Direct shear test stress detection device based on electronic universal testing machine

Abstract

The invention discloses a direct shear test stress detection device based on an electronic universal testing machine in the technical field of geotechnical engineering test equipment, a stress conversion device, an upper shear box and a lower shear box are mounted in the electronic universal testing machine in an up-down overlapping manner, and the stress conversion device can adjust the stress angle; according to the device, the precise displacement control function of the electronic universal testing machine can be fully utilized to realize precise adjustment of the shearing rate, so that more accurate interface mechanical parameter test data can be obtained, and through vertical force application of the electronic universal testing machine, the mechanical performance of the interface can be improved. The force in the vertical direction is accurately decoupled, and the normal force and the shear force of the test soil body can be accurately obtained by combining the tandem type three-dimensional load sensor, so that the data relevance is stronger, the stress analysis of the soil body is facilitated, and the test accuracy is improved. Therefore, the device simulates the real working conditions of non-constant stress ratio in projects such as pile-soil interface lateral loading and retaining wall gradual sliding.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering test equipment, in particular to a direct shear test stress detection device based on an electronic universal testing machine. BACKGROUND

[0002] In the field of geotechnical engineering, soil and concrete interface shear test is an important method to obtain the mechanical parameters between different materials and soil interface. The portability of the test device and the accurate determination of test data play a key role in pile foundation design, retaining wall stability analysis and other engineering practices.

[0003] In the field of geotechnical engineering, the study of the interaction characteristics of soil and concrete interface has important value for key engineering problems such as uplift pile bearing capacity evaluation, anchor pullout force determination and pile side friction analysis. However, the existing test technology system still has certain technical limitations: first, the in-situ test method is significantly affected by environmental factors, and the test results show large dispersion; second, the traditional direct shear test equipment relies on a special hydraulic loading system, and the equipment purchase cost is high; third, the conventional uniaxial force sensor cannot realize the synchronous measurement of normal force and shear force; in addition, the existing shear loading method is too single, resulting in systematic errors in test data;

[0004] The current indoor test equipment is limited in function and cannot fully utilize the test precision advantage of the electronic universal testing machine. The existing test method cannot realize the simultaneous measurement of normal force and shear force, and the system precision is insufficient.

[0005] Based on this, the present application designs a direct shear test stress detection device based on an electronic universal testing machine to solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a direct shear test stress detection device based on an electronic universal testing machine. The device is optimized in design, which can fully utilize the precise displacement control function of the electronic universal testing machine to realize precise adjustment of the shear rate, so as to obtain more accurate interface mechanical parameter test data. Through the vertical force of the electronic universal testing machine, the vertical force can be accurately decoupled in the same experiment, and the normal force and shear force of the test soil can be obtained, so that the experimental data is more accurate, the experimental efficiency is high, and the data correlation is stronger, which is beneficial to the stress analysis of soil, so that the device can simulate the real working conditions of non-constant stress ratio in engineering such as lateral loading of pile-soil interface and gradual sliding of retaining wall.

[0007] The present application is implemented as follows: a direct shear test stress detection device based on an electronic universal testing machine, comprising:

[0008] a testing machine, a stress conversion device, an upper shear box, a lower shear box and a sliding block.

[0009] The testing machine is a square-frame-shaped electronic universal testing machine. An upper actuating rod is vertically installed on the top of the testing machine, and a lower actuating rod is vertically installed at the bottom of the inner frame of the testing machine.

[0010] The lower shear box is a box with an open top. The lower shear box is horizontally and stably locked to the upper end of the lower action rod. A shearing groove is provided on each of the front and rear sides of the top of the lower shear box. The two shearing grooves are recessed in the left and right direction on the top of the lower shear box.

[0011] The upper shear box is a hollow box with openings at the top and bottom. The upper shear box slides horizontally on top of the lower shear box in the left-right direction via a shearing groove.

[0012] A rangefinder is installed on each of the left and right vertical sidewalls of the upper shear box, and the detection direction of the rangefinder is directly facing the vertical side bar of the testing machine.

[0013] The top opening of the upper shear box is covered by a permeable stone slab, and permeable holes are provided on the permeable stone slab, which are connected to the inner cavity of the upper shear box.

[0014] The force conversion device is a foldable force transmission structure. One force conversion device is locked to the lower end of the upper action rod, and the other force conversion device is connected and fixed to the three-dimensional load sensor and the pressure plate. The three-dimensional load sensor is sandwiched between the lower force conversion device and the pressure plate.

[0015] The force conversion device includes an inclined pressure plate, a flat load plate, and an adjusting support rod;

[0016] The flat plate is set horizontally, and one side edge of the inclined pressure plate is set at an angle to the flat plate via a hinge. Adjustable struts are vertically set on the open sides of the inclined pressure plate and the flat plate. The inclined pressure plate, the flat plate, and the adjustable struts form a triangular support frame.

[0017] The flat plate of the force conversion device above is locked to the upper actuating rod by a flange;

[0018] The flat plate of the force conversion device below is locked with the three-dimensional load sensor and the pressure plate, with the three-dimensional load sensor located between the flat plate and the pressure plate;

[0019] The two force conversion devices, one above the other, are symmetrically arranged as mirror images of each other;

[0020] The upper and lower inclined pressure plates of the force conversion device are equipped with sliders, and the upper and lower inclined pressure plates slide against each other through the sliders, and the sliding surface of the sliders is inclined.

[0021] The two force conversion devices mentioned above are slidably spliced ​​together to form a square force-bearing frame structure.

[0022] Furthermore, the inclined pressure plate of the force conversion device described below is inclined with the left side lower and the right side higher, and a guide rail is also provided on the top of the inclined pressure plate in the left and right direction. The trajectory of the guide rail is also consistent with the inclination angle of the plane where the inclined pressure plate is located.

[0023] The inclined pressure plate of the force conversion device mentioned above is also inclined with the left side lower and the right side higher, and the two inclined pressure plates are parallel to each other;

[0024] The slider is installed at the center of the bottom inclined surface of the upper inclined pressure plate, and the slider slides inside the guide rail.

[0025] Furthermore, an adjusting support rod is vertically installed on each of the front and rear sides of the flat plate;

[0026] A sliding groove hole is opened on each of the front and rear sides of the inclined pressure plate. The sliding groove hole is an oblong hole opened in the left and right direction. Each of the adjusting support rods is inserted into a sliding groove hole.

[0027] Furthermore, two adjusting nuts are provided on the same adjusting support rod. The two adjusting nuts are respectively clamped on the upper and lower sides of the sliding groove hole. The adjusting support rod is mounted on the inclined pressure plate with adjustable position through the two adjusting nuts.

[0028] The adjusting nut is a trapezoidal nut.

[0029] Furthermore, the three-dimensional load sensor is located at the center of the top of the pressure plate;

[0030] The pressure plate is a stainless steel flat plate, and the pressure plate is horizontally arranged.

[0031] The upper shear box is sealed by a permeable stone slab. There are two permeable holes, which are symmetrically arranged on both sides of the inlet stone slab, and the pressure plate does not block the permeable holes.

[0032] Furthermore, an electronic angle gauge is also installed on the hinge between the inclined pressure plate and the flat plate.

[0033] The beneficial effects of this invention are: 1. This device no longer uses direct shear testing equipment, but uses an electronic universal testing machine. The electronic universal testing machine monitors more data, detects a wider range of force analysis data, and obtains more complete force analysis data.

[0034] 2. This device also includes a force conversion device, which can convert vertical forces into oblique normal and shear forces, making data monitoring more convenient. Moreover, it can obtain forces in both directions at the same time, which is convenient for experiments. Furthermore, the two forces obtained in one experiment are more correlated. The old direct shear test could only obtain the shear force by changing the normal force. This device obtains the overall stress structure and overall stress analysis, resulting in a higher degree of simulation for soil stress analysis.

[0035] 3. This device adds flexible adjustment of the adjusting strut and adjusting nut, as well as the angle adjustment of the inclined pressure plate and the flat support plate, and the cooperation of the slider and the guide rail, realizing the precise decoupling of normal force and shear force. It also realizes in-situ precise measurement of interface force through a three-dimensional force sensor. This device solves the technical problems of traditional equipment being unable to simulate variable stress ratio paths and having large measurement errors. It provides a reliable experimental research method for engineering problems such as pile-soil interaction and underground structure interfaces, and significantly improves the accuracy of interface mechanical parameter testing and the scientific nature of engineering design. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Fig. 1 This is a schematic diagram of the overall structure of the present invention;

[0038] Fig. 2 This is a schematic diagram of the overall front structure of the present invention;

[0039] Fig. 3 This is a schematic diagram of the assembly structure of the upper and lower shear boxes of the present invention;

[0040] Fig. 4 This is a schematic diagram of the overlapping and docking structure of the two force conversion devices of the present invention;

[0041] Fig. 5 This is a schematic diagram of the superimposed and docked structure of the two force conversion devices of the present invention at another angle;

[0042] Fig. 6 This is a schematic diagram of the force conversion device structure of the present invention.

[0043] The attached diagram lists the components represented by each number as follows:

[0044] 1-Testing machine, 11-Upper actuating rod, 12-Lower actuating rod, 2-Force conversion device, 21-Inclined pressure plate, 22-Flat load plate, 23-Adjusting support rod, 24-Adjusting nut, 25-Slide groove hole, 3-Upper shear box, 31-Pressure plate, 32-Range measuring instrument, 33-Three-dimensional load sensor, 34-Permeable hole, 35-Permeable stone slab, 4-Lower shear box, 41-Shear slide groove, 5-Slider, 51-Slide rail, 52-Electronic angle ruler. Detailed Implementation

[0045] Please see Figs. 1 to 6 As shown, the present invention provides a direct shear test force detection device based on an electronic universal testing machine. In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] In a specific embodiment of the technical solution of the present invention:

[0047] It includes a testing machine 1, a force conversion device 2, an upper shear box 3, a lower shear box 4, and a slider 5;

[0048] The testing machine 1 is a square-shaped electronic universal testing machine. The upper actuating rod 11 is vertically installed on the top of the testing machine 1, and the lower actuating rod 12 is vertically installed at the bottom of the inner frame of the testing machine 1. Both the upper actuating rod 11 and the lower actuating rod 12 are driving rods that can be raised and lowered vertically.

[0049] The lower shear box 4 is a box with an open top. The lower shear box 4 is horizontally and stably locked at the upper end of the lower action rod 12, which can be locked by a flange. A shearing groove 41 is provided on each of the front and rear sides of the top of the lower shear box 4. The two shearing grooves 41 are recessed in the left and right direction on the top of the lower shear box 4.

[0050] The upper shear box 3 is a hollow box with openings at the top and bottom. It slides horizontally onto the top of the lower shear box 4 via a shearing groove 41. The shearing groove 41 and the upper shear box 3 are fitted together by a concave-convex groove, and the sliding surface is covered with PTFE to ensure smoothness, reduce the coefficient of friction, and minimize test errors. A rangefinder 32 is installed on each of the left and right vertical sidewalls of the upper shear box 3, with the detection direction of the rangefinder 32 facing the vertical side bar of the testing machine 1.

[0051] The top opening of the upper shear box 3 is covered by a permeable stone slab 35, and a pressure plate 31 is laid on the top of the permeable stone slab 35. A three-dimensional load sensor 33 is installed on the top of the permeable stone slab 35, and permeable holes 34 are opened on the permeable stone slab 35, which are connected to the inner cavity of the upper shear box 3.

[0052] The force conversion device 2 is a foldable force transmission structure. One force conversion device 2 is locked at the lower end of the upper action rod 11, and the other force conversion device 2 is connected and fixed to the three-dimensional load sensor 33 and the pressure plate 31. The three-dimensional load sensor 33 is sandwiched between the lower force conversion device 2 and the pressure plate 31.

[0053] The three-dimensional load sensor 33 is located at the center of the top of the pressure plate 31. The three-dimensional load sensor 33 is a sensor that can detect three-dimensional loads and can be used to monitor the three-dimensional load transmitted from the top of the upper shear box 3 by the downward pressure of the force conversion device 2.

[0054] The pressure plate 31 is a stainless steel flat plate, and the pressure plate 31 is set horizontally;

[0055] The upper shear box 3 is sealed by a permeable stone slab 35. There are two permeable holes 34, which are symmetrically arranged on both sides of the permeable stone slab 35, and the pressure plate 31 does not block the permeable holes 34.

[0056] The measurement system built into the electronic testing machine 1, and the three-dimensional load sensor 33 connected to the force conversion device 2, are directly connected in series with the upper shear box 3 to avoid errors caused by the force conversion device 2 and the upper action rod 11 applying pressure.

[0057] This device can directly measure the shear force and normal force generated when the interface of a soil test sample is subjected to shear.

[0058] Laser rangefinders 32, fixed to the two side walls of the upper shear box 3 perpendicular to the shearing direction, are used to measure the shear displacement and compare it with the displacement set by the electronic universal testing machine 1, making the test more accurate.

[0059] The force conversion device 2 includes an inclined pressure plate 21, a flat load plate 22, and an adjusting support rod 23;

[0060] The flat plate 22 is set horizontally, and one side edge of the inclined pressure plate 21 is set at an angle to the flat plate 22 via a hinge. An electronic angle gauge 52 is also set on the hinge between the inclined pressure plate 21 and the flat plate 22, so as to facilitate accurate detection of the angle between the inclined pressure plate 21 and the flat plate 22, and facilitate the judgment and recording of actual data.

[0061] Adjustable struts 23 are vertically installed on the opening sides of the inclined pressure plate 21 and the flat load plate 22. The inclined pressure plate 21, the flat load plate 22 and the adjustable struts 23 form a triangular support frame.

[0062] An adjusting support rod 23 is vertically installed on each of the front and rear sides of the flat plate 22;

[0063] A sliding groove hole 25 is opened on each of the front and rear sides of the inclined pressure plate 21. The sliding groove hole 25 is a waist-shaped hole opened in the left and right direction. Each adjusting support rod 23 is inserted into a sliding groove hole 25.

[0064] Furthermore, two adjusting nuts 24 are provided on the same adjusting support rod 23. The two adjusting nuts 24 are clamped on the upper and lower sides of the slide hole 25 respectively. The adjusting support rod 23 is installed on the inclined pressure plate 21 in an adjustable position through the two adjusting nuts 24.

[0065] The adjusting nut 24 is a trapezoidal nut. By adjusting the trapezoidal nut, the adjusting nut 24 can be used to engage the adjusting support rod 23 in the slide hole 25 at the required appropriate position, thereby achieving the purpose of adjusting the fitting angle between the inclined pressure plate 21 and the flat plate 22. It is not necessary to disassemble the adjusting support rod 23. Only by changing the position of the adjusting nut 24 on the adjusting support rod 23, the adjusting support rod 23 can be stably supported with the inclined pressure plate 21 at different height positions, which is convenient for adjustment.

[0066] Furthermore, special angle markings of 30°, 45°, and 60° are reserved according to the length of the inclined pressure plate 21 and the flat support plate 22; an electronic digital angle ruler 52 is installed and fixed at the connection between the inclined pressure plate 21 and the flat support plate 22 to measure the tilt angle in real time for accurate recording.

[0067] After confirming the target angle using the digital angle ruler 52, the upper and lower adjusting nuts 24 are used to lock the adjusting support rod 23, and the inclined pressure plate 21 and the flat plate 22 maintain the designed angle.

[0068] Stress ratio variation at different angles:

[0069] At a 30° angle, the stress ratio (shear force / normal force) is approximately 0.58 (tan30°).

[0070] At a 45° angle, the stress ratio is 1.00.

[0071] At a 60° angle, the stress ratio is approximately 1.73.

[0072] This device can simulate real working conditions with non-constant stress ratios in engineering projects, such as lateral loading at the pile-soil interface and progressive sliding of retaining walls.

[0073] The flat plate 22 of the upper force conversion device 2 is locked to the upper actuating rod 11 by a flange;

[0074] The force conversion device 2 below is connected and fixed to the three-dimensional load sensor 33 and the pressure plate 31. The three-dimensional load sensor 33 is located between the flat plate 22 and the pressure plate 31.

[0075] The two force conversion devices 2 are symmetrically arranged, mirror images of each other;

[0076] The inclined pressure plates 21 of the upper and lower force conversion devices 2 are equipped with sliders 5. The upper and lower inclined pressure plates 21 slide against each other through the sliders 5, and the sliding surface of the sliders 5 is inclined.

[0077] The two force conversion devices 2 are slidably spliced ​​together to form a square force-bearing frame structure.

[0078] The inclined pressure plate 21 of the lower force conversion device 2 is inclined with the left side lower and the right side higher, and the top of the inclined pressure plate 21 is also provided with a guide rail 51 in the left and right direction. The trajectory of the guide rail 51 is also consistent with the inclination angle of the plane where the inclined pressure plate 21 is located.

[0079] The inclined pressure plate 21 of the upper force conversion device 2 is also inclined on the left and right, and the two inclined pressure plates 21 are parallel to each other.

[0080] The slider 5 is installed at the center of the bottom inclined surface of the upper inclined pressure plate 21, and the slider 5 is slidably set in the guide rail 51.

[0081] The slider 5 is detachably mounted on the upper inclined pressure plate 21 by bolts, which facilitates disassembly and assembly, thereby increasing the length of the slider. Therefore, the slider 5 requires multiple replacement parts with different height dimensions to facilitate flexible adjustment of the distance between the upper and lower inclined surfaces.

[0082] The slider 5 is directly fitted into the guide rail 51, allowing the slider 5 and the guide rail 51 to be directly pulled apart and disassembled. This facilitates the assembly of the slider, reduces the need to change the tilt angle as in the traditional way, and avoids the tedious steps of adjusting the connection length of the slider.

[0083] It should be noted that:

[0084] 1. Before conducting the experiment, calculate the vertical load that the electronic universal testing machine needs to apply based on the normal force acting on the soil. This can be achieved through the geometric relationship of the adjustable tilt guide rail: Vertical load = Normal force ÷ (cosθ × cosθ);

[0085] This device moves along the inclined guide rail 51 via the slider 5, and the forces applied vertically by the forced separation test machine are normal force and shear force, thereby achieving direct decoupling in the structure;

[0086] The tilt angle is precisely set using an electronic digital angle ruler 52 to ensure accurate resolution.

[0087] Then, the decomposed normal force and shear force are directly measured by the three-dimensional load sensor 33, which effectively avoids indirect calculation errors;

[0088] 2. The computer system of the electronic universal testing machine 1 controls the rotation of the servo motor through the controller and the speed regulation system. After being decelerated by the deceleration system, the moving crossbeam is driven to rise and fall through the precision lead screw pair to complete various mechanical property tests such as tensile, compression, bending and shear tests of the specimen. The use of the electronic universal testing machine 1 in this device makes vertical force measurement more convenient and flexible.

[0089] During the experiment,

[0090] Sample preparation: Using a mold, a concrete sample with the same dimensions and shape as the internal space of the lower shear box 4 is made. Concrete blocks with different roughness can be designed according to the test.

[0091] Installation of the testing apparatus: Connect a force conversion device 2 to the upper actuating rod 11 of the electronic universal testing machine 1 via a flange connection;

[0092] The lower shear box 4 is connected and fixed to the lower action rod 12 via a flange; the prepared concrete module is installed in the lower shear box 4, and a layer of polytetrafluoroethylene film is embedded in the shearing groove 41 of the lower shear box 4; the bottom of the upper shear box 3 is aligned with the shearing groove 41 of the lower shear box 4 and slidably installed.

[0093] The laser rangefinder 32 needs to be fixed at the center of the left and right side walls of the upper shear box 3, which are perpendicular to the shearing direction.

[0094] The test soil is compacted in layers to fill the upper shear box 3, and the permeable stone slab 35 is placed over the opening of the upper shear box 3. The three-dimensional load sensor 33 is clamped in the middle by the upper force conversion device 2 and the bearing plate 31 of the upper shear box 3 to detect the load. Then, according to the preset normal force, the upper action rod 11 is slowly adjusted to make the bearing plate tightly adhere to the permeable stone slab 35, keeping the force constant. Then, the electronic universal testing machine 1 is set to a fixed descent rate to carry out the direct shear test.

[0095] By adjusting the movable adjusting nut 23 of the force conversion device 2 to the preset 45° mark, the upper and lower inclined pressure plates 21 are connected by the slider 5, keeping the upper and lower inclined pressure plates 21 within a suitable distance range; start the electronic universal testing machine 1, and apply force by adjusting the upper action rod 11 and the lower action rod 12 to make the pressure plate 31 and the permeable stone slab 35 in seamless contact, and connect the three-dimensional load sensor 33 to the processing computer of the testing machine 1 for data connection.

[0096] Shear test: Different shear forces and normal forces are distributed by setting the tilt angle of the pre-set force conversion device 2.

[0097] The applied pressure of the electronic universal testing machine 1 is calculated based on the normal force required by the experimental design. The applied pressure of the electronic universal testing machine 1 is preset to first apply the force to the soil of the lower shear box 4, and then the speed and displacement are preset to make the slider 5 move downward along the precision guide rail 51 of the lower inclined pressure plate 21. However, since the slider 5 is fixed on the top of the inclined pressure plate 21, the slider 5 cannot move laterally. The slider 5 can only follow the upper action rod 11 to rise and fall vertically.

[0098] Therefore, only the lower triangular force-bearing part of the force conversion device 2 connected to the precision guide rail 51 will undergo lateral translation. The precision guide rail 51 moves in the opposite direction to the slider 5, which in turn drives the upper shear box 3 to move horizontally to the right. The upper shear box 3 slides on top of the lower shear box 4, generating interface shearing.

[0099] Experimental Results Analysis: By plotting multiple sets of data results under different vertical applied forces, such as 20 kPa, 50 kPa, 100 kPa, and 200 kPa, the curves formed by shear stress and displacement under these different vertical pressure conditions were used to determine the ultimate shear stress value at the concrete-soil interface under different vertical pressures.

[0100] A scatter plot was drawn with vertical pressure as the abscissa and ultimate shear stress as the ordinate. A linear fitting method was then used to fit the plot to obtain the shear strength line of the concrete-soil interface.

[0101] The slope of the straight line is the internal friction angle of the interface, and the intercept of the straight line on the vertical axis is the interfacial cohesion. The experiment was completed, and the experimental data obtained were more accurate. Two sets of normal force and shear force results related to the vertical force were obtained by applying force once. The data are accurate and have strong correlation.

[0102] Furthermore, in the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0103] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A direct shear test force detection device based on an electronic universal testing machine, characterized in that, include: The testing machine (1), the force conversion device (2), the upper shear box (3), the lower shear box (4), and the slider (5) are all included. The testing machine (1) is a square-shaped electronic universal testing machine. The top of the testing machine (1) is vertically equipped with an upper action rod (11), and the bottom of the inner frame of the testing machine (1) is vertically equipped with a lower action rod (12). The lower shear box (4) is a hollow box with a closed bottom and an open top. The lower shear box (4) is horizontally and stably locked to the upper end of the lower action rod (12). A shearing groove (41) is provided on each of the front and rear sides of the top of the lower shear box (4). The two shearing grooves (41) are recessed in the left and right direction on the top of the lower shear box (4). The upper shear box (3) is a hollow box body. The upper shear box (3) has openings at the top and bottom. The upper shear box (3) slides horizontally on the top of the lower shear box (4) in the left and right direction through the shearing groove (41). A rangefinder (32) is installed on each of the left and right vertical sidewalls of the upper shear box (3), and the detection direction of the rangefinder (32) is directly opposite to the vertical side bar of the testing machine (1). The top opening of the upper shear box (3) is covered by a permeable stone slab (35), and a pressure plate (31) is laid on the top of the permeable stone slab (35). A three-dimensional load sensor (33) is installed on the top of the pressure plate (31). Water permeable holes (34) are also opened on the permeable stone slab (35), and the water permeable holes (34) are connected to the inner cavity of the upper shear box (3). The force conversion device (2) is a foldable force transmission structure. One of the force conversion devices (2) is locked at the lower end of the upper action rod (11), and the other force conversion device (2) is locked at the top of the upper shear box (3). The three-dimensional load sensor (33) is sandwiched between the lower force conversion device (2) and the pressure plate (31). The force conversion device (2) includes an inclined pressure plate (21), a flat load plate (22), and an adjusting support rod (23); The flat plate (22) is set horizontally, and one side edge of the inclined pressure plate (21) is set at an angle to the flat plate (22) by a hinge. An adjusting support rod (23) is set vertically on the opening side of the inclined pressure plate (21) and the flat plate (22). The inclined pressure plate (21), the flat plate (22) and the adjusting support rod (23) form a triangular support frame. The flat plate (22) of the force conversion device (2) above is locked to the upper actuating rod (11) by a flange; The three-dimensional load sensor (33) is connected below the flat plate (22) of the force conversion device (2) below. The three-dimensional load sensor (33) is connected to the top of the pressure plate (31). The flat plate (22), the three-dimensional load sensor (33) and the pressure plate (31) are connected as an integral force-bearing structure. The two force conversion devices (2) are symmetrically arranged as mirror images of each other; The inclined pressure plates (21) of the upper and lower force conversion devices (2) are equipped with sliders (5), and the upper and lower inclined pressure plates (21) slide against each other through the sliders (5), and the sliding surface of the sliders (5) is inclined. The two force conversion devices (2) are slidably spliced ​​together to form a square force-bearing frame structure.

2. The direct shear test force detection device based on an electronic universal testing machine according to claim 1, characterized in that: The inclined pressure plate (21) of the force conversion device (2) below is inclined with the left side lower and the right side higher, and the top of the inclined pressure plate (21) is also provided with a guide rail (51) in the left and right direction. The trajectory of the guide rail (51) is also consistent with the inclination angle of the plane where the inclined pressure plate (21) is located. The inclined pressure plate (21) of the force conversion device (2) mentioned above is also inclined with the left side lower and the right side higher, and the two inclined pressure plates (21) are parallel to each other; The slider (5) is installed at the center of the bottom inclined surface of the upper inclined pressure plate (21), and the slider (5) slides in the guide rail (51).

3. The direct shear test force detection device based on an electronic universal testing machine according to claim 2, characterized in that: An adjusting support rod (23) is vertically installed on each of the front and rear sides of the flat plate (22); The inclined pressure plate (21) has a sliding groove hole (25) on each of its front and rear sides. The sliding groove hole (25) is a waist-shaped hole opened in the left and right direction. Each of the adjusting support rods (23) is inserted into a sliding groove hole (25). Two adjusting nuts (24) are provided on the same adjusting support rod (23). The two adjusting nuts (24) are clamped on the upper and lower sides of the slide hole (25) respectively. The adjusting support rod (23) is installed on the inclined pressure plate (21) with its position adjustable by the two adjusting nuts (24). The adjusting nut (24) is a trapezoidal nut.

4. The direct shear test force detection device based on an electronic universal testing machine according to claim 1, characterized in that: The three-dimensional load sensor (33) is located at the center of the top of the pressure plate (31); The pressure plate (31) is a stainless steel plate, and the pressure plate (31) is set horizontally; The upper shear box (3) is sealed by a permeable stone slab (35). There are two permeable holes (34), which are symmetrically arranged on both sides of the permeable stone slab (35), and the pressure plate (31) does not block the permeable holes (34).

5. The direct shear test force detection device based on an electronic universal testing machine according to claim 1, characterized in that: An electronic angle gauge (52) is also provided on the hinge between the inclined pressure plate (21) and the flat plate (22).

Images