JP6480745B2 - How to install water injection wells - Google Patents

Description

  The present invention relates to a method for installing a water injection well. More specifically, for example, when excavating in a ground having a high groundwater level, the water injection well is installed to return groundwater pumped up to lower the groundwater level into the ground. Regarding the method.

  When excavating the ground to construct an underground structure, if the groundwater level is high, countermeasures such as a groundwater level lowering method or a chemical injection method are implemented. The groundwater level lowering method is a method for stabilizing the ground by pumping water from the ground and lowering the groundwater level at the necessary construction site. This groundwater level lowering construction method is a reliable groundwater countermeasure construction method against the waterstop construction method such as the chemical solution injection construction method, and is therefore excellent in safety especially in the construction under the railway.

  By the way, if the groundwater pumped up by the groundwater level lowering method is discharged into the sewers and rivers as it is, it will cause damage such as subsidence of the surrounding ground and lowering of the water level of the wells. For this reason, a method of returning the pumped groundwater to the ground, that is, a recharge method is widely implemented.

  In this recharge method, clogging occurs in the pore walls and filters of the water injection well due to suspended suspended solids, bacteria, and dissolved iron oxides contained in the groundwater. For this reason, the return efficiency is deteriorated, and in some cases, it may be forced to drain into a sewer or a river.

  Under such circumstances, the applicant has developed a condensate well structure that pressurizes the groundwater pumped up and returns it to the ground (see Patent Document 1). Since this well structure is a structure in which a large number of water injection holes are provided in the pipe wall of the water injection pipe itself, the pressurized return water is injected from the water injection hole toward the filter material layer at an increased flow rate. As a result, the strainer part and the filter material layer were not clogged.

  However, when the ground used as the water injection position is a hard ground layer such as a gravel layer, the return water does not enter the ground but rises around the well and springs up. And it became clear that such a phenomenon is remarkable especially when the ground on a hard ground layer is a soft ground layer.

Japanese Patent No. 4255462

The present invention has been made based on the technical background as described above, and achieves the following object.
The objective of this invention is providing the installation method of the water injection well which can prevent that the water injected into the ground springs.

The present invention employs the following means in order to achieve the above object.
That is, the present invention is a method for installing a water injection well when a hard ground layer composed of a gravel layer is used as a water injection position, and the ground above the hard ground layer is a soft ground layer ,
Over a predetermined depth range including the water injection position, the advance turbulent to the hard ground layer,
In the water injection well installation method, an improved body having a predetermined thickness is formed in advance so that the water injection well is surrounded in the soft ground layer .

  In order to disturb the hard ground, means for injecting high-pressure water can be employed.

More specifically, the present invention is a method for installing a water injection well with a hard ground layer composed of a gravel layer as a water injection position,
Drilling the ground with a casing pipe to the lower part of a predetermined depth range including the water injection position in the hard ground layer;
Inserting an injection pipe having an injection hole in the lower side wall into the casing pipe;
After the casing pipe is pulled up to above the predetermined depth range, it is pulled up while rotating the injection pipe, and at the same time, high-pressure water is injected from the injection hole, thereby disturbing the column-shaped disturbed ground over the predetermined depth range. Forming a region;
A step of drilling again with the casing pipe to the water injection position in the disturbed ground area after pulling out the injection pipe;
Inserting a water injection pipe into the casing pipe;
A step of introducing a well constituent material such as a filter material between the hole-drilling wall and the water injection pipe while pulling out the casing pipe;
It is in the installation method of the water injection well characterized by comprising.

  When the ground above the hard ground layer is a soft ground layer, after forming the disturbed ground region, in the soft ground layer in the middle of pulling out the spray pipe, pull up while rotating the spray pipe, simultaneously It is good to employ | adopt the structure provided with the process of injecting an improvement material from the said injection hole and producing the improvement body of predetermined thickness.

Furthermore, the present invention is more specifically a method for installing a water injection well having a hard ground layer composed of a gravel layer as a water injection position,
Drilling the ground with a casing pipe to the lower part of a predetermined depth range including the water injection position in the hard ground layer;
Inserting an injection pipe having an injection hole in the lower side wall into the casing pipe;
After the casing pipe is pulled up to above the predetermined depth range, it is pulled up while rotating the injection pipe, and at the same time, high-pressure water is injected from the injection hole, thereby disturbing the column-shaped disturbed ground over the predetermined depth range. Forming a region;
After pulling out the injection pipe, positioning the tip of the casing pipe in the disturbed ground region, leaving the casing pipe as a water injection pipe; and
It is in the installation method of the water injection well characterized by comprising.

  Even when this casing pipe is used as a water injection pipe, when the ground above the hard ground layer is a soft ground layer, the soft ground layer in the middle of pulling out the spray pipe after forming the disturbed ground region In the above, it is preferable to adopt a configuration including a step of pulling up while rotating the injection pipe and simultaneously forming an improved body having a predetermined thickness by injecting the improvement material from the injection hole.

  According to the present invention, when the water injection well is installed with the water injection position as the hard ground layer, the hard ground layer is disturbed in advance, so that the injected water can easily enter the disturbed ground region and prevent the ground water from springing. can do. Moreover, even if there is a soft ground layer above the hard ground layer, it is possible to prevent the injected water from flowing into the ground by creating an improved body in which the water injection well is surrounded in advance.

It is sectional drawing which shows 1st Embodiment of this invention. It is sectional drawing which shows 2nd Embodiment of this invention. FIG. 3 is a cross-sectional view showing a step that follows the step shown in FIG. 2. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows 4th Embodiment of this invention. It is sectional drawing which shows the example of the installed water injection well.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention. In the figure, the ground layer indicated by symbol H is a hard ground layer such as a gravel layer, and a water injection well is installed with this hard ground layer H as a water injection position. This water injection well is used, for example, as a condensate well in the recharge method, but is not limited thereto.

  At the time of construction, as shown in FIG. 1A, the ground is first drilled by the casing tube 1 until reaching the lower part of the predetermined depth range R including the water injection position. Next, as shown in FIG. 2B, the injection pipe 2 is inserted into the casing pipe 1. As the injection pipe 2, a triple pipe used in a high-pressure injection method known as one of ground improvement methods can be used. This triple pipe is a well-known one, and an injection hole for injecting high-pressure water, compressed air and a solidified material is provided on the side wall, although not shown.

  Next, as shown in FIG. 3C, after the casing pipe 1 is pulled up to above the predetermined depth range R, the jet pipe 2 is pulled up while rotating, and at the same time, high-pressure water is horizontally jetted from the jet holes (at this time). Compressed air may be injected so as to surround the high-pressure water using the function of the triple pipe). Thereby, the hard ground layer H is crushed and disturbed by the impact force of high-pressure water. After the hard ground layer H is disturbed over the predetermined depth range R by this high-pressure water jet to form a cylindrical disturbed ground region A, the jet pipe 2 is pulled out as shown in FIG. Then, the casing pipe 1 drills again up to the water injection position in the disturbed ground region A.

Next, the water injection pipe 4 is inserted into the casing pipe 1 as shown in FIG. Then, as shown in FIG. (F), while pulling the casing pipe 1, the well configuration material of the filter material or the like between the drilling wall 5 and water injection tube 4 was charged, water injection wells 10 in this manner Is installed.

  FIG. 6 is a cross-sectional view illustrating details of the water injection well 10 installed. This well structure is the same as that disclosed in Patent Document 1. That is, the water injection pipe 4 has a strainer portion 6 at the lower portion, and a large number of water injection holes 7 are provided on the peripheral wall of the strainer portion 6 over a predetermined length range. The installation position of the strainer section 6 corresponds to the water injection position referred to in this specification.

  A filter material layer 8 is formed around the strainer portion 6, a water shielding material layer 9 is formed on the filter material layer 8, and a sealing material layer 11 is further formed on the water shielding material layer 9. . The materials of the filter material layer 8, the water shielding material layer 9, and the sealing material layer 11 are described in detail in Patent Document 1.

  The water injection pipe 4 is connected to a ground line 13 having a pressure pump 12, and water pressurized by the pressure pump 12 is injected into the hard ground H through the water injection pipe 4 through the water injection hole 7 of the strainer section 6. The Since the hard ground H is formed with a ground area A that is disturbed over a predetermined depth range R including the installation position of the strainer section 6, that is, the water injection position, water enters the hard ground layer H without difficulty. Therefore, the injected water does not spring on the ground.

  2 and 3 are sectional views showing a second embodiment of the present invention. This embodiment is applied when the ground on the hard ground layer H is the soft ground layer S. At the time of construction, as shown in FIG. 2 (a), first, the ground is drilled by the casing tube 1 until reaching the lower part of the predetermined depth range R including the water injection position, and then the casing tube as shown in FIG. 2 (b). Each step of inserting the injection pipe 2 made of a triple pipe into 1 is the same as in the first embodiment.

  In this embodiment, after the injection pipe 2 is inserted, the casing pipe 1 is once pulled out as shown in FIG. Then, the injection pipe 2 is pulled up while rotating, and at the same time, high-pressure water is horizontally injected from the injection holes. When the cylindrical ground region A is formed over the predetermined depth range R by this high-pressure water jet, the spray pipe 2 is pulled up to the soft ground layer S as shown in FIG. In this soft ground layer S, the injection pipe 2 is pulled up while being rotated, and at the same time, the ground is crushed by injecting high-pressure water and compressed air from the injection holes in the same manner as the well-known ground improvement method, and the ground part is cemented. Inject improvement material. Thereby, the improvement body B of the predetermined thickness is created above the disturbed ground region A.

Next, as shown in FIG. 5E, the casing pipe 1 again drills holes up to the water injection position in the disturbed ground region A. At this time, naturally, the casing tube 1 penetrates the improved body B. Next, as in the first embodiment, as shown in FIG. 3 (f), the water injection pipe 4 is inserted into the casing pipe 1, and further, as shown in FIG. by introducing a well construction material of the filter material or the like between the hole wall 5 and the water injection pipe 4, water injection wells as illustrated in FIG. 6 in this manner is installed.

  According to this embodiment, since the water injection well 10 is surrounded by the improved body B in the soft ground layer S, the improved body B even if the injected water may rise along the circumference of the well. It is blocked by and does not spring on the ground.

  FIG. 4 is a sectional view showing a third embodiment of the present invention. In this embodiment, the casing pipe 1 is used as a water injection pipe. In the construction, as shown in FIG. 4 (a), the ground is first drilled by the casing pipe 1 until reaching the lower part of the predetermined depth range R including the water injection position, and then the casing pipe as shown in FIG. 4 (b). A jet pipe 2 composed of a triple pipe is inserted into 1.

  Next, as shown in FIG. 2C, after the casing pipe 1 was pulled up above the predetermined depth range R, the jet pipe 2 was pulled up while being rotated, and at the same time, high-pressure water was horizontally jetted from the jet holes and disturbed. Each process until the ground region A is formed is the same as that in the first embodiment. In this embodiment, as shown in FIG. 4D, the casing tube 1 is disposed so that the tip of the casing tube 1 is located in the ground region A where the tip is disturbed (in the drawing, located at the upper end of the region A). Leave it behind. That is, the casing pipe 1 is used as a water injection pipe.

  According to this embodiment, the water injection well which does not spring on the ground can be installed by a simple process. In the case of the embodiment in which the casing pipe 1 is used as a water injection pipe, as shown in FIG. 5 as the fourth embodiment, when the ground above the hard ground layer H is the soft ground layer S, the soft ground The improved body B may be formed on the layer S. In this case, in the step shown in FIG. 4C, after the casing tube 1 is once pulled out and the improved body B is formed on the soft ground layer S by the injection tube 2, the casing tube is moved to the water injection position in the disturbed ground region A. The hole is drilled again by 1 and the casing pipe 1 is used as a water injection pipe.

  The above embodiment is merely an example, and the present invention can take various aspects. For example, the structure of the water injection well shown in FIG. 6 is an example, and is not limited to this. Moreover, in each said embodiment, although high pressure water is injected in a horizontal direction, it is not limited to this, The case where high pressure water is injected in the diagonal direction is also included by this invention.

1: Casing pipe 2: Injection pipe 4: Water injection pipe 5: Hole wall 6: Strainer section 7: Water injection hole 8: Filter material layer 9: Water blocking material layer 10: Water injection well 11: Sealing material layer H: Hard ground layer A : Disturbed ground area S: Soft ground layer

Claims (6)

A method for installing a water injection well when a hard ground layer composed of a gravel layer is used as a water injection position and the ground above the hard ground layer is a soft ground layer ,
Over a predetermined depth range including the water injection position, the advance turbulent to the hard ground layer,
An installation method for a water injection well, wherein an improved body having a predetermined thickness is created in advance so that the water injection well is surrounded by the soft ground layer .   2. The water injection well installation method according to claim 1, wherein the hard ground layer is disturbed by injecting high-pressure water. A method for installing a water injection well with a hard ground layer composed of gravel layers as the water injection position,
Drilling the ground with a casing pipe to the lower part of a predetermined depth range including the water injection position in the hard ground layer;
Inserting an injection pipe having an injection hole in the lower side wall into the casing pipe;
After the casing pipe is pulled up to above the predetermined depth range, it is pulled up while rotating the injection pipe, and at the same time, high-pressure water is injected from the injection hole, thereby disturbing the column-shaped disturbed ground over the predetermined depth range. Forming a region;
A step of drilling again with the casing pipe to the water injection position in the disturbed ground area after pulling out the injection pipe;
Inserting a water injection pipe into the casing pipe;
A step of introducing a well constituent material such as a filter material between the hole-drilling wall and the water injection pipe while pulling out the casing pipe;
A method for installing a water injection well characterized by comprising: When the ground above the hard ground layer is a soft ground layer, after forming the disturbed ground region, in the soft ground layer in the middle of pulling out the spray pipe, pull up while rotating the spray pipe, simultaneously A method for installing a water injection well according to claim 3, further comprising: a step of injecting an improvement material from the injection hole to form an improvement body having a predetermined thickness. A method for installing a water injection well with a hard ground layer composed of gravel layers as the water injection position,
Drilling the ground with a casing pipe to the lower part of a predetermined depth range including the water injection position in the hard ground layer;
Inserting an injection pipe having an injection hole in the lower side wall into the casing pipe;
After the casing pipe is pulled up to above the predetermined depth range, it is pulled up while rotating the injection pipe, and at the same time, high-pressure water is injected from the injection hole, thereby disturbing the column-shaped disturbed ground over the predetermined depth range. Forming a region;
After pulling out the injection pipe, positioning the tip of the casing pipe in the disturbed ground region, leaving the casing pipe as a water injection pipe; and
A method for installing a water injection well characterized by comprising:   When the ground above the hard ground layer is a soft ground layer, after forming the disturbed ground region, in the soft ground layer in the middle of pulling out the spray pipe, pull up while rotating the spray pipe, simultaneously The method for installing a water injection well according to claim 5, further comprising: injecting an improvement material from the injection hole to form an improvement body having a predetermined thickness.

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