JP2018091040A - Withdrawal method of underground water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of withdrawal wellholes.SOLUTION: A withdrawal method of underground water is a method to withdraw underground water from a first block area R1 and a second block area R2 of a subsoil 10 which is segmented by a grid-like subsoil improvement body 22. The underground water is withdrawed from the second block area R2 from a withdrawal wellhole 16 formed in the first block area R1 via a water passage W formed in the grid-like subsoil improvement body 22.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for pumping groundwater.

  A lattice-like ground improvement body formed in a lattice shape in plan view is known (see, for example, Patent Document 1).

Japanese Patent No. 5919429

  By the way, when excavating a ground having a high groundwater level, it is necessary to lower the groundwater level by, for example, drawing groundwater from a pumping well formed in the ground.

  However, in the ground on which the grid-like ground improvement body is formed, the ground is partitioned into a plurality of areas (hereinafter referred to as “partition areas”) by the grid-like ground improvement body. Therefore, a pumping well must be provided in each division area, and the number of pumping wells may increase.

  In view of the above facts, the present invention aims to reduce the number of pumping wells.

  The groundwater pumping method according to claim 1 is a groundwater pumping method for pumping up groundwater in the first section area and the second section area of the ground sectioned by the ground improvement body, and is provided in the first section area. The groundwater in the second section area is pumped up from the pumped well through a water passage provided in the ground improvement body.

  According to the groundwater pumping method according to the first aspect, the ground is partitioned into the first partitioned region and the second partitioned region by the ground improvement body. The ground improvement body is provided with a water flow portion.

  Here, when the ground improvement body does not have a water passage portion, it is necessary to provide a pumping well in each of the first partition area and the second partition area in order to pump up the ground water in the first partition area and the second partition area.

  On the other hand, in this invention, as mentioned above, a ground improvement body is provided with a water flow part. Thereby, the ground water of a 2nd division area can be pumped up from the pumping well provided in the 1st division area through the water flow part. Therefore, the pumping well in the second section area can be omitted. Therefore, the number of pumping wells can be reduced.

  A groundwater pumping method according to a second aspect is the groundwater pumping method according to the first aspect, wherein the ground improvement body is formed in a lattice shape in a plan view.

  According to the groundwater pumping method according to claim 2, the ground improvement body is formed in a lattice shape in plan view. Thereby, liquefaction of the ground can be efficiently suppressed while reducing the number of pumping wells.

  The groundwater pumping method according to claim 3 is the groundwater pumping method according to claim 1 or 2, wherein the water flow portion is an unimproved ground portion provided in the ground improvement body.

  According to the groundwater pumping method of the third aspect, the water flow portion is an unimproved ground portion provided in the ground improvement body. Therefore, a water flow part can be easily provided in the ground improvement body.

  As described above, according to the groundwater pumping method according to the present invention, the number of pumping wells can be reduced.

It is a longitudinal cross-sectional view which shows the ground where the groundwater pumping method which concerns on one Embodiment is applied. FIG. 2 is a sectional view taken along line 2-2 of FIG. It is a longitudinal cross-sectional view which shows the partition wall part in which the water flow part shown by FIG. 1 was provided. It is a longitudinal cross-sectional view equivalent to FIG. 1 which shows the state which pumped up groundwater from the ground. It is a longitudinal cross-sectional view equivalent to FIG. 1 which shows the lattice-like ground improvement body which concerns on a comparative example. FIG. 6 is a sectional view taken along line 6-6 of FIG. It is a longitudinal cross-sectional view equivalent to FIG. 1 which shows the modification of the groundwater pumping method which concerns on one Embodiment. (A) And (B) is sectional drawing equivalent to FIG. 2 which shows the modification of the ground improvement body which concerns on one Embodiment.

  Hereinafter, a groundwater pumping method according to an embodiment will be described with reference to the drawings.

(ground)
FIG. 1 shows a ground 10 to which the groundwater pumping method according to the present embodiment is applied. As an example, the ground 10 includes a non-liquefied layer 10A and a liquefied layer 10B deposited on the non-liquefied layer 10A.

  The liquefied layer 10B is configured to include sandy soil, and is a layer having a high possibility of liquefaction when an earthquake of a predetermined scale or larger occurs. Further, the liquefied layer 10B is an aquifer having higher water permeability than the non-liquefied layer 10A, and the groundwater is easy to flow. On the other hand, the non-liquefiable layer 10A is a hardly water-permeable layer having a lower water permeability than the liquefied layer 10B, and is a layer having a low possibility of being liquefied.

  In addition, the groundwater pumping method which concerns on this embodiment is applicable not only to said ground 10 but various grounds which 10 A of non-liquefied layers do not exist, for example.

(Lattice-like ground improvement body)
The liquefied layer 10B is provided with a grid-like ground improvement body 22. The grid-like ground improvement body 22 suppresses liquefaction of the liquefied layer 10B at the time of an earthquake. This grid-like ground improvement body 22 is formed in the liquefied layer 10B with the cement-type solidification material, for example.

  In the present embodiment, the lower end portion of the grid-like ground improvement body 22 reaches the non-liquefaction layer 10A, but the lower end portion of the grid-like ground improvement body 22 does not reach the non-liquefaction layer 10A. Also good. The grid-like ground improvement body 22 is an example of a ground improvement body.

  As shown in FIG. 2, the lattice-like ground improvement body 22 is formed in a lattice shape in plan view. By applying shear rigidity to the liquefied layer 10B by the lattice-like ground improvement body 22, liquefaction of the liquefied layer 10B is suppressed. In addition, the arrow F suitably shown in each figure has shown the flow of groundwater.

  The lattice-like ground improvement body 22 has an outer peripheral wall portion 24 and a plurality of partition wall portions 26. The outer peripheral wall portion 24 is formed in a rectangular frame shape in plan view and surrounds the liquefied layer 10 </ b> B of the ground 10. Note that the arrow X direction and the arrow Y direction shown in FIG. 2 indicate two horizontal directions orthogonal to each other.

  The plurality of partition walls 26 include a plurality of partition walls 26A disposed along the arrow Y direction and a plurality of partition walls 26B disposed along the arrow X direction. The plurality of partition wall portions 26A are arranged at intervals in the arrow X direction. Further, the plurality of partition wall portions 26B are arranged at intervals in the arrow Y direction. The plurality of partition wall portions 26A and the partition wall portions 26B are connected in a lattice shape in plan view. By these partition wall portions 26A and 26B, a region (liquefied layer 10B) inside the outer peripheral wall portion 24 is partitioned into a plurality of regions (hereinafter referred to as “partition regions”) R. Hereinafter, the partition wall portions 26A and 26B are collectively referred to as the partition wall portion 26.

(Water passage)
Each partition wall portion 26 is provided with a plurality of water passage portions W through which groundwater passes. As shown in FIG. 3, the water flow portion W is an unimproved ground portion partially provided on the partition wall portion 26. In this water passing portion W, the ground is not improved. That is, in the water flow portion W, a solidifying material such as a cement-based solidifying material is not injected into the ground 10. Thereby, in the water flow part W, groundwater can flow. This water flow part W is constructed by the following method, for example.

  That is, the partition wall portion 26 of the present embodiment includes a plurality of columnar improvement bodies 28A and 28B that are continuous in a wall shape. The columnar improvement body 28A does not include the water flow portion W. This columnar improvement body 28A is constructed by a mechanical stirring method. Specifically, the columnar improvement body 28A excavates the ground 10 while injecting a solidifying material such as a cement-based solidifying material from the tip of a drilling auger (not shown), and stirs and mixes the excavated soil and the solidified material. It has been created.

  On the other hand, the columnar improvement body 28B includes a water flow portion W. This columnar improvement body 28B is constructed by a high-pressure jet stirring method. Specifically, the solidified material is injected at a high pressure from the tip 32T of the rotating rod 32 of the high pressure injection device 30 driven into the ground 10, and the rotating rod 32 is pulled up while rotating. Thereby, a solidification material is inject | poured into the ground 10 near the front-end | tip part of the rotating rod 32, and the columnar improvement body 28B is formed in order from the lower end.

  Here, when the tip portion 32T of the rotating rod 32 passes through the water passage portion W, the high-pressure injection of the solidified material from the tip portion 32T is temporarily stopped. Thereby, in the water flow part W, a solidification material is not inject | poured into the ground 10, but the water permeability of the ground 10 is maintained.

  In this way, by forming the columnar improvement body 28 </ b> B while temporarily stopping the high-pressure injection of the solidifying material, a plurality of water flow portions W are provided in the partition wall portion 26. Moreover, in the high-pressure jet stirring method, since the switching management between the injection and stop of the solidified material is easy as compared with the mechanical stirring method, the workability of the water passing portion W is improved.

  In addition, the water flow part W can also be formed in the mechanical stirring method while temporarily stopping the injection of the solidifying material. Moreover, the number, arrangement | positioning, shape, and magnitude | size of the water flow part W provided in the partition wall part 26 can be changed suitably. Moreover, when the rigidity of the partition wall part 26 falls by the water flow part W, the thickness of the partition wall part 26 may be thickened, or the space | interval of the adjacent partition wall part 26 may be narrowed.

(Groundwater pumping method)
Next, the effect of this embodiment will be described while explaining an example of a method for pumping groundwater.

  As shown in FIG. 4, in this embodiment, the ground 10 provided with the grid-like ground improvement body 22 is excavated, and, for example, an unillustrated underground structure is constructed. At this time, the groundwater of the ground 10 is pumped up, and the groundwater level L0 before excavation is lowered to the target groundwater level L1 or less.

  In the following, for convenience of explanation, among the plurality of partition regions R, the partition region R located at the center of the grid-like ground improvement body 22 is referred to as a first partition region R1, and other partitions adjacent to the first partition region R1. The region R is defined as a second partition region R2. Further, a partition region R other than the first partition region R1 adjacent to the second partition region R2 is defined as a third partition region R3 (see FIG. 2).

  First, the ground 10 inside the lattice-shaped ground improvement body 22 is excavated to form an underground space 40. Next, the pumping well 16 is provided in the first partition region R1 of the grid-like ground improvement body 22. The pumping well 16 is formed, for example, by driving a steel pipe having a plurality of pumping openings 16A into the ground 10.

  Next, a pumping pipe (not shown) is inserted into the pumping well 16, and a pumping pump provided in the pumping pipe is operated. As a result, the groundwater in the first section region R1 is pumped up from the pumping port 16A of the pumping well 16 to the ground. Thereby, the groundwater level L2 in the lattice-like ground improvement body 22 is lowered below the target groundwater level L1.

  Here, as a comparative example, as shown in FIGS. 5 and 6, when there is no water passage W in the grid-like ground improvement body 22, the first partition region R 1, the second partition region R 2, and the third partition region In order to pump up the groundwater of R3, it is necessary to provide the pumping wells 100 in the second partition region R2 and the third partition region R3 in addition to the first partition region R1.

  On the other hand, in this embodiment, as shown in FIG. 2, a water passage W is provided in the partition wall portion 26 between the first partition region R1 and the second partition region R2. Thereby, as shown by the arrow F, the groundwater of 2nd division area | region R2 can be pumped up from the pumping well 16 provided in 1st division area | region R1 through the water flow part W. FIG. Therefore, the pumping well in the second partition region R2 can be omitted. Therefore, the number of pumping wells 16 can be reduced.

  Moreover, in this embodiment, the water flow part W is provided in all the partition wall parts 26 of the grid | lattice-like ground improvement body 22. FIG. That is, in this embodiment, the water flow part W is provided also in the partition wall part 26 between 2nd partition area | region R2 and 3rd partition area | region R3. Thereby, as shown by the arrow F, the groundwater of 3rd division area | region R3 can be pumped up from the pumping well 16 provided in 1st division area | region R1 via 2nd division area | region R2. Therefore, the pumping well 100 (refer FIG. 5) of 3rd division area | region R3 can also be abbreviate | omitted. Therefore, the number of pumping wells 16 can be further reduced.

  Further, the water passing portion W is an unimproved ground portion provided on the partition wall portion 26 of the lattice-shaped ground improving body 22. Therefore, the water flow portion W can be easily provided in the grid-like ground improvement body 22.

  Furthermore, the grid-like ground improvement body 22 of this embodiment is formed in a grid shape in plan view. Thereby, liquefaction of the liquefied layer 10B of the ground 10 can be efficiently suppressed while reducing the number of the pumping wells 16.

(Modification)
Next, a modification of the above embodiment will be described.

  In the said embodiment, although the ground water of the ground 10 was pumped up with the excavation of the ground 10, the said embodiment is not restricted to this. For example, as shown in FIG. 7, the ground water of the ground 10 may be pumped up without excavating the ground 10. In this case, the groundwater pumped up from the ground 10 can be used for construction water, for example.

  Moreover, in the said embodiment, although the pumping well 16 was provided in the division area R (1st division) in the center of the grid | lattice-like ground improvement body 22, you may provide the pumping well 16 in another division area R. In this case, the partition area R provided with the pumping well 16 is the first partition area, and another partition area R adjacent to the first partition area is the second partition area.

  Further, a plurality of pumping wells 16 may be provided for one partition region R, or pumping wells 16 may be provided for a plurality of partition regions R, respectively.

  Moreover, in the said embodiment, although the water flow part W was provided in each division wall part 26 of the lattice-like ground improvement body 22, in the said embodiment, it is not restricted to this. The water flow portion W can be provided at least in the partition wall portion 26 between the first partition region R1 and the second partition region R2 where the pumping well 16 is provided.

  Moreover, in the said embodiment, although a ground improvement body is made into the grid | lattice-like ground improvement body 22, the said embodiment is not restricted to this. For example, as shown in FIG. 8A, the ground improvement body 50 may be formed in a “day” shape in a plan view.

  Specifically, the ground improvement body 50 includes an outer peripheral wall portion 52 and a partition wall portion 54. The partition wall portion 54 partitions a region (liquefied layer 10B) inside the outer peripheral wall portion 52 into a first partition region R1 and a second partition region R2. In this case, the pumping well 16 is provided in the first partition region R <b> 1, and the water flow portion W is provided in the partition wall portion 54. Thereby, as shown by the arrow F, the groundwater in 2nd division area | region R2 can be pumped up from the pumping well 16 provided in 1st division area | region R1 through the water flow part W. FIG. The ground improvement body may be formed in the shape of a “field” in plan view.

  Moreover, in the said embodiment, although the area of several division area R (1st division area R1, 2nd division area R2, 3rd division area R3) is substantially the same, for example, FIG. 8 (B) Like the ground improvement body 60 shown by (4), the width of the division area | region R may differ.

  Specifically, the ground improvement body 60 has an outer peripheral wall portion 62 and a plurality of partition wall portions 64. The plurality of partition walls 64 partition a region (liquefied layer 10B) inside the outer peripheral wall 62 into a plurality of partition regions R having different sizes. Here, in this modification, the narrowest partitioned area R is defined as a first partitioned area R1, and another partitioned area R adjacent to the first partitioned area R1 is defined as a second partitioned area R2.

  In this case, the pumping well 16 is provided in the first partition region R1, and the water passing portion W is provided in the partition wall portion 64 between the first partition region R1 and the second partition region R2. Thereby, as shown by the arrow F, the groundwater in 2nd division area | region R2 can be pumped up from the pumping well 16 provided in 1st division area | region R1 through the water flow part W. FIG.

  Moreover, in the said embodiment, although the water flow part W was provided in the partition wall part 26 of the lattice-like ground improvement body 22, the said embodiment is not restricted to this. A water flow part can be provided in the predetermined part of a ground improvement body according to the shape and structure of a ground improvement body.

  Furthermore, the groundwater pumping method according to the embodiment is applicable to various grounds where groundwater exists.

  As mentioned above, although one embodiment of the present invention was described, the present invention is not limited to such an embodiment, and one embodiment and various modifications may be used in combination as appropriate, and the gist of the present invention will be described. Of course, various embodiments can be implemented without departing from the scope.

10 Ground 12 Structure 16 Pumping well 22 Lattice ground improvement body (Ground improvement body)
50 Ground improvement body 60 Ground improvement body R1 1st division area R2 2nd division area W Water flow part

Claims (3)

A groundwater pumping method for pumping up groundwater in the first section area and the second section area of the ground sectioned by the ground improvement body,
From the pumping well provided in the first section area, through the water flow section provided in the ground improvement body, pumping up the groundwater of the second section area,
Groundwater pumping method. The ground improvement body is formed in a lattice shape in plan view,
The groundwater pumping method according to claim 1. The water flow portion is an unimproved ground portion provided in the ground improvement body,
The groundwater pumping method of Claim 1 or Claim 2.