JP2021080658A - Soil drainage device - Google Patents

Abstract

To provide a soil drainage device capable of simultaneously carrying out work for depositing soil to be treated and work for forcibly sucking and discharging gap water from the soil to be treated efficiently with a simple structure.SOLUTION: The soil drainage device comprises: a catchment facility for catching gap water from soil to be treated; and a negative pressure application facility for applying negative pressure on the soil via the catchment facility. The catchment facility comprises a water permeable mat laid on the foundation with a lower surface and a peripheral edge closed and with the soil deposited on an upper surface, and a horizontal drain material buried in the water permeable mat. The negative pressure application facility comprises a water storage tank for storing the gap water, a drainage device that discharges the gap water stored in the water storage tank, and a pressure reduction device that reduces pressure in the water storage tank. The water storage tank and the horizontal drain material are communicated with each other through a connection tube.SELECTED DRAWING: Figure 1

Description

The present invention relates to a soil drainage device for forcibly discharging pore water from the soil to be treated.

Conventionally, when land reclamation or water reclamation work is carried out using dredged soil, construction-generated soil, or earth and sand cut from mountains, when the landfill material is soft soil with a high water content such as cohesive soil. Generally, a step of depositing a landfill material in a landfill area to form a landfill board and a step of improving the ground such as dehydration treatment on the landfill board to increase the strength of the landfill board are carried out.

For example, in Patent Document 1, a landfill board is constructed on a sand mat provided in a landfill area surrounded by a revetment wall, and a vertical drain material is placed on the landfill board so that the lower end is connected to the sand mat. To do. In addition, an impermeable layer is formed on the upper surface of the landfill board containing the vertical drain material, and a plurality of water collecting wells in which the intake pipe and the intake pump are provided are arranged in the landfill board so as to communicate with the sand mat. After that, a vacuum pressure is applied to the landfill board through the sand mat and the vertical drain material by using the water collecting well, and the water in the landfill board is collected in the water collecting well.

Further, in Patent Document 2, after constructing a dam having a plurality of sand layers in which drain material is horizontally buried and well points around the landfill, the drain material is horizontally arranged in the landfill and inside the dam. After connecting with the drain material of, the dredged soil is reclaimed to the specified layer thickness. Then, while operating the well point, the above process is repeated to perform forced drainage from the dredged soil.

Japanese Unexamined Patent Publication No. 2001-279657 Japanese Unexamined Patent Publication No. 2001-182046

As described above, if a method of forcibly discharging pore water is adopted as a means for increasing the strength of the landfill ground, it is possible to cause uniform consolidation settlement in the entire ground and surely increase the ground strength.

However, Patent Document 1 is a method of constructing a landfill board and then applying a vacuum pressure after forming an impermeable layer on the upper surface thereof. Therefore, the work of constructing the landfill board and the vacuum pressure are applied to the landfill board. The work cannot be done in parallel, and the construction period tends to be long.

On the other hand, in Patent Document 2, it is possible to perform the work of reclaiming the dredged soil and the work of forcibly discharging the pore water from the reclaimed dredged soil in parallel. However, not only is the work of providing a plurality of sand layers in which the drain material is horizontally buried in the dam is complicated, but also the drain material and the sand layer provided in the dam are constructed so as to communicate with the outer area of the landfill area. It is not possible to efficiently suck and discharge the interstitial water of the dredged soil.

The present invention has been made in view of the above problems, and its main purpose is to efficiently deposit the soil to be treated with a simple structure and to forcibly suck and discharge the pore water from the soil to be treated. It is to provide a soil drainage device that can perform the work to be done in parallel.

In order to achieve such an object, the soil drainage device of the present invention includes a water collecting facility for collecting the interstitial water of the soil to be treated and a negative pressure acting device for applying a negative pressure to the soil to be treated via the water collecting facility. A soil drainage device including, the water collecting facility is laid on the ground, the lower surface and the peripheral edge are closed, and the soil to be treated is deposited on the upper surface, and the water permeable mat. A horizontal drain material to be buried is provided, and the negative pressure acting facility decompresses the inside of the water storage tank, a water storage tank for storing the pore water, a drainage device for draining the pore water stored in the water storage tank, and the water storage tank. It is characterized in that the water storage tank and the horizontal drain material are communicated with each other via a connecting pipe.

According to the soil drainage device of the present invention, the horizontal drain material of the water collecting facility and the water storage tank of the negative pressure acting facility are communicated with each other via a connecting pipe. As a result, even if the negative pressure acting equipment is installed outside the permeable mat by adjusting the length of the connecting pipe appropriately in order to secure a working space for depositing the soil to be treated above the permeable mat, the pressure is reduced. A negative pressure can be applied to the soil to be treated through the connecting pipe, the horizontal drain material and the permeable mat only by operating the device to reduce the pressure in the water storage tank. Therefore, it is possible to efficiently carry out the work of depositing the soil to be treated on the permeable mat and the work of forcibly sucking and discharging the pore water from the soil to be treated in parallel. Moreover, since both operations can be started almost at the same time, it is possible to contribute to shortening the construction period.

In addition, since the lower surface and the peripheral edge of the permeable mat are closed, even if the permeable mat is laid on the ground under any construction conditions, negative pressure is applied only to the soil to be treated deposited on the upper surface. It is possible to efficiently drain the interstitial water of the soil to be treated.

The soil drainage device of the present invention is characterized in that the water collecting facility is provided with a vertical drain material having a lower end in contact with the water permeable mat and an upper end arranged in the soil to be treated.

According to the soil drainage device of the present invention, not only the negative pressure can be uniformly applied to the soil to be treated from the entire lower surface through the horizontal drain material and the permeable mat, but also the treatment target is to be treated through the vertical drain material. Negative pressure can also be applied in the height direction of the soil, making it possible to efficiently drain pore water from the entire soil to be treated.

The soil drainage device of the present invention is characterized in that a wall-shaped portion is provided facing the water-permeable mat, and the water storage tank is arranged along the wall-shaped portion.

According to the soil drainage device of the present invention, since the water storage tank is arranged along the wall-shaped portion, the top end of the wall can be used as a work area for arranging the water storage tank, and the negative pressure acting equipment can be easily used. It becomes possible to carry out the installation work of. In addition, the top of the wall can be used as an arrangement area for arranging pipes, electric wires, or equipment for drainage devices and decompression devices installed in water storage tanks, making it possible to improve the efficiency of maintenance work related to negative pressure action equipment. Become.

The soil drainage device of the present invention is characterized in that the water permeable mat is laid in a landfill area surrounded by a revetment embankment body.

According to the soil drainage device of the present invention, in the landfill area surrounded by the revetment embankment body, the work of depositing the landfill soil which is the soil to be treated and the work of forcibly sucking and draining the interstitial water of the deposited soil. Can be efficiently implemented in parallel. In addition, since both works can be started almost at the same time, it is possible to contribute to shortening the construction period and reducing the construction cost of the reclamation work performed in the water area such as the coast.

Further, since the negative pressure generators can be centrally arranged on the revetment embankment body, the work efficiency can be significantly improved without obstructing the traffic of dredging vessels and work vessels in the landfill area.

According to the present invention, since the horizontal drain material embedded in the water permeable mat and the water storage tank of the negative pressure acting facility are communicated with each other via the connecting pipe, the water permeable mat can be adjusted by adjusting the length of the connecting pipe. A negative pressure generating facility can be installed on the outside of the water tank to secure a work space for depositing the soil to be treated above the permeable mat. It is possible to efficiently carry out the work of sucking and draining water in parallel.

It is a figure which shows the soil drainage apparatus used for the landfill work in embodiment of this invention. It is a figure which shows the connection with the horizontal drain material and the connecting pipe in embodiment of this invention. It is a figure which shows the installation method of the soil drainage apparatus in embodiment of this invention (the 1). It is a figure which shows the installation method of the soil drainage apparatus in embodiment of this invention (the 2). It is a figure which shows the other example of the construction using the soil drainage apparatus in embodiment of this invention. It is a figure which shows the other example of the water collection equipment in embodiment of this invention.

The case where the soil drainage device of the present invention is adopted for landfill work performed in the sea area is taken as an example, and the details thereof will be described below with reference to FIGS. 1 to 6.

The soil to be treated includes, for example, dredged soil generated by dredging work, soil generated by construction work such as earth and sand generated by underground excavation, and mud such as construction sludge and sludge. It shall include all mixed sediment mixes.

≪Soil drainage device≫
As shown in FIGS. 1 (a) and 1 (b), the dredged soil D1 which is the soil to be treated is deposited in the landfill area 10 partitioned by the concrete levee body E to form a landfill board. , A soil drainage device 1 for forcibly draining the interstitial water of the dredged soil D1 is installed.

The soil drainage device 1 includes a water collecting facility 2 for collecting the interstitial water of the dredged soil D1 and a negative pressure acting facility 3 for applying a negative pressure to the dredged soil D1 via the water collecting facility 2.

≪Water collection equipment≫
As shown in FIG. 1A, the water collecting facility 2 includes a water permeable mat 21 having closed portions 211a and 211b on the peripheral edge and the lower surface, a horizontal drain material 22 embedded in the water permeable mat 21, and a water permeable mat. It is composed of a vertical drain material 23 connected to 21.

The water permeable mat 21 is a sand mat that is a highly permeable sand made of high-quality sand material, and as shown in FIG. 1 (b), is formed on the seabed ground of the landfill area 10 with the revetment body E. It is laid with a predetermined distance between them. The sand mat may contain gravel, and the water permeable mat 21 has high water permeable performance and can be laid in a plane with respect to the upper surface of the ground. Also, for example, a three-dimensional net-like body, a gravel mat, or the like may be adopted.

Further, as shown in FIG. 1A, the closed portions 211a and 211b provided on the peripheral edge portion and the lower surface of the water permeable mat 21 have very small water permeability and air permeability as compared with the water permeable mat 21, and are impermeable to water. Any material or structure generally used for property and air permeability may be used.

In the present embodiment, the dredged soil D1 is deposited so as to cover the peripheral edge of the permeable mat 21, and this is used as the closed portion 211a, and the seabed ground provided with the landfill area 10 is used as the permeable mat 21. It is used as a closing portion 211b provided on the lower surface of the above. The seabed ground can be used as the closed portion 211b when its water permeability is sufficiently smaller than that of the water permeable mat 21 (for example, about 1/100) and is about the same as the dredged soil D1 or smaller than the dredged soil D1.

If the seabed ground does not meet the above conditions, dredging soil D1 may be spread on the seabed ground before the permeable mat 21 is laid, and this may be used as the closed portion 211b, or the ground is improved on the seabed ground. Therefore, this ground improvement portion may be used as the closing portion 211b. Further, when the seabed ground is soft and a ground improvement portion is provided in advance, this may be used as the closing portion 211b.

The horizontal drain material 22 is made of a long drainage material having water permeability, and is embedded in the water permeable mat 21 so as not to be exposed. As the horizontal drain material 22, any long member such as a porous pipe or a strainer pipe that allows moisture and air to permeate but can suppress the inflow of earth and sand may be used, but in the present embodiment, any of them may be adopted. , Adopts a strip-shaped board drain.

As shown in FIG. 2A, the board drain is a non-woven fabric or the like that has high water permeability but does not allow the granular material to permeate through the long core material 221 in which a plurality of grooves are formed in the longitudinal direction. It is coated with the filter material 222 of.

As shown in FIG. 1 (b), a plurality of horizontal drain materials 22 having such a configuration are arranged vertically and horizontally at intervals so that they are distributed over the entire plane when the water permeable mat 21 is viewed in a plane. Has been done. At this time, the horizontal drain material 22 is arranged so that at least one end is located near the peripheral edge of the water permeable mat 21, but the horizontal drain material 22 is arranged so that both ends can be arranged near the peripheral edge of the water permeable mat 21. The length of 22 may correspond to the size of the water permeable mat 21.

As shown in FIG. 1A, the vertical drain material 23 is made of a long drainage material having water permeability similar to that of the horizontal drain material 22, and stands in the dredged soil D1 deposited on the upper surface of the water permeable mat 21. It is arranged in the installed state. Then, as shown in FIG. 1B, when the water permeable mat 21 is viewed in a plane, a plurality of mats are dispersedly arranged with respect to the entire plane.

Further, the vicinity of the upper end portion of the vertical drain material 23 is buried in the dredged soil D1 so as not to be exposed in the air with the airtight cap 232 installed, and the vicinity of the lower end portion is inserted in the water permeable mat 21. It is arranged so as to.

The material used as the vertical drain material 23 may be any long member that allows moisture and air to permeate but can suppress the inflow of earth and sand, etc., but the dredged soil D1 later discharges the interstitial water. Considering that the volume is reduced by the above, a deformable board drain similar to that used in the horizontal drain material 22 is preferable.

As shown in FIG. 1 (b), the water collecting facility 2 having the above-described configuration is connected to a plurality of negative pressure acting facilities 3 installed along the revetment embankment body E.

≪Negative pressure action equipment≫
As shown in FIG. 1A, the negative pressure acting equipment 3 has a connecting pipe 31 having one end connected to the horizontal drain material 22 of the water collecting equipment 2 and a water storage tank 32 connected to the other end of the connecting pipe 31. A decompression device 33 for depressurizing the inside of the water storage tank 32 and a drainage device 34 for discharging the interstitial water stored in the water storage tank 32 are provided.

The connecting pipe 31 is an airtight and watertight pipe material that connects the horizontal drain material 22 and the water storage tank 32 in a communicating state, and the connection with the horizontal drain material 22 is as shown in FIG. 2 (b). In the horizontal drain material 22, the airtight cap 223 fixed to the end portion arranged at the peripheral edge of the water permeable mat 21 is used.

The water storage tank 32 is a cylindrical container having watertightness and airtightness, and an opening (not shown) is provided in a part thereof, and the other end of the connecting pipe 31 is connected to the water storage tank 32. As a result, the water storage tank 32 is in a state of communicating with the horizontal drain material 22. The shape and structure of the water storage tank 32 may be any shape as long as it can be sealed, for example, an airtight lid material is provided at the upper end portion so that the water storage tank 32 can be opened and closed.

The decompression device 33 includes an exhaust pipe 331 having one end inserted into the water storage tank 32, and a vacuum pump 332 to which the other end of the exhaust pipe 331 is connected. By operating the vacuum pump 332, the air temporarily stored in the water storage tank 32 is exhausted and depressurized through the exhaust pipe 331.

The drainage device 34 includes a pumping pipe 341 having one end inserted into the water tank 32, and a pumping pump 342 connected to the pumping pipe 341 in the water tank 32. The drainage device 34 pumps the pore water that is primarily stored in the water storage tank 32 by operating the pump pump 342.

In the soil drainage device 1 having such a configuration, when the vacuum pump 332 and the pumping pump 342 are operated to reduce the pressure in the water storage tank 32, the dredged soil D1 is passed through the connecting pipe 31, the horizontal drain material 22, and the permeable mat 21. Negative pressure can be applied to the entire lower surface.

As a result, the interstitial water of the dredged soil D1 is forcibly sucked and efficiently drained to the water storage tank 32 via the permeable mat 21, the horizontal drain material 22, and the connecting pipe 31, and the vacuum widely used in the ground improvement method. It is possible to bring about the same ground improvement effect as the consolidation method.

Further, since the lower surface and the peripheral edge of the water permeable mat 21 are closed by the closed portions 211a and 211b, a negative pressure can be applied only to the dredged soil D1 deposited on the upper surface. Further, a negative pressure can be applied to the entire height direction of the dredged soil D1 through the vertical drain material 23 whose lower end contacts the water permeable mat 21, and the pore water of the dredged soil D1 can be efficiently drained. It will be possible.

The position of the negative pressure generating equipment 3 is not limited as long as the water storage tank 32 is connected to the horizontal drain material 22 via the connecting pipe 31. Therefore, in order to secure a working space for depositing the dredged soil D1 above the permeable mat 21, the length of the connecting pipe 31 is appropriately adjusted, and the negative pressure acting facility 3 is installed outside the permeable mat 21. It is also possible.

Therefore, in the present embodiment, as shown in FIG. 1B, the water storage tank 32 is arranged along the inner wall surface Ef of the revetment wall body E, and the negative pressure acting equipment 3 is collectively arranged. ..

As a result, the work of depositing the dredging soil D1 on the permeable mat 21 and the work of forcibly sucking and draining the interstitial water of the deposited dredging soil D1 without obstructing the traffic of the dredging vessel, the work boat, etc. The work to be done can be carried out efficiently in parallel. In addition, since both works can be started almost at the same time, it is possible to contribute to shortening the construction period and reducing the construction cost of the reclamation work performed in the water area such as the coast.

Further, the top end of the revetment wall body E can be used as a work area for installing the water storage tank 32 and the like, and the installation work of the negative pressure acting equipment 3 can be easily performed. Further, the top end of the revetment wall body E can be used as an arrangement area for arranging pipes, electric wires, or equipment of the drainage device 34 and the decompression device 33 provided in the water storage tank 32, and maintenance work related to the negative pressure acting equipment 3 can be performed. It is also possible to improve efficiency.

≪How to install soil drainage device≫
The procedure for installing the soil drainage device 1 having the above-described configuration will be described below with reference to FIGS. 3 and 4.

In the present embodiment, a case where the dredged soil D1 to be treated is adopted as the closed portion 211a of the peripheral portion of the permeable mat 21 and the seabed ground is adopted as the closed portion 211b of the lower surface is taken as an example.

As shown in FIG. 3A, the sand material 21'constituting the permeable mat 21 is sprinkled to about half of the planned layer thickness on the landfill area 10 having the closed portion 211b made of the seabed ground. At this time, a space necessary for securing the closed portion 211a of the peripheral portion of the permeable mat 21 is provided between the revetment embankment body E and the levee body E.

Next, as shown in FIG. 3B, a plurality of horizontal drain materials 22 are laid on the upper surface of the sprinkled sand material 21', and a water storage tank 32 is installed along the inner wall surface Ef of the revetment embankment body E. , The horizontal drain material 22 and the water storage tank 32 are communicated with each other via the connecting pipe 31.

Then, as shown in FIG. 3C, the remaining sand material is sprinkled so as to bury the entire horizontal drain material 22, and a water permeable mat 21 having a predetermined layer thickness is formed. Further, before, after, or at the same time, the decompression device 33 and the drainage device 34 are installed in the water storage tank 32.

When the soil drainage device 1 is constructed, as shown in FIG. 4A, dredging soil D1 is dropped on the upper surface of the permeable mat 21 to form a closed portion 211a at the peripheral edge of the permeable mat 21, and the permeable mat 21 is formed. Covers the entire surface of 21.

After confirming that the entire surface of the water permeable mat 21 was covered with the dredged soil D1, the vacuum pump 332 of the negative pressure acting facility 3 was operated to reduce the pressure in the water storage tank 32, and the pump 342 was operated to store water. The interstitial water drained into the tank 32 is pumped.

In this way, the work of depositing the dredged soil D1 on the permeable mat 21 and the work of forcibly sucking and draining the interstitial water of the deposited dredged soil D1 were started almost at the same time, and thereafter, both works proceeded in parallel. Let me.

When the deposited dredging soil D1 reaches a predetermined height, the deposition work of the dredging soil D1 is temporarily interrupted, and as shown in FIG. 4B, a vertical drain material 23 is struck at a predetermined position in the dredging soil D1. Set up. An anchor member 231 is installed at the lower end of the vertical drain material 23, and the anchor member 231 is driven into the water permeable mat 21 or until it reaches the closing portion 221b located on the lower surface of the water permeable mat 21.

After all the vertical drain material 23 has been placed, or in parallel with the driving work, the dredging soil D1 dropping work is resumed, and as shown in FIG. 4 (c), the upper end of the vertical drain material 23 is completely removed. Dredged soil D1 is deposited until it is buried.

Since the airtight cap 232 is provided at the upper end of the vertical drain material 23, even if the vertical drain material 23 is placed while applying a negative pressure to the dredged soil D1, the vertical drain material 23 During the period until the upper end is completely covered, the phenomenon that the vertical drain material 23 sucks the outside air can be suppressed.

Further, an impermeable layer using another material instead of the dredged soil D1 may be formed shallower than the upper end of the vertical drain material 23. Further, even if the vertical drain material 23 is not used, it is not always necessary to use the vertical drain material 23 when the dehydration effect can be obtained above the dredged soil D1.

When the dredging soil D1 reaches a desired height, the dropping work of the dredging soil D1 is completed, but the vacuum pump 332 and the pumping pump 342 of the negative pressure acting equipment 3 converge or sink the dredging soil D1. Operate until the amount is below the specified value.

The soil drainage device 1 of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

In the present embodiment, the water storage tank 32 of the negative pressure acting device 3 is installed along the vertical inner wall surface Ef of the revetment body E, but the present invention is not necessarily limited to this, and FIG. The water storage tank 32 may be arranged along the inclined inner wall surface Ef as shown by.

Further, in the present embodiment, the case where the soil drainage device 1 is adopted for the landfill work performed in the sea area is given as an example, but the present invention is not limited to this.

For example, as shown in FIG. 5B, it is also possible to use it for land reclamation work in which the underground hole 11 provided in the ground is reclaimed with the construction-generated soil D2. In this case, a water-impervious sheet 4 may be laid in the underground hole 11 and used as the closed portions 211a and 211b of the peripheral portion and the lower surface of the water-permeable mat 21. Further, the water storage tank 32 of the negative pressure acting equipment 3 may be arranged on the wall edge at the top end along the inner wall surface 111 of the underground hole 11.

Further, as shown in FIG. 5C, the soil drainage device 1 may be used when the embankment material D3 is deposited on the ground to construct the embankment 12. In this case, for example, a concrete pit 5 may be provided on the ground, and this may be used as the peripheral portion and the lower surface closing portions 211a and 211b of the water permeable mat 21.

Further, as shown in FIG. 6, the horizontal drain material 22 of the water collecting facility 2 does not necessarily have to be laid independently one by one, and the horizontal drain material 22 intersecting with the horizontal drain material 22 may be added in parallel or in series. The horizontal drain members 22 adjacent to the above may be connected and communicated with each other.

Further, the negative pressure acting device 3 and the horizontal drain material 22 do not necessarily have to be provided as a pair, and one body is used for connecting and communicating the adjacent horizontal drain materials 22 in parallel or in series. A negative pressure acting device 3 may be provided.

1 Soil drainage device 2 Water collection equipment 21 Water permeation mat 211a Blocking part 211b Blocking part 22 Horizontal drain material 221 Core material 222 Filter material 223 Airtight drain material 231 Vertical drain material 231 Anchor member 232 Airtight cap 3 Negative pressure action equipment 31 Connecting pipe 32 Water storage Tank 33 Decompression device 331 Exhaust pipe 332 Vacuum pump 34 Drainage device 341 Pumping pipe 342 Pumping pump 4 Impermeable sheet 5 Pit 10 Landfill area 11 Underground hole 111 Inner wall surface (wall-shaped part)

12 Embankment D1 Dredging soil (soil to be treated)
D2 Construction soil (soil to be treated)
D3 embankment material (soil to be treated)
E Revetment embankment body Ef Inner wall surface (wall-shaped part)

Claims (4)

A water collection facility that collects the interstitial water of the soil to be treated,
Negative pressure acting equipment that applies negative pressure to the soil to be treated via the water collecting equipment,
It is a soil drainage device equipped with
The water collection facility
A permeable mat that is laid on the ground, the lower surface and the peripheral edge are closed, and the soil to be treated is deposited on the upper surface.
With a horizontal drain material embedded in the permeable mat,
The negative pressure acting equipment
A water tank that stores the pore water and
A drainage device for draining the interstitial water stored in the water tank, and
A decompression device for depressurizing the inside of the water storage tank is provided.
A soil drainage device characterized in that the water storage tank and the horizontal drain material are communicated with each other via a connecting pipe. In the soil drainage device according to claim 1,
A soil drainage device characterized in that the water collecting facility is provided with a vertical drain material whose lower end is in contact with the water permeable mat and whose upper end is arranged in the soil to be treated. In the soil drainage device according to claim 1 or 2.
A wall-shaped portion is provided facing the water-permeable mat.
A soil drainage device characterized in that the water storage tank is arranged along the wall-shaped portion. In the soil drainage device according to any one of claims 1 to 3,
A soil drainage device characterized in that the permeable mat is laid in a landfill area surrounded by a revetment body.

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