Rod plate shearing equipment capable of measuring pore water pressure

Abstract

The utility model relates to the technical field of soil exploration, in particular to vane shearing equipment capable of measuring pore water pressure, which comprises a dual-purpose static penetrometer body and a vane probe, the vane probe comprises a central column and four detection plates fixedly connected to the peripheral wall of the central column, and the lower end surfaces of the detection plates are flush with the lower end surface of the central column. The upper end of the central column is detachably connected to a drill rod of the dual-purpose static penetrometer body, the central column and the drill rod are coaxial, the upper part of the central column is provided with a pressure detection cavity, the central column is provided with a pore water pressure gauge arranged in the pressure detection cavity, and the peripheral wall of the central column is provided with a water inlet hole communicated with the pressure detection cavity. The vane shearing equipment has the effect of improving the detection integration level of the vane shearing equipment.

Description

Technical Field

[0001] The present application relates to the technical field of soil exploration, and in particular to a cross-plate shearing device capable of measuring pore water pressure. Background Art

[0002] In geological disaster prevention and control, in-situ soil testing is often required. Common in-situ testing methods include static cone penetration and cross-plate shear testing. The static cone penetration tester uses a mechanical drive to press a probe into the soil. The resistance change signal is transmitted to surface-level measuring instruments, allowing the user to identify vertical and horizontal changes in the strata. The cross-plate test presses a cross-plate head into soft soil and then rotates it. The torque required for rotation is measured until the soil fails, allowing the undrained shear strength of the soil to be calculated.

[0003] Currently, static penetration tests and cross-plate shear tests can be performed using a static penetration tester. The static penetration tester consists of a frame, a jacking device mounted on the frame, a torsion device, and a probe rod. During a static penetration test, a trench is first dug in the ground, the frame is placed on the trench, and the static probe is mounted on the probe rod. The probe rod is then driven down by the jacking device, which presses the static probe into the soil for the static penetration test. During a cross-plate shear test, a cross-plate probe is installed. The probe rod is first driven by the jacking device, which presses the cross-plate probe into the soil. The probe rod is then rotated by the torsion device, which causes the cross-plate probe to rotate, and the cross-plate test is performed.

[0004] However, although the existing cross-plate shear test can measure the undrained shear strength and sensitivity of in-situ saturated soft clay soils, it cannot directly calculate the effective shear strength of the soil. The pore water pressure of the soil needs to be measured separately with the help of a pore water pressure gauge. This leads to a low degree of test integration, increased operational complexity and time cost, and therefore needs further improvement. Utility Model Content

[0005] In order to improve the detection integration of the cross-plate shear device, the present application provides a cross-plate shear device capable of measuring pore water pressure.

[0006] The cross-plate shearing device provided in this application for measuring pore water pressure adopts the following technical solution:

[0007] A cross-plate shear device capable of measuring pore water pressure comprises a dual-purpose static penetration instrument body, a cross-plate probe and a data output terminal instrument. The cross-plate probe comprises a central column and four detection plates fixedly connected to the outer peripheral wall of the central column. The lower end faces of the detection plates are flush with the lower end face of the central column. The upper end of the central column is detachably connected to the drill rod of the dual-purpose static penetration instrument body. The central column and the drill rod are coaxial. The upper part of the central column has a pressure detection cavity. The central column is provided with a pore water pressure gauge built into the pressure detection cavity. The outer peripheral wall of the central column is provided with a water inlet hole connected to the pressure detection cavity.

[0008] By adopting the above technical solution, when conducting a cross-plate shear test, the cross-plate probe is replaced, the center column is installed on the drill rod of the dual-purpose static penetration instrument body, and the drill rod is driven down by the jacking device on the dual-purpose static penetration instrument body, thereby pressing the cross-plate probe into the soil. The water in the soil can enter the pressure detection cavity through the water inlet hole. After the pore water pressure of the soil is measured by the pore water pressure gauge, the drill rod is rotated by the torsion device, and the drill rod drives the cross-plate probe to rotate, and a cross-plate test is carried out to obtain the undrained shear strength. The effective shear strength of the soil is directly obtained by subtracting the pore water pressure from the drained shear strength, thereby improving the detection integration of the cross-plate shear equipment and thus improving the convenience of the cross-plate shear test.

[0009] Preferably, a data output terminal instrument is also included, and a sensor is provided at the upper end of the center column. The sensor includes a torsion column and a resistance strain gauge detachably connected to the upper end of the center column. The upper end of the torsion column is detachably connected to the drill pipe. The torsion column has an installation cavity, and the resistance strain gauge is built into the installation cavity. The resistance strain gauge and the pore water pressure gauge are both electrically connected to the data output terminal instrument through a transmission cable.

[0010] By adopting the above technical solution, the pore water pressure readings of the soil are measured by the data output terminal instrument. When conducting the cross-plate shear test, the resistance strain gauge is set on the cross-plate probe. As the cross-plate probe rotates, the resistance strain gauge will be subjected to shear stress, causing its resistance to change. The undrained shear strength of the soil is calculated by the data output terminal instrument. The detachable connection design of the torsion column and the center column facilitates the assembly and maintenance of the equipment and improves the reliability and service life of the equipment.

[0011] Preferably, the upper part of the pressure detection chamber extends to the upper end surface of the center column, so that the upper end of the center column is open, and the lower end of the torsion column is coaxially fixedly connected to the lower screw column, and the lower screw column is threadedly connected to the upper part of the center column. The lower end surface of the lower screw column is provided with a first wire hole connected between the pressure detection chamber and the installation chamber, and the outer peripheral wall of the torsion column is provided with a second wire hole connected to the installation chamber, and the transmission cable is passed through the first wire hole / second wire hole.

[0012] By adopting the above technical solution, the transmission cable is connected to the pore water pressure gauge and the resistance strain gauge through the first wire hole and the second wire hole to realize data transmission.

[0013] Preferably, the sensor further includes a sleeve sleeved on the torsion column.

[0014] By adopting the above technical solution, the sleeve is sleeved on the torsion column, which effectively protects the internal sensor component from the influence of the external environment and ensures the normal operation of the resistance strain gauge.

[0015] Preferably, the upper end of the torsion column is coaxially fixedly connected to an upper screw column, and the upper screw column is threadedly connected to the lower end of the drill rod.

[0016] By adopting the above technical solution, the upper end of the torsion column is coaxially fixedly connected to the upper screw column, and the upper screw column is threadedly connected to the lower end of the drill rod, so that a reliable connection is achieved between the torsion column and the drill rod, ensuring that during the cross-plate shear test, the drill rod can effectively transmit torque, ensuring the accuracy and reliability of the test. At the same time, this connection method is easy to disassemble and assemble, and facilitates maintenance and replacement of the equipment.

[0017] Preferably, a guide plate is fixedly connected to the inner wall of the pressure detection chamber, and a guide hole is coaxially penetrated through the guide plate for inserting the pore water pressure gauge. The upper part of the pore water pressure gauge is coaxially fixedly connected to a sealing ring plate that abuts the upper end face of the guide plate, and a sealing resin is poured in the pressure detection chamber to seal the pore water pressure gauge.

[0018] By adopting the above technical solution, the guide plate and the guide hole can ensure that the pore water pressure gauge is accurately inserted into the predetermined position, reduce the possibility of the pore water pressure gauge tilting, and ensure measurement accuracy; the cooperation between the sealing ring plate and the guide plate can effectively prevent water from leaking into the installation cavity and protect the electronic components in the torsion column; the sealing resin seals the pore water pressure gauge and further seals the cooperation between the sealing ring plate and the guide plate.

[0019] Preferably, a positioning hole is formed on the upper end surface of the guide plate, and a positioning rod protrudes from the lower end surface of the sealing ring plate and is fixedly inserted into the positioning hole.

[0020] By adopting the above technical solution, the pore water pressure gauge is slidably inserted into the guide hole, and the positioning rod on the sealing ring plate is inserted into the positioning hole, which effectively prevents the pore water pressure gauge from rotating around its own axis.

[0021] Preferably, the inner peripheral wall of the guide hole is fixedly connected with a sealing ring that abuts against the outer peripheral wall of the pore water pressure gauge.

[0022] By adopting the above technical solution and adding a sealing ring, on the one hand, it can effectively prevent water from entering the installation cavity, and on the other hand, it can effectively reduce the possibility of sealing resin flowing into the inner cavity below the guide plate when pouring sealing resin into the pressure detection cavity, thereby causing the water inlet hole to be blocked.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. When conducting a cross-plate shear test, replace the cross-plate probe and install the center column on the drill rod of the dual-purpose static penetration instrument body. The drill rod is driven down by the jacking device on the dual-purpose static penetration instrument body, thereby pressing the cross-plate probe into the soil. Water in the soil can enter the pressure detection chamber through the water inlet hole. After the pore water pressure of the soil is measured by the pore water pressure gauge, the drill rod is rotated by the torsion device. The drill rod drives the cross-plate probe to rotate, and the cross-plate test is performed to obtain the undrained shear strength. The effective shear strength of the soil is directly obtained by subtracting the pore water pressure from the drained shear strength. This improves the detection integration of the cross-plate shear equipment, thereby improving the convenience of the cross-plate shear test.

[0025] 2. The guide plate and guide hole can ensure that the pore water pressure gauge is accurately inserted into the predetermined position, reduce the possibility of the pore water pressure gauge tilting, and ensure measurement accuracy; the cooperation between the sealing ring plate and the guide plate can effectively prevent water from leaking into the installation cavity and protect the electronic components in the torsion column; the sealing resin seals the pore water pressure gauge and further seals the joint between the sealing ring plate and the guide plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the overall structure of a cross-plate shearing device capable of measuring pore water pressure in Example 1;

[0027] Figure 2 Schematic diagram of the structure of the cross-plate probe in Example 1;

[0028] Figure 3 is a schematic structural diagram of the sensor in Example 1;

[0029] Figure 4 yes Figure 3 A local enlarged schematic diagram at point A;

[0030] Figure 5 Schematic diagram of the connection structure between the lower screw column and the central column in Example 2;

[0031] Figure 6 It is a schematic diagram of the connection structure between the lower screw column and the central column in Example 3.

[0032] In the figure, 1. Dual-purpose static penetration instrument body; 11. Drill pipe; 2. Cross-plate probe; 21. Center column; 22. Detection plate; 23. Pressure detection chamber; 24. Water inlet hole; 25. Guide plate; 251. Guide hole; 252. Sealing ring; 253. Positioning hole; 26. Sealing resin; 3. Data output terminal instrument; 4. Pore water pressure gauge; 41. Sealing ring plate; 42. Positioning rod; 5. Sensor; 51. Torsion column; 511. Installation cavity; 52. Resistance strain gauge; 53. Sleeve; 54. Second wire hole; 55. Lower screw column; 551. First wire hole; 56. Upper screw column; 57. Compression spring; 58. Pressure plate; 581. Third wire hole; 6. Transmission cable. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1-6 This application is described in further detail.

[0034] Example 1:

[0035] The present application discloses a cross-plate shearing device capable of measuring pore water pressure, referring to Figure 1 , including a dual-purpose static penetration instrument body 1, a cross-plate probe 2 and a data output terminal instrument 3. The dual-purpose static penetration instrument body 1 is an existing technology and will not be described here in detail.

[0036] Reference Figure 2 、 Figure 3 、 Figure 4 The cross-plate probe 2 includes a central column 21 and four detection plates 22 fixedly connected to the outer circumferential wall of the central column 21. The lower end surfaces of the detection plates 22 are flush with the lower end surface of the central column 21, and a pressure detection cavity 23 is axially defined on the upper end surface of the central column 21. The central column 21 is provided with a pore water pressure gauge 4 built into the pressure detection cavity 23. Specifically, a guide plate 25 is coaxially fixedly connected to the upper portion of the inner wall of the pressure detection cavity 23. The guide plate 25 coaxially penetrates and defines a guide hole 251 for inserting the pore water pressure gauge 4. A sealing ring 252 is fixedly connected to the inner circumferential wall of the guide hole 251 and abuts against the outer circumferential wall of the pore water pressure gauge 4. The lower end of the pore water pressure gauge 4 is the detection end. The upper part of the pore water pressure gauge 4 is coaxially fixedly connected to a sealing ring plate 41 that abuts against the upper end surface of the guide plate 25. A positioning hole 253 is provided on the upper end surface of the guide plate 25. A positioning rod 42 protrudes from the lower end surface of the sealing ring plate 41 and is fixedly inserted into the positioning hole 253. The outer peripheral wall of the center column 21 is provided with a water inlet hole 24 that is connected to the lower part of the pressure detection chamber 23.

[0037] A sensor 5 is provided at the upper end of the center column 21. The sensor 5 includes a torsion column 51, a resistance strain gauge 52, and a sleeve 53. The torsion column 51 has an installation cavity 511. The resistance strain gauge 52 is built into the installation cavity 511. The sleeve 53 is coaxially fixedly sleeved on the torsion column 51. In this embodiment, the sleeve 53 and the torsion column 51 are fixed by epoxy resin. The lower end and the upper end face of the torsion column 51 are coaxially fixedly connected with a lower screw column 55 and an upper screw column 56 respectively. The lower screw column 55 and the upper screw column 56 are integrally formed with the torsion column 51. The lower screw column 55 is threadedly connected to the upper part of the center column 21. Specifically, the outer peripheral wall of the lower screw column 55 has an external thread, and the upper inner peripheral wall of the pressure detection cavity 23 has an internal thread. The upper screw column 56 is threadedly connected to the lower end of the drill pipe 11 of the dual-purpose static penetration instrument body 1.

[0038] After the lower screw post 55 is locked to the center post 21, the lower end face of the lower screw post 55 abuts the upper end face of the pore-water pressure gauge 4, thereby securing the pore-water pressure gauge 4. A first wire hole 551 is coaxially defined on the lower end face of the lower screw post 55, connecting the pressure detection chamber 23 and the mounting chamber 511. Second wire holes 54 are radially defined on the outer circumference of the sleeve 53 and the torsion post 51, connecting the mounting chamber 511. The resistance strain gauge 52 and the pore-water pressure gauge 4 are both electrically connected to the data output terminal instrument 3 via a transmission cable 6. The transmission cable 6 of the pore-water pressure gauge 4 is sequentially threaded through the first wire hole 551 and the second wire hole 54, while the transmission cable 6 of the resistance strain gauge 52 is threaded through the second wire hole 54.

[0039] The testing method of a cross-plate shear device capable of measuring pore water pressure in an embodiment of the present application is as follows: the cross-plate probe 2 is calibrated before the test to determine the calibration coefficient of the cross-plate probe 2. During the calibration process, the cross-plate probe 2, the transmission cable 6 and the data output terminal instrument 3 are first connected to the system.

[0040] Step a: Before the test, install and level the dual-purpose static penetration instrument body 1 and fix it with a ground anchor.

[0041] Step b: Connect the cross-plate probe 2 to the sensing device and tighten it, connect the plug of the attached transmission cable 6 to the cable socket of the data output terminal instrument 3, so that the resistance strain gauge 52 and the pore water pressure meter 4 are both electrically connected to the data output terminal instrument 3.

[0042] Step c: The drill rod 11 is pressed downward by the jacking device of the dual-purpose static cone body 1, thereby vertically pressing the cross-plate probe 2 into the soil to a predetermined depth. Water in the soil can enter the pressure detection chamber 23 through the water inlet hole 24, and the pore water pressure of the soil is measured by the pore water pressure gauge 4.

[0043] Step d: Apply torque to the drill rod 11 and rotate the torque crank on the dual-purpose static penetration tester body 1 at a constant speed. Each rotation of the torque crank rotates the cross-plate probe 2 one degree. The torque crank rotates once every 10 seconds, and a strain reading is recorded for each rotation. Once the reading reaches a peak or stabilizes, continue recording for another minute. After the cross-plate probe 2 is inserted to the predetermined depth, it must remain stationary for 2-5 minutes before initiating torsional shear. Peak strength should be measured within 2 minutes.

[0044] Step e, complete the test.

[0045] The data from the electrical cross-plate shear test can be divided into two categories: the first category is the reading Ry at the time of shear failure of the original soil and the reading Rc at the time of shear failure of the reshaped soil measured by in-situ shear; the second category is the calibration coefficient of sensor 5 and the diameter and height of the cross-plate probe 2.

[0046] According to the measured data, the following data processing is performed:

[0047] The undrained shear strength c of the original soil is obtained using the following formula: u and the undrained shear strength c of the remolded soil ′ u :

[0048] c u =K·ξ·R y

[0049] c ′ u =K·ξ·R c

[0050] Where: c u —undrained shear strength of soil (kPa);

[0051] K——cross plate shear constant (m -2 );

[0052] ξ——Regulation coefficient of resistance strain gauge cross-plate sensor (kN / με);

[0053] R y ——maximum microstrain value of undisturbed soil during shear damage (με);

[0054] R c ——Maximum microstrain value during shear damage of disturbed soil (με).

[0055] According to the sensing frequency obtained by the pore water pressure gauge, the pore water pressure u is obtained using the following formula:

[0056]

[0057] Where: u——pore water pressure (kPa);

[0058] K0——sensor calibration coefficient;

[0059] f——operating frequency value of pore water pressure gauge;

[0060] f0——initial frequency value of pore water pressure gauge;

[0061] Finally, referring to the soil shear strength formula, the effective shear strength c of the soil can be obtained. ′ :

[0062] c ′ =c u -u

[0063] c″=c ′ u -u

[0064] Where: c ′ ——effective shear strength of undisturbed soil (kPa);

[0065] c″—effective shear strength of remolded soil (kPa).

[0066] Example 2:

[0067] The difference from Example 1 is that, referring to Figure 5 A sealing resin 26 for sealing the pore water pressure gauge 4 is poured into the pressure detection cavity 23. After the sealing resin 26 solidifies, a resin layer is formed. After the lower screw column 55 is locked to the center column 21, the lower end surface of the lower screw column 55 abuts against the upper end surface of the resin layer.

[0068] Example 3:

[0069] The difference from Example 1 is that, referring to Figure 6 The lower end face of the lower screw column 55 is fixedly connected with a compression spring 57, and the lower end of the compression spring 57 is fixedly connected with a pressure plate 58. After the screw column is locked to the center column 21, the lower end face of the pressure plate 58 abuts against the upper end face of the pore water pressure gauge 4, and the compression spring 57 is in a compressed state. The pressure plate 58 is coaxially opened with a third wire hole 581 for the transmission cable 6 of the pore water pressure gauge 4 to pass through.

[0070] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A cross-plate shearing device capable of measuring pore water pressure, characterized in that: The invention comprises a dual-purpose static penetration instrument body (1) and a cross-plate probe (2). The cross-plate probe (2) comprises a central column (21) and four detection plates (22) fixedly connected to the outer peripheral wall of the central column (21). The lower end surface of the detection plate (22) is flush with the lower end surface of the central column (21). The upper end of the central column (21) is detachably connected to the drill rod (11) of the dual-purpose static penetration instrument body (1). The central column (21) and the drill rod (11) are coaxial. The upper part of the central column (21) has a pressure detection cavity (23). The central column (21) is provided with a pore water pressure gauge (4) built into the pressure detection cavity (23). The outer peripheral wall of the central column (21) is provided with a water inlet hole (24) connected to the pressure detection cavity (23).

2. The cross-plate shearing device capable of measuring pore water pressure according to claim 1, characterized in that: The invention also includes a data output terminal instrument (3), wherein a sensor (5) is provided at the upper end of the center column (21), and the sensor (5) includes a torsion column (51) and a resistance strain gauge (52) detachably connected to the upper end of the center column (21). The upper end of the torsion column (51) is detachably connected to the drill pipe (11), the torsion column (51) has a mounting cavity (511), and the resistance strain gauge (52) is built into the mounting cavity (511). The resistance strain gauge (52) and the pore water pressure gauge (4) are both electrically connected to the data output terminal instrument (3) via a transmission cable (6).

3. The cross-plate shearing device capable of measuring pore water pressure according to claim 2, characterized in that: The upper portion of the pressure detection chamber (23) extends to the upper end surface of the center column (21), so that the upper end of the center column (21) is open. The lower end of the torsion column (51) is coaxially fixedly connected to a lower screw column (55). The lower screw column (55) is threadedly connected to the upper portion of the center column (21). The lower end surface of the lower screw column (55) is provided with a first wire hole (551) connected between the pressure detection chamber (23) and the installation chamber (511). The outer peripheral wall of the torsion column (51) is provided with a second wire hole (54) connected to the installation chamber (511). The transmission cable (6) is passed through the first wire hole (551) / the second wire hole (54).

4. The cross-plate shearing device capable of measuring pore water pressure according to claim 2, characterized in that: The sensor (5) further comprises a sleeve (53) sleeved on the torsion column (51).

5. The cross-plate shearing device capable of measuring pore water pressure according to claim 2, characterized in that: The upper end of the torsion column (51) is coaxially fixedly connected to an upper screw column (56), and the upper screw column (56) is threadedly connected to the lower end of the drill rod (11).

6. The cross-plate shearing device capable of measuring pore water pressure according to claim 2, characterized in that: A guide plate (25) is fixedly connected to the inner wall of the pressure detection chamber (23); a guide hole (251) for inserting the pore water pressure gauge (4) is coaxially penetrated through the guide plate (25); a sealing ring plate (41) abutting against the upper end surface of the guide plate (25) is coaxially fixedly connected to the upper part of the pore water pressure gauge (4); and a sealing resin (26) for sealing the pore water pressure gauge (4) is poured into the pressure detection chamber (23).

7. The cross-plate shearing device capable of measuring pore water pressure according to claim 6, characterized in that: The upper end surface of the guide plate (25) is provided with a positioning hole (253), and the lower end surface of the sealing ring plate (41) protrudes a positioning rod (42) fixedly inserted into the positioning hole (253).

8. The cross-plate shearing device capable of measuring pore water pressure according to claim 6, characterized in that: The inner peripheral wall of the guide hole (251) is fixedly connected with a sealing ring (252) that abuts against the outer peripheral wall of the pore water pressure gauge (4).

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