow section vent pipe 41 and the second upflow section vent pipe 42 with construction material to backfill it, or wrapping the second upflow section vent pipe 42, including the bottom of the first upflow section vent pipe 41, in concrete to form an integrated structure.

When a double-pipe structure is used, the downstream ends of the first upflow section vent pipe 41 and the second upflow section vent pipe 42 are connected to the bottom of the downstream manhole C provided at the upstream end of the downstream sewer pipe, as shown in FIG. 2. The other end of the second upflow section vent pipe 42, which is the upstream end, is connected to the hole in the bottom side main pipe wall of the first upflow section vent pipe 41 at a position upstream of the first upflow section vent pipe 41, as shown in FIG. 2, via a 90-degree or 45-degree elbow (long) joint. Depending on the ground conditions and construction depth, this joint may be completely wrapped in concrete to form an integrated structure with the first upflow section vent pipe 41.

Next, the arrangement of the second upflow section vent pipe 42 when the upflow section vent pipe 4 has a double pipe structure will be described. When using a double pipe structure, it is preferable to attach the second upflow section vent pipe 42 to the bottom side of the inner wall of the first upflow section vent pipe 41 by adhesive bonding to form a double pipe.

In the case of a double pipe structure, the downstream ends of the first upflow section vent pipe 41 and the second upflow section vent pipe 42 are connected to the bottom of the downstream manhole C provided at the upstream end of the downstream sewer pipe 6, as shown in Figure 3. Here, in the case of a double pipe structure, the downstream end of the second upflow section vent pipe 42 opens with its tip cut at an angle, as shown in Figure 3. In addition, the other end, the upstream end, of the second upflow section vent pipe 42 extends to a position closer to the upstream end of the first upflow section vent pipe 41, as shown in Figure 3, and opens with a small opening at the bottom side inner wall of the first upflow section vent pipe 41 with its tip cut at an angle, facing the center of the flow path. In this way, by cutting the upstream end of the second upflow vent pipe 42 in the double pipe structure at an angle, it is possible to prevent larger pieces of paper or clothing that flow into the sewer from getting caught on the small opening of the end of the second upflow vent pipe and becoming retained. It is further preferable that the end of the second upflow vent pipe 42 is chamfered.

As described above, by configuring the upflow section vent pipe 4 in the vent pipe underpass structure as a two-pipe configuration combining the thick first upflow section vent pipe 41 and the thinner second upflow section vent pipe 42, a sweeping force sufficient to cause sand particles with a diameter of 5 mm or less to run up the upflow section vent pipe is generated in the thin pipe, the second upflow section vent pipe 42, and it becomes possible to remove settleable impurities that tend to accumulate and settle at the connection between the lateral upflow section vent pipe 3 and the upflow section vent pipe 4 using only the flow force of everyday sewage. Note that the reason why "sand particles with a diameter of 5 mm" are used as the standard for the sweeping force sufficient to remove settleable impurities is based on the consideration of "the flow velocity required to remove sediments" on pages 271-272 of Non-Patent Document 1.

Next, the settling impurity removal means 8 provided in the upflow vent pipe 4 will be described with reference to Figures 2 to 5. The settling impurity removal means 8 of the present invention comprises air outlet holes 81a, 82a that supply compressed air to the two upflow vent pipes 41, 42, respectively, and air pipes 81, 82 that communicate with the air outlet holes, respectively. Note that Figures 2(a) and 3(a) are schematic diagrams and do not accurately depict the positional relationship between the two upflow vent pipes 41, 42 and the air pipes 81, 82. As a specific embodiment, for example, air pipes 81, 82 can be provided as shown in Figures 2(b), 3(b), 4, and 5. With this configuration, compressed air is supplied to each of the two upflow vent pipes 41 and 42, and the settling impurities that have settled and accumulated mainly near the joint between the lateral flow vent pipe 3 and the upflow vent pipe 4 are lifted by the buoyancy of the air ejected from the air outlets 81a and 82a, and are removed by flowing the settling impurities downstream with the flow force of the sewage.

The specific configuration of the settling impurities removal means 8 of the present invention, as shown in FIG. 4, has at least one air discharge hole 81a, 82a that opens toward the downstream direction of the sewage flow at a position spaced a predetermined distance from the upstream end of the upflow section vent pipe (first upflow section vent pipe 41) toward the downstream direction of the sewage flow, and air pipes 81, 82 that communicate with the air discharge holes 81a, 82a, respectively, and ejects compressed air from the air discharge holes 81a, 82a toward the downstream direction through the air pipes 81, 82 appropriately for a predetermined period of time.

A preferred specific configuration of the air discharge holes 81a, 82a and the air pipes 81, 82 communicating with these air discharge holes includes an air discharge hole (hereinafter referred to as the low-stage air discharge hole 81a) that opens on the bottom surface of the inner wall on the upstream side of the first upflow section vent pipe 41, and an air discharge hole (hereinafter referred to as the high-stage air discharge hole 82a) that opens into the second upflow section vent pipe 42 at a position downstream of the low-stage air discharge hole 81a, and it is preferable that the low-stage air pipe 81 communicating with the low-stage air discharge hole 81a has a pipe diameter smaller than the pipe diameter of the high-stage air pipe 82 communicating with the high-stage air discharge hole 82a. The settling impurities removal means 8 provided in the upflow section vent pipe 4 with such a configuration further enhances the sweeping force of the upflow section vent pipes 41, 42, which have a two-pipe configuration with the same gradient as described above, and enhances their functionality. That is, by combining the two-pipe configuration 41, 42 of the upward flow vent pipe, which plays a role in continuously removing settleable impurities on a daily basis, with the settleable impurities removal means 8 equipped with a compressed air ejection mechanism to play an emergency role in the event of a temporary increase in the inflow of impurities into the sewer in emergencies such as heavy rain disasters and earthquakes, the maintenance and management of the vent pipe can be easily and effectively performed. Therefore, by installing both of these together, a synergistic effect can be achieved.

2 and 4, at least two air discharge holes 81a, 82a are provided: a low-stage air discharge hole 81a made of a U-shaped pipe that protrudes from the bottom surface of the inner wall of the upstream side of the upflow section vent pipe 4 and discharges compressed air, and a high-stage air discharge hole 82a made of a U-shaped pipe that protrudes to the small opening of the upstream end of the second upflow section vent pipe at a position downstream of the low-stage air discharge hole 81a. The air pipe for supplying compressed air is composed of a low-stage air pipe 81 communicating with the low-stage air discharge hole 81a and a high-stage air pipe 82 communicating with the high-stage air discharge hole 82a, and as shown in FIG. 2, the downstream end of each of them extends to an air valve 83 provided under the cover of a downstream manhole C provided at the connection between the upflow section vent pipe 4 and the downstream sewer pipe 6. When injecting compressed air, for example, a portable engine-equipped compressor D is connected to this air valve via an air pipe 84, and compressed air is sent toward the air discharge holes 81a and 82a. Here, the air pipe 84 branches into a low-stage air pipe 81 and a high-stage air pipe 82 at the air valve 83, so the injected air is simultaneously branched and injected into the low-stage air pipe 81 and the high-stage air pipe 82 at the same pressure, and compressed air is simultaneously discharged from the low-stage air pipe discharge hole 81a and the high-stage air discharge hole 82a, respectively. The downstream manhole C is generally buried under a public road. For this reason, opening the lid to perform compressed air injection work may cause road traffic to be disrupted. In such a case, a water supply handhole or the like may be provided at a point that does not disrupt road traffic, and an air valve for connecting to the air pipe may be attached inside the handhole.

It is preferable that the low-stage air pipe 81 and the high-stage air pipe 82, which are branched off from a single air pipe 84 connected to the compressor, have different pipe diameters. This makes it possible to utilize the characteristic that a thinner air pipe will forcefully discharge a smaller amount of air when air is injected from the compressor at the same air pressure. In other words, by making the low-stage air pipe 81, which communicates with the low-stage air discharge hole 81a that opens at the bottom side of the upward flow section vent pipe 4, a pipe thinner than the high-stage air pipe 82, it is possible to discharge air more forcefully from the low-stage air discharge hole 81a, effectively stirring up settleable impurities that have accumulated and adhered to the bottom of the vent pipe.

As shown in FIG. 4, the low-stage air discharge hole 81a is provided on the bottom side of the first upflow section vent pipe 41, slightly upstream from the upstream end of the upflow section vent pipe 4. By providing the low-stage air discharge hole 81a at this position, the gravelly soil deposited near the connection between the horizontal upflow section vent pipe 3 and the upflow section vent pipe 4, where settling impurities are likely to accumulate and remain, is dug up and disturbed in the sewage water flow, and settling impurities such as gravelly soil are transported to the vicinity of the high-stage air discharge hole 82a provided in the second upflow section vent pipe 42, where they can be removed by flowing down. The position at which the low-stage air discharge hole 81a is provided can be appropriately set at an appropriate position near the connection between the horizontal upflow section vent pipe 3 and the upflow section vent pipe 4, within the range where such an effect can be exerted. Generally, the allowable blockage rate of the vent pipe is set to an upper limit of 30% of the inner diameter of the pipe. When implementing the settleable impurity removal means 8 of the present invention, the number and position of the low-stage air discharge holes 81a will be appropriately set according to the size of the vent pipe and the installation conditions so that pipe blockage due to the accumulation of settleable impurities falls within this allowable blockage rate.

This gravelly soil is formed by the fine clayey soil entering the gaps between the sand and gravel at night when the sewage flow rate is low, resulting in solidification and the formation of a sedimentary layer. If left for a long period of time, it will change over time and become a stronger sedimentary layer. For such a sedimentary layer, it is effective to excavate it by injecting compressed air into it and use the buoyancy of the air to make it flow down. Furthermore, as described above, by making the low-stage air pipe 81 thinner than the high-stage air pipe 82 and injecting compressed air into both pipes at the same time, air can be forcefully ejected from the low-stage air outlet hole 81a that communicates with the thinner air pipe with a smaller amount of air, which is more effective for such solidified sedimentary layers. Specifically, if the inner diameter of the first upward flow section vent pipe 41 is 350 mm or less, it is effective to make the low-stage air pipe 81 have an inner diameter of about 2 mm. In addition, when the first upflow section vent pipe 41 has an inner diameter of approximately 400 mm or more, it is preferable to use a pipe that is approximately 8 to 10 mm thicker as the low-stage air pipe 81, i.e., one with an inner diameter of approximately 10 to 13 mm, and to provide two or three low-stage air discharge holes 81a so that the branched low-stage air pipes 81 communicate with each low-stage air discharge hole 81a. In this way, by ejecting compressed air from multiple discharge holes through a thick air pipe, even if the first upflow section vent pipe 41 is thick, it is possible to significantly excavate and flow down the gravel-like soil that has solidified at the bottom of the vent pipe. In this way, when multiple air discharge holes 81a are provided, it is preferable to install each air discharge hole at an interval of approximately 1 cm with a height difference between the upstream end of the upflow section vent pipe and the downstream end 2 to 5 cm away.

The high-stage air discharge hole 82a is provided near the upstream end of the second upflow section vent pipe 42 as shown in FIG. 4, for example, so that compressed air acting biased toward the downstream direction in the second upflow section vent pipe is ejected. Specifically, when the upflow section vent pipe is configured as a double-pipe structure, the high-stage air discharge hole 82a is provided at a position upstream from the upstream end of the upflow section vent pipe by a length of 0.2 to 1.0 times the inner diameter of the first upflow section vent pipe 41, as shown in FIG. 4. This position is the upstream end of the second upflow section vent pipe 42, that is, the position where the connection part of the first upflow section vent pipe 41 and the second upflow section vent pipe 42 is set, and in this embodiment, the connection part is formed using a 90-degree to 45-degree elbow-shaped joint. As shown in FIG. 4, the high-stage air discharge hole 82a is provided at the top of this joint by U-shaped piping.

In addition, as shown in FIG. 4, the high-stage air pipe 82 connected to the high-stage air discharge hole 82a is configured to extend upstream from the bottom of the downstream manhole C, attached to the outer wall of the first upflow section vent pipe 41, and penetrate the bottom pipe wall of the first upflow section vent pipe 41 just before the opening of the upstream end of the second upflow section vent pipe 42, and enter the first upflow section vent pipe once, and its tip enters the second upflow section vent pipe and bends to face downstream, forming a U-shaped pipe, and a high-stage air discharge hole 82a that acts exclusively in the downstream direction can be provided.

When the second upflow section vent pipe 42 is provided in a double pipe configuration, the high-stage air discharge hole 82a is provided inside the second upflow section vent pipe 42 as shown in FIG. 5. More specifically, the high-stage air discharge hole 82a is provided so as to open toward the downstream side inside the second upflow section vent pipe near the small mouth of the upstream opening, which is the upstream end of the second upflow section vent pipe 42 with the tip cut at an angle.

Considering the injection of compressed air as the settling impurities removal means 8, it is found that injecting compressed air directly into the narrower vent pipe in the two-pipe configuration can remove settling impurities more efficiently than injecting compressed air directly into the vent pipe of a single-pipe configuration or into the vent pipe with a larger pipe diameter in a two-pipe configuration. As described above, in order to effectively remove settling impurities on a daily basis, the inner diameter of the second upflow section vent pipe 42 is set to 100 mm or less, which is smaller than the inner diameter of the first upflow section vent pipe 41. Injecting air directly into the narrower second upflow section vent pipe 42 as the settling impurities removal means 8 is advantageous not only in terms of the above effects but also in terms of the effect of injecting compressed air. That is, even when comparing cases where the amount of compressed air injected and the injection pressure are the same, the compressed air acts more strongly when injected into a thinner vent pipe with an inner diameter of 100 mm or less, so even heavy and large gravel soil can run up the second upward flow vent pipe 42 and be removed by flowing down. Furthermore, since it can also handle the inflow of metal pieces and glass pieces, it is easy to respond to emergencies in which larger impurities may be mixed into the sewage.

It is desirable that the settling impurities removal means 8 of the present invention is implemented simultaneously with the two-strand pipe configuration of the upflow section vent pipe, which is also the present invention. For this reason, the following describes an embodiment in which the upflow section vent pipe has a two-strand pipe configuration, but the present invention is not limited to this. An embodiment of the actual installation of the air pipe of the settling impurities removal means 8 of the present invention will be described. An example of the installation when the upflow section vent pipe has a double structure is shown in the cross-sectional view of FIG. 2(b). Also, an example of the installation when the upflow section vent pipe has a double structure is shown in the cross-sectional view of FIG. 3(b). Thus, in the actual installation, the air pipe of the settling impurities removal means, both the high-stage air pipe 82 and the low-stage air pipe 81, can be installed in the gap part of the splice part of the first upflow section vent pipe 41 and the second upflow section vent pipe 42. This installation method can be installed by pasting it in the gap part, or by a known splice means. Also, as shown in Figures 4 and 5, the high-stage air pipe 82 and the low-stage air pipe 81 may be installed by bonding them together along the bottom outer wall of the first upflow section vent pipe 41 or the second upflow section vent pipe 42.

In this embodiment, the air discharge holes include a low-stage air discharge hole 81a that discharges compressed air from the bottom surface of the upstream side of the upflow section, and a high-stage air discharge hole 82a that discharges air to the small opening at the upstream end of the second upflow section vent pipe at a position downstream of the low-stage air discharge hole 81a. The air discharge hole uses a U-shaped pipe that acts only on the downstream side from one point on the bottom side of the flow path cross section, and compressed air is ejected from this air discharge hole in the downstream direction at approximately 1.0 MPa (megapascals). By supplying this compressed air, sand and pebbles with a particle size larger than sand with a particle size of 5 mm are scooped up from the second vent pipe 42 and removed by flowing down. Therefore, in emergencies such as earthquakes and heavy rain disasters, by supplying compressed air to the second upflow section vent pipe 42 for a specified time, the maintenance and management of the vent pipe underpass can be further improved.

The air discharge hole (opening hole) in the compressed air injection means disclosed in JP 2011-220106 A was configured as an air pipe with a 90-degree bend (elbow). Here, when the inner diameter of the upward flow section vent pipe is 200 mm, the pipe thickness of the vent pipe is 6.5 mm, so the air discharge hole is provided with this 6.5 mm pipe thickness as a margin. In this way, when compressed air is ejected from the part with a thin adhesive surface in a direction perpendicular to the flow path at a pressure of approximately 1.0 MPa, there is a risk that the adhesive surface of the opening hole will crack or peel due to the action of the reaction force. If cracks or peeling occur on the adhesive surface of the opening hole, soil and sand will enter the vent pipe through the gap, increasing the risk of clogging of the vent pipe. In order to improve this point, when setting up the settling impurities removal means 8 of the present invention, it is desirable to use U-shaped piping for both the low stage air discharge hole 81a and the high stage air discharge hole 82a, which act only downstream from one point on the bottom of the flow path cross section, as described above. This allows the pipe to withstand the reaction force when compressed air is discharged, and no distortion stress is generated due to the connection of the air pipe to the upflow section vent pipe 4, and the entire amount of compressed air injected toward the downstream direction acts on the downstream side. In addition, damage to the upflow section vent pipe can be prevented even if the relative positions of the upflow section vent pipe and the air pipe are misaligned due to earthquakes, land subsidence, etc.

For the low-stage air pipe 81, it is particularly preferable to use an air fiber tube with an outer diameter of approximately 1.8 mm, an inner diameter of approximately 1.2 mm, and a pressure resistance of approximately 1.47 MPa. Other suitable tubes include silicone tubes and resin tubes that do not swell. For the high-stage air pipe 82, it is particularly preferable to use a polyurethane tube with an outer diameter of approximately 10 mm and an inner diameter of approximately 6 mm. Other suitable tubes include silicone tubes and resin tubes that do not swell.

In the applicant's experience, there have been no cases where the deterioration of polyurethane tubes used in the hidden structure over time has become a problem, but it is preferable to use a sheath tube for greater safety. Specifically, a water pipe made of impact-resistant hard polyvinyl chloride with an inner diameter of 13 mm and an outer diameter of 18 mm is used as the sheath tube, and a polyurethane tube with an outer diameter of approximately 10 mm and an inner diameter of approximately 6 mm is inserted into this as the air tube 82, making a double tube with an outer diameter of 18 mm and an inner diameter of approximately 6 mm that can be used as the high-stage air tube 82. Furthermore, in cases where extremely long-term use is expected, it is preferable to make the joint between the high-stage air discharge hole 82a and the polyurethane tube a screw type for even greater safety. With this configuration, in the unlikely event that deterioration is found in the polyurethane tube, it is possible to pull out only the deteriorated polyurethane tube from the air valve part 83 provided under the cover of the downstream manhole C to which the upstream end of the air tube 82 is connected. After pulling out the polyurethane tube, it is possible to continue using the remaining 13 mm water pipe as the high-stage air tube 82.

In addition, when the first upflow section vent pipe 41 has an inner diameter of approximately 2000 mm or more, in addition to forming the upflow section vent pipe 4 as a double pipe structure as described above, two or three second upflow section vent pipes 42 may be added. In that case, the two or three added second upflow section vent pipes 42 can be attached to either the inner wall or the outer wall of the first upflow section vent pipe 41, or to both the inner wall and the outer wall. Furthermore, it is preferable to make the high-stage air pipe 82 a pipe about 8 mm thick, i.e., a pipe with an inner diameter of approximately 14 mm, and further provide two or three high-stage air discharge holes 82a, and to branch the high-stage air pipe 82 to communicate with each high-stage air discharge hole. In this way, by installing multiple second upflow section vent pipes 42 for the first upflow section vent pipe 41 and ejecting compressed air from multiple discharge holes through a thick air pipe, it is possible to reliably achieve the effect of removing sedimentary impurities accumulated at the bottom of the vent pipe, even in a vent pipe with a large inner diameter. When multiple air discharge holes are provided in this way, the arrangement of each air discharge hole can be, for example, as follows. When three discharge holes are provided, one air discharge hole is provided at the bottommost part of the second upflow section vent pipe 42, and the other two air discharge holes are provided at positions separated from this discharge hole on opposite sides in the circumferential direction. The interval between each discharge hole can be, for example, 7.8 cm. When two discharge holes are provided, the one at the bottommost part of the pipe in the above three cases is omitted, and the interval between the discharge holes can be, for example, 5.2 cm.

In the vent pipe underpass structure 1 of the present invention, as a measure against floating impurities, it is desirable to provide a straightening section 51 in a predetermined section of the upstream sewer pipe 5 connected to the upstream side of the underpass, as shown in Figure 1. Here, the straightening section 51 refers to a section in a predetermined section of the upstream sewer pipe 5 whose pipe diameter is equal to or smaller than the pipe diameter of the downflow vent pipe 2. Up until now, in the vent pipe underpass structure, in order to ensure the sweeping force of the underpass, it has been common for the pipe diameter of the underpass to be set smaller than the pipe diameter of the upstream sewer pipe. In other words, this means that the pipe diameter usually changes at the point where the sewage enters the vent pipe underpass structure 1, i.e., at the upstream end of the downflow vent pipe 2, and the sewer pipe downstream from that point (the vent pipe underpass structure 1) becomes a sewer pipe thinner than the upstream sewer pipe 5. In contrast, in the present invention, by providing a straightening section 51 in a predetermined section of the upstream sewer pipe 5, the point where the pipe diameter changes is the upstream end of the straightening section 51, i.e., a point further upstream by the length of the straightening section 51 from the upstream end of the downflow section vent pipe 2, which is the point where the sewage enters the downflow section. As a result, in the vent pipe downflow structure 1 of the present invention, from the middle of the upstream sewer pipe 5 just before the downflow section, the sewer pipe has a diameter smaller than that of a normal upstream sewer pipe 5 and equal to or smaller than that of the downflow vent pipe. In this way, by providing the straightening section 51 in a predetermined section of the upstream sewer pipe 5, the sewage flow flows into the vent pipe with a smaller cross-sectional area while remaining in a state of being adapted to the large cross-sectional area of the upstream sewer pipe 5, and it is possible to prevent impurities from adhering to and accumulating near the water surface in an uneven and overcrowded state in the flow path of the downflow section vent pipe 2. In other words, by providing the flow straightening section 51, the mixture of impurities in the sewage (the order of impurities) is adjusted before it enters the overflow vent pipe, and then the sewage is allowed to flow into the downward flow vent pipe 2, preventing the impurities from gathering or becoming unevenly distributed.

A more specific embodiment will be described below with reference to FIG. 1. As shown in FIG. 1, the straightening section 51 is provided by, for example, setting a manhole A provided in the middle of the upstream sewer pipe 5 as a boundary point, and setting the pipe diameter of the sewer pipe extending downstream from there to a pipe diameter equal to or smaller than the pipe diameter of the downflow section vent pipe 2. In this embodiment, the downstream end of the straightening section 51 is the upstream end of the downflow section vent pipe 2, where an upstream manhole B is provided. The section distance of the straightening section 51 is preferably set to approximately 1.5 to 20 m according to the size of the overflow, since this makes it possible to sufficiently adjust the order of impurities before they flow into the overflow.

Thus, in this embodiment, at the boundary point where manhole A is located (the upstream end of the straightening section 51, i.e., the straightening section inlet), the diameter of the sewer pipe changes to a smaller diameter than the sewer pipe 5 upstream of the boundary point, and the smaller diameter is maintained while connecting to the downflow vent pipe 2. The specific diameter of the sewer pipe in the straightening section 51 is determined as follows, taking into account the margin in the pipe diameter of the planned sewage flow rate. The prescribed value of the margin in the pipe diameter of the planned sewage flow rate is 50% (see Non-Patent Document 2). However, when the straightening section 51 of the present invention is provided, it is preferable to determine the pipe diameter and gradient of the straightening section 51 by setting the maximum water level to 80% of the pipe diameter when the sewer pipe shape is a circular pipe or a horseshoe culvert, and to 90% of the pipe diameter when the sewer pipe shape is a square culvert. For example, if the upstream sewer pipe 5 has an inner diameter of 400 mm, it is preferable to set the inner diameter of the straightening section 51 and the inverted vent pipe to 350 mm. In actual construction, it is recommended to use standard sewer pipes, and in terms of construction costs, it is desirable to use a sewer pipe in the straightening section 51 that has an inner diameter one rank smaller than the upstream sewer pipe 5.

In addition, when determining the pipe gradient of the straightening section 51, the ideal flow velocity of the sewer pipe must also be taken into consideration. The ideal flow velocity in a sewer pipe is said to be 1.0 to 1.8 m/s (see Non-Patent Document 2). For example, in the case of a vent pipe in which the inner diameter of the upstream sewer pipe 5 is 400 mm and the inner diameter of the downflow vent pipe 2 is 350 mm, if the flow velocity of the upstream sewer pipe is 1.8 m/s, which is the upper limit of the ideal flow velocity, and if it flows into the downflow vent pipe 2 as is, there is a risk that air will be drawn into the downflow vent pipe. In order to avoid this, the pipe gradient of the upstream sewer pipe 5 (inner diameter 400 mm) can be set to 7.0/1000 to achieve a flow velocity of 1.79 m/s, which is within the range of the ideal flow velocity. However, when providing the straightening section 51 with an inner diameter of 350 mm in the upstream sewer pipe 5 with an inner diameter of 400 mm (gradient: 7.0/1000), it is necessary to take into consideration that the water level in the straightening section reaches 80% of the height of the pipe cross section under this condition. If the gradient of the straightening section 51 is set to take over the gradient of the upstream sewer pipe 5 (7.0/1000) and applied to the Manning flow calculation formula that is generally used to calculate the flow velocity, the flow velocity in the straightening section will exceed 1.8 m/s, which is the upper limit of the ideal flow velocity. Therefore, in order to provide the straightening section 51 with an inner diameter of 350 mm in the upstream sewer pipe 5 with an inner diameter of 400 mm (gradient: 7.0/1000), the gradient of the straightening section 51 needs to be reduced to 6.5/1000. It was confirmed that the value of the flow velocity becomes 1.58 m/s by reducing the gradient, which is within the range of the ideal flow velocity. According to Manning's flow rate calculation formula, if the flow velocity in the flow straightening section 51 is still approximately 1.8 m/s or more, it is preferable to set a section about 2 to 5 m upstream from the downstream end of the flow straightening section 51 as a Level section with zero gradient.

When setting the straightening section 51, it is necessary to consider the water level WL in the sewer pipe. That is, as shown in FIG. 6(a), it is necessary to avoid the occurrence of a so-called reverse water level gradient, in which the water level (WL2) in the straightening section 51 downstream of the upstream sewer pipe 5 is higher than the water level (WL1) in the upstream sewer pipe 5. For example, when the upstream sewer pipe 5 is a circular pipe with an inner diameter of 400 mm and the sewer pipe in the straightening section 51 is a circular pipe with an inner diameter of 350 mm, and a manhole A is provided at the boundary between the upstream sewer pipe 5 and the straightening section 51, the following considerations are made when considering the margin value at each sewer pipe cross section. In this case, the manhole A at the boundary is the boundary, and the water level (WL1) in the upstream sewer pipe 5 upstream of it is 200 mm, which is 1/2 of the inner diameter of 400 mm. In contrast, the water level (WL2) in the pipe in the straightening section 51 downstream of manhole A is 280 mm, which is 80% of the inner diameter of 350 mm. Therefore, between the upstream sewer pipe 5 and the straightening section 51, there is a reverse water level gradient of WL2-WL1=280 mm-200 mm=80 mm.

This reverse gradient of the water level can be eliminated by setting as follows. First, if there is a margin of 80 mm or more in the head loss H of the overflow, the reverse gradient of the water level can be eliminated by lowering the pipe bottom of the straightening section 51 by 80 mm at the bottom of the sewer pipe (b) at the position corresponding to the downstream outermost edge of the manhole A at the boundary so that the upstream sewer pipe 5 and the straightening section 51 are in water surface contact (Figure 6 (b)). Also, if there is not a margin of 80 mm or more in the head loss H of the overflow, the pipe bottom of the upstream sewer pipe 5 is set to be raised by 80 mm at the point (a) of the manhole A. Specifically, the water level difference (80 mm) that causes the reverse gradient of the water level can be eliminated by reducing the pipe gradient of the distance sufficient to raise the pipe bottom of the upstream sewer pipe 5 by 80 mm at the point (a) from 7.0/1000 to 6.5/1000.

If the water level difference cannot be eliminated even when the pipe gradient of the upstream sewer pipe 5 is set to 6.5/1000, it is preferable to eliminate the reverse gradient of the water level by lowering the gradient of the upstream sewer pipe 5 from the normal value so as to lower the flow velocity of the sewer pipe within a range that does not fall below the lower limit of the ideal flow velocity (1.0 m/s). Furthermore, if the reverse gradient of the water level is not eliminated due to the relationship between the flow capacity and the planned sewage flow rate even when the gradient of the upstream sewer pipe 5 is set to be lowered to the lower limit, this can be addressed by moving manhole A, which is the boundary point between the upstream sewer pipe 5 and the straightening section 51, downstream to shorten the length (extension) of the straightening section 51. Specifically, in this case, it is appropriate to make the straightening section 51 approximately 15 m long.

The above-mentioned ideal flow velocity of 1.0 to 1.8 m/s is examined at the lower limit of 1.0 m/s as follows: In the case of an upstream sewer pipe 5 with an inner diameter of 400 mm, a pipe gradient of 2.2/1000, a flow velocity of 1.0 m/s, and a planned sewage flow rate of 0.061 ^m3 /s at 50% water level, if this is carried over to a straightening section 51 with an inner diameter of 350 mm, where the pipe gradient is 2.6/1000, the flow velocity is 1.0 m/s, the water level is 73%, and the pipe flow rate is 0.061 ^m3 /s, the pipe water level will be +200 mm at point (A) of manhole A and 256 mm at point (B), resulting in a reverse water level gradient of 56 mm. In this case, since the flow velocity is already 1.0 m/s, which is the lower limit of the ideal flow velocity, it is not desirable to try to eliminate the reverse water level gradient by adjusting the sewer pipe gradient. Therefore, it can be said that it is desirable to lower the pipe bottom by 56 mm at point (b) in manhole A to achieve a water surface junction while ensuring an ideal flow velocity and achieving a smooth water level gradient.

As described above, it is expected that providing a straightening section 51 in the upstream sewer pipe 5 section, where the pipe diameter is narrower downstream than upstream, will have disadvantages such as making it difficult to ensure an ideal flow rate and causing a reverse gradient in the water level. However, providing the straightening section 51 will straighten the flow of sewage into the overflow, for example with an inner diameter of 350 mm, so that the water level in the pipe is 73-80% before it flows into the overflow, and this flow will flow into the overflow vent pipe (350 mm) of the same diameter at 100% water level (full pipe), which has the great advantage of avoiding sudden contraction of the fluid at the inflow point into the overflow, preventing excessive uneven distribution of impurities, and preventing the accumulation of impurities on the water surface when the water is stopped in the vent pipe. Therefore, even if providing the straightening section 51 results in an inverse gradient or a non-ideal flow velocity, it is desirable to deal with this by taking the measures mentioned above, i.e., by comprehensively adjusting the pipe inner diameter, pipe gradient, flow rate, flow velocity, and section length (extension) of the straightening section in the upstream sewer pipe 5 and the straightening section 51. Considering this, it is preferable to design an inverted vent structure when providing a straightening section 51 by first determining the conditions of the straightening section (inner diameter, extension, etc.), and then selecting the inner diameter of the inverted vent pipe accordingly.

When establishing the rectification section 51 of the present invention, as shown in FIG. 6(a), it is desirable to provide a manhole A at the boundary between the upstream sewer pipe 5 and the rectification section 51. However, if the rectification section 51 is established within an existing pipe, the installation of a manhole can be omitted.

Next, the joining of the boundary between the upstream sewer pipe 5 and the rectifying section 51 will be described. The shape of the pipe bottom at the joining part of the boundary is set to a semicircular groove (Fig. 7(b)) in which the pipe diameter gradually narrows from the upstream side to the downstream side (Fig. 7(a)), as shown in the plan view of Fig. 7(a) and the cross-sectional view of Fig. 7(b). Usually, for smooth flow, a manhole is installed at the change point of the cross section, and a semicircular groove (invert) is installed at the bottom. In the present invention, the invert is made to gradually narrow from the upstream side to the downstream side as shown in Fig. 7, so as to correspond to a sudden narrowing. When the rectifying section 51 is provided in an existing pipe, it is also possible to provide the rectifying section 51 by inserting a Hume pipe (half pipe) or a polyvinyl chloride pipe of the same diameter as the inner diameter of the rectifying section 51 inside the existing pipe.

Next, as shown in FIG. 8, a case where another sewer pipe 52 is joined in the middle of the straightening section 51 will be described. In urban areas, all sewers are laid under roads, so it may be necessary to join a sewer pipe at a point in the middle of the straightening section 51. In that case, in order to deal with the increase in the flow rate due to the joining, a joining point junction manhole B2 is installed at the joining point in the middle of the straightening section 51 as shown in FIG. 8. For the sake of convenience, the upstream side will be referred to as the straightening section 51a and the downstream side as the straightening section 51b. Here, the pipe diameter of the straightening section 51b is larger than that of the straightening section 51a (not shown). Accordingly, the pipe diameter of the downward flow section vent pipe 2 is also the same diameter as that of the straightening section 51b. Specifically, for example, when the pipe diameter of the upstream sewer pipe 5 is 400 mm, it is preferable that the pipe diameter of the straightening section 51a is 350 mm, the pipe diameter of the straightening section 51b is 400 mm, and the pipe diameter of the downflow section vent pipe 2 is the same diameter of 400 mm. In this way, when setting the straightening section 51 of the present invention, if there is a confluence of another sewer pipe 52 within the straightening section, the inner diameter of the sewer pipe of the straightening section 51 will be different on the upstream side and downstream side of the confluence. In other words, the inner diameter of the sewer pipe of the straightening section 51 is equal to or smaller than the inner diameter of the downflow section vent pipe 2 in the straightening section 51a upstream of the confluence, and is equal to the inner diameter of the downflow section vent pipe 2 in the straightening section 51b downstream of the confluence. In actual construction, when establishing the straightening section 51 in this manner, it is advantageous in terms of design and construction to use a pipe with a standard inner diameter one rank lower than that of the upstream sewer pipe 5 in the straightening section 51a, and a pipe with a standard inner diameter one rank higher than that of the straightening section 51a in the straightening section 51b.

Furthermore, in the vent pipe underpass structure 1 of the present invention, as shown in FIG. 9, it is desirable to set the inclination angle (bent angle) θ1 of the downward flow section vent pipe 2 to 30 degrees or less in addition to setting the straightening section 51 described above. Generally, the inclination angle θ2 of the downward flow section vent pipe in the underpass structure is set to 45 degrees. By setting this inclination angle to 30 degrees or less, the sweeping force against floating impurities can be increased, as described below.

In the present invention, a straightening section 51 is provided in a predetermined section of the upstream sewer pipe 5, and the inclination angle of the downward flow vent pipe 2 is set to 30 degrees or less, thereby mitigating the turbulent state at the junction where the water flows from the upstream sewer pipe 5 into the vent pipe, and preventing the generation of air bubbles in the vent pipe, thereby preventing the potential energy due to the required head loss H from being reduced. This makes it possible to constantly remove floating impurities by the flow force of the sewage itself without relying on mechanical force. In addition, in the event of a heavy rain disaster, when more floating impurities than expected flow in and need to be removed, the effect of spraying pressurized water by the floating impurity removal means of the present invention described below is enhanced, creating a state in which floating impurities in the sewage can be removed more effectively. Furthermore, when the inclination angle of the downflow vent pipe 2 is 30 degrees or less, the water surface area of both the inlet water surface w1 of the downflow vent pipe 2 and the water surface w2 when the water is stopped is larger than when the inclination angle of the downflow vent pipe 2 is generally 45 degrees (Figure 9). Therefore, the layer thickness of the floating impurities can be expected to be thinner, and the required unit sweep force can be reduced. Furthermore, by setting the inclination angle of the downflow vent pipe 2 to 30 degrees or less, the horizontal component force of the flow flowing downstream is increased, making it easier for the impurities to pass through without hindrance. In other words, when comparing the horizontal component force, when the inclination angle of the downflow vent pipe 2 is 45 degrees, it is cos45 = 1 / √2, and when the inclination angle is 30 degrees, it is cos30 = √3 / 2, so there is an advantage that a larger force is generated and it is advantageous for the floating matter removal effect.

When the inclination angle of the downflow vent pipe 2 is set to 30 degrees or less, it is not affected by various conditions such as the inner diameter of the vent pipe, the head loss H value for each inverted structure, the length of the downflow vent pipe, and the material of the vent pipe, so it is preferable to set the inclination angle of the downflow vent pipe 2 to 30 degrees or less in any case. The specific angle depends on the conditions at the site where the inverted structure is installed, but it is preferable to make the inclination of the downflow vent pipe as gentle as possible, with an angle as small as conditions permit.

Below, a specific embodiment of the downflow vent pipe 2 when the inclination angle is set to 30 degrees or less will be described. To set the downflow vent pipe 2 to an inclination angle of 30 degrees or less, as shown in FIG. 10, a flexible bend pipe (short pipe) 21 and a rubber ring joint for forming the desired angle are used at the connection part of the downflow vent pipe 2 and the lateral flow vent pipe 3. When the inclination angle of the downflow vent pipe 2 with an inner diameter of 150 to 300 mm is set to 30 degrees or less, a standardized hard polyvinyl chloride pipe for sewerage consisting of a flexible water stop joint can be used as this flexible bend pipe. Furthermore, since the rubber ring joint has a range of motion of 15 degrees or less in the front, back, left and right directions, the range of motion of this rubber ring joint can be used in addition to the curvature of the bent pipe. In other words, by combining a rubber ring joint with a 15-degree or 30-degree flexible bend pipe, the inclination angle of the downflow vent pipe 2 can be set to a desired angle having a fraction of 30 degrees or less. This also makes it possible to construct a hidden structure with a flow path other than a longitudinal flow path while maintaining an inclination angle of 30 degrees or less with a single bent pipe. For example, as shown in Figure 11, in addition to an L-shaped flow path, it can also be used when various linear flow paths such as T-shaped and U-shaped are required.

In addition, when the inner diameter of the downward flow vent pipe 2 is 350 mm or more, by using a special bend pipe (flange bend pipe) or a ductile cast iron arbitrary bend pipe (inner surface coating), etc., there are standardized bend pipes of 1 degree to 5 degrees, 5/8 to 11 degrees, 1/4 to 22 degrees, 1/2 to 30 degrees in increments of 1 degree, so the inclination angle can be set to a desired angle with a fraction of 30 degrees or less. However, here, it is necessary to consider that there are no standardized freely bent pipes (standardized rigid polyvinyl chloride pipes for sewerage) when the inner diameter of the vent pipe is 350 mm or more. For this reason, in order to not only set an inclination angle in the longitudinal flow direction of the vent pipe, but also to bend it in the horizontal linear direction at the same time, it is necessary to use two bend pipes connected together. For example, as shown in Figure 11, if the vent pipe is L-shaped so that the sewer pipe is parallel to the river, etc., a 60-degree bend pipe is connected to the horizontal flow vent pipe 3 so that the desired inclination angle is set at one bending point. Here, in order to avoid creating two bending points in the inclination angle, a construction method in which a horizontal linear bend is set using a 60-degree bend, and then a vertical bend with an inclination angle of 30 degrees or less should be avoided. Such a construction method will result in a horizontal 60-degree bending point and a vertical bend of 30 degrees or less, and the increase in bending points will increase the head drop ΔH, which corresponds to the head loss in the inclination route.

In addition, when a sewer pipe, which is generally buried under a public road, is made to pass through a river, etc., a case will be described in which the sewer pipe is constructed to avoid being directly under the bridge of the road, as shown in Figure 12, in order to avoid additional loads from bridge abutments during earthquakes, etc. on the bridge. As shown in Figure 12, the upstream sewer pipe 5 and downstream sewer pipe 6 are constructed directly under the road, but the horizontal upflow vent pipe 3 of the vent pipe hidden structure may be buried in the general riverbed, avoiding being directly under the bridge of the road. In this structure, the downstream vent pipe 2 gradually moves away from directly under the road and heads toward the horizontal upflow vent pipe 3 buried in the general riverbed, while the upstream vent pipe 4 gradually moves away from the general riverbed where the horizontal upflow vent pipe is buried and returns to being directly under the road, and a curved pipe structure that bends both in the longitudinal direction and in the horizontal direction is required. However, when the inner diameter of the sewer pipe is 350 mm or more, since there is no freely curved pipe as a standard product of rigid polyvinyl chloride pipe for sewerage, for example, at the joint of the horizontal upflow section vent pipe 3 and the downflow section vent pipe 2, a 60-degree curved pipe is installed in the lower stage so as to be bent horizontally, and then a 30-degree curved pipe is connected to the upper stage so as to be bent upwardly, so that a curved pipe structure that bends in the longitudinal direction and the horizontal direction may be constructed, and the required head loss is appropriately increased. In the curved pipe structure at the joint of the horizontal upflow section vent pipe 3 and the upflow section vent pipe 4 constructed in this way, if compressed air is supplied by the above-mentioned settling impurities removing means 8 installed in the upflow section vent pipe 4, the following problem occurs. That is, even if compressed air is supplied to the 60-degree curved pipe bent horizontally at the lower stage of the joint, no effect can be expected because the supply position is at the same altitude as the horizontal upflow section vent pipe 3. Furthermore, even if compressed air is supplied to the 30-degree bent pipe at the top of the joint, it is supplied to a position away from the sedimentary layer of settleable impurities, so it is not effective enough to suspend the settleable impurities.

However, in the case of a vent pipe with an inner diameter of 150 to 300 mm, a standardized rigid polyvinyl chloride pipe for sewerage consisting of a flexible water stop joint can be used as a flexible bend pipe, and in the case of a vent pipe with an inner diameter of 350 mm or more, a special bend pipe (flange bend pipe) or a ductile cast iron bend pipe (inner surface coated) can be used to make a bend pipe that bends in both the longitudinal and horizontal directions at the same time. In addition, when the sewer pipe is installed in such a structure that avoids the bridge portion, the length of the downflow vent pipe 2 and the upflow vent pipe 4 will inevitably be increased, which has the advantage of making it easier to ensure a smaller inclination angle of the downflow vent pipe of 30 degrees or less required in this invention. As a result, the adoption of the vent pipe underpass structure of this invention makes it possible to make a vent pipe underpass structure that is less susceptible to the effects of earthquake loads on both the bridge foundation and the sewer pipe while providing an effective means for removing impurities, even when the sewer pipe is installed to avoid such bridge portions.

Next, referring to FIG. 13, the floating impurity removal means 7 provided in the downflow vent pipe will be described. The floating impurity removal means 7 of the present invention ejects pressurized water from at least one pressurized water discharge hole 72 that opens near the water surface of the downflow vent pipe 2 when water is stopped toward the water surface in the downflow vent pipe 2 when water is stopped for a predetermined period of time as necessary, thereby removing floating impurities that have accumulated near the water surface of the downflow vent pipe 2 when water is stopped.

In the vent pipe underpass structure of the present invention, the setting of the straightening section 51 and the adjustment of the inclination angle of the downward flow vent pipe prevent floating impurities that flow into the sewer on a daily basis from being piled up and deposited near the water surface when the water is stopped in the downward flow vent pipe 2. In contrast, the floating impurities removal means 7 described here is provided as a precaution against unexpected situations such as when an unusually large amount of leaves, dead grass, clothing, etc., flows into the underpass of the vent pipe during a heavy rain disaster or earthquake. It can also be used to deal with other unusual unexpected situations such as the inflow of a large amount of oils and fats, or water-insoluble paper. In this way, the floating impurity removal means 7 of the present invention is positioned as a means for temporarily increasing the ability to remove floating impurities by operating as an emergency measure in the event of a situation that cannot be dealt with by setting the straightening section 51 and adjusting the inclination angle of the downward flow section vent pipe alone. Therefore, the floating impurity removal means 7 of the present invention is not operated all the time on a daily basis, but can be said to deal with such unusual accumulations of impurities by spraying pressurized water for a specified period of time when the need arises.

The applicant previously proposed a method of supplying compressed air to remove floating impurities that tend to accumulate near the water surface when the water is stopped in the downflow vent pipe 2 (JP Patent Publication No. 2011-220106). However, in this method of discharging compressed air, the supplied compressed air tends to rise toward the inlet (upstream end) of the downflow vent pipe against the flow force of the sewage due to its buoyancy. This makes it less effective as a means of removing floating impurities. In addition, in the conventional inverted structure, the inclination angle (bent angle) of the downflow vent pipe is set to 45 degrees, so the supplied air escapes to a manhole provided at the upstream end of the downflow vent pipe, and no exhaust problems occur. However, in the case of adopting the inverted structure of the present invention, the inclination angle of the downflow vent pipe 2 is set to 30 degrees or less as described above, so the buoyancy of the air is less likely to work. For this reason, if the floating impurity removal means using compressed air disclosed in JP 2011-220106 A is applied to the vent pipe underpass structure of the present invention, there is a problem that the air discharged into the downflow section vent pipe 2 remains inside the vent pipe, generating an air mass. If an air mass is generated inside the vent pipe, the relative density of the water column decreases by the required head loss H equivalent to the head loss in the vent pipe underpass path, and the hydrostatic pressure acting on the vent pipe decreases, reducing the potential energy and reducing the flow force of the sewage. For this reason, in the vent pipe underpass structure of the present invention in which the inclination angle of the downflow section vent pipe 2 is set to 30 degrees or less, a floating impurity removal means using a method other than discharging air is required.

The floating impurities removal means 7 of the present invention has at least one pressurized water discharge hole 72 that opens near the water surface when the water is stopped in the downflow vent pipe 2 and a pressurized water injection pipe 71 that communicates with the pressurized water discharge hole 72, and pressurized water is supplied from the pressurized water discharge hole 72 through the pressurized water injection pipe 71 to the water surface near the water surface when the water is stopped in the downflow vent pipe for a predetermined time as necessary. Here, the water surface when the water is stopped refers to the position of the water surface in the downflow vent pipe when sewage is not flowing, that is, the elevation position in the downflow vent pipe 2 that corresponds to the elevation of the bottom of the downstream sewer pipe 6 at the downstream end of the upflow vent pipe 4 installed downstream of the vent pipe underpass structure.

With this configuration, by supplying pressurized water instead of compressed air near the water surface of the downstream vent pipe 2 when the water is stopped, it is possible to create a section with a faster flow rate within the same flow path within the cross section of the vent pipe. A slower flow rate containing floating impurities is attracted to this section with a higher flow rate, forming a vortex, which causes the floating impurities to flow downstream and be removed. This powerful effect makes it possible to remove impurities that could not be removed by the impurity removal means that uses compressed air discharged as disclosed in JP 2011-220106 A.

Since the floating impurity removal means 7 of the present invention is not operated on a daily basis as described above, it is preferable to use rainwater stored in the following configuration as the water supplied as pressurized water. As shown in FIG. 1, in the vent pipe underpass structure, a deodorizing intake and exhaust tank 9 is provided to accommodate the exhaust of air and the movement of intake air due to fluctuations in the water level of the upstream sewer pipe 5. It is preferable to provide an underground water tank 91 of, for example, about 0.1 to 0.3 cubic meters in the lower structure of this deodorizing intake and exhaust tank 9 to store rainwater, and to connect, for example, a portable mini booster pump to supply this stored water to the floating impurity removal means 7 when necessary. Note that, as shown in FIG. 13, it is preferable that the underground water tank 91 provided in the deodorizing intake and exhaust tank 9 has a funnel-shaped water collection section 92 above the water tank, so that rainwater passes through a grating on the upper surface and accumulates in the underground water tank 91. It is preferable to configure the so-called foot pipe, which extends downward from the tip of the cone of the funnel-shaped water collection section 92, to a position slightly above the bottom of the underground water tank (for example, about 5 cm above the bottom). With this configuration, rainwater collected during rainfall flows into the bottom of the underground water tank 91, and excess water flows from the upper overflow pipe of the underground water tank 91 into a gutter or drainage channel, so that the stored water is replaced every time rainfall occurs, which is preferable in terms of managing the stored water.

Next, the pressurized water discharge hole 72 of the floating impurities removal means 7 of the present invention will be described. The pressurized water discharge hole 72 is provided so as to spray pressurized water toward the vicinity of the water surface of the downflow vent pipe 2 when water is stopped, and in the floating impurities removal means 7 of the present invention, at least one pressurized water discharge hole 72 is provided at the top of the downflow vent pipe 2 so as to open toward the sewage flow direction (i.e., the downstream direction). Specifically, it is preferable to provide one to three pressurized water discharge holes 72 in accordance with the inner diameter of the vent pipe. When providing multiple pressurized water discharge holes 72, it is preferable to provide them at positions spaced apart by a predetermined distance on the upstream or downstream side, centered on the water surface of the downflow vent pipe 2 when water is stopped. The position of the pressurized water discharge hole 72 will be described in detail below.

Specifically, when the inner diameter of the downflow vent pipe 2 is 200 mm or less, it is preferable to provide only the first pressure water discharge hole 72a at a single location at the height of the water surface when the water is stopped in the downflow vent pipe 2.
In addition, when the inner diameter of the downflow vent pipe is 250 mm to 350 mm, it is preferable to provide a first pressure water discharge hole 72a at the height of the water surface when water is stopped, and a second pressure water discharge hole 72b at a position upstream from the first pressure water discharge hole 72a at a height above the water surface when water is stopped, so that the pipe is opened at two positions in total. Furthermore, when the inner diameter of the downflow vent pipe is 400 mm or more, it is preferable to provide a third pressure water discharge hole 72c at a position downstream from the first pressure water discharge hole 72a at a position below the water surface when water is stopped, so that the pipe is opened at three positions in total. The predetermined distance here is, for example, approximately 5 cm.

By adopting the above-mentioned configuration, the vent pipe inverted structure of the present invention can create a so-called maintenance-free state, since impurities are rarely stacked or precipitated in the vent pipe. Therefore, there is no need to install a spare pipe for cleaning, and it is also unnecessary to install a switchover weir or gate valve to the spare sewage pipe at the starting point of the vent pipe, which is necessary when installing a spare pipe. This means that there is no increase in the required head loss due to these weirs and valves. Furthermore, since there is no change in the inner diameter of the sewer pipe due to the installation of a weir or valve, the sewage flows into the inverted vent pipe while maintaining its state in the sewer pipe. This reduces the resistance of floating impurities at the boundary point where they flow from the natural flow in the sewer pipe to the vent pipe, which is a pressure pipe, making it possible for floating impurities to flow downstream more smoothly. In this way, by comprehensively adopting the configuration of the vent pipe underpass structure of the present invention and eliminating the need for a spare cleaning pipe, the ability of the vent pipe underpass structure of the present invention to remove impurities by flowing down can be more effectively utilized.

It can be widely used in industries related to sewer pipe overpass structures.

1. Bend pipe structure 2. Downflow vent pipe 21. Freely curved pipe (short pipe)
Description of the Reference Signs 3 Horizontal upflow section vent pipe 4 Upflow section vent pipe 41 First upflow section vent pipe 42 Second upflow section vent pipe 5 Upstream sewer pipe 51 Straightening section 6 Downstream sewer pipe 7 Floating impurity removal means 71 Pressurized water injection pipe 72a First pressurized water outlet hole 72b Second pressurized water outlet hole 72c Third pressurized water outlet hole 8 Settling impurity removal means 81 Low stage air pipe 81a Low stage air outlet hole 82 High stage air pipe 82a High stage air outlet hole 83 Air valve 84 Air pipe 9 Deodorizing type intake and exhaust tank 91 Underground water tank 92 Water collection section A, B Upstream manhole C Downstream manhole D Portable engine-equipped compressor

Claims (5)

A vent pipe that passes under obstacles such as rivers and underground passages,
and a sedimentation impurity removing means for removing impurities adhering to or accumulating inside the vent pipe.
The vent pipe is
A downflow vent pipe extending from a downstream end of the upstream sewer pipe at an incline downward in the downstream direction;
a lateral upflow section vent pipe extending downstream from a lower end of the downflow section vent pipe through under the obstacle;
an upflow section vent pipe extending from a downstream end of the horizontal upflow section vent pipe to an upstream end of the downstream sewer pipe at an incline upward in the downstream direction,
The upflow section vent pipe comprises a first upflow section vent pipe and at least one second upflow section vent pipe having the same slope;
This second upward flow section vent pipe is,
The first upward flow section vent pipe is disposed along an inner wall or an outer wall, or along both the inner and outer walls,
And the diameter is smaller than the diameter of the first upward flow section vent pipe.
Vent pipe underground structure. The sedimentable impurities removing means includes:
At least two air discharge holes opening toward the downstream direction at positions spaced apart from each other by a predetermined distance from the upstream end of the upflow section vent pipe;
an air pipe communicating with each of the air discharge holes,
The air discharge hole includes a low-stage air discharge hole that opens into the first upward flow section vent pipe;
a high-stage air discharge hole that opens into the second upflow section vent pipe at a position downstream of the low-stage air discharge hole,
The diameter of the low stage air pipe communicating with the low stage air discharge hole is
a diameter of the high stage air pipe communicating with the high stage air discharge hole is smaller than the diameter of the high stage air pipe,
The vent pipe overflow structure according to claim 1, characterized in that compressed air is supplied downstream for a predetermined period of time through air pipes connected to the low stage air discharge hole and the high stage air discharge hole, respectively. The inclination angle of the downflow vent pipe is 30 degrees or less,
A straightening section is provided in a predetermined section of the upstream sewer pipe,
2. The vent pipe underpass structure according to claim 1, wherein the pipe diameter of the straightening section is equal to or smaller than the pipe diameter of the downward flow section vent pipe. The downstream vent pipe is provided with a floating impurity removal means,
The floating contaminant removing means includes:
At least one pressure water discharge hole that opens near the water surface when the water is stopped in the downward flow section vent pipe;
a pressure water injection pipe communicating with the pressure water discharge hole,
From the pressure water discharge hole through the pressure water injection pipe,
When the water is stopped in the downward flow vent pipe, toward the water surface,
4. The vent pipe underpass structure according to claim 3, wherein pressurized water is supplied appropriately for a predetermined period of time. The plurality of pressure water discharge holes provided in the downward flow section vent pipe,
Near the water surface when the water is stopped in the downward flow vent pipe,
5. The vent pipe overhang structure according to claim 4, which is provided at a position spaced a predetermined distance upstream or downstream.

Images