Packer device and method for measuring groundwater pressure

Abstract

This invention provides a packer device that can be reliably installed even when the drilling distance of a borehole is long, and a method for measuring groundwater pressure using this packer device. [Solution] The system comprises a water sampling pipe 3 placed in a borehole BH, a front packer 4 surrounding the tip of the water sampling pipe 3, and a rear packer 5 surrounding the water sampling pipe 3 behind the front packer 4. The water sampling pipe 3 has a water passage 35 that guides spring water WG taken in from an intake port 33 that opens on the tip side of the front packer 4 toward the base end, a first packer passage 36 that guides water flowing in from an outlet port 34 that opens on the base side of the rear packer 5 toward the front packer 4, and a second packer passage 37 that guides a portion of the water that has flowed into the front packer 4 toward the rear packer 5. The second packer passage 37 is provided with a check valve 371 that prevents backflow of water that has flowed into the rear packer 5.

Description

Technical Field

[0001] The present invention relates to a packer device used for measuring water gushing pressure in tunnel construction and a method for measuring water gushing pressure.

Background Art

[0002] In tunnel construction, it is important to grasp in advance the geology in front of the face and the situation of the water gushing section for ensuring the stability of the ground and the safety management of the construction. As a method for exploring the geology in front of the face and the groundwater situation (hydrogeological characteristics, etc.), horizontal investigation boring may be carried out. When measuring the groundwater pressure by horizontal investigation boring, a packer is expanded near the water gushing section at the tip of the boring hole to separate it from other sections, and the water gushing in the water gushing section separated by the packer is measured.

[0003] As such a groundwater pressure measurement method, for example, there is a method disclosed in Patent Document 1. In the groundwater pressure measurement method of Patent Document 1, a pipe material having a packer at the tip is disposed at a predetermined position by pushing it in with a rod added to the base end side, and then the packer is expanded. The rod is formed by connecting a plurality of rod members (pipe materials).

[0004] However, in medium- and long-distance investigation boring with a long hole cutting distance (for example, 100 meters or more), the work of adding rods when inserting the packer and the work of removing rods when recovering the packer are time-consuming, and the water pressure in the water gushing section in front of the face cannot be measured quickly. Therefore, there are cases where horizontal investigation boring affects the construction period of tunnel construction or cases where detailed measurement of water gushing pressure has to be abandoned.

[0005] Therefore, the applicant discloses a packer device that can be easily installed and retrieved without being limited by the drilling distance of the borehole, comprising a water intake pipe, a switching valve connected to the base end of the water intake pipe, a base end channel connected to the water intake pipe via the switching valve, a front packer arranged around the water intake pipe and expanding at the tip of the borehole, a rear packer arranged around the water intake pipe behind the front packer and expanding inside the casing, and a packer channel from the switching valve to the front packer or rear packer (see Patent Document 2). In this packer device, the tip of the packer device is made to protrude from the tip of the casing by the pressure of water pumped from the borehole side of the casing, and then the switching valve is switched by increasing the water pressure and guiding the water into the packer channel to expand the front packer and rear packer and position them at the tip of the borehole. After that, the switching valve is returned to its original position by decreasing the pressure of the water pumped from the borehole side of the casing, and the groundwater is taken into the casing while maintaining the expanded state of the front packer and rear packer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-011622 [Patent Document 2] Japanese Patent Publication No. 2022-024800 [Overview of the project] [Problems that the invention aims to solve]

[0007] The technology described in Patent Document 2 involves using the pressure of water pumped from the casing's opening side to position a packer device at the tip of the casing and to expand the front and rear packers. However, when expanding the front and rear packers, the pressure inside the casing and the rear packer become equal, which may result in insufficient expansion of the rear packer.

[0008] The present invention aims to provide a packer device that can be installed more reliably even when the drilling distance of a borehole is long (for example, about 100 to 150 m), and a method for measuring groundwater pressure that can be used to quickly measure the groundwater pressure in the groundwater section ahead of the tunnel face, thereby enabling the tunnel construction to be resumed promptly. [Means for solving the problem]

[0009] To solve the aforementioned problems, the packer device of the present invention is provided at the tip of a drilling rod (casing) piped into a borehole to take in seepage water from the tip of the borehole into the casing, and comprises a water intake pipe positioned so as to protrude from the tip of the casing, a front packer provided around the tip of the water intake pipe and expanding at the tip of the borehole, and a rear packer provided around the water intake pipe behind the front packer and expanding within the casing. The water intake pipe has a water passage that guides seepage water taken in from an intake opening on the tip side of the front packer toward the base end, a first packer passage that guides water flowing in from an outlet opening on the base side of the rear packer toward the front packer, and a second packer passage that guides a portion of the water flowing into the front packer toward the rear packer. The second packer passage is provided with a check valve to prevent backflow of water flowing into the rear packer.

[0010] Furthermore, the present invention provides a method for measuring groundwater pressure, comprising: a drilling step of drilling a borehole and installing a casing in the borehole; an installation step of installing the packer device at the tip of the borehole; a measurement step of measuring the pressure of groundwater flowing into the borehole from the tip of the packer device; and an installation step of recovering the packer device. The installation step includes a casing retraction operation in which the casing is retracted to create a gap between the tip of the casing and the tip surface of the borehole; a packer device installation operation in which the tip of the packer device is positioned at the tip of the casing with the pressure of water pumped from the borehole side of the casing causing the tip of the packer device to protrude from the tip of the casing; and a packer expansion operation in which water pumped from the borehole side of the casing is guided into the first packer flow path to expand the front packer and expand the rear packer via the second packer flow path. Furthermore, in the measurement step, while maintaining the expanded state of the front and rear packers, the spring water taken in from the intake port is introduced into the casing via the water passage. In the packer expansion operation, it is desirable to expand the rear packer by repeatedly increasing and decreasing the pressure of the water pumped from the casing's opening side.

[0011] This packer device and the method for measuring groundwater pressure using this packer device make it possible to easily install and retrieve the packer device even when the drilling distance is long (for example, around 100-150m), and to quickly measure the water pressure in the groundwater section ahead of the tunnel face, allowing for a swift resumption of tunnel construction. In other words, by adjusting the water pressure inside the casing, it is possible to feed the packer device, expand the packer, and take in groundwater. Therefore, there is no need to use a pushing rod for the packer device, and the measurement of groundwater pressure at a predetermined position can be carried out quickly. Furthermore, during packer expansion work, water is supplied to the rear packer via a second packer channel equipped with a check valve, so that the water supplied to the rear packer does not flow back to the front packer side, and the expanded state of the rear packer can be maintained.

[0012] Furthermore, if the packer device is equipped with a pressure reduction mechanism, the pressure of the water supplied into the casing decreases in front of the pressure reduction mechanism. In other words, the pressure loss when the water supplied into the casing passes the pressure reduction mechanism causes the water pressure around the rear packer to decrease below the water pressure behind the pressure reduction mechanism, thus enabling more reliable expansion of the rear packer. Therefore, the installation of the packer device and the intake of groundwater can be carried out more reliably.

[0013] The pressure reduction mechanism preferably has a ring-shaped member that deforms to stand upright against the outer surface of the water intake pipe due to the pressure of the water pumped from the base end of the casing. The ring-shaped member may be a resin member with a V-shaped or L-shaped cross-section. Furthermore, it is even more preferable that the pressure reduction mechanism has multiple ring-shaped members arranged at intervals. This ensures that even if one of the ring-shaped members is damaged during the pumping of the packer device, at least one of the members will still function. With such a packer device, since the ring-shaped member deforms in response to the pressure of the water pumped into the casing, the water pressure around the rear packer is reduced by the pressure reduction mechanism when the rear packer is expanded, preventing the expansion of the rear packer from being hindered by the surrounding water pressure. By making the cross-sectional shape of the ring member V-shaped or L-shaped, the water pressure pumped from the hole side of the casing is efficiently received, and the function of quickly sending the packer device to the tip of the borehole is realized. Furthermore, it has the function of promoting an increase in water pressure inside the casing by reducing the gap (annulus) between the outer circumference of the packer device and the inner wall of the casing, thereby reducing water leakage from the bit tip. In addition, it exhibits excellent deformation of the ring-shaped member when the water pressure inside the casing is increased.

[0014] In addition, when a water intake pipe in which a first pipe and a second pipe are connected is adopted, by pulling the casing, the first packer flow path and the second packer flow path are separated, and water in the front packer and the rear packer is drained from the separated first packer flow path and second packer flow path, so that the front packer and the rear packer contract. That is, by simply applying a tensile force to the casing, the packer contracts and the packer device can be recovered, so that it can be recovered simply.

Effects of the Invention

[0015] According to the packer device and the water gushing pressure measurement method of the present invention, even when the drilling distance is a long distance (for example, about 100 to 150 m), it can be easily installed and recovered, and the water pressure in the water gushing section in front of the face can be quickly measured, and tunnel construction can be resumed promptly.

Brief Description of the Drawings

[0016] [Figure 1] It is a cross-sectional view showing an outline of the water gushing pressure measurement method. [Figure 2] It is a cross-sectional view showing a packer device according to an embodiment of the present invention. [Figure 3] It is an enlarged cross-sectional view showing a pressure reducing mechanism, (a) is normal, and (b) is deformed. [Figure 4] It is a flowchart showing a water gushing pressure measurement method using the packer device of the present embodiment. [Figure 5] It is a cross-sectional view showing an outline of the drilling process of the water gushing pressure measurement method. [Figure 6] It is a cross-sectional view showing the rod retraction operation in the device installation process. [Figure 7] It is a cross-sectional view showing the device pumping operation in the device installation process. [Figure 8] It is a cross-sectional view showing the device pumping operation in the device installation process following FIG. 7. [Figure 9] It is a cross-sectional view showing an outline of the packer expansion operation in the device installation process. [Figure 10] It is a cross-sectional view showing the device recovery process.

Best Mode for Carrying Out the Invention

[0017] In this embodiment, as shown in FIG. 1, in tunnel construction, when it is predicted that the tunnel T will cross a water gushing section G such as a fault or a crushed zone W a water pressure measurement method for grasping the water gushing situation in front of the face K when crossing and a packer device 1 used therefor will be described. Note that FIG. 1 is a cross-sectional view showing an outline of the water pressure measurement situation in tunnel construction. In the water pressure measurement method, a boring hole BH is formed from the face K of the tunnel T toward the water gushing section G W and the water gushing pressure is measured using this boring hole BH. The measurement of the water gushing pressure is performed at the base end (the hole opening of the boring hole BH) of the casing 2 by taking the water gushing from the tip of the boring hole BH into the casing 2 through the packer device 1 (FIG. 2).

[0018] FIG. 2 is a cross-sectional view showing the packer device 1 of this embodiment. As shown in FIG. 2, the packer device 1 is provided at the tip of the casing 2 piped in the boring hole BH, and is arranged so that the tip portion projects from the tip of the casing 2. It includes a water intake pipe 3, a front packer 4 provided around the tip of the water intake pipe 3 and expanding at the tip of the boring hole BH, and a rear packer 5 provided around the water intake pipe 3 behind the front packer 4 and expanding inside the casing 2. The packer device 1 is inserted into the casing 2 (drilling rod 21) when measuring the water gushing pressure, and is sent to the tip of the casing 2 (the tip of the boring hole BH) by the pressure of the water sent into the casing 2 from the base end (hole opening) side of the casing 2.

[0019] The water intake pipe 3 has a water flow path 35 that guides the water gushing WG taken in from the water intake port 33 opening on the tip side of the front packer 4 to the base end side, a first packer flow path 36 that guides the water flowing in from the outflow inlet 34 opening on the base end side of the rear packer 5 to the front packer 4, and a second packer flow path 37 that guides a part of the water flowing into the front packer 4 to the rear packer 5.

[0020] The water intake pipe 3 comprises a pipe body 30 and a first pipe material 31 and a second pipe material 32 arranged around the pipe body 30. The pipe body 30 is a pipe material that functions as a water passage channel 35 that guides the spring water WG taken in from the water intake port 33 which opens at its tip to the outlet port 34 which opens at its base. The pipe body 30 may be formed by connecting multiple pipe materials, or it may be composed of a single pipe material.

[0021] The first pipe member 31 and the second pipe member 32 are arranged around the main pipe body 30. That is, the main pipe body 30 is inserted into the first pipe member 31 and the second pipe member 32. The first pipe member 31 is positioned at the tip of the main pipe body 30, and the second pipe member 32 is connected to the rear end (the end on the hole side) of the first pipe member 31, while housing the rear part of the main pipe body 30. In addition, the first pipe member 31 is surrounded by a front packer 4, and the second pipe member 32 is surrounded by a rear packer 5.

[0022] The first pipe member 31 is slidable relative to the pipe body 30. The inner diameter of the first pipe member 31 is the same as the outer diameter of the pipe body 30, and the outer diameter of the first pipe member 31 is smaller than the inner diameter of the casing 2 (drilling rod 21 and drilling bit 22).

[0023] A front packer 4 is installed at the tip of the first pipe member 31. A step 311 is formed on the outer surface of the base end of the first pipe member 31, and an insertion portion 312 is formed on the base end side of the step 311. In other words, the insertion portion 312 is a reduced diameter portion formed at the rear end of the first pipe member 31.

[0024] The second pipe 32 is a bottomed pipe with its base end shielded and is fixed to the main pipe 30. A wire 7 extending from the opening is connected to the base end face of the second pipe 32. A housing portion 321 is formed at the tip of the second pipe 32. The inner diameter of the housing portion 321 is the same as the outer diameter of the insertion portion 312 of the first pipe 31, and the two pipes fit together when the insertion portion 312 is inserted into the housing portion 321. A connecting pin 39 protruding inward (towards the insertion portion 312) is fixed to the housing portion 321. The first pipe 31 and the second pipe 32 are connected via the connecting pin 39. The connecting pin 39 is made of, for example, a resin material or a metal material with a weak point (e.g., a notch) formed at the interface between the insertion portion 312 and the housing portion 321, and is configured to break at the interface between the insertion portion 312 and the housing portion 321 when a pulling force is applied between the first pipe material 31 and the second pipe material 32.

[0025] A rear packer 5 is installed around the middle section of the second pipe member 32. Furthermore, a flow path switching space 322 is formed inside the rear section of the second pipe member 32. The base end of the pipe body 30 fits into the flow path switching space 322. The flow path switching space 322 is a cavity with a width (inner diameter) larger than the inner diameter of the pipe body 30. A switching valve 8 is housed in the flow path switching space 322.

[0026] An inlet / outlet port 34 is open at the base end of the second pipe 32. The inlet / outlet port 34 is connected to the flow path switching space 322. In other words, the inlet / outlet port 34 is connected to the water flow path 35 via the flow path switching space 322.

[0027] The first pipe 31 and the second pipe 32 have a first packer channel 36 and a second packer channel 37 formed within them. The base end of the first packer channel 36 opens into the channel switching space 322, and the tip end opens inside the front packer 4. That is, the first packer channel 36 connects the inside of the first pipe 31 and the inside of the second pipe 32, is connected to the inlet / outlet 34 via the channel switching space 322, and is connected to the front packer 4 without opening inside the rear packer 5. The second packer channel 37 connects the inside of the first pipe 31 and the second pipe 32, and is a water passage connecting the front packer 4 and the rear packer 5. A check valve 371 is provided in the portion of the second packer channel 37 located inside the first pipe 31, which only allows flow from the front packer 4 to the rear packer 5 and prevents flow from the rear packer 5 to the front packer 4. This check valve 371 suppresses backflow of water that has flowed into the rear packer 5. Thus, the first packer channel 36 guides the water flowing in from the outlet 34, which opens at the base end, to the forward packer 4, and the second packer channel 37 guides the water in the forward packer 4 to the rear packer 5 (see Figure 9).

[0028] A switching valve 8 is provided in the flow path switching space 322. The switching valve 8 switches the connection between the inlet 34 and the first packer flow path 36 or the water flow path 35 based on the pressure of the water flowing in from the inlet 34. The switching valve 8 comprises a front part 81 capable of shielding the water flow path 35 of the pipe body 30, a cylindrical rear part 82 provided behind the front part 81 and having an outer shape equivalent to the cross-sectional shape of the flow path switching space 322, and a spring material 83 interposed between the front part 81 and the base end of the pipe body 30. The front part 81 is movable in the axial direction of the pipe body 30 within the flow path switching space 322. A water passage is formed on the outer circumferential surface of the front part 81. The rear part 82 is slidable on the inner circumferential surface of the second pipe material 32. A valve flow path 84 is formed in the rear part 82.

[0029] The switching valve 8 is movable forward and backward (left and right in Figure 2) within the flow path switching space 322. The rear part 82 of the switching valve 8 is biased backward by a spring material 83. Under normal conditions, the switching valve 8 has communication between the inlet / outlet 34 and the valve flow path 84 (water flow path 35). At this time, the opening of the first packer flow path 36 facing the flow path switching space 322 is shielded by the outer circumferential surface of the switching valve 8 (rear part 82). On the other hand, when the switching valve 8 moves forward and the rear end of the rear part 82 moves forward of the opening of the first packer flow path 36, the opening of the first packer flow path 36 is exposed and communication between the inlet / outlet 34 and the first packer flow path 36 is established.

[0030] The front packer 4 is positioned around the tip of the first pipe 31 (water sampling pipe 3). The front packer 4 is an annular tube that is continuous in the circumferential direction of the first pipe 31 and is made of a shrinkable material such as rubber. The front packer 4 expands outward from the first pipe 31 due to water (fluid) pumped through the first packer passage 36 (see Figure 9). Under normal conditions, the front packer 4 is reduced in diameter so that its outer surface does not come into contact with the inner surface of the casing 2 or the inner wall of the borehole BH (see Figure 7). On the other hand, when the front packer 4 expands at the tip of the borehole BH due to water, it comes into close contact with the inner wall of the borehole BH.

[0031] The rear packer 5 is located behind the front packer 4 and is circumferentially installed in the middle section of the second pipe material 32 (water intake pipe 3). The rear packer 5 is an annular tube that is continuous in the circumferential direction of the second pipe material 32 and is made of a shrinkable material such as rubber. The rear packer 5 expands outward from the second pipe material 32 by water pressurized from the front packer 4 via the second packer flow path 37 (see Figure 9). Under normal circumstances, the rear packer 5 is reduced in diameter so that its outer surface does not come into contact with the inner surface of the casing 2 (see Figure 7). On the other hand, when the rear packer 5 expands inside the casing 2 (drilling rod 21) due to water, it comes into close contact with the inner surface of the casing 2.

[0032] A pressure reducing mechanism 6 is provided on the outer surface of the second pipe material 32 (water sampling pipe 3). The pressure reducing mechanism 6 is positioned between the outlet 34 and the rear packer 5 and has the function of shielding or reducing the gap between the water sampling pipe 3 and the casing 2. Figure 3 shows the pressure reducing mechanism 6. As shown in Figures 3(a) and (b), the pressure reducing mechanism 6 has a ring-shaped member 61 that deforms to stand upright on the outer surface of the water sampling pipe 3 by the pressure of the water W pumped from the base end side of the casing 2. The ring-shaped member 61 in this embodiment is made of a resin member with a V-shaped or L-shaped cross-section. The pressure reducing mechanism 6 consists of a plurality of ring-shaped members 61, 61, ... arranged at intervals in the axial direction of the second pipe material 32.

[0033] Referring to the drawings, a method for measuring groundwater pressure using the packer device 1 will be described. The groundwater pressure measurement method is used, for example, when performing horizontal boring from the tunnel face K of the tunnel T and checking the groundwater pressure in the borehole BH to confirm the ground conditions ahead of the tunnel face. Figure 4 is a flowchart of the groundwater pressure measurement method of this embodiment. As shown in Figure 4, the groundwater pressure measurement method of this embodiment comprises a drilling step S1, an equipment installation step S2, a measurement step S3, and an equipment retrieval step S4.

[0034] Figure 5 is a cross-sectional view showing an overview of the drilling process S1. As shown in Figure 5, the drilling process S1 is a process of drilling into the ground G to form a borehole BH and arranging a drilling rod 21 (casing 2) in the borehole BH. In this embodiment, a drilling bit 22 is fixed to the tip of the drilling rod 21. The drilling bit 22 is an annular bit fixed to the tip of the drilling rod 21. The inner diameter of the drilling bit 22 is smaller than the inner diameter of the drilling rod 21, and the drilling bit 22 protrudes into the inside of the drilling rod 21. The drilling process S1 is performed with an inner bit 23 attached to the internal part of the drilling bit 22. When drilling the borehole BH, the drilling rod 21 is rotated while being struck around its central axis by the power of a boring machine (not shown), thereby cutting the entire cross-section of the ground G with the drilling bit 22 and the inner bit 23. In this embodiment, the borehole BH is formed approximately horizontally (including a state where the tip is higher than the base). However, the drilling direction of the borehole BH is not limited to approximately horizontal; for example, it may be drilled downward, upward, or vertically. Once a borehole BH of a predetermined length (depth) has been formed, the inner bit 23 is retrieved.

[0035] The equipment installation process S2 is the process of installing the packer device 1 at the tip of the borehole BH. In the equipment installation process S2, the water sampling pipe 3 is positioned so that its tip protrudes from the tip of the casing 2 (see Figure 2). In the equipment installation process S2, as shown in Figure 4, the first rod retraction operation S21, the packer device installation operation S22, and the packer expansion operation S23 are performed.

[0036] Figure 6 is a cross-sectional view showing an overview of the first rod retreat operation S21. In the first rod retreat operation S (casing retreat operation) 21, as shown in Figure 6, the drilling rod 21 (casing 2) is retreated to create a gap between the tip of the drilling rod 21 and the front surface (bottom) of the borehole BH. That is, the front part of the borehole BH becomes exposed to the ground G.

[0037] Figures 7 and 8 are cross-sectional views illustrating the outline of the packer device placement operation S22. In the packer device placement operation S22, as shown in Figure 7, the packer device 1 is pumped by the pressure of water W pumped from the hole side of the casing 2. The tip of the packer device 1 (first pipe material 31) protrudes from the tip of the casing 2, as shown in Figure 8. After the packer device 1 is transported to the tip of the casing 2 by water pressure, the locking portion 38 formed on the outer surface of the water sampling pipe 3 is locked to the drilling bit 22, so that the tip (first pipe material 31) remains protruding from the tip of the drilling bit 22.

[0038] Figure 9 is a cross-sectional view showing an overview of packer expansion operation S23. In packer expansion operation S23, as shown in Figure 9, the front packer 4 and the rear packer 5 are expanded. Specifically, once the packer device 1 is locked to the tip of the casing 2, the water pressure of the water W supplied into the casing 2 is increased. When the pressure of the water W is increased, the switching valve 8 moves forward due to the water pressure (the position of the switching valve 8 is switched). When the switching valve 8 moves forward, the rear end of the pipe body 30 is shielded by the front part 81 of the switching valve 8, and the first packer flow path 36 is exposed to the flow path switching space 322, so that the water W in the flow path switching space 322 is guided into the first packer flow path 36. As a result, water W is pressed into the front packer 4 via the first packer flow path 36. The front packer 4 expands due to the water pressure and adheres tightly to the inner wall of the borehole BH. In addition, some of the water guided into the front packer 4 is pressed into the rear packer 5 via the second packer flow path 37. The rear packer 5 expands due to water pressure and adheres tightly to the inner surface of the casing 2.

[0039] Furthermore, when the water pressure W is increased while the packer device 1 is locked to the tip of the casing 2, the ring-shaped member 61 surrounding the outer surface of the second pipe material 32 is erected by the water W, as shown in Figure 3(b). When the ring-shaped member 61 is erected, the gap between the water intake pipe 3 and the casing 2 is shielded or reduced. As a result, the amount of water W guided around the rear packer 5 inside the casing 2 is reduced, and the water pressure (external pressure) acting around the rear packer 5 is reduced, so the expansion of the rear packer 5 is less likely to be hindered by external pressure.

[0040] Furthermore, even if the pressure of the water W in the gap between the casing 2 and the rear packer 5 (external pressure) acts on the rear packer 5, a check valve 371 is provided in the second packer passage 37, so the water W in the rear packer 5 does not flow back into the front packer 4, and the rear packer 5 does not shrink. If the expansion of the rear packer 5 is affected by the pressure of the water W in the casing 2, the rear packer 5 is expanded and made to tightly adhere to the inner surface of the casing 2 by repeatedly increasing and decreasing the pressure of the water W supplied from the hole side of the casing 2. Specifically, when the pressure of the water W supplied to the casing 2 is reduced when the front packer 4 is sufficiently expanded, the water pressure inside the casing 2 decreases, and the external pressure acting on the rear packer 5 also decreases. At this time, the pressure inside the front packer 4 is higher than the water pressure inside the casing 2, so the water W inside the front packer 4 is supplied to the rear packer 5 via the second packer passage 37. Subsequently, the forward packer 4 is expanded by increasing the pressure of the water W being pumped from the port side of the casing 2 again. By repeatedly increasing and decreasing the pressure of the water W being pumped from the port side of the casing 2 in this manner, the forward packer 4 and the rear packer 5 can be raised to the target expansion pressure.

[0041] In measurement step S3, the spring water WG flowing into the borehole BH is collected from the tip of the packer device 1 (water sampling pipe 3), and the pressure of the spring water WG is measured (see Figure 2). In measurement step S3, the pressure of the water W being pumped from the borehole side is reduced. When the pressure of the water W becomes less than the pressure of the spring water WG, the switching valve 8 returns to its original position due to the pressure of the spring water WG taken into the water sampling pipe 3 and the reaction force of the spring material 83 (see Figure 2). Here, as shown in Figure 2, the front packer 4 is in close contact with the inner wall of the borehole BH, preventing the spring water WG generated at the tip of the borehole BH from flowing out behind the front packer 4, thus guiding the spring water WG into the pipe body 30. Also, when the switching valve 8 returns to its original state, the base end side of the first packer flow path 36 is shielded, preventing the outflow of water W from the front packer 4, and allowing the spring water WG to be taken in while maintaining the expanded state of the front packer 4 and the rear packer 5. The spring water WG, taken in from the tip of the pipe body 30, passes through the switching valve 8 from the pipe body 30, is taken into the casing 2 via the outlet 34, and is guided to the hole opening. At the hole opening of the casing 2, the spring water pressure is measured using a pressure gauge or the like.

[0042] The equipment retrieval process S4 is the process of retrieving the packer equipment 1. Figure 10 shows an overview of the equipment retrieval process S4. In the equipment retrieval process S4, first, as shown in Figure 10, the casing 2 is pulled toward the borehole opening to retract the casing 2 (second rod retraction operation S41). At this time, the front packer 4 and the rear packer 5 are maintained in an expanded state. Because the rear packer 5 is in close contact with the casing 2, when the casing 2 is retracted, the second pipe material 32 retracts together with the casing 2. On the other hand, the first pipe material 31 is maintained in a fixed state in the borehole BH because the front packer 4 is expanded and in close contact with the inner surface of the borehole BH. As a result, the connecting pin 39 is cut by the force (tensile force) that retracts the casing 2, and the first pipe material 31 and the second pipe material 32 are separated. When the first pipe material 31 and the second pipe material 32 are separated, the first packer flow path 36 and the second packer flow path 37 are separated. When the first packer channel 36 and the second packer channel 37 are separated, the water W in the front packer 4 and the water W in the rear packer 5 flow out from this section, causing the front packer 4 and the rear packer 5 to shrink. Subsequently, the packer device 1 is recovered by winding up the wire 7 with a winch or the like (not shown) (device extraction operation S42).

[0043] According to the packer device 1 of this embodiment and the groundwater pressure measurement method using this packer device 1, even when the drilling distance is long (for example, about 100 to 150 m), the packer device 1 can be easily installed and retrieved, and the water pressure in the groundwater section ahead of the tunnel face can be quickly measured, allowing tunnel construction to be resumed promptly. In other words, by adjusting the water pressure inside the casing 2, it is possible to feed in the packer device 1, expand the packers (front packer 4 and rear packer 5), and take in the groundwater. Therefore, there is no need to use a pushing rod for the packer device 1, and the groundwater pressure at a predetermined position can be measured quickly.

[0044] Since a check valve 371 is provided in the second packer passage 37, water supplied to the rear packer 5 does not flow back into the front packer. Therefore, even if external pressure acts on the rear packer 5, the contraction of the rear packer 5 is suppressed, and the expansion of the rear packer 5 can be performed more reliably.

[0045] Thus, by utilizing the first packer channel 36 and the second packer channel 37 equipped with a check valve 371, the forward packer 4 and the rear packer 5 can be sufficiently expanded, and the expansion pressure can be maintained at a high level. As a result, the hydraulic pumping type packer device 1 can be applied even in ground with relatively high ground pressure (for example, 2.0 to 3.0 MPa). Therefore, groundwater investigation using simple and rapid horizontal boring becomes possible under a wider range of ground conditions, and consequently, safe and reliable tunnel construction can be carried out.

[0046] Furthermore, because the packer device 1 is equipped with a pressure reduction mechanism 6, the pressure of the water sent into the casing 2 decreases in front of the pressure reduction mechanism 6. Specifically, in response to the pressure of the water W pumped into the casing 2, the ring-shaped member 61 deforms (stands upright), shielding or reducing the gap between the water intake pipe 3 and the casing 2, causing a pressure loss when the water sent into the casing 2 exceeds the pressure reduction mechanism 6. This pressure loss reduces the water pressure around the rear packer 5 to less than the water pressure behind the pressure reduction mechanism 6, thus enabling more reliable expansion of the rear packer 5. Therefore, the installation of the packer device 1 and the intake of groundwater can be carried out more reliably.

[0047] Furthermore, since the pressure reduction mechanism 6 is provided with multiple ring-shaped members 61, even if some of the ring-shaped members 61 are damaged during pumping by the packer device 1, the damage can be compensated for by any of the other ring-shaped members 61. Because the cross-sectional shape of the ring-shaped member 61 is V-shaped or L-shaped, it efficiently receives the water pressure from the borehole side of the casing 2, enabling it to quickly feed the packer device 1 to the tip of the borehole. Furthermore, the deformation performance of the ring-shaped member 61 when the water pressure inside the casing 2 is increased is excellent.

[0048] Furthermore, by pulling the casing 2, the first pipe 31 and the second pipe 32 are separated, and the water W inside the front packer 4 and the rear packer 5 is drained through the separated first packer channel 36 and the second packer channel 37, causing the front packer 4 and the rear packer 5 to contract. In this way, the packers (front packer 4 and rear packer 5) contract simply by applying tensile force to the casing 2 from the hole side, making it possible to recover the packer device 1, thus allowing for easy recovery.

[0049] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and each of the above-mentioned components can be modified as appropriate without departing from the spirit of the present invention. For example, the pressure reduction mechanism 6 may be provided as needed. Furthermore, the configuration of the pressure reduction mechanism 6 is not limited and can be determined as appropriate. For example, the number and arrangement of the ring-shaped members 61 can be determined as appropriate. Also, the cross-sectional shape of the ring-shaped members 61 is not limited to L-shape or V-shape. Moreover, the pressure reduction mechanism 6 does not necessarily have to be composed of resin ring-shaped members 61.

[0050] The water sampling pipe 3 does not necessarily have to include a pipe body 30, a first pipe material 31, and a second pipe material 32, and the configuration of the water sampling pipe 3 is not limited. The configuration of the locking portion 38 on the outer surface of the second pipe material 32 is not limited and may be, for example, a step that locks onto the drilling rod 21, or a projection that locks onto the drilling rod 21.

[0051] In the above embodiment, the boring hole BH is formed by the drilling rod 21, thereby simultaneously drilling the boring hole BH and installing the casing 2. However, the installation of the casing 2 may be performed separately from the drilling of the boring hole BH, after the boring hole BH has been formed. In the drilling embodiment, the case in which the entire cross-section is cut with the inner bit 23 attached to the drilling bit 22 was described. However, when taking a boring core, a core barrel may be attached to the drilling bit 22 instead of the inner bit 23.

[0052] In the above embodiment, the case in which the wire 7 is connected to the base end of the second pipe 32 was described, but the method of connecting the wire 7 is not limited. Also, the wire 7 may be detachable from the water sampling pipe 3. [Explanation of symbols]

[0053] 1 Packer device 2 Casing 21 Drilling Rod 3 Water sampling pipe 30 Pipe body 31 First pipe material 32 Second pipe material 33 Water intake 34 Outlet 35 Water passage 36 First packer channel 37 Second packer channel 371 Check valve 4. Front Packer 5. Rear Packer 6. Pressure reduction mechanism 7 wires 8. Switching valve BH borehole G Ground T Tunnel W water WG Spring Water

Claims

1. A packer device provided at the tip of a casing piped into a borehole, for drawing in seepage water from the tip of the borehole into the casing, A water sampling pipe is positioned so that its tip protrudes from the tip of the casing, A front packer is provided around the tip of the water intake pipe and expands at the tip of the borehole, The system comprises a rear packer that is positioned behind the front packer, surrounding the water intake pipe, and expanding within the casing, The aforementioned water intake pipe has a water passage that guides the spring water taken in from the intake opening which is located at the tip end of the front packer toward the base end, A first packer channel guides water flowing in from an outlet opening on the proximal end side of the rear packer to the front packer, It has a second packer channel that guides a portion of the water that flows into the front packer to the rear packer, A packer device characterized in that the second packer passage is provided with a check valve to prevent backflow of water that has flowed into the rear packer.

2. The packer device according to claim 1, characterized in that a pressure reduction mechanism is provided on the outer surface of the water sampling pipe between the outlet and the rear packer, which shields or reduces the gap between the water sampling pipe and the casing.

3. The packer device according to claim 2, characterized in that the pressure reduction mechanism has a ring-shaped member that deforms to stand upright on the outer surface of the water intake pipe by the pressure of water pumped from the base end side of the casing.

4. The packer device according to claim 3, characterized in that the ring-shaped member is a resin member having a V-shaped or L-shaped cross-section.

5. The packer device according to claim 3, characterized in that the pressure reduction mechanism is provided by a plurality of ring-shaped members arranged at intervals from each other.

6. The water intake pipe comprises a first pipe member on which the front packer is arranged around it, and a second pipe member on which the rear packer is arranged around it. The first pipe member and the second pipe member are connected such that they separate when a tensile force is applied to the casing from the opening side while the front packer and the rear packer are expanded. The packer device according to claim 1, characterized in that the first packer channel and the second packer channel are separated when the first pipe material and the second pipe material are separated.

7. A drilling step in which a borehole is drilled and a casing is placed in the borehole, A device installation step of installing the packer device according to any one of claims 1 to 6 at the tip of the borehole, A measurement step of measuring the pressure of the seepage water flowing into the borehole from the tip of the packer device, A method for measuring spring water pressure, comprising a device retrieval step for retrieving the packer device, In the aforementioned equipment installation process, A casing retraction operation is performed to retract the casing to create a gap between the tip of the casing and the tip surface of the borehole, A packer device placement operation in which the tip of the packer device is positioned at the tip of the casing with the pressure of water pumped from the hole side of the casing causing the tip of the packer device to protrude from the tip of the casing, A packer expansion operation is performed in which water pumped from the opening side of the casing is guided into the first packer passage to expand the front packer, and the rear packer is expanded via the second packer passage, Perform A method for measuring spring water pressure, characterized in that, in the measurement step, spring water taken in from the water intake is taken into the casing via the water passage while maintaining the expanded state of the front packer and the rear packer.

8. The method for measuring groundwater pressure according to claim 7, characterized in that the rear packer is expanded by repeatedly increasing and decreasing the pressure of the water pumped from the opening side of the casing during the packer expansion operation.

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