JP2018009298A - Ground water level lowering system and method of constructing the same - Google Patents

Abstract

An object of the present invention is to provide a groundwater level lowering system and the like that can easily reduce the groundwater level of a permeable layer in a deep position.
In a groundwater level lowering system, a riser pipe 11 having a well point 13 at a lower end portion is installed in a hole 9 formed in the ground 1. The hole 9 is formed so as to penetrate the upper water-permeable layer 3 and the impermeable layer 5 below the upper water-permeable layer 3 and reach the lower water-permeable layer 7 below the water-impermeable layer 5. The riser pipe 11 is installed so that the well point 13 at the lower end is positioned at the lower water permeable layer 7. A water permeable material 15 is provided between the riser pipe 11 and the hole wall, and when the vacuum pump of the pumping unit 20 is operated, the groundwater in the upper permeable layer 3 and the lower permeable layer 7 is pumped up simultaneously.
[Selection] Figure 1

Description

  The present invention relates to a groundwater level lowering system and a construction method thereof.

  When excavating the ground, etc., the groundwater level may be lowered by pumping up the groundwater for smooth construction. The deep well method and well point method are known as methods for lowering the groundwater level. The former is often applied to a permeable layer at a relatively deep position, and the latter is applied to a permeable layer at a relatively shallow position. It is often applied (see, for example, Patent Documents 1 to 3).

  FIG. 7A is a diagram showing an outline of the deep well method. In the deep well construction method, a hole 115 having a predetermined depth is formed in a pumped portion of the ground 101, and a well pipe 117 with a slit is installed in the hole 115. Inside the well pipe 117, a pumping pump 121 and a discharge pipe 123 are installed, and a water-permeable quartz sand 119 is provided between the well pipe 117 and the hole wall.

  In this example, the ground 101 is, in order from the ground surface, an upper permeable layer 103 having a thickness of about 7 to 8 m, an impermeable layer 105 having a thickness of about 2 to 3 m below the upper permeable layer 103, and an impermeable layer 105. The hole 115 is formed so as to penetrate the upper permeable layer 103 and the impermeable layer 105 and reach the lower permeable layer 107.

  Reference numeral 125 denotes the groundwater level at the pumping point and its surroundings. Reference numeral 125a denotes the head of groundwater (groundwater level) in the lower permeable layer 107. In this example, the groundwater in the lower permeable layer 107 is pressurized groundwater and the head 125a is above the impermeable layer 105. Shall.

  In the deep well method, groundwater in the upper permeable layer 103 and the lower permeable layer 107 collected in the well pipe 117 is pumped by the pumping pump 121, so that the groundwater level 125 is lowered widely and deeply as shown in FIG. be able to. It is also possible to lower only the groundwater level of an arbitrary permeable layer by changing the position of the slit of the well pipe 117 or by providing an impermeable material between the well pipe 117 and the impermeable layer 105.

  FIG. 8A is a diagram showing an outline of the well point method. In the well point construction method, a riser pipe 129 having a well point 131 at the lower end is built in a pumping point of the ground 101. A plurality of such riser pipes 129 are arranged at predetermined intervals, and the upper end of each riser pipe 129 is connected to a header pipe (not shown) provided on the ground using a vinyl hose or the like.

  In the well point method, the inside of the header pipe, the riser pipe 129, the well point 131, etc. is evacuated by a pumping unit (not shown) such as a vacuum pump, and the well point 131 is separated from the well point 131 by the pressure difference between the atmospheric pressure acting on the groundwater and the vacuum. Suck ground water. Thereby, the groundwater level 125 can be lowered as shown in FIG.

Patent No. 5528200 JP 2013-204413 A Patent No. 5016517

  In cases where the excavation part is formed in a band shape, such as when constructing the underground structure of a tunnel, it is necessary to lower the groundwater level in the band area along the excavation part, and pumping water from multiple pumping points Is required.

  In this regard, the deep well method is a large-scale one provided with the well pipe 117, the pumping pump 121, the discharge pipe 123, and the like. In addition, when the hole 115 is formed, a large-scale excavation is often performed by the all casing method. Construction will increase the construction period and construction costs. Moreover, since the groundwater level in a wide range is deeply lowered in the deep well method, there is also a problem that ground subsidence outside the construction range is likely to occur.

  On the other hand, in the well point method, pumping can be performed with a simple configuration using the riser pipe 129 provided with the well point 131. Further, by ejecting jet water from the well point 131, the riser pipe 129 can be built on the ground 101 manually, and a large number of riser pipes 129 can be easily installed. In addition, the groundwater level in a wide range is not lowered as in the deep well method, and pumping is performed using the plurality of riser pipes 129 provided at a predetermined interval as described above, so that the groundwater level in the belt-like range is reduced. It can be reliably lowered.

  However, the length of the riser pipe 129 used for a general well point method is about 5.5 m, the length of the well point 131 is about 1.0 m, and the total length is about 6.5 m. For this reason, the well point method is a method for lowering the groundwater level when the excavation depth is relatively shallow, as shown in FIG. 8 (a), in the case of lowering the groundwater level of the shallow permeable layer (upper permeable layer 103). Often used.

  For example, in a case where a water-impervious wall (not shown) is provided so as to penetrate the upper permeable layer 103 and the impermeable layer 105 and reach the lower permeable layer 107 and the ground 101 on the side thereof is excavated, it is at a deeper position. In some cases, it may be desired to lower the groundwater level of the lower permeable layer 107, but when there is an impermeable layer 105 below the well point 131 as shown in FIG. It cannot be lowered.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a groundwater level lowering system and the like that can easily reduce the groundwater level of a permeable layer in a deep position.

  1st invention for achieving the objective mentioned above has a riser pipe provided with a well point at a lower end, and a pumping unit for pumping ground water from the well point, the riser pipe, Groundwater level drop characterized by being installed so that the well point of the lower end reaches the lower permeable layer below the impermeable layer, passing through the upper permeable layer of the ground and the impermeable layer below the upper permeable layer System.

For example, the riser pipe is installed in a hole formed in the ground, and a water-permeable material is provided between the riser pipe and the hole wall. An impermeable material may be provided between the riser pipe and the hole wall at a depth corresponding to the impermeable layer.
A plurality of the riser pipes may be provided at predetermined intervals in the plane.

  A second invention is a construction method of a groundwater level lowering system having a riser pipe having a well point at a lower end and a pumping unit for pumping groundwater from the well point, wherein the riser pipe Groundwater characterized in that the riser pipe is provided so as to pass through an upper permeable layer of the ground and an impermeable layer below the upper permeable layer and a well point at a lower end reaches the lower permeable layer below the impermeable layer. This is a method for constructing a position lowering system.

For example, a hole that penetrates the upper permeable layer and the impermeable layer and reaches the lower permeable layer is formed in the ground, the riser pipe is inserted into the hole, and a permeable material is inserted between the riser pipe and the hole wall. Fill. An impermeable material may be provided between the riser pipe and the hole wall at a depth corresponding to the impermeable layer.
A plurality of the riser pipes may be provided at a predetermined interval on the plane.

  In the present invention, the riser pipe is provided so as to pass through the upper permeable layer of the ground and the impermeable layer below the impermeable layer and reach the lower permeable layer below the impermeable layer, thereby being deeper by the well point at the lower end thereof. It becomes possible to lower the groundwater level of the lower permeable layer. In the present invention, since pumping is performed with a simple configuration using a riser pipe provided with well points, the cost is lower than the configuration of the deep well method described above. Also, the riser pipe can be easily installed, so the construction period and construction cost can be reduced, and a large number of riser pipes can be installed at low cost. If a plurality of riser pipes are provided at predetermined intervals, the groundwater level in the belt-shaped range can be suitably lowered, and the groundwater level in the unnecessary range is not lowered.

  In the present invention, by excavating a hole that penetrates the upper permeable layer and the impermeable layer and reaches the lower permeable layer, inserting a riser pipe into the hole, and filling the hole with a permeable material such as silica sand, Even when there is a hard layer on the ground, the riser pipe can be suitably installed. Moreover, if water can be transferred between the upper permeable layer and the lower permeable layer by the permeable material, the groundwater in the upper permeable layer and the lower permeable layer can be pumped at the same time, and the groundwater level can be lowered. Alternatively, by providing a water-impermeable material at a depth corresponding to the water-impermeable layer, water can be blocked between the upper water-permeable layer and the lower water-permeable layer, and only the groundwater of the lower water-permeable layer can be pumped up.

  ADVANTAGE OF THE INVENTION According to this invention, the groundwater level fall system etc. which can fall easily the groundwater level of the permeable layer in a deep position can be provided.

The figure which shows the outline of the groundwater level lowering system 2 The figure which shows arrangement | positioning of the riser pipe 11 The figure explaining the fall of the groundwater level by the groundwater level fall system 2 The figure explaining the construction method of the groundwater level lowering system 2 The figure which shows the outline of the groundwater level lowering system 2a The figure explaining the fall of the groundwater level by the groundwater level fall system 2a Diagram showing the outline of the deep well method Diagram showing the outline of the well point method

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
(1. Groundwater level lowering system 2)
FIG. 1 is a diagram showing an outline of a groundwater level lowering system 2 according to the first embodiment of the present invention. The groundwater level lowering system 2 lowers the groundwater level by pumping up groundwater in the ground 1 and includes a riser pipe 11, a well point 13, a water permeable material 15, a header pipe 17, a pumping unit 20, and the like.

  Also in this embodiment, the ground 1 has an upper permeable layer 3 having a thickness of about 7 to 8 m, an impermeable layer 5 having a thickness of about 2 to 3 m below the upper permeable layer 3 and an impermeable layer in order from the ground surface. 5 has a lower water-permeable layer 7 below. Here, the impermeable layer refers to an impermeable layer in a broad sense including what is called a hardly permeable layer.

  Similarly to the above, 28 indicates the groundwater level at the pumping point and its surroundings, and 28a indicates the water head (groundwater level) in the lower permeable layer 7. Also in this embodiment, it is assumed that the groundwater in the lower permeable layer 7 is pressurized groundwater and the head 28 a is on the impermeable layer 5.

  The riser pipe 11 is installed in a hole 9 formed in the ground 1. The hole 9 is formed so as to penetrate the upper water-permeable layer 3 and the water-impermeable layer 5 and reach the lower water-permeable layer 7, and the depth from the ground surface is 10 m or more.

  The riser pipe 11 is a long steel tube, and a well point 13 is provided at the lower end thereof. The well point 13 is provided with a hole for allowing water to pass therethrough. The total length of the riser pipe 11 and the well point 13 is 10 m or more in accordance with the depth of the hole 9, the riser pipe 11 passes through the upper permeable layer 3 and the impermeable layer 5, and the lower well point 13 is connected to the lower permeable layer 7. Install to reach.

  The water permeable material 15 is provided between the riser pipe 11 and the hole wall. The water permeable material 15 is a material having high water permeability such as silica sand, but is not particularly limited as long as it allows water to pass through.

  As shown in FIG. 2, in this embodiment, a plurality of riser pipes 11 are provided in a line at a predetermined interval (for example, about 1.0 to 2.0 m) on a plane, and the upper ends of the riser pipes 11 are grounded by a vinyl hose or the like. The header pipe 17 is connected.

  As shown in FIG. 1, a pumping unit 20 is connected to the header pipe 17. The pumping unit 20 is for pumping up groundwater from the well point 13. As the pumping unit 20, a known unit having a separate tank, a vacuum pump, or the like can be used, and the configuration thereof is not particularly limited as long as groundwater can be pumped.

(2. Reduction of groundwater level by groundwater level lowering system 2)
The pumping unit 20 operates the vacuum pump to evacuate the inside of the header pipe 17, the riser pipe 11, the well point 13, etc., and sucks up the groundwater from the well point 13 by the pressure difference between the atmospheric pressure acting on the groundwater and the vacuum. Then, it flows into the separate tank through the header pipe 17.

  In this embodiment, the well point 13 is at the depth of the lower permeable layer 7, but the groundwater of the upper permeable layer 3 also moves through the permeable material 15 to the well point 13, so that not only the lower permeable layer 7 but also the upper permeable layer Layer 3 groundwater is also pumped at the same time. Therefore, the groundwater level 28 is lowered as shown in FIG. 3, and the water head 28a of the lower permeable layer 7 is similarly lowered. The width of the decrease can be, for example, about 5 to 6 m at the position of the well point 13 and about 3 to 4 m at the periphery.

  In this embodiment, since the riser pipes 11 are arranged in a row at a predetermined interval as shown in FIG. 2, when the vacuum pump of the pumping unit 20 is operated, a band-like shape along the arrangement direction of the riser pipes 11 is used. In the range, the groundwater level of the upper permeable layer 3 and the lower permeable layer 7 can be pumped to reliably lower the groundwater level.

(3. Construction method of groundwater level lowering system 2)
When constructing the groundwater level lowering system 2, the ground 1 is excavated as shown in FIG. 4 (a) to form the above-mentioned hole 9, and the riser pipe 11 is inserted into the hole 9 as shown in FIG. 4 (b). To do.

  After the riser pipe 11 and the well point 13 are provided in the hole 9 in this way, a water-permeable material 15 such as silica sand is filled between the hole wall and the riser pipe 11 as shown in FIG.

  By providing a plurality of riser pipes 11 as shown in FIG. 2 by the above method, and connecting the upper ends of the riser pipes 11 to the header pipes 17 and connecting the header pipes 17 and the pumping unit 20 described above, A groundwater level lowering system 2 is constructed.

  Thus, in the first embodiment, the riser pipe 11 is provided so as to pass through the upper permeable layer 3 of the ground 1 and the impermeable layer 5 below the upper permeable layer 5 and reach the lower permeable layer 7 below the impermeable layer 5. Thus, it becomes possible to reduce the water head 28a (groundwater level) of the lower permeable layer 7 at a deep position by the well point 13 at the lower end thereof. In the present embodiment, pumping is performed with a simple configuration using the riser pipe 11 provided with the well points 13, so that the cost is lower than the configuration of the deep well method described above. Further, since the riser pipe 11 can be easily installed, the construction period and construction cost can be reduced, and a large number of riser pipes 11 can be installed at low cost. By providing the plurality of riser pipes 11 at a predetermined interval, the groundwater level in the belt-shaped range can be suitably lowered, and the groundwater level in the unnecessary range is not lowered.

  Further, in the present embodiment, a hole 9 that penetrates the upper permeable layer 3 and the impermeable layer 5 and reaches the lower permeable layer 7 is preliminarily excavated, and a riser pipe 11 is inserted into the hole 9. By filling the water-permeable material 15 such as, the riser pipe 11 can be suitably installed even when the ground 1 has a hard layer. Further, by allowing water to flow between the upper permeable layer 3 and the lower permeable layer 7 by the permeable material 15, the groundwater in the upper permeable layer 3 and the lower permeable layer 7 can be pumped at the same time, and the groundwater level can be lowered. .

  However, the present invention is not limited to this. For example, in the present embodiment, the total length of the riser pipe 11 and the well point 13 is about 10 m, but a plurality of riser pipes 11 are connected vertically to increase the total length, thereby lowering the groundwater level of the deeper permeable layer. You can also. Moreover, the groundwater of the lower permeable layer 7 is not limited to the groundwater under pressure, and may be ungrounded groundwater.

  Next, a second embodiment of the present invention will be described. The second embodiment will mainly describe differences from the first embodiment, and the same points will be denoted by the same reference numerals in the drawings and the like, and description thereof will be omitted.

[Second Embodiment]
FIG. 5 is a diagram showing a groundwater level lowering system 2a according to the second embodiment of the present invention.

  The groundwater level lowering system 2a of the second embodiment is different from that of the first embodiment in that an impermeable material 31 is provided between the riser pipe 11 and the hole wall at a depth corresponding to the impermeable layer 5. As the water-impermeable material 31, a packer made of a material having low water permeability such as bentonite pellets can be used, but is not limited thereto.

  The construction method of the groundwater level lowering system 2 a is substantially the same as that described with reference to FIG. 4 and the like, and the impermeable material 31 is provided when the hole 9 is filled with the permeable material 15.

  Also in this example, as shown in FIG. 2, a plurality of riser pipes 11 are provided in a line at a predetermined interval on a plane, and the upper ends of the riser pipes 11 are connected to the header pipe 17 on the ground by a vinyl hose or the like. The

  In the second embodiment, since the water-impermeable material 31 is provided at a depth corresponding to the water-impermeable layer 5, the ground water in the upper water-permeable layer 3 moves to the well point 13, unlike the first embodiment. There is no. Therefore, when the vacuum pump of the pumping unit 20 is operated, as shown in FIG. 6, only the groundwater of the lower permeable layer 7 is pumped, and only the water head 28a (groundwater level) of the lower permeable layer 7 is lowered.

  In this way, in the second embodiment, since the water impermeable material 31 blocks the passage of water between the upper permeable layer 3 and the lower permeable layer 7, only the groundwater level of the lower permeable layer 7 can be lowered. .

  A part of the plurality of riser pipes 11 is built at the depth of the upper permeable layer 3 as described with reference to FIG. 8 (a), and thereby the groundwater level (groundwater level 28) in the upper permeable layer 3 is set. It can also be reduced.

  In this embodiment, the riser pipe 11 is provided in the hole 9 that has been excavated in advance. The upper permeable layer 3, the impermeable layer 5, and the lower permeable layer 7 are excavated by jet water from the well point 13, and the riser pipe 11 is grounded. 1 can be penetrated, and in this case, the prior excavation of the hole 9 becomes unnecessary, and the construction period and construction cost can be further reduced.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

1, 101; ground 2, 2a; groundwater level lowering system 3, 103; upper permeable layer 5, 105; impermeable layer 7, 107; lower permeable layer 9, 115; hole 11, 129; riser pipe 13, 131; Point 15, 119; Water permeable material 17; Header pipe 20; Pumping section 28 and 125; Groundwater level 28 a and 125 a; Water head 31; Water impermeable material 117;

Claims (8)

A riser pipe with a well point at the lower end,
A pumping unit for pumping groundwater from the well point;
Have
The riser pipe is installed so as to pass through the upper permeable layer of the ground and the impermeable layer below the upper permeable layer, and the well point at the lower end reaches the lower permeable layer below the impermeable layer. And groundwater level lowering system. The riser pipe is installed in a hole formed in the ground,
The groundwater level lowering system according to claim 1, wherein a water-permeable material is provided between the riser pipe and the hole wall.   The groundwater level lowering system according to claim 2, wherein an impermeable material is provided between the riser pipe and the hole wall at a depth corresponding to the impermeable layer.   The groundwater level lowering system according to any one of claims 1 to 3, wherein the plurality of riser pipes are provided at predetermined intervals in a plane. A construction method of a groundwater level lowering system having a riser pipe provided with a well point at a lower end and a pumping unit for pumping up groundwater from the well point,
Providing the riser pipe so that the riser pipe passes through the upper permeable layer of the ground and the impermeable layer below the upper permeable layer, and the well point at the lower end reaches the lower permeable layer below the impermeable layer. The construction method of the characteristic groundwater level lowering system.   A hole penetrating the upper water-permeable layer and the water-impermeable layer and reaching the lower water-permeable layer is formed in the ground, the riser pipe is inserted into the hole, and a water-permeable material is filled between the riser pipe and the hole wall. The construction method of the groundwater level fall system of Claim 5 characterized by the above-mentioned.   The method for constructing a groundwater level lowering system according to claim 6, wherein an impermeable material is provided between the riser pipe and the hole wall at a depth corresponding to the impermeable layer. The construction method of a groundwater level lowering system according to any one of claims 5 to 7, wherein the plurality of riser pipes are provided at predetermined intervals in a plane.

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