Strainer for groundwater level lowering method

Abstract

To provide a strainer for groundwater level lowering methods that has a simple structure and can be easily reconfigured to the optimal setting according to the site conditions. [Solution] A cylindrical strainer 1 for use in the deep well construction method, comprising a cylindrical pipe 10 and a mesh section 20, wherein multiple slits 11 for water passage are provided on the side of the cylindrical pipe at a predetermined height from the lower end of the cylindrical pipe on the side facing the ground, and an inner mesh 21 and an outer mesh 22 for preventing sand and gravel from entering are wrapped around the side circumference to cover the slits, and the mesh is fastened to the cylindrical pipe at multiple points from above with stainless steel hose clamps 23.

Description

Technical Field

[0001] The present invention relates to a strainer used at an excavation site of an underground structure or other places where it is necessary to forcibly lower the groundwater level, and particularly to a strainer for a groundwater level lowering method that can be recombined according to the appearance of sediment and gravel and realizes appropriate pump drainage.

Background Art

[0002] Conventionally, strainers used in the groundwater level lowering method basically have holes or slits provided in a cylindrical pipe. However, in such a so-called bare strainer, clogging may occur due to sediment and gravel, and conversely, sediment may sequentially flow into the pipe, in any case hindering proper drainage. Therefore, measures such as winding a cloth bag may be taken at the site, but in any case, there is a problem that it is difficult to achieve stable and proper drainage. In addition, it is possible to adopt a strainer with a complex structure, but there is a problem that a large number of strainers need to be embedded during the construction period, resulting in high costs.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made in view of the above, and an object thereof is to provide a strainer for a groundwater level lowering method that has a simple structure and can be easily recombined into an optimal configuration according to the situation at the site. Furthermore, the description of the problems that the above invention solves does not preclude the existence of other problems. Moreover, one aspect of this invention does not need to solve all of these problems. Other problems will naturally become clear from the description in the specification, drawings, and claims, and it is possible to extract other problems from the description in the specification, drawings, and claims. [Means for solving the problem]

[0005] The strainer described in claim 1 is a cylindrical strainer used in the deep well construction method, characterized in that a plurality of water-passing slits are provided on the side of the cylinder at a predetermined height from the lower end of the cylinder on the side that is positioned below ground level, and a mesh body for preventing sand and gravel from entering is wrapped around the side circumference so as to cover the slits, and the mesh body is fastened to the cylinder at multiple points from above with stainless steel bands.

[0006] The strainer according to claim 2 is the strainer according to claim 1, characterized in that the mesh body is made of resin mesh or resin-coated wire mesh, with at least one turn of mesh of 5.0 to 8.0 mesh on the inside and at least one turn of mesh of 3.0 to 5.0 mesh fastened on the outside.

[0007] The strainer according to claim 3 is characterized in that, in the strainer according to claim 1, the inner diameter of the strainer is 200 mm to 700 mm in diameter, the slit is rectangular and drilled so as to be rotationally symmetric with respect to the cylindrical axis and the longitudinal side is parallel to the cylindrical axis, the long side is 200 mm to 400 mm and the short side is 25 mm to 45 mm.

[0008] Strainers can also be referred to as strainer tubes, perforated casing tubes, etc. "Providing it at a predetermined height" means that, since the slit has a length, there is naturally a range. For example, it can be set at a height of 15 cm to 100 cm from the bottom end. Depending on the specifications, it may also be provided closer to the top end. The materials used for the strainer and mesh are not particularly limited, but it is preferable to use materials that are resistant to rust. The net does not prevent it from being wrapped around multiple times. The bands should preferably be easy to fasten and detach. For example, hose clamps, adjustable bands, and utility pole clamps can be used. The length of the strainer is not particularly limited; for example, strainers ranging from 3m to 30m can be used. [Effects of the Invention]

[0009] According to this invention, it is possible to provide a strainer for groundwater level lowering methods that has a simple structure and can be easily reconfigured to the optimal setting according to the site conditions. [Brief explanation of the drawing]

[0010] [Figure 1] This is a conceptual cross-sectional view of a deep well with the strainer of this invention embedded in it. [Figure 2] This is a diagram showing the configuration of the strainer of the present invention. [Modes for carrying out the invention]

[0011] The embodiments of this invention will be described in detail below with reference to the drawings. Here, we will describe the strainer used when draining water using the deep well method. Figure 1 is a conceptual cross-sectional view of a deep well with the strainer of this invention embedded. Although the figure shows a conceptual view with one strainer embedded, in reality, multiple strainers are embedded and drainage is performed. Figure 2 shows an example of the configuration of the strainer according to the present invention. Of these, Figure 2(a) is a front view, Figure 2(b) is a cross-sectional view AA of (a), and Figure 2(c) is a partially enlarged view of (b). Please note that, for the sake of explanation, the scale of any of the diagrams does not necessarily match the actual dimensions.

[0012] An example of the deep well construction method is as follows: <1. Drilling and Excavation> First, a hole for installing the well is dug vertically. For drilling, rotary boring or auger drilling can be used. The drilling diameter should be slightly larger than the outer diameter of Strainer 1 (35 cm). For example, adding 15 cm, a hole with a diameter of 50 cm will be drilled. In this example, the hole depth will be 6.8 m.

[0013] <2. Installation of the strainer> Next, the strainer 1 is lowered into the excavated hole using a crane or similar device. Here, the strainer 1 is a cylindrical iron pipe with an outer diameter of 35 cm, an inner diameter of 33 cm, and a length of 7 m. If the hole is deep, a cylindrical pipe of the same diameter is joined to the strainer 1 as needed using a special joint. As shown in Figure 2, the strainer 1 mainly consists of a cylindrical tube 10 and a mesh section 20. As mentioned above, the cylindrical tube 10 is an iron cylinder with an outer diameter of 35 cm, an inner diameter of 33 cm, and a length of 7 m. From 15 cm to 45 cm from the bottom end, and again from 55 cm to 85 cm, two slits 11 are made, each 30 cm long and 35 mm wide. Additionally, 12 slits 11 are made around the circumference at intervals of approximately 8.5 cm (with 30° rotational symmetry, resulting in a 12 slits × 2-stage configuration). Because the slit 11 is opened in a rotationally symmetrical manner, smooth and complete inflow of groundwater can be achieved from any direction. Furthermore, smooth and complete inflow can also be achieved by using a two-stage configuration. The mesh section 20 consists of an inner mesh 21, an outer mesh 22, and a hose clamp 23. Both the inner mesh 21 and the outer mesh 22 are polyvinyl chloride coated wire mesh. Here, the inner mesh 21 has a wire thickness of 0.7 mm and uses 6.5 mesh, while the outer mesh 22 has a wire thickness of 0.9 mm and uses 4 mesh. Each is made with a single winding. This mesh is fastened to the cylindrical pipe 10 from the outside with a hose clamp that is 2 cm wide and 2 mm thick. Incidentally, by looking at the state of the single strainer 1 that was struck first, the inner net 21 can be double-wound or the mesh size can be changed to configure it to respond to the site. The net part 20 is suitable because it has good operability by using the hose band 23 and the net can be easily replaced.

[0014] <3. Feeding of Filter Material> Next, gravel is poured into the gap between the strainer 1 and the excavation hole. This is to hold the strainer 1 and prevent fine earth and sand around it from entering the pipe. Since this gravel functions as a filter, it also helps to avoid pump failures and suppress ground settlement.

[0015] <4. Dewatering> After the above installation is completed, the muddy water and fine sand inside the strainer 1 are first discharged by a sand pump. This stabilizes the filter material and improves the water flow. <5. Installation of Submersible Pump> The submersible pump P is installed at the bottom inside the strainer 1. Note that it should be placed at a position lower than the planned water level so as not to cause an air operation. [[ID=1,7]] The water pumped out by the pump P is led to a drainage ditch or a sedimentation pond through the hose H. <6. Start of Pumping> After the above preparations, the pump P is operated throughout the day. This allows the groundwater level to be continuously kept low in subsequent construction work. Note that the actual lowering of the water level to the target value is confirmed by an observation well (not shown) provided around the site as appropriate. Also, it is regularly monitored whether the pumped water is mixed with earth and sand.

[0016] In the above construction method, the point of only draining water without sucking sand is important. This can be relatively easily achieved in a gravel layer, but in a layer with a lot of fine sand, the selection of the mesh of the strainer 1 becomes important. Therefore, in the field, the mesh and the number of windings of the net part 20 are appropriately changed so as not to accidentally lift sand.

[0017] According to this invention, a strainer for groundwater level lowering methods can be provided that has a simple structure and can be easily reconfigured to the optimal setting according to the site conditions, thereby enabling highly reliable construction work. [Industrial applicability]

[0018] The above explanation was given as an example of its use in deep well construction, but it can also be used, for example, when draining water from a pond of a certain depth, in order to prevent aquatic plants and sediment from entering. [Explanation of symbols]

[0019] 1 Strainer 10 Cylindrical tubes 11 slits 20 Amibe 21 Inner net 22 Outer mesh 23 Hose clamp

Claims

1. A cylindrical strainer used in the deep well construction method, Multiple water-permeable slits are provided on the side of the cylinder at a predetermined height from the lower end of the cylinder that is positioned below ground level. A strainer characterized by wrapping a mesh body around the side circumference to prevent sand and gravel from entering, so as to cover the slit, and then fastening the mesh body to the cylinder at multiple points from above with stainless steel bands.

2. The strainer according to claim 1, characterized in that the mesh body is made of resin mesh or resin-coated wire mesh, with at least one turn of 5.0 to 8.0 mesh mesh fastened to the inside and at least one turn of 3.0 to 5.0 mesh mesh fastened to the outside.

3. The inner diameter of the strainer is 200 mm to 700 mm. The strainer according to claim 1, characterized in that the slit is rectangular, is drilled so as to be rotationally symmetric with respect to the cylindrical axis and its longitudinal side is parallel to the cylindrical axis, with the long side being 200 mm to 400 mm and the short side being 25 mm to 45 mm.

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