A device and method for measuring the dislocation displacement of the interface shear of a GCL interlayer by a large direct shear apparatus

Abstract

The present invention provides a device and method for measuring the dislocation displacement of an interface shear of a GCL interlayer by a large direct shear apparatus. The test device includes a grab tooth plate system and a real-time displacement monitoring system. The grab tooth plate system can achieve uniform and reliable fixation of a geosynthetic specimen during the interface static and dynamic shear test through the bottom plate grab teeth. The real-time displacement monitoring system can achieve accurate measurement of the dislocation displacement between the geotextiles on the upper and lower surfaces of the GCL through the precise cooperation of ultra-fine steel wires penetrating inside the bottom plate and displacement sensors. The device of the present invention has a simple structure and is easy to operate. It can be embedded in a large conventional geotechnical direct shear apparatus test system as a functional unit module, filling the current functional defects of the geotechnical direct shear apparatus, and greatly promoting the accurate division of the failure stage and the accurate revelation of the instability mechanism during the interface shear test of GCL and other geotechnical materials.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering. Background Art

[0002] Landfill is the most main way to dispose of municipal solid waste. In order to isolate pollutants and harmful substances in the landfill and prevent them from leaking into the surrounding soil and groundwater of the landfill, a liner system needs to be set at the bottom of the landfill.

[0003] The liner system is the core structural component for the landfill to function as a permanent closed container for harmful substances. Therefore, the structural characteristics and mechanical properties of the liner system have always been placed at the core research position in the landfill stability research.

[0004] The geosynthetic clay liner GCL (usually composed of upper and lower surface geotextiles and an intermediate bentonite layer. The bottom geotextile uses the needling method to pierce its geotextile fibers through the bentonite layer and the overlying geotextile layer to form a sandwich structure with a reinforcing effect, connecting the three layers of materials into one body, thus having good integrity) is used to replace part of the compacted clay layer with its relatively thin thickness and good anti-seepage performance, and is combined with a geomembrane to form a composite liner structure, which is the commonly used core liner structure in the current landfill bottom liner system.

[0005] However, under the action of seismic loads, large relative displacements are likely to occur between the upper and lower surface layers (interlayers) of the GCL or at the contact interface between the GCL and other media (such as geomembranes, compacted clay), which are extremely likely to cause the instability and failure of the landfill, resulting in inestimable property losses and environmental hazards.

[0006] Therefore, the interface shear failure test between the GCL and other media and the revelation of the corresponding interface shear failure mechanism have always been the key research topics of researchers at home and abroad. However, since the failure surface of the above shear failure test may occur either between the upper and lower geotextile interlayers of the GCL or at the contact interface between the GCL and other media, it is impossible to give the specific occurrence position of the failure surface during the test with the existing large-scale geotechnical interface direct shear apparatus, and only the possible position of the failure surface can be inferred reversely through the failure form of the specimen after the test (if large dislocation displacements occur in the GCL interlayer and a large number of geotextile fibers have traces of being broken, the failure surface may be located between the GCL interlayers; conversely, if the dislocation displacement of the GCL interlayer is small, the geotextile fibers are hardly broken, and the relative displacement of the contact interface between the GCL and other media is large, the failure surface may be located at the contact interface between the GCL and other media). This undoubtedly weakens the rigor and credibility of the test. In addition, no matter which of the above two positions the failure surface is located in, relative displacements will occur between the GCL interlayers and at the contact interface between the GCL and other media during the shear test, and Figure 7The existing instruments shown (Patent CN201410243598.7, or the paper "Lin Hai, Han Zhuowei, Shi Jianyong. Analysis of Interface Shear Failure Mechanism and Peak Strength of Geosynthetics [J]. Journal of Huazhong University of Science and Technology (Natural Science Edition), 2020, 48(07): 99-106. DOI: 10.13245 / j.hust.200717.") cannot give the relative displacement of each of these two positions, but only provide the sum of the two, that is, the total displacement, which seriously hinders the accurate description of the shear failure stage and the correct interpretation and revelation of the shear mechanism during the shear test by researchers.

[0007] Therefore, in order to facilitate the experimenters to judge the position of the shear failure surface in real time during the interface shear test between GCL and other media, correctly analyze the occurrence process of shear failure, and accurately reveal the interface shear mechanism, it is urgent to develop a functional test device that can be applied to a conventional large-scale geotechnical interface direct shear instrument and can monitor the dislocation displacement of the upper and lower interlayers of GCL during the interface shear test between GCL and other media in real time and accurately. Summary of the Invention

[0008] In view of the deficiencies in the prior art, the present invention provides a grab-tooth plate device and method for measuring the dislocation displacement of the GCL interlayer in the interface shear of a large direct shear instrument. This measuring device can accurately measure the dislocation displacement between the upper and lower surfaces of GCL during the direct shear test of the interface between geosynthetic clay liner (GCL) and other geotechnical materials.

[0009] The technical solution of the present invention:

[0010] A device for measuring the dislocation displacement of the GCL interlayer in the interface shear of a large direct shear instrument includes: a grab-tooth plate system and a displacement real-time monitoring system.

[0011] Among them, the grab-tooth plate system includes: a bottom plate (1), grab teeth (2) and connecting ear plates (3);

[0012] The bottom plate (1) is a stainless steel cuboid;

[0013] The grab teeth (2) are neatly arranged on the lower surface of the bottom plate (1) and are used to uniformly fix the geosynthetic material specimen on the shear surface during the interface shear test;

[0014] Among the grab teeth (2), except for several grab teeth with wire holes (8) penetrated, they are inverted stainless steel regular square pyramid grab teeth (201), and the rest are all stainless steel regular square pyramid grab teeth with the same size and the tooth tips facing downwards;

[0015] The connecting ear plates (3) are flat-connected to both sides of the upper surface of the bottom plate (1) and are used to fix the bottom plate (1) to the bottom of the upper shear box (11);

[0016] Among them, the displacement real-time monitoring system includes: a fixed bracket (4), an automatic retractable steel wire reel (5), an ultra-fine steel wire (6), a displacement sensor (7), a steel wire duct (8), a geomembrane gasket (9), and a data collector (10);

[0017] The main body of the fixed bracket (4) is a rectangular stainless-steel frame, which is welded to the top of the left side of the bottom plate (1) at a certain inclination angle. Several stainless-steel restraint rods (401) extend obliquely downward from the outer-end crossbar of the fixed bracket (4) to provide a spatial fulcrum for the automatic retractable steel wire reel (5);

[0018] The automatic retractable steel wire reel (5) is fixed at the end of the stainless-steel restraint rod (401), can provide the ultra-fine steel wire (6) required for the test, and has a certain automatic retraction tension to ensure that the ultra-fine steel wire (6) is always in a taut state during the interface shear test;

[0019] The ultra-fine steel wire (6) is pulled out from the automatic retractable steel wire reel (5), passes through the displacement sensor (7), and after passing through the steel wire duct (8), stays at the bottom of the bottom plate (1) to measure the displacement of the GCL (15) interlayer during the interface shear test;

[0020] The displacement sensor (7) is fixed to the left side of the bottom plate (1) through a stainless-steel restraint rod (701) to continuously monitor the length of the ultra-fine steel wire (6) pulled out from the automatic retractable steel wire reel (5);

[0021] The steel wire duct (8) is formed by drilling a hole at the half-height position on the left side of the bottom plate (1), extending horizontally to the right for a certain distance, and then vertically penetrating the lower surface of the bottom plate (1) to form an outlet, which assists the ultra-fine steel wire (6) in measuring the displacement of the GCL (15) interlayer at different longitudinal and transverse positions;

[0022] The geomembrane gasket (9) is circular, is arranged at the bottom of the GCL (15), and is sewn to the geotextile (1503) at the bottom layer of the GCL (15) through the ultra-fine steel wire (6) to ensure that the fixed point of the ultra-fine steel wire (6) on the geotextile (1503) does not shift with the interface shear movement;

[0023] The data collector (10) is connected to the displacement sensor (7) through a data cable to collect the data monitored by the displacement sensor (7) and perform the calculation and output of the displacement value.

[0024] Furthermore, there are four connecting ear plates (3), which are symmetrically and flatly connected to both sides of the upper surface of the bottom plate (1), with two stainless-steel connecting ear plates (3) on each side, for fixing the bottom plate (1) to the bottom of the upper shear box (11).

[0025] Further, three wire channels (8) are arranged in parallel. Along the horizontal direction of the bottom plate (1) from left to right, they are the first wire channel (801), the second wire channel (802), and the third wire channel (803) respectively. They respectively assist the ultra-fine wire (6) to measure the interlayer dislocation displacement at different longitudinal and transverse positions of the GCL (15), and then take the average value to reduce the detection error.

[0026] Further, three displacement sensors (7) are arranged in parallel, and are respectively used to monitor in real time the lengths of the three ultra-fine wires (6) passing through the first wire channel (801), the second wire channel (802), and the third wire channel (803) pulled out from the automatic retractable wire reel (5).

[0027] Further, for the total horizontal shear displacement x, the elongation displacement s of the ultra-fine wire (6) caused by dislocation, and the real-time height h of the bentonite in the middle layer of the GCL, the data collector (10) can calculate:

[0028] The inclined length of the ultra-fine wire (6) in the bentonite (1502) in the middle layer of the GCL is h + s;

[0029] The dislocation displacement between the upper geotextile (1501) of the GCL and the bottom geotextile (1503) of the GCL is ((h + s) 2 -h 2 ) 1 / 2 ;

[0030] The relative displacement between the interface of the bottom geotextile (1503) of the GCL and the geomembrane (16) is x - ((h + s) 2 -h 2 ) 1 / 2 .

[0031] Taking the shear test of the interface between the GCL and the geomembrane as an example, the usage method of the device of the present invention is as follows:

[0032] A usage method of a device for measuring the interlayer dislocation displacement of the interface shear of the GCL by a large direct shear apparatus includes the following steps:

[0033] The first step: Cut out a geosynthetic clay liner GCL (15) with the same bottom surface area as the bottom plate (1). Align the GCL (15) with the bottom surface of the bottom plate (1), then tie the ultra-fine wire (6) led out from the wire channel (8) to a straight needle and pierce through the center of the GCL (15) and the geomembrane gasket (9) in sequence. Then replace the straight needle with a hook needle, and perform cross-stitching on the geomembrane gasket (9) and the bottom geotextile (1503) of the GCL through the ultra-fine wire (6). After completion, cut off the excess ultra-fine wire (6) flush.

[0034] Step 2: Align the connecting ear plate (3) on the top surface of the bottom plate (1) with the connecting ear plate (3) on the bottom surface of the upper shear box (11), then insert the fixing screw (12) through the circular hole on the connecting ear plate (3), and tighten it with the fixing nut (13);

[0035] Step 3: Cut out a geomembrane (16) with the same area as the top surface of the lower shear box (14), and align it and place it on the grabbing teeth (2) on the top surface of the lower shear box (14);

[0036] Step 4: Push and adjust the lower shear box (14) horizontally so that its left edge is completely aligned with the left edge of the upper shear box (11), then use the displacement control mode to control the vertical actuator, slowly drop the upper shear box (11), until the GCL (15) and the geomembrane (16) are about to come into contact, switch the control mode of the vertical actuator to axial force control, and accurately control the rate of change of the interface positive pressure until the vertical load (17) required for the test is reached, and then the interface is kept under the load for a certain period of time;

[0037] Step 5: After the interface is maintained, the extension and retraction state of the horizontal actuator is controlled so that the lower shear box moves horizontally along the horizontal guide rail in a set motion mode under the action of the horizontal thrust (18), and an interface shearing action begins to occur between the GCL (15) and the geomembrane (16);

[0038] Step 6: The horizontal displacement sensor provided by the conventional large-scale direct shear instrument provides the total horizontal shear displacement x, the tooth plate device of the present invention records the elongation displacement s of the ultrafine steel wire (6) caused by the displacement of the GCL (15) interlayer, and the vertical displacement sensor provided by the conventional large-scale direct shear instrument monitors the vertical displacement change of the interface material under the current stable vertical load (17) (the thickness of the upper geotextile (1501) of the GCL, the bottom geotextile (1503) of the GCL and the geomembrane (16) itself is relatively small, and the thickness change under the stable vertical load can be ignored), and then the real-time height h of the bentonite in the middle layer of the GCL is obtained, thereby calculating the inclined length of the ultrafine steel wire (6) in the bentonite (1502) in the middle layer of the GCL as (h+s), and according to the Pythagorean theorem, the displacement between the upper geotextile (1501) of the GCL and the bottom geotextile (1503) of the GCL is ((h+s) 2 -h 2 ) 1 / 2 , and the relative displacement between the interface of the GCL bottom geotextile (1503) and the geomembrane (16) is (x-((h+s) 2 -h 2 ) 1 / 2 );

[0039] Step 7: After the interface shear test is completed, gradually unload the horizontal and vertical pressures step by step, then lift the upper shear box (11), remove the GCL (15) and geomembrane (16), turn off the machine and clean the shear platform.

[0040] Due to the adoption of the above scheme, the beneficial effects of the present invention are as follows:

[0041] The device of the present invention not only realizes the uniform and reliable fixation of the geosynthetic specimen during the static and dynamic interface shear test, but also realizes the accurate measurement of the relative displacement between the geotextiles on the upper and lower surfaces of the GCL; the device has a simple structure and is easy to operate, and can be embedded into a large-scale conventional geotechnical direct shear test system as a functional unit module, filling the functional defects of the current geotechnical direct shear instrument, and greatly promoting the accurate division of the failure stage and the accurate revelation of the instability mechanism during the interface shear test between the GCL and other geotechnical materials. Description of the Drawings

[0042] Figure 1 It is a front view structural schematic diagram of the test device of the present invention.

[0043] Figure 2 It is a top view structural schematic diagram of the test device of the present invention.

[0044] Figure 3 It is an overall three-dimensional structural schematic diagram of the regular square pyramid grab teeth of the test device of the present invention.

[0045] Figure 4 It is a planar structural schematic diagram of the stitching of the geomembrane gasket and the bottom geotextile of the GCL of the test device of the present invention.

[0046] Figure 5 It is a front view structural schematic diagram of the test device of the present invention in the preparation state for carrying out the GCL interface shear test. (Application scenario)

[0047] Figure 6 It is a front view structural schematic diagram of the test device of the present invention in the working state for carrying out the GCL interface shear test. (Application scenario)

[0048] Figure 7 It is a schematic diagram of the existing test device.

[0049] Reference numerals: 1 - bottom plate,

[0050] 2 - grab teeth, 201 - regular square pyramid grab teeth,

[0051] 3 - connecting ear plate,

[0052] 4 - Fixed support, 401 - Constraint rod, 5 - Automatic retractable wire reel, 6 - Ultra - fine wire, 7 - Displacement sensor, 8 - Wire duct, 801 - Wire duct one, 802 - Wire duct two, 803 - Wire duct three, 10 - Data collector,

[0053] 11 - Upper shear box, 12 - Fixing screw, 13 - Fixing nut, 14 - Lower shear box,

[0054] 15 - GCL, 1501 - Upper geotextile of GCL, 1502 - Middle bentonite of GCL, 1503 - Lower geotextile of GCL, 16 - Geomembrane, 9 - Geomembrane gasket,

[0055] 17 - Vertical load, 18 - Horizontal thrust. Specific implementation manner

[0056] The present invention provides a device and method for measuring the dislocation displacement of the interface shear of the GCL interlayer by a large - scale direct shear apparatus.

[0057] The following further illustrates the present invention in conjunction with embodiments.

[0058] Embodiment:

[0059] A device for measuring the dislocation displacement of the interface shear of the GCL interlayer by a large - scale direct shear apparatus in this embodiment includes the following structural components: bottom plate 1, grab teeth 2, regular square pyramid grab teeth 201, connecting ear plates 3, fixed support 4, constraint rod 401, automatic retractable wire reel 5, ultra - fine wire 6, displacement sensor 7, wire duct 8, wire duct one 801, wire duct two 802, wire duct three 803, geomembrane gasket 9, data collector 10.

[0060] The device for measuring the dislocation displacement of the interface shear of the GCL interlayer by a large - scale direct shear apparatus in this embodiment includes: a grab - tooth plate system and a displacement real - time monitoring system. As Figure 1 , Figure 2 .

[0061] Among them, the grab - tooth plate system includes: bottom plate 1, grab teeth 2 and connecting ear plates 3; the bottom plate 1 is a stainless - steel cuboid; the grab teeth 2 are neatly arranged on the lower surface of the bottom plate 1 and are used to uniformly fix the geosynthetic material sample on the shear surface during the interface shear test; among the grab teeth 2, except for several grab teeth with wire ducts 8 passing through them which are inverted stainless - steel regular square pyramid grab teeth 201 (such as Figure 3 ), the rest are all stainless - steel regular square pyramid grab teeth with the same size and the tooth tips facing downwards; four of the connecting ear plates 3 are symmetrically and flatly connected to both sides of the upper surface of the bottom plate 1, with two stainless - steel connecting ear plates 3 on each side, and are used to fix the bottom plate 1 to the bottom of the upper shear box 11 (such as Figure 5 , Figure 6 );

[0062] The displacement real-time monitoring system includes: a fixed bracket 4, an automatic retractable wire reel 5, an ultra-fine wire 6, a displacement sensor 7, a wire duct 8, a geomembrane gasket 9, and a data collector 10;

[0063] The main body of the fixed bracket 4 is a rectangular stainless-steel frame, which is welded to the top end of the left side of the bottom plate 1 at a certain inclination angle. Several stainless-steel restraint rods 401 extend obliquely downward from the outer end crossbar of the fixed bracket 4, providing a spatial fulcrum for the automatic retractable wire reel 5;

[0064] The automatic retractable wire reel 5 is fixed to the end of the stainless-steel restraint rod 401, can provide the ultra-fine wire 6 required for the test, and has a certain automatic retraction tension, which can ensure that the ultra-fine wire 6 is always in a taut state during the interface shear test;

[0065] The ultra-fine wire 6 is pulled out from the automatic retractable wire reel 5, passes through the displacement sensor 7, and after passing through the wire duct 8, stays at the bottom of the bottom plate 1, and is used to measure the dislocation displacement of the GCL15 interlayer during the interface shear test;

[0066] The displacement sensor 7 is fixed to the left side of the bottom plate 1 through a stainless-steel restraint rod 701, and is used to monitor the length of the ultra-fine wire 6 pulled out from the automatic retractable wire reel 5 in real time;

[0067] The wire duct 8 is formed by drilling a hole at the half-height position on the left side of the bottom plate 1, extending horizontally to the right for a certain distance, and then passing vertically through the lower surface of the bottom plate 1 to form an outlet. Three wire ducts 8 are arranged in parallel. Along the horizontal direction of the bottom plate 1 from left to right, they are wire duct one 801, wire duct two 802, and wire duct three 803 respectively, which respectively assist the ultra-fine wire 6 to measure the interlayer dislocation displacement at different longitudinal and transverse positions of the GCL15;

[0068] Such as Figure 4 , the geomembrane gasket 9 is circular, is arranged at the bottom of the GCL15, and is sewn together with the geotextile 1503 at the bottom layer of the GCL15 through the ultra-fine wire 6 to ensure that the fixed point of the ultra-fine wire 6 on the geotextile 1503 does not shift with the interface shear movement;

[0069] The data collector 10 is connected to the displacement sensor 7 through a data line, and is used to collect the data monitored by the displacement sensor 7.

[0070] The usage method of a large direct shear apparatus for measuring the dislocation displacement of the GCL interlayer during interface shear in this embodiment, taking the interface shear test between the GCL and the geomembrane as an example, includes the following steps:

[0071] Step 1: Cut out a geosynthetic clay liner GCL15 with the same bottom area as the bottom surface of the bottom plate 1. Align the GCL15 with the bottom surface of the bottom plate 1. Then tie the ultra-fine steel wire 6 led out from the steel wire duct 8 to a straight needle and pierce through the center of the GCL15 and the geomembrane gasket 9 in sequence. Next, replace the straight needle with a hooked needle and perform cross-stitching on the geomembrane gasket 9 and the GCL bottom geotextile 1503 through the ultra-fine steel wire 6. After finishing, cut off the excess ultra-fine steel wire 6 flush;

[0072] Step 2: Align the connecting ear plate 3 on the top surface of the bottom plate 1 with the connecting ear plate 3 on the bottom surface of the upper shear box 11. Then pass the fixing screw 12 through the round hole on the connecting ear plate 3 and tighten it with the fixing nut 13;

[0073] Step 3: Cut out a geomembrane 16 with the same top surface area as the top surface of the lower shear box 14 and place it aligned on the grabbing teeth 2 on the top surface of the lower shear box 14;

[0074] Step 4: Horizontally push and adjust the lower shear box 14 to make its left edge completely aligned with the left edge of the upper shear box 11. Then control the vertical actuator in the displacement control mode and slowly lower the upper shear box 11 until the GCL15 and the geomembrane 16 are about to come into contact. At this time, switch the control mode of the vertical actuator to axial force control, precisely control the change rate of the interface normal pressure until the vertical load 17 required for the test is reached. Then the interface remains under this load for a certain period of time;

[0075] Step 5: After the interface holding is completed, by controlling the telescopic state of the horizontal actuator, make the lower shear box move horizontally along the horizontal guide rail under the horizontal thrust 18, and the interface shear action starts to occur between the GCL15 and the geomembrane 16;

[0076] Step 6: The total horizontal shear displacement x is recorded by the horizontal displacement sensor connected to the lower shear box 14. The elongation displacement s of the ultra-fine steel wire 6 caused by the dislocation of the GCL15 interlayer is recorded by the grabbing tooth plate device of the present invention. The vertical displacement change of the interface material under the current stable vertical load 17 can be monitored in real time by the vertical displacement sensor (the thicknesses of the GCL upper geotextile 1501, the GCL bottom geotextile 1503, and the geomembrane 16 itself are relatively small and the thickness change can be ignored under the stable vertical load 17). Then the real-time height h of the GCL middle bentonite 1502 can be obtained. From this, the inclined length of the ultra-fine steel wire 6 in the GCL middle bentonite 1502 can be calculated as (h + s). According to the Pythagorean theorem, the dislocation displacement between the GCL upper geotextile 1501 and the GCL bottom geotextile 1503 is ((h + s) 2 -h 2 ) 1 / 2 , and the relative displacement between the GCL15 and the geomembrane 16 interfaces is (x - ((h + s)2 -h 2 ) 1 / 2 );

[0077] Step 7: After the interface shear test is completed, gradually unload the horizontal and vertical pressures step by step, then raise the upper shear box 11, remove the GCL 15 and geomembrane 16, turn off the machine and clean the shear platform.

[0078] The above description of the embodiments is intended to enable those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments. Any improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A device for measuring the displacement of the interface shear and GCL interlayer dislocation of a large direct shear apparatus, characterized in that It includes a grab tooth plate system and a real-time displacement monitoring system; Among them, the grab tooth plate system includes: a bottom plate (1), grab teeth (2) and connecting ear plates (3); Among them, the real-time displacement monitoring system includes: a fixed bracket (4), an automatically retractable steel wire reel (5), an ultra-fine steel wire (6), a displacement sensor (7), a steel wire duct (8), a geomembrane gasket (9) and a data collector (10); The grab teeth (2) are neatly arranged on the lower surface of the bottom plate (1) to uniformly fix the geosynthetic specimen on the shear surface during the interface shear test; The connecting ear plates (3) are flat-connected to both sides of the upper surface of the bottom plate (1) to fix the bottom plate (1) to the bottom of the upper shear box (11); The main body of the fixed bracket (4) is a rectangular stainless steel frame, which is welded to the top end of the left side of the bottom plate (1) at a certain inclination angle. Several stainless steel restraint rods (401) extend obliquely downward from the outer end crossbar of the fixed bracket (4) to provide a spatial fulcrum for the automatically retractable steel wire reel (5); The automatically retractable steel wire reel (5) is fixed at the end of the stainless steel restraint rod (401), provides the ultra-fine steel wire (6) required for the test, and has an automatically retractable tension to ensure that the ultra-fine steel wire (6) is always in a taut state during the interface shear test; The ultra-fine steel wire (6) is pulled out from the automatically retractable steel wire reel (5), passes through the displacement sensor (7), and after passing through the steel wire duct (8), stays at the bottom of the bottom plate (1) to measure the displacement of the GCL (15) interlayer dislocation during the interface shear test; The displacement sensor (7) is fixed to the left side of the bottom plate (1) by a stainless steel restraint rod (701) to continuously monitor the length of the ultra-fine steel wire (6) pulled out from the automatically retractable steel wire reel (5); The steel wire duct (8) is formed by drilling a hole at the half-height position on the left side of the bottom plate (1), extending horizontally to the right for a certain distance, and then vertically penetrating the lower surface of the bottom plate (1) to form an outlet, assisting the ultra-fine steel wire (6) to measure the interlayer dislocation displacement at different longitudinal and transverse positions of the GCL (15); The geomembrane gasket (9) is circular, is arranged at the bottom of the GCL (15), and is sewn to the geotextile (1503) at the bottom layer of the GCL (15) through the ultra-fine steel wire (6) to ensure that the fixed point of the ultra-fine steel wire (6) on the geotextile (1503) does not shift with the interface shear movement; The data collector (10) is connected to the displacement sensor (7) through a data line to collect the data monitored by the displacement sensor (7) and calculate and output the dislocation displacement value; The total horizontal shear displacement x, the elongation displacement s of the ultra-fine steel wire (6) caused by dislocation, the real-time height h of the bentonite in the middle layer of the GCL, the data collector (10) calculates: The inclined length of the ultra-fine steel wire (6) in the bentonite (1502) in the middle layer of the GCL is h + s; The displacement of the upper geotextile (1501) of the GCL relative to the lower geotextile (1503) of the GCL is ((h + s) 2 -h 2 ) 1 / 2 ; The relative displacement between the interface of the GCL bottom geotextile (1503) and the geomembrane (16) is x - ((h + s) 2 -h 2 ) 1 / 2 .

2. The measuring device according to claim 1, wherein: The bottom plate (1) is a stainless steel cuboid; Among the grabbing teeth (2), several grabbing teeth with wire channels (8) penetrating through them are inverted stainless steel regular square pyramid grabbing teeth (201), and the rest are all stainless steel regular square pyramid grabbing teeth with the same size and the tooth tips facing downwards.

3. The measuring device according to claim 1, characterized in that: There are four connecting ear plates (3), symmetrically and flatly connected to both sides of the upper surface of the bottom plate (1), with two stainless steel connecting ear plates (3) on each side, used to fix the bottom plate (1) to the bottom of the upper shear box (11).

4. The measuring device according to claim 1, characterized in that: There are three wire channels (8) arranged in parallel. Along the horizontal direction of the bottom plate (1), from left to right, they are wire channel one (801), wire channel two (802), and wire channel three (803). They respectively assist the ultra-fine wire (6) to measure the interlayer displacement of different positions in the longitudinal and transverse directions of the GCL (15), and then reduce the detection error by taking the average value.

5. The measuring device according to claim 4, characterized in that: There are three displacement sensors (7) arranged in parallel, respectively used to monitor in real time the lengths of three ultra-fine wires (6) passing through wire channel one (801), wire channel two (802), and wire channel three (803) pulled out from the automatic retractable wire reel (5).

6. A method for using a device for measuring the dislocation displacement of the interface shear of a GCL interlayer by a large direct shear apparatus as described in claim 1, characterized in that: It includes the following steps: The first step: Cut out a geosynthetic clay liner GCL (15) with the same bottom surface area as the bottom plate (1). Align the GCL (15) with the bottom surface of the bottom plate (1), then tie the ultra-fine wire (6) led out from the wire channel (8) to a straight needle and pierce through the GCL (15) and the center of the geomembrane gasket (9) in sequence. Then replace the straight needle with a hooked needle, and perform cross-stitching on the geomembrane gasket (9) and the bottom layer geotextile (1503) of the GCL through the ultra-fine wire (6). After completion, cut off the excess ultra-fine wire (6) flush. The second step: Align the connecting ear plates (3) on the top surface of the bottom plate (1) with the connecting ear plates (3) on the bottom surface of the upper shear box (11), then pass the fixing screws (12) through the round holes on the connecting ear plates (3), and tighten and fix them with fixing nuts (13). The third step: Cut out a geomembrane (16) with the same top surface area as the lower shear box (14), and align and place it on the grabbing teeth (2) on the top surface of the lower shear box (14). The fourth step: Horizontally push and adjust the lower shear box (14) so that its left edge is completely aligned with the left edge of the upper shear box (11). Then control the vertical actuator in the displacement control mode, slowly lower the upper shear box (11). When the GCL (15) is about to contact the geomembrane (16), switch the control mode of the vertical actuator to axial force control, control the change rate of the normal pressure on the control interface until the required vertical load (17) for the test is reached, and then the interface remains under this load for a certain period of time. The fifth step: After the interface holding is completed, by controlling the telescopic state of the horizontal actuator, make the lower shear box move horizontally in a set motion mode under the action of the horizontal thrust (18), and the interface shear action starts between the GCL (15) and the geomembrane (16). Step 6: The total horizontal shear displacement x is provided by the horizontal displacement sensor connected to the lower shear box (14) of the conventional large direct shear apparatus. The elongation displacement s of the ultra-fine steel wire (6) caused by the dislocation of the GCL (15) interlayer is recorded by the grab-tooth plate device. The vertical displacement change of the interface material under the action of the current stable vertical load (17) is monitored by the vertical displacement sensor connected to the upper shear box (11) of the conventional large direct shear apparatus. Subsequently, the real-time height h of the bentonite in the middle layer of the GCL is obtained. Thus, the inclined length of the ultra-fine steel wire (6) in the bentonite (1502) in the middle layer of the GCL is calculated as (h + s). According to the Pythagorean theorem, the dislocation displacement between the upper geotextile (1501) and the lower geotextile (1503) of the GCL is ((h + s) 2 -h 2 ) 1 / 2 . The relative displacement between the interface of the lower geotextile (1503) of the GCL and the geomembrane (16) is (x - ((h + s) 2 -h 2 ) 1 / 2 ); The seventh step: After the interface shear test is completed, first unload the horizontal and vertical pressures step by step, then raise the upper shear box (11), remove the GCL (15) and the geomembrane (16), shut down and clean the shear platform.

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