Water pressure measuring device and water pressure measuring method

Abstract

To propose a spring water pressure measurement device and a spring water pressure measurement method that make it possible to shorten the time required to recover a packer that is pumped using water pressure and placed at a tip of a borehole, and also to shorten the time required to measure groundwater pressure.SOLUTION: A spring water pressure measurement device 1 includes a packer device 2 that is installed at a tip of a borehole pipe 5 disposed in a borehole H and takes spring water at the tip of the borehole pipe 5 into the borehole pipe 5, a branch pipe 3 attached to a base end of the borehole pipe 5, and a water pressure gauge 4 attached to the branch pipe 3. The branch pipe 3 is branched into a water pipe 31 disposed coaxially with the borehole pipe 5 and a wire line pipe 32 branched from the water pipe 31. A wire 6 extending into the borehole pipe 5 is connected to the packer device 2 via a wire line pipe 32.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a groundwater pressure measuring device and a groundwater pressure measuring method used for measuring groundwater pressure in tunnel construction. [Background technology]

[0002] In tunnel construction, understanding the geological conditions and groundwater seepage ahead of the tunnel face is crucial for ensuring the stability of the ground and managing construction safety. Horizontal boring is sometimes used as a method for exploring the geological conditions and groundwater conditions (hydraulic characteristics, etc.) ahead of the tunnel face. When measuring groundwater pressure using horizontal investigation boring, the packer is expanded near the seepage section at the tip of the borehole to separate it from other sections, and the water pressure of the seepage is measured in the seepage section separated by the packer. One such method for measuring groundwater pressure is the method disclosed in Patent Document 1. In the groundwater pressure measurement method of Patent Document 1, a pipe material having a packer at its tip is positioned in a predetermined location by pushing it in with a rod extended to the base end, and then the packer is expanded. However, in medium- to long-distance exploratory borings with drilling distances of 100 meters or more, the process of extending the rod when inserting the packer and removing the rod when retrieving the packer is time-consuming, making it impossible to quickly measure the water pressure in the seepage area ahead of the drilling face. Therefore, Patent Document 2 discloses a method for measuring groundwater pressure that enables increased work efficiency by using water pressure to pump a packer into the borehole, measuring the groundwater pressure, and then retrieving it using a wire line. In the groundwater pressure measurement method of Patent Document 2, the packer is retrieved by pumping a retrieval device attached to the end of a wire into the borehole using water pressure, fitting it onto the rear end of the packer, and then winding up the wire. However, the drainage channel from the tip of the borehole is smaller than the channel through which the recovery device is pumped, which limits the amount of water that can be pumped to the tip of the borehole, thus making it time-consuming to pump the recovery device. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-011622 [Patent Document 2] Japanese Patent Publication No. 2022-024800 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention aims to propose a groundwater pressure measuring device and method that enable a reduction in the time required for packer retrieval, and consequently, a reduction in the time required for groundwater pressure measurement, in relation to a groundwater pressure measuring method using a packer that is pumped by water pressure. [Means for solving the problem]

[0005] To solve the aforementioned problems, the present invention provides a groundwater pressure measuring device comprising a packer device for drawing groundwater from a drilling pipe installed in a borehole into the drilling pipe, a branch pipe attached to the base end of the drilling pipe, a drifter attached to the base end of the branch pipe, and a water pressure gauge attached to the branch pipe. The branch pipe is branched into a water supply pipeline installed coaxially with the drilling pipe and a wire line pipeline branched from the water supply pipeline. The packer device is installed at the tip of the drilling pipe by being pumped by water pressure, and a wire extending into the drilling pipe is connected to the packer device via the wire line pipeline. The water pressure gauge is provided in a drainage pipeline branched from the water supply pipeline. Furthermore, the present invention's method for measuring groundwater pressure comprises a drilling step of drilling a borehole and installing the drilling pipe in the borehole, an installation step of installing the groundwater pressure measuring device in the borehole, a measurement step of measuring the pressure of the groundwater at the tip of the borehole, and an installation step of recovering the packer device. In the installation step, the branch pipe is attached to the base end of the drilling pipe, and the packer device is installed at the tip of the drilling pipe. In the measurement step, the water pressure of the groundwater taken into the drilling pipe via the packer device is measured using the pressure gauge. In the installation step, the packer device is recovered by winding up the wire.

[0006] With this groundwater pressure measuring device and method, since the wire is pre-connected to the packer device, there is no need to individually feed the wire into the borehole. Therefore, the time required to connect the wire to the packer device, which was necessary in conventional groundwater pressure measuring methods, can be eliminated. Furthermore, since the wire is inserted through the wire line conduit of the branch pipe, the wire connected to the packer device can be fed in and wound up even when a drifter, a device having a rotating mechanism and a striking mechanism, is attached to the branch pipe (water supply conduit). [Effects of the Invention]

[0007] The groundwater pressure measuring device and method of the present invention make it possible to shorten the time required for packer recovery, and consequently, shorten the time required for groundwater pressure measurement. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing a spring water pressure measuring device according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view showing a packer device, where (a) is in the normal state and (b) is in the packer expansion state. [Figure 3] This is a cross-sectional view showing a branch pipe. [Figure 4](a) to (c) are cross-sectional views showing examples of the water stop member. [Figure 5] (a) is a flowchart showing the operation procedure of the water gushing pressure measurement method, (b) is a flowchart showing the operation procedure of the device installation process of the water gushing pressure measurement method, and (c) is a flowchart showing the operation procedure of the device recovery process of the water gushing pressure measurement method. [Figure 6] It is a cross-sectional view showing an overview of the drilling process, where (a) is the drilling situation and (b) is the inner bit recovery situation. [Figure 7] It is a cross-sectional view showing the device installation process, where (a) is the operation from the drilling pipe retraction operation to the device installation operation, and (b) is the device installation operation following (a). [Figure 8] It is a cross-sectional view showing the device installation process, where (a) is the device installation operation following Fig. 7(b), and (b) is the packer expansion operation. [Figure 9] It is a cross-sectional view showing an overview of the measurement process. [Figure 10] It is a cross-sectional view showing an overview of the drilling pipe retraction operation in the device recovery process. [Figure 11] It is a cross-sectional view showing an overview of the wire winding operation in the device recovery process. [Figure 12] It is a cross-sectional view showing an overview of the device recovery operation in the device recovery process.

Embodiments for Carrying out the Invention

[0009] In this embodiment, in tunnel construction where water gushing is predicted, a case of grasping the water gushing situation of the ground G in advance using the water gushing pressure measurement device 1 will be described. Fig. 1 shows the water gushing pressure measurement device 1 of this embodiment. As shown in Fig. 1, the water gushing pressure measurement device 1 includes a packer device 2, a branch pipe 3, a water pressure gauge 4, and a wire 6. The packer device 2 is provided at the tip of the drilling pipe 5 disposed in the boring hole H. The tip of the packer device 2 protrudes from the tip of the drilling pipe 5 and takes in the water gushing at the tip of the drilling pipe 5 into the drilling pipe 5. A wire 6 extending in the drilling pipe 5 is connected to the base end of the packer device 2. Figure 2 shows the packer device 2. As shown in Fig. 2(a), the packer device 2 includes a front packer 21, a rear packer 22, and a water intake pipe 23. The packer device 2 is inserted into the perforation pipe 5 when measuring the water gushing pressure at the tip of the perforation pipe 5, and is sent into the tip of the perforation pipe 5 (the tip of the boring hole H) by the pressure of the water sent into the perforation pipe 5 from the wellhead side of the perforation pipe 5. Further, after measuring the water gushing pressure, the packer device 2 can be recovered from the tip of the perforation pipe 5 by winding up the wire 6 (see Fig. 1).

[0010] The front packer 21 is an annular member provided around the water intake pipe 23 and is made of a material having shrinkability such as rubber. The front packer 21 expands outwardly of the water intake pipe 23 by the water (fluid) pumped through the water intake pipe 23. Normally, the front packer 21 is contracted on the outer surface of the water intake pipe 23 so that the protruding height from the outer surface of the water intake pipe 23 is minimized, as shown in Fig. 2(a). On the other hand, when the front packer 21 expands by water, it protrudes outside the outer peripheral surface of the water intake pipe 23, as shown in Fig. 2(b). The front packer 21 expands at the tip of the boring hole H to adhere to the inner wall of the boring hole H and shield the gap between the packer device 2 and the boring hole H.

[0011] The rear packer 22 is provided around the water intake pipe 23 behind the front packer 21. The rear packer 22 is an annular member made of a material having shrinkability such as rubber. The rear packer 22 expands outwardly of the water intake pipe 23 by the water pumped through the water intake pipe 23. Normally, the rear packer 22 is contracted so that the protruding height from the outer surface of the water intake pipe 23 is minimized, as shown in Fig. 2(a). On the other hand, when the rear packer 22 expands by water, it protrudes outside the outer peripheral surface of the water intake pipe 23, as shown in Fig. 2(b). The rear packer 22 expands in the perforation pipe 5 to adhere to the inner surface of the perforation pipe 5 and shield the gap between the perforation pipe 5 and the packer device 2.

[0012] As shown in Figures 2(a) and (b), the water intake pipe 23 comprises an inner pipe 24, a first outer pipe 25 and a second outer pipe 26 arranged around the inner pipe 24, and a base end member 28. The inner pipe 24 is a pipe material that functions as a channel for collecting groundwater from the tip and transporting it to the rear (hole side). The inner pipe 24 is inserted into the first outer pipe 25 and the second outer pipe 26. A front packer 21 is installed around the tip of the inner pipe 24. The first outer pipe 25 is positioned around the tip of the inner pipe 24 and behind the front packer 21. The inner diameter of the first outer pipe 25 is larger than the outer diameter of the inner pipe 24, and a gap 25a is formed between the inner pipe 24 and the first outer pipe 25. This gap 25a communicates with the front packer 21 adjacent to the front end surface of the first outer pipe 25 and functions as a packer channel for supplying water to the front packer 21. In this embodiment, a stepped portion 25b with a reduced outer diameter is formed at the base end of the first outer pipe 25, and the tip of the second outer pipe 26 (stepped portion 26c) is superimposed on the outer surface of this stepped portion 25b.

[0013] The second outer tube 26 is positioned around the inner tube 24 at the rear (hole side) of the first outer tube 25. A rear packer 22 is also positioned around the longitudinal center of the second outer tube 26. At the tip of the second outer tube 26 (further forward than the rear packer 22), a stepped portion 26c is formed, with an enlarged inner diameter, so as to overlap with the stepped portion 25b of the first outer tube 25. The first outer tube 25 and the second outer tube 26 are connected via a connecting pin 23a at the overlapping portion of the stepped portion 25b and the stepped portion 26c. Furthermore, the second outer tube 26 has an inner diameter equivalent to that of the first outer tube 25 in the section between the stepped portion 26c and the rear packer 22, and an inner diameter equivalent to the outer diameter of the inner tube 24 at the base end side of the rear packer 22. In addition, a portion of the base end of the second outer tube 26 protrudes towards the hole side beyond the base end of the inner tube 24. An outer pipe water channel 26a is formed in the pipe wall at the base end of the second outer pipe 26. The base end of the outer pipe water channel 26a opens into the inner surface of the second outer pipe 26 on the hole side of the base end of the inner pipe 24. On the other hand, the tip of the outer pipe water channel 26a communicates with the rear packer 22. That is, the outer pipe water channel 26a functions as a packer channel for supplying water to the rear packer 22. In addition, the gap 26b between the inner pipe 24 and the second outer pipe 26 in the section between the rear packer 22 and the stepped section 26c communicates with a drain port formed on the front of the rear packer 22 and is continuous with the gap 25a between the inner pipe 24 and the second outer pipe 26, and functions as a packer channel for supplying water to the front packer 21.

[0014] The base end member 28 is provided at the base end of the water intake pipe 23. The base end member 28 shields the base end side (the borehole side of the borehole H) of the space (flow channel switching section 27) enclosed by the base end of the inner pipe 24 and the second outer pipe 26. A water passage 27a opening to the outer surface of the water intake pipe 23 is formed at the boundary between the base end member 28 and the second outer pipe 26. The water passage 27a is a flow channel that connects the flow channel switching section 27 to the outside of the water intake pipe 23. A switching valve 27b is provided in the flow channel switching section 27. The switching valve 27b switches between the connection of the inner cavity 24a of the inner pipe 24 to the water passage 27a and the connection of the packer flow channel (outer pipe water passage 26a) to the water passage 27a. In other words, the switching valve 27b functions as a means to switch between a state in which groundwater can be collected via the inner pipe 24 and a state in which water can be supplied to the front packer 21 and the rear packer 22.

[0015] The packer flow path is a flow path from the flow path switching section 27 to the rear packer 22 and the front packer 21. The packer flow path consists of an outer pipe water passage 26a from the flow path switching section 27 to the rear packer 22, and gaps 25a and 26b from the rear packer 22 to the front packer 21. In this way, the packer flow path guides the water taken in by the water passage 27a to the rear packer 22, and then guides the water discharged from inside the rear packer 22 to the front packer 21.

[0016] As shown in Figure 1, the branch pipe 3 is attached to the base end of the drilling pipe 5 at the opening of the borehole H. Figure 3 shows the branch pipe 3. As shown in Figure 3, the branch pipe 3 comprises a water supply pipeline 31 arranged coaxially with the drilling pipe 5, a wire line pipeline 32 branched from the water supply pipeline 31, and a drainage pipeline 33 branched from the water supply pipeline 31. The water supply pipeline 31 consists of a hollow straight pipe, with its tip connected to the base end of the drilling pipe 5. A drifter 7 is connected to the base end of the water supply pipeline 31 (branch pipe 3). The drifter 7 is a device that has a rotation mechanism to impart rotational force to the drilling pipe via the branch pipe 3 during drilling, a striking function to apply impact during drilling, and a water supply function to supply water when sending the packer device 2, etc., to the tip of the drilling pipe 5.

[0017] The wire line conduit 32 is a conduit branched off from the water supply conduit 31 in the longitudinal middle section. A wire 6 connected to the packer device 2 is inserted through the wire line conduit 32 (see Figure 1). A water-sealing member 34 through which the wire 6 can be inserted is attached to the base end of the wire line conduit 32, thereby suppressing the outflow of water from the branch pipe 3. The water-sealing member 34 is designed to allow the wire 6 to be inserted and to ensure watertightness. An example of the water-sealing member 34 is shown in Figure 4. The water-sealing member 34 may be, for example, a screw-on cap as shown in Figure 4(a). A packing 35 is provided around the wire 6 at the base end of the wire line conduit 32, and the packing 35 is compressed by the water-sealing member 34 (cap), causing the packing 35 to adhere tightly to the water-sealing member 34 and improving watertightness. Alternatively, the water-sealing member 34 may be a hollow rubber material provided at the base end of the wire line conduit 32, as shown in Figure 4(b). In this case, water is injected into the water-stopping member 34 (rubber material) under pressure, and the outer surface of the expanded water-stopping member 34 is pressed tightly against the inner surface of the wire line conduit 32 to stop the water flow. Alternatively, if the wire 6 is cut and does not protrude from the wire line conduit 32, the base end of the wire line conduit 32 can be shielded with a cap-shaped water-stopping member 34, as shown in Figure 4(c).

[0018] As shown in Figure 3, the pressure gauge 4 is attached to the branch pipe 3 and measures the water pressure of the spring water taken into the drilling pipe 5. In this embodiment, the pressure gauge 4 is installed in the drainage pipe 33. The drainage pipe 33 is branched off from the water supply pipe 31 in the middle of its longitudinal direction. A valve 36 is provided in the drainage pipe 33. The valve 36 opens and closes the drainage pipe 33 and controls the drainage and shut-off of water from the drainage pipe 33. The pressure gauge 4 can measure the pressure of the water (spring water) flowing out of the drainage pipe 33.

[0019] Next, with reference to the drawings, a method for measuring groundwater pressure using the groundwater pressure measuring device 1 of this embodiment will be described. The groundwater pressure measuring method is used, for example, when performing horizontal boring from the tunnel face and checking the groundwater pressure in the borehole H to confirm the ground conditions ahead of the tunnel face. Figure 5 shows the procedure for the groundwater pressure measuring method. As shown in Figure 5, the groundwater pressure measuring method comprises a drilling step S1, a device installation step S2, a measurement step S3, and a device retrieval step S4.

[0020] Figure 6 shows an overview of the drilling process S1. As shown in Figure 6(a), the drilling process S1 is a process of drilling into the ground G to form a borehole H and placing a drilling pipe 5 in the borehole H. A drilling bit 51 is fixed to the tip of the drilling pipe 5 in this embodiment. The drilling bit 51 is an annular bit fixed to the tip of the drilling pipe 5. The inner diameter of the drilling bit 51 is smaller than the inner diameter of the drilling pipe 5, and the drilling bit 51 protrudes into the inside of the drilling pipe 5. The drilling process S1 is performed with an inner bit 52 attached to the internal part of the drilling bit 51. When drilling the borehole H, the drilling pipe 5 is rotated around its central axis by the power of a boring machine (not shown) and struck, thereby cutting the entire cross-section of the ground G with the drilling bit 51 and the inner bit 52. In this embodiment, the borehole H is formed approximately horizontally (including a state where the tip is higher than the base). However, the drilling direction of the borehole H is not limited to approximately horizontal; for example, it may be drilled downward, upward, or vertically. Once a borehole H of a predetermined length (depth) has been formed, the inner bit 52 is recovered as shown in Figure 6(b). The inner bit 52 is recovered by using hydraulic pressure to pump a recovery device 55 attached to the tip of the wire 53 into the borehole H, fitting it onto the rear end of the inner bit 52, and then winding up the wire 53. The base end of the drilling pipe 5 is supported by a pre-bender 54 installed at the borehole opening H. In this embodiment, the case in which the entire cross-section is cut with the inner bit 52 attached to the drilling bit 51 has been described, but when taking a boring core, drilling may be performed with the inner bit 52 removed. In this case, it is preferable to attach a core barrel to the drilling bit 51 instead of the inner bit 52.

[0021] The equipment installation process S2 is the process of installing the groundwater pressure measuring device 1 in the borehole H. In the equipment installation process S2, a branch pipe 3 is attached to the base end of the drilling pipe 5, and a packer device 2 is installed at the tip of the drilling pipe 5. The equipment installation process S2 comprises drilling pipe retraction work S21, equipment installation work S22, and packer expansion work S23. Figures 7 and 8 show the work status of the equipment installation process S2. In drilling pipe retreat operation S21, the drilling pipe 5 is retreated to create a gap between the tip of the drilling pipe 5 and the front surface (bottom) of the borehole H (see Figure 7(a)). In other words, the front of the borehole H becomes exposed to the ground G.

[0022] In the equipment installation operation S22, the packer device 2 is pumped to the tip of the borehole H by the pressure of water W pumped from the borehole side of the drilling pipe 5. Specifically, first, as shown in Figure 7(a), the packer device 2 is set at the base end of the drilling pipe 5. Next, the wire 6 is fixed to the base end of the packer device 2. The wire 6 is inserted through the wire line conduit 32 of the branch pipe 3. Next, as shown in Figure 7(b), the branch pipe 3 is fixed to the base end of the drilling pipe 5. In this embodiment, the drifter 7 is set in advance at the base end of the branch pipe 3. Subsequently, as shown in Figure 8(a), water W is supplied to the water supply conduit 31, and the packer device 2 is pumped to the tip of the drilling pipe 5 by the water pressure of the water W. If the packer device 2 gets caught on the unevenness inside the drilling pipe 5 during pumping, this is resolved by applying impact vibration with the drifter 7. The tip of the packer device 2 protrudes from the tip of the drilling pipe 5. After being transported to the tip of the drilling pipe 5 by water pressure, the packer device 2 is locked onto the drilling bit 51, so that its tip remains protruding from the tip of the drilling bit 51. The water W used to pump the packer device 2 flows out to the tip of the borehole H through the gap between the packer device 2 and the drilling pipe 5, and through the inside of the packer device 2 (inner pipe 24), and is then drained to the borehole opening side of the borehole H through the gap between the borehole H and the drilling pipe 5.

[0023] In packer expansion operation S23, the front packer 21 and rear packer 22 are expanded as shown in Figure 8(b). Figure 8 shows the packer device 2 installed at the tip of the drilling pipe 5. As shown in Figure 8(a), once the packer device 2 is locked to the tip of the drilling pipe 5, the water pressure of the water W supplied into the drilling pipe 5 is increased. When the pressure of the water W is increased, the switching valve 27b moves forward due to the water pressure as shown in Figure 2(b) (the position of the switching valve 27b is switched). When the switching valve 27b moves forward, the rear end of the inner pipe 24 is shielded by the front of the switching valve 27b, and the outer pipe water passage 26a (packer passage) is exposed to the passage switching section 27, so that the water W in the passage switching section 27 is guided into the packer passage. As a result, water W is pressed into the rear packer 22 and the front packer 21 via the packer passage. The front packer 21 expands due to the water pressure and adheres tightly to the inner wall of the borehole H. Furthermore, the rear packer 22 expands due to water pressure and adheres tightly to the inner surface of the drilling pipe 5.

[0024] In measurement step S3, seepage water W at the tip of the borehole H flows into the borehole H. G The spring water W is collected from the tip of the packer device 2 (water sampling pipe 23). G The pressure is measured by the water pressure gauge 4. Figure 9 shows the work status of measurement step S3. In measurement step S3, the pressure of the water W being pumped from the hole side is reduced. The pressure of the water W is reduced by the pressure of the spring water W G When the pressure becomes lower than the above, the spring water W taken into the water intake pipe 23 (inner pipe 24) G The switching valve 27b returns to its original position due to pressure, etc. At this time, as shown in Figure 9, the front packer 21 is in close contact with the inner wall of the borehole H, and seepage water W generated at the tip of the borehole H G Because it is prevented from flowing out behind the front packer 21, the seeping water W enters the inner pipe 24. G This is induced. Also, when the switching valve 27b returns to its original state, the base end side of the packer flow path (outer pipe water channel 26a) is shielded, so the outflow of water W in the front packer 21 and rear packer 22 is prevented, and the spring water W is maintained in the expanded state of the front packer 21 and rear packer 22. G It can take in the spring water W taken in from the tip of the inner pipe 24.G The water is taken from the inner pipe 24 through the flow path switching section 27 into the drilling pipe 5 and guided to the branch pipe 3. In the branch pipe 3, while draining water from the drainage pipeline 33, the groundwater pressure is measured by the pressure gauge 4.

[0025] The equipment retrieval process S4 is the process of retrieving the packer equipment 2. The equipment retrieval process S4 comprises the drilling pipe retraction operation S41, the wire winding operation S42, and the equipment retrieval operation S43. Figure 10 shows the drilling pipe retraction operation S41. In drilling pipe retraction operation S41, the drilling pipe 5 is retracted by pulling it toward the borehole opening. At this time, the front packer 21 and the rear packer 22 are maintained in an expanded state. As shown in Figure 10, since the rear packer 22 is in close contact with the drilling pipe 5, when the drilling pipe 5 is retracted, the second outer pipe 26 retracts together with the drilling pipe 5. On the other hand, the first outer pipe 25 remains fixed in the borehole H because the front packer 21 is expanded and in close contact with the inner surface of the borehole H. As a result, the connecting pin 23a breaks due to the force (tensile force) that retracts the drilling pipe 5, and the first outer pipe 25 and the second outer pipe 26 separate. When the first outer pipe 25 and the second outer pipe 26 separate, the packer flow path is divided. When the packer flow path is interrupted, the water W in the front packer 21 and the water W in the rear packer 22 flow out from this section, causing the front packer 21 and the rear packer 22 to contract.

[0026] Figure 11 shows the wire winding operation S42. In the wire winding operation S42, as shown in Figure 11, the wire 6 is wound up using a winch or the like (not shown), thereby pulling the packer device 2 towards the base end of the drilling pipe 5. Figure 12 shows the equipment retrieval procedure. In the equipment retrieval procedure S43, as shown in Figure 12, the branch pipe 3 is removed from the drilling pipe 5, and the packer device 2 is removed from the drilling pipe 5. To resume drilling into the borehole H, the inner bit 52 is placed at the tip of the drilling pipe 5, and drilling with the drilling pipe 5 is resumed.

[0027] As described above, according to the water inrush pressure measuring device 1 and the water inrush pressure measuring method of the present embodiment, since the wire 6 is connected to the packer device 2 in advance, there is no need to individually feed the wire 6 into the perforated pipe 5. The time required to connect the wire 6 required in the conventional water inrush pressure measuring method to the packer device 2 can be omitted. Therefore, the packer device 2 can be easily installed and recovered without being limited to the drilling distance of the boring hole H, and the water pressure in the water inrush section in front of the face can be quickly measured, so that the tunnel construction can be promptly resumed. Further, since the wire 6 is inserted into the wire line pipe 32 of the branch pipe 3, the wire 6 connected to the packer device 2 can be fed and wound even when the drifter 7, which is a device having a rotation mechanism, is attached to the branch pipe 3 (water supply pipe 31).

[0028] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the foregoing embodiments, and each of the above-described components can be appropriately changed without departing from the spirit of the present invention.

Explanation of Reference Numerals

[0029] 1 Water inrush pressure measuring device 2 Packer device 21 Front packer 22 Rear packer 23 Water intake pipe 24 Inner pipe 25 First outer pipe 26 Second outer pipe 27 Flow path switching section 3 Branch pipe 31 Water supply pipe 32 Wire line pipe 33 Drainage pipe 4 Water pressure gauge 5 Perforated pipe 6 Wire 7 Drifter H Boring hole G Rock mass W G Water inrush

Claims

1. A packer device that takes in seepage water from the tip of a drilling pipe installed in a borehole into the drilling pipe, A branch pipe attached to the base end of the drilling pipe, A drifter attached to the base end of the branch pipe, A spring water pressure measuring device comprising a water pressure gauge attached to the branch pipe, The aforementioned branch pipe is divided into a water supply pipeline arranged coaxially with the drilling pipe and a wire line pipeline branched off from the water supply pipeline. The packer device is installed at the tip of the borehole pipe by being pumped by water pressure. A groundwater pressure measuring device characterized in that a wire extending into the borehole pipe is connected to the packer device via the wire line conduit.

2. A drainage pipeline branches off from the aforementioned water supply pipeline. The spring water pressure measuring device according to claim 1, characterized in that the water pressure gauge is installed in the drainage pipe.

3. A drilling step in which a borehole is drilled and the drilling pipe is placed in the borehole, A device installation step of installing the groundwater pressure measuring device according to claim 1 or claim 2 in the borehole, A measurement step for measuring the pressure of seepage water at the tip of the borehole, A method for measuring spring water pressure, comprising a device retrieval step for retrieving the packer device, In the apparatus installation process, the branch pipe is attached to the base end of the drilling pipe, and the packer device is installed at the tip of the drilling pipe. In the measurement step, the water pressure of the spring water taken into the borehole via the packer device is measured by the pressure gauge. A method for measuring spring water pressure, characterized in that the packer device is recovered by winding up the wire in the device recovery step.

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