JPS5836686B2 - Soil covering method on soft and sticky soil - Google Patents

Description

[Detailed Description of the Invention] The present invention effectively and economically confines soft cohesive soil over a wide area by directly covering the soft cohesive soil with soil, without the need for improvement work over the cohesive soil. The present invention relates to the provision of an earth-covering method that enables the construction of stable and firm new ground.

For civil engineering work such as reclamation and reclamation of coasts, rivers, lakes, etc.
Soft viscosity deposits that are blown up from the seabed using pump dredgers and the like have an extremely high water content and the top surface of the ground is extremely soft, making it difficult for humans to walk on.
Of course, it is completely impossible for bulldozers and other heavy machinery for use in extremely wet areas to enter the area.

For this reason, when improving this soft and viscous ground, it is necessary to inject a soil improvement agent into the soft and viscous ground to harden the ground, which requires enormous cost and time, as well as mechanical power. Ground improvement work is required, and by covering the top surface of such improved ground with general earth and sand, it is possible to carry out construction work using various mechanized means.

In addition, in the case where such improvement work is not used, the soft and cohesive soil is left for a considerable period of time (on the order of several years) and is left to dry naturally and harden, but this poses significant restrictions on the purpose and use of the land. At the same time, when drying naturally, even though the surface layer dries out and surface cracks occur due to the shrinkage of the viscous soil, the inside hardly dries due to the poor water permeability of the viscous soil itself, and the viscous soil still has a high moisture content. This prevents bulldozers, dump trucks, and other heavy construction equipment from entering and driving through the viscous ground, making it impossible to begin various types of land reclamation and construction work on the viscous ground.

Therefore, wait for the surface of the viscometer to dry naturally for a long period of time, and then use a bulldozer for ultra-wetlands to gradually spread sand, etc. on top of it from the front to slightly improve the supporting capacity of the surface layer, and then use sand drains, paper drains, etc. Drainage method, or method of introducing soil improvement agent mentioned above, such as quicklime pile method, etc.
Full-scale ground improvement is required.

Conventional techniques for improving the bearing capacity of soft and viscous soil, even if it collapses, are inefficient and uneconomical.

In this regard, the present applicant has first developed a new technology (see Japanese Patent Publication No. 50-23005) in which the surface layer of the viscous ground, that is, the shallow layer, is mixed and stirred with a ground improvement agent as an improvement technology for soft viscous ground. The proposed method is completely different from the conventional technology, and uses a mobile soil dispersion device that can directly enter the top of the soft viscous soil, and directly onto the top surface of the viscous soil without the need for ground improvement work. By scattering and covering the earth and sand,
It confines soft soil in a suppressed manner, making it easy for various types of heavy construction machinery to enter.Their characteristic is that it is possible to easily move in from the earth and sand dispersion equipment supported by a traveling device that floats on the soft, weakly viscous soil. A submerged embankment for preventing skidding of cohesive soil is created by dispersing the discharged soil into the clay soil in a concentrated manner so that the top of the soil protrudes above the cohesive soil and extends almost linearly. The clay soil is uniformly spread on the upper surface of the cohesive soil in the area separated by the submerged embankment by moving the soil dispersion device to a thin layer that does not move, and this first covering layer is applied. By repeating the same thin-layer scattering covering on the upper surface until it reaches the predetermined top, and repeating the same covering work starting with the submerged embankment mentioned above to expand the covered area, soil can be directly applied onto the soft viscosity embankment. It's time to cover it with soil.

The present invention will be described in detail below based on the illustrated embodiments. Fig. 1 shows how two soil dispersing devices according to the present invention are used to transport soil from a soil conveying device installed on an existing submerged embankment according to the present invention. , a side view of the next submerged embankment being constructed, Fig. 2 is a side cross-sectional view showing the condition of the submerged embankment area covered with a thin layer of earth and sand on the upper surface of the viscometer, and Fig. 3 is a side view of the submerged embankment being constructed. Fig. 1 is a plan view of the state, and Fig. 4 is a plan view of the same state using four soil spreading devices. In Fig. 1, 1 is a shiftable conveyor, which will be described later. It will be installed along the longitudinal direction on the existing submerged embankment d created by the construction method of the present invention, and earth and sand for covering soil will be conveyed onto the conveyor 1.

A rail 3 is installed parallel to the conveyor 1 via a skid 2, and a stacker 4 that runs along the conveyor 1 is installed on the rail 3. The earth and sand is supplied to the earth and sand dispersion equipment side by a receiving and supplying conveyor, etc., and the sick bull conveyor 1 skid 2 rail 3 and stacker 4 become the earth and sand transporting equipment.However, the parts and structure of the earth and sand transporting equipment are only examples. It is not limited to.

Reference numeral 5 designates the earth and sand dispersion device according to the present invention, and in the illustrated example, a crawler spreader type device is used.

That is, in the illustrated example, a is solid ground such as the seabed or riverbed in the target construction area, and b is a soft and weakly viscous ground on this ground a, and if a person enters onto such soft and weakly viscous ground b, In order to be able to travel freely, the earth and sand spreading device 5 using the same crawler spreader has, for example, crawlers 7, 7 arranged on both sides of the float body 6, so that it can travel freely on the viscosity bar b. A receiving conveyor 9 and a spread conveyor 10 for spreading are installed via a swing base 8 via a boom frame 11 that can be raised and lowered, and are also equipped with a self-propelled drive mechanism, a conveyor drive mechanism, etc. This can be easily obtained by making some necessary modifications to the conventional crawler spreader, and the receiving conveyor 9 receives the covering soil from the supply conveyor 12 in the stacker 4 on the side of the existing submerged embankment d, and transfers it to the spread conveyor. 1
0 and can be spread from the conveying end of the conveyor 10.

Therefore, although there are two soil dispersing devices 5 in the illustrated case, by connecting the spread conveyor 10 of the devices 5, 5 and the receiving conveyor 9, it is possible to By using any number of devices 5 together, it is possible to proceed with the soil covering work more effectively.

In addition to the crawler spreader, this soil spreading device can also be used with a crawler conveyor type, and in short, it can enter and travel on soft and weak viscosity ±b, and can continuously receive and spread soil. Any mechanical model is acceptable, and amphibious models are preferred.

The direct covering of soil on soft viscosity ±6 by the soil spreading device 5 of the present invention is characterized by the following points.

In other words, when soil is poured all at once and partially onto the soft viscous soil b up to a predetermined covering layer thickness, the weight of the soil pushes the viscous soil b aside in the lateral direction and the soil sinks into the viscous soil b. It is impossible to cover the soil with soil.

In order to prevent this infiltration of earth and sand, the earth and sand should be uniformly spread over the top surface of the clayey soil b in a very thin layer to prevent lateral movement of the clayey soil b due to the weight of the sand and the required soil covering. It is necessary to cover soil up to a predetermined top (upper end of the soil covering surface) by dividing the soil into several layers and repeating successive thin layer spreading.

That is, in the present invention, in the case where the soft clay soil b is blown up and deposited on the firm ground a as shown in the first figure, the clay soil B is spread over the whole surface of the clay soil b by scattering the soil C over the clay soil b. In order to contain the soil and make it possible for various types of construction machinery to run, thin layers of earth and sand C are repeatedly constructed in a sequential manner on top of the cohesive soil B, and the soft cohesive soil B is completely suppressed by the covering layer of the desired thickness. It was designed to contain the
Figure 2 shows the outline.

That is, in FIG. 2, when the earth and sand for covering soil is spread by the earth and sand spreading device 5, the earth and sand are first spread evenly on the first layer c1 under a thin layer such that the clayey soil b does not move laterally. When the entire target area is covered with soil with the first layer c1, a thin second layer C2 is formed on top of the first layer c1 in the same manner, and a third layer is formed as shown in the figure. Layer C3, fourth layer C
As shown in step 4..., the soil covering layer is formed in a stacked manner repeatedly, and the soil is covered up to a predetermined top to confine the soft and cohesive soil b.

At this time, the earth and sand transporting device 4 moves on the rails 3 in response to the movement of the spreading device 5, and continuously supplies the earth and sand on the shiftable conveyor 1 to the spreading device 5 side.

In this way, the entire area of a certain size is covered with soil, but depending on the area as shown in the figure, it is possible to use two soil spreading devices 5 in series, or furthermore, as shown in Fig. 4. Although it is possible to use four devices 5 in conjunction, it is also possible to cover a certain area with soil, and then continue to cover the soft and viscous upper part of the uncovered soil with soil. , instead of further increasing the number of the devices 5, a shiftable conveyor 1 skid 2 installed on the submerged embankment d
The entire earth and sand transporting device including the rail 3 and the stacker 4 may be moved and set from the submerged embankment d to the end of the area covered with soil, and from there, the spreading device 5 may be used to cover the soil with new soil. It can be adopted freely depending on the number of units and other factors.

When the covering work is completed over a certain area of the soft cohesive soil b as described above, at the final end of the covering soil, due to the covering load, the soft cohesive soil moves in an arc, that is, the cohesive layer moves, and the end capping layer There is a risk of collapse and subsidence.

If there is such a risk, it is necessary to create a stepped soil covering layer that is wide enough to prevent arcuate slippage.

This can be done by sequentially covering the stepped edges of the first layer c1 to the top layer of covering soil up to the required crown, but it is possible to If the distance between the stage submerged embankments d is long and it becomes uneconomical to use a large number of earth and sand spreaders 5 in series in order to widen the spraying range to that extent, the method shown in Figs. , 4, the submerged embankment d may be created in advance at the connection end (planned soil-covering end) by the earth and sand dispersion device 5.

This is an embankment-like structure whose cross section is almost trapezoidal and extends linearly, and a considerable amount of earth and sand is concentratedly scattered at that location, with the bottom reaching firm ground a and the top reaching soft and viscous soil b. It is constructed so that it protrudes below the required height from the top surface.

According to this, it is possible to partition a certain area by creating the submerged embankment d in advance, and the above-mentioned soil covering work can be carried out safely, stably and easily on the soft and weak viscosity ±b within the range divided by the submerged embankment d. Therefore, it can be suitably used when covering a large area of soft and cohesive soil.

The number of earth and sand spreading devices 5 to be connected is determined within the most economical range by considering various conditions such as the layer thickness of the soft and viscous soil b, the width of the area covered with soil, and the cost of machinery and equipment. Also select the order.

In addition, the range of the thin layer of the first sprayed covering soil in the covering layer is selected depending on the strength of the target soft and cohesive soil a,
If the cohesive soil b is accompanied by a large amount of floating mud on the surface immediately after dredging, etc., when the earth and sand dispersion device 5 starts its approach from the beginning,
It is expected that the viscous resistance that overcomes the running resistance will not be obtained and it will be difficult to run, but in such a case, instead of using the crawler spreader soil spreading device 5, a crawler conveyor machine will be used in advance to carry out the first One layer c1 is formed, and this first layer c1 is formed.
If the device 5 runs on the layer c1, the construction can be carried out smoothly, and the layer thickness can be gradually increased from the first layer C1 to the upper soil covering layer.

The above-mentioned one-time selection of the soil covering layer thickness can be easily and freely handled by changing the traveling speed and turning speed of the earth and sand dispersion device 5 when the amount of earth and sand has a constant processing capacity.

In other words, if you want to make the spray layer thinner, you need to increase the speed, and if you want to make it thicker, you need to slow it down.

Therefore, the traveling speed and turning speed of the device 5 are variable.

In addition, as mentioned earlier, the device 5 is a float body 6, and in order to ensure the freedom of movement when entering a soft and weak viscous vessel, the crawler 7 is supported by a frame that constitutes a large floater. It does not sink into the viscosity ±b of 5.

The present invention is as described above, and conventional methods for covering this type of soft viscous soil include using a dump truck from one side of the land and sequentially reclamation offshore by discharging the soil. With such conventional methods, the side-sliding movement of the soft cohesive soil b causes the accumulation or extrusion of large cohesive particles, making it difficult to obtain a stable soil-covering structure, and at the same time being extremely inefficient and requiring a long period of time. Coupled with the fact that the soil for covering soil sinks into the cohesive soil, it is difficult to provide solid support, and as mentioned earlier, it takes a lot of time and money to repair the ground in the cohesive soil. Improvement work is needed, and soil is being covered over it.

On the other hand, according to the present invention, the earth and sand released by the device is first applied to the soft and viscous ground by using an earth and sand dispersion device supported by a traveling device that can float on the soft and viscous soil. By intensively spreading the earth and sand in a linear manner, the concentrated pressure of the soil penetrates the soft viscosity layer and reaches the solid ground, and the top of the levee protrudes above the viscous layer by creating a submerged embankment. In addition to dividing the viscosity ground into limited areas, this submerged levee can reliably prevent the soft viscosity ground from sliding sideways within the limited area. The soil covering work is carried out effectively by repeated layering of thin layers of earth and sand, and it is possible to reliably obtain soil covering without protrusions of soft and viscous soil.In addition, when replenishing and continuously discharging earth and sand to the earth and sand spreading equipment, The upper surface of the submerged embankment can be suitably used as a transport path for earth and sand, and the earth-covering work can be performed with high efficiency by using the earth-spreading device in a limited area.

Moreover, since the submerged embankment is made of the same quality as the covering soil, complete integration of the covering soil layer and the submerged embankment can be achieved.
A wide range of soft and viscous ground can be efficiently constructed one after another in the order of spreading and covering a limited soil area in a thin layer, and the entire area can be easily and systematically covered with soil.

Moreover, according to this, if conventional land equipment such as crawler conveyors and crawler spreaders is equipped with a float means, it can be used as a movable earth and sand dispersion device, and the previously constructed submerged embankment can be used to directly spread earth and sand from the land side. It can be used as a transport route for materials one after another, and by combining the continuous replenishment of large amounts of earth and sand with continuous construction within the submerged bank area, it is possible to significantly shorten the construction period and completely cover a vast area of soft and viscous ground. can be,
It is an economical and efficient construction method that enables the quick and easy creation of a stable and firm soil cover layer for soft and sticky soil such as reclaimed land and reclaimed land, and is extremely superior in terms of its economical and efficient construction method. The more advantageous the construction method of the present invention is, the more useful it becomes as it enables the early construction of new, solid ground.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the main part of an embodiment of the present invention construction method, Figure 2 is an enlarged side sectional view showing the main part of the same earth covering method, Figure 3 is a plan view of the state shown in Figure 1, and Figure 4 is a large number of machines. FIG. 2 is a plan view of an example of the construction method of the present invention using an earth and sand dispersion device. 1... Shiftable conveyor, 2... Skid, 3... Rail, 4... Stacker, 5... Sediment spreading device, 6 ...Float body, 7...Crawler, 8...Swivel mount, 9,10...Conveyor, a...
・Bottom ground, b... Soft viscosity, C...
・Covering layer, d... submergence

Claims (1)

[Claims] 1. Sediment discharged from an earth and sand spreading device supported by a traveling device floating on soft and viscous soil is transferred into the viscous soil through the movement of the earth and sand spreading device, with the top end protruding above the viscous surface, and the whole being approximately Build a submerged embankment to prevent skidding due to viscosity by intensively distributing it in a linear manner, and scatter the soil in a thin layer to the extent that the embankment does not move on the top surface of the embankment in the area formed by the submerged embankment. Spread coating evenly through moving equipment,
A similar thin layer of scattering is applied to the upper surface of this first soil covering layer until it reaches a predetermined top, and the soil covering area is expanded by repeating the same soil covering work starting with the construction of the submerged embankment described above. A method of covering soft soil, which is characterized by directly covering earth and sand on top of the soil.