JPH0718160B2 - How to build an earth anchor on a steep slope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a construction method for constructing an earth anchor having a groundwater removing function for preventing collapse of a steep slope.

[Conventional technology]

The steep slope is an immovable ground consisting of hard layers as shown in Fig. 8.
Since it consists of 10 and the collapsed mass 11 composed of the permeable layer above it, if there is a large amount of rainfall, the weight of the slope mass increases due to the infiltration of rainwater, the ground strength decreases, the shallow groundwater level rises, and heavy rainfall causes heavy rain. Collapse occurs due to a large amount of accumulated water.

In the figure, the arrows indicate the movement of water. 12 is precipitation, 13 is evaporation, 14 is intermediate runoff, 15 is infiltration, 16 is underground runoff, and 17 is surface runoff.

In order to prevent this steep landslide, there have been various methods from the past, roughly classified as pile construction, anchor construction, and
There are retaining wall works, slope protection works as restraint works, surface water drainage works, and groundwater drainage works, but it can be said that the cause of collapse of steep slopes is rain, so prevention of steep slope collapse As a method, sufficient suppression of ground surface drainage and groundwater drainage can be expected.

However, this kind of work is generally done after the slope collapse or when the road surface expansion work etc. was performed to remove the end clods that would interfere with the slope formation. Suppression works (pile work, anchor work, retaining wall work) are selected to stabilize, and then suppression works (slope protection work, surface water drainage work, groundwater drainage work) to remove the cause of future collapse. Is usually selected.

As a construction method for preventing steep landslides, the ground anchor is the most widely adopted method, and Fig. 9 shows the construction drawing of the tightening earth anchor 20. The collapsed earth mass 11 is tightened on the immovable ground 10 to anchor the entire slope. 20a need to be placed.

[Problems to be solved by the invention]

However, in the tightening anchor 20, a pre-stress equal to the design anchor force is applied, but since the pre-stress is not constant over a long period of time and decreases with time, it is necessary to re-tension, and further, at a time on soft ground. If all prestresses are applied, there is a problem that the surrounding ground will be destroyed, and furthermore, the bearing member 20b covers the entire slope 20c, which is an obstacle to greening.

On the other hand, there are no such problems with the detent anchor that arranges the earth anchor almost horizontally to the slope, but it is necessary to carry out restraint work to prevent future collapse regardless of which construction method is adopted. Therefore, as a groundwater drainage work, a method of inserting and draining a 40 mm to 50 mm drain pipe into the hole provided by horizontal boring is used.

In the above method, there are things that should be improved, such as increasing the diameter of the drainage pipe to increase the water collection capacity, or improving the shape of the water collection hole to make it less likely to become clogged, but groundwater drainage work by horizontal boring Since it is constructed underground, it is not conspicuous.I do not know whether there is drainage as planned even if it is constructed, and it is difficult to express clearly how much effect there is even with drainage, and it is related to the construction cost There is a problem that it is difficult to proactively improve when considering.

The present invention has been made in view of such circumstances, and is an earth anchor that improves the conventional retaining anchor construction method, has a low construction cost, enables slope greening, and efficiently prevents collapse of steep slopes due to rainfall. The purpose is to provide a construction method.

[Means for solving problems]

The method for constructing a ground anchor for a steep slope according to the above object is the outer pipe and the inside of the outer pipe at a portion corresponding to a tensile portion of a retaining anchor that is constructed substantially horizontally with respect to the steep slope. A method of constructing a ground anchor for a steep slope, in which a drainage pipe composed of an inner pipe and an inner pipe is arranged, the base portion of which is attached to a tip portion of the outer pipe and the inner pipe in a gap between the outer pipe and the inner pipe. A perforated tube having a water collecting hole formed at an appropriate position is provided on the outer tube located on the inner side of the tension section while providing a blade tip, and a non-perforated tube is provided on the outer tube located on the front side of the tension section. Is used to guide and remove groundwater flowing through the permeable layer from the water collection hole between the outer pipe and the inner pipe.

Further, the ground anchor construction method for steep slopes according to claim 2 is the construction method according to claim 1, wherein the outer pipe is made of a synthetic resin pipe, and the inner pipe and the cutting edge attached to the tip of the inner pipe are made of iron. It is configured as follows.

[Action]

In the method of constructing a ground anchor for a steep slope according to claim 1 or 2, a drain pipe composed of an outer pipe and an inner pipe is used for a tension part of the anchor, and water is collected in an outer pipe located on the back side of the tension part. Since a perforated pipe with holes is used and a non-perforated pipe is used for the outer pipe located on the front side of the tensile part, this effectively causes the groundwater flowing through the permeable layer and sliding surface, which are collapsed soil blocks, to flow. Water is collected to prevent softening of the ground (that is, the surface layer) near the insertion port.

Further, since the tip ends of the outer pipe and the inner pipe are provided with blade tips for closing the gap, a drainage pipe can be driven and the tip ends of the outer pipe and the inner pipe are closed by the blade tips. The water collected by the perforated tube does not impair the original function of the anchor by actively infiltrating the anchor body and its surroundings.

Further, since these works are performed at the same time when the detent anchor is installed, it is not necessary to provide extra boring.

〔Example〕

Next, an embodiment of a method for constructing a ground anchor for a steep slope embodying the present invention will be described in detail with reference to the accompanying drawings, for the understanding of the present invention.

First, the construction procedure of the method for constructing a ground anchor on a steep slope according to the embodiment of the present invention will be described with reference to FIG. 2. As shown in FIG. Boring is performed by using a casing pipe 24 whose inner diameter is larger than the diameter of the anchor body 23 at a portion corresponding to the tension portion 22 of the anchor. Even after the boring of the pulling portion 22 is finished, the casing pipe 24 is left as it is, and the portion of the anchor body 23 is bored through another casing pipe 25, and the casing pipe 25 is left as it is and the tension member 26
After inserting, the casing pipes 24 and 25 are pulled out as shown in FIG. 2 (B).

After that, the drain pipe 27 having a double structure is pushed into the pulling portion 22 as shown in FIG. 2 (C). The outer diameter of the drain pipe 27 is slightly smaller than the outer diameter of the casing pipe 24, but can be driven in if it is difficult to enter. Next, cement or mortar (hereinafter referred to as grout 23a) is injected into the anchor body 23, and when finished, the grout 23a is continuously injected into the tension portion 22 as shown in FIG. Here, as shown in FIG. 3, a cloth bag (also referred to as a cloth packer) 23b is arranged on the anchor body 23, and the grout 23a is injected into the cloth bag 23b to inflate it, and then the grout 23 is attached to the anchor body at the tip.
It is also free to enable pressure injection by injecting a.

The end of the drain pipe 27 is attached to the immovable ground 28 as shown in FIG.
Try to enter ~ 2m. Then, a perforated pipe 30 having a large number of elongated water collecting holes 29 formed in the outer pipe as shown in FIG. 6 is arranged on the front side of the drain pipe 27, that is, on the rear side, and the front pipe is arranged on the front side. Is a non-perforated tube
31 is provided to prevent weakening of the ground near the hole for permeated water due to water leakage from the drain pipe 27. Here, the earth anchor is constructed somewhat downward from the horizontal, but if it is horizontal or upward, the grout injected into the anchor body 23 will flow out, and if it contracts, a cavity will be created in the anchor body 23. is there. As a result, it is installed slightly downward from the horizontal, but the groundwater has a considerable head difference, so it can be sufficiently drained. Here, the water collecting holes 29 are elongated so as to expand the water collecting area, but the present invention is not limited to this shape, and may be circular holes, each hole, or mesh holes, for example.

The reason why the drainage pipe 27 is doubled is that if the single drainage pipe is considered to be single, the water flowing part is between the drainage pipe and the sheath pipe covered with the tension member, and it should be slightly inclined. As a result, the water stored will permeate around the anchor body and hinder the original function of the anchor.

The drain pipe 27 having the double structure will be described in more detail. As shown in FIG. 7, the drain pipe 27 includes an outer pipe 32, an inner pipe 33, and a joint 34.
In this case, the joint 34 is fixed by screwing it into a male screw formed at the end of the inner pipe 33, and in this case, the outer pipe 32 is sandwiched.

The joint 34 is for connecting the inner pipe 33 and the outer pipe 32 at the same time. As shown in FIG. 4 and FIG.
6 and 37 are engraved, and several water passage holes 38 are provided in the periphery. The outer pipe 32 is made of a corrosion-resistant polyvinyl chloride pipe, which is an example of a synthetic resin pipe, and includes the perforated pipe 30 having the water collecting hole 29 and the non-perforated pipe 31 having no water collecting hole as described above. Inner tube 33
Since male threads 38a are processed on both sides, they can be connected through the joint 34, the drain pipe 27 can be made longer sequentially by assembling, and the perforated pipe 30 and the non-perforated pipe 31
Can be freely placed where needed.

A blade edge 35 is attached to the tip of the drain pipe 27, and the blade edge is
The 35, the joint 34, and the inner pipe 33 are made of iron so that they can be hardened as a whole and driven, and can withstand external forces such as twisting and pressing. The cutting edge 35 is screwed into the outer side of the inner tube 33 and is fitted into the inner side of the outer tube 32. Therefore, the ends of the inner tube 33 and the outer tube 32 are closed, and the direction of the anchor body 23 directly. Stops the flow of water.

The collapsed soil layer 40 on a steep slope is relatively thin and has a sliding surface 40a (first
The hardness and permeability of the ground are significantly different above and below the boundary (shown in the figure), and the collapsed soil mass 40 is soft and permeable, but the immovable ground 28 below is tight and firm,
Often semi-permeable or impermeable.

Therefore, if rain continues and the water supply continues, the water level in the soil rises, the water content ratio and the pore water pressure increase, and the collapsing soil mass 40 fluidizes and begins to slide, so a construction method that can sufficiently remove groundwater is desired.

FIG. 1 is a construction drawing of the earth anchor construction method for the steep slope, in which the collapsed mass 40 is supported by the bearing wall 41, and the anchor body 23 and the anchor body 23 are connected to the bearing wall 41 so that the bearing wall 41 is not pushed down. A drainage anchor 42 having a drainage pipe 27 is used to hold it. According to this method, the slope is divided into several blocks, and as shown in the figure, the bearing wall 41 and the drainage anchor 42 are constructed for each block.

In this example, the cut sloped slope 43 has a direct height of 5 m.
The berms 44 provided in prospect spacing degree width 1~2m as a standard, build and bearing capacity wall 41 and the groove 45 along the small step 44. Bearing wall
41 is made continuously in the lateral direction and shrink joints are provided at appropriate points. The height of the bearing wall 41 is about 1.5 m, and the shape is trapezoidal as a concrete structure, the front surface is vertical with a slight slope and the back surface is slightly inclined, it is convenient to expand the ground contact area with soil and support the collapsed mass 40 Form.

The drainage anchor 42 is located approximately in the center of the bearing wall 41 and faces downward from the horizontal 3
Build in degrees. The drainage pipe 27 is fitted to the immovable ground 28 for 1 to 2 m from the sliding surface 43a to prevent the cross section of the anchor portion and the drainage pipe portion from shifting, and the drainage water can be sufficiently collected and drained from the groundwater zone 46 above the sliding surface 40a. Is removed by the gutter 45 together with the surface water outside the collapse zone. The slopes 43 between the bearing walls 41 can be harmonized with the surroundings because the slope protection measures mainly for greening can be adopted.

〔The invention's effect〕

As is clear from the above description, the method of constructing a ground anchor for a steep slope according to claims 1 and 2 uses a perforated pipe in which a water collecting hole is formed in the outer pipe located on the inner side of the tensile portion, Since the non-perforated pipe is used as the outer pipe located on the front side of the tension portion, this enables efficient collection of groundwater flowing through the permeable layer and sliding surface, which are collapsed soil blocks, and the insertion port of the anchor. It is possible to prevent the softening of the surrounding ground and further prevent the surface layer from collapsing.

Further, since the tip ends of the outer pipe and the inner pipe constituting the drain pipe are provided with the blade edges, the drain pipe can be driven into the immovable ground, and further, the tip portions of the outer pipe and the inner pipe are mounted. Further, the water that is blocked by the base of the blade edge and collected by the perforated pipe can prevent the anchor body and its surroundings from actively inundating, thereby preventing the anchor body from loosening.

Moreover, since the drainage pipe can be formed at the same time when the earth anchor is constructed, no extra construction is required, and the construction cost can be reduced and the construction period can be shortened.

In addition, since the bearing wall that stops the collapsed soil blocks can be placed in each block, slope greening has become possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a steep slope on which a method for constructing a ground anchor for a steep slope according to an embodiment of the present invention has been applied, and FIGS. 2 (A), (B), (C), and (D) show the intermediate portion. A cross-sectional view showing the procedure for constructing the ground anchor of the steep slope, which is omitted in detail, FIG. 3 is a cross-sectional view in which the intermediate portion of the completed ground anchor is partially omitted, and FIG. 5 and 5 are sectional views of the same side, FIG. 6 is a partial side view of the drainage pipe, FIG. 7 is a partial sectional view showing an assembled state of the drainage pipe, and FIG. 8 is a sectional view of a steep slope. FIG. 9 is a sectional view showing a ground anchor construction method according to a conventional example. [Explanation of reference symbols] 22 ... tension part of anchor, 23 ... anchor body, 24, 25 ...
… Casing pipe, 26 …… Tensile material, 27 …… Drain pipe, 28
...... Fixed ground, 29 ...... water collection hole, 30 ...... perforated pipe, 31 ...... non-perforated pipe, 32 …… outer pipe, 33 …… inner pipe, 34 …… joint, 35 …… cutting edge, 36, 37 …… Female thread, 38 …… Water passage hole, 38a …… Male thread, 40 …… Collapse layer, 40a …… Sliding surface, 41 …… Bearing wall, 42
…… Drainage anchor, 43 …… Slope, 44 …… Small stage, 45 …… Gutter

Claims (2)

[Claims] 1. A steep slope where a drainage pipe consisting of an outer pipe and an inner pipe arranged inside the outer pipe is arranged at a portion corresponding to a tension portion of a retaining anchor which is constructed substantially horizontally with respect to the steep slope. In the method of constructing an earth anchor, the tip of the outer tube and the inner tube is provided with a cutting edge whose base portion is mounted in a gap between the outer tube and the inner tube, and the position is located on the inner side of the tension section. Using a perforated pipe in which water collecting holes are formed at appropriate places in the outer pipe, and using a non-perforated pipe in the outer pipe located on the front side of the tension portion, the ground water flowing through the permeable layer is collected. A method for constructing a ground anchor on a steep slope, characterized by guiding and excluding from a hole between an outer pipe and an inner pipe. 2. The outer tube is made of a synthetic resin tube, and the inner tube and the cutting edge attached to the tip of the inner tube are made of iron.
Construction method for earth anchor on steep slope.