Indoor large direct shear tester for geotechnical engineering

Abstract

The invention discloses a large indoor direct shear tester for geotechnical engineering, and relates to the technical field of geotechnical shear tests.The large indoor direct shear tester for geotechnical engineering comprises a sample container system, a shear loading system, a data acquisition control system and a base protection system.The sample container system is formed by splicing a plurality of modular sample containers; the modularized sample container is connected through a detachable connecting fastener, a replaceable lining plate is arranged in the container and is used for adjusting the size and interface conditions of the sample container, and an embedded porous pressure plate is arranged at the bottom of the container and is used for measuring the pore pressure change in the sample seepage process. By installing the base, the protection system and the normal loading system, the function of uniformly applying normal force in the shearing process is achieved, the problem that the test result is affected by eccentric errors in the shearing process is solved, and the precision and stability of the shearing test are improved.

Description

Technical Field

[0001] The invention relates to the technical field of rock and soil shear testing, in particular to a large direct shear testing instrument for indoor use in rock and soil engineering. Background Art

[0002] Shear test in geotechnical engineering is an important experimental method to study the mechanical properties and deformation behavior of soil under different loads and environmental conditions. Direct shear test is to observe the stress-strain changes of soil samples during shearing by applying normal load and shear load, so as to evaluate the engineering properties of soil such as shear strength, friction angle and cohesion.

[0003] However, traditional field shear test equipment has problems such as complex structure, uneven loading, and inaccurate data collection, which affect the accuracy and reliability of the experimental results. In order to overcome these problems, this application designs a large-scale direct shear tester for indoor geotechnical engineering. The device provides a more efficient and accurate experimental tool for indoor geotechnical engineering research by accurately controlling the loading process, optimizing the measurement method, and simulating the environment.

[0004] 1. Patent document CN113959865B discloses a convenient field rock and soil shear test equipment. The above patent achieves the effect of replacing the traditional pull rod with a pulling cable, using new thinking and new design to make the rock and soil shear test equipment more convenient to carry, but the above patent cannot achieve the function of uniformly applying the normal force during the shearing process.

[0005] 2. Patent document CN108760535B discloses a high-speed shear test device and method for geotechnical materials. The above patent realizes stable high-speed shear of geotechnical materials in a closed and relatively insulated space, thereby completing the quantitative study of the high-speed shear vaporization effect of geotechnical materials. However, the above patent cannot achieve the reaction force limiting stabilization effect on the shear tester.

[0006] 3. Patent document CN113049405B discloses a double-sided shear test device and method for non-demolding reshaped geotechnical materials. The above patent effectively solves the problems of distortion of test results caused by demolding and installation of reshaped material samples, difficulty in testing the expansion of reshaped material samples, and difficulty in simulating engineering conditions in single-sided shear tests. However, the above patent cannot simulate the soil function under different climatic conditions.

[0007] 4. Patent document CN118624426B discloses a large-scale three-dimensional dynamic rock-soil integrated shear test system and test method. The above patent realizes three-dimensional direct shear, three-dimensional single shear or three-dimensional cyclic shear test of rock and soil under constant normal load, constant normal stiffness and dynamic normal load conditions. It can study the influence of the multi-directionality of seismic motion on the dynamic characteristics of rock, which is helpful to reveal the dynamic instability mechanism of slope, but the above patent cannot realize the real-time monitoring and processing function of test parameters.

[0008] In summary, the above patents cannot achieve the function of uniformly applying normal force during shearing, the limiting and stabilizing effect on the reaction force of the shear tester, the function of simulating soil under different climatic conditions, and the real-time monitoring and processing of test parameters, resulting in eccentricity error, unstable shear loading, inability to adapt to the changes in the mechanical properties of the specimens under different environmental conditions, and poor accuracy of data acquisition and analysis; To this end, the present application proposes a large-scale direct shear tester for indoor use in geotechnical engineering that can realize the functions of uniformly applying normal force during the shear process, limiting and stabilizing the reaction force of the shear tester, simulating soil functions under different climatic conditions, and real-time monitoring and processing of test parameters. Summary of the invention

[0009] The purpose of the present invention is to provide a large-scale direct shear tester for indoor use in geotechnical engineering, so as to solve the technical problems proposed in the above-mentioned background technology that the normal force cannot be evenly applied during the shear process, the reaction force limiting stabilization effect on the shear tester, the function of simulating soil under different climatic conditions and the real-time monitoring and processing function of the test parameters cannot be realized, resulting in eccentricity error, unstable shear loading, inability to adapt to changes in the mechanical properties of samples under different environmental conditions and poor accuracy of data acquisition and analysis.

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a large-scale direct shear tester for indoor use in geotechnical engineering, comprising a sample container system, a shear loading system, a data acquisition control system and a base protection system, wherein the sample container system is formed by splicing a plurality of modular sample containers, the modular sample containers are connected by detachable connecting buckles, a replaceable lining plate is provided inside the container for adjusting the size and interface conditions of the sample container, and an embedded porous pressure plate is provided at the bottom of the container for measuring the change of pore pressure during the seepage process of the sample; The base and protection system include: a base, an anti-vibration damping component and a transparent protective cover, which are used to observe the test process and protect the operator. The outer wall of the base is provided with an anti-vibration damping component, which includes: a shock-absorbing pad and a reaction pad. The bottom of the outer wall of the base is fixedly installed with a shock-absorbing pad. The shear loading system is connected and installed in the reaction structure frame through the reaction pad. A transparent observation window is provided on one side of the modular sample container, and the transparent observation window is used to observe the shear band evolution process inside the sample through a camera.

[0011] Preferably, a shear loading system is fixedly installed on the side of the outer wall of the container, and the shear loading system is used to apply constant speed and constant force shear loading to the sample; The shear loading system includes: a shear loading drive device and a shear loading guide rail. The shear loading drive device is powered by a servo motor. The speed of the shear loading system is precisely adjusted within the range of 0.001mm / min-10mm / min, and the shear deformation is monitored by a displacement sensor. The shear loading system supports bidirectional loading and is used to study the strength attenuation characteristics and residual strength changes of soil under multi-cycle shear conditions.

[0012] Preferably, a normal loading system is movably installed on the top of the outer wall of the container; The normal loading system includes: a servo hydraulic loading device and a loading sensor unit; The servo-hydraulic loading device is used to apply an adjustable normal pressure, and the loading sensor unit is used to monitor the normal force value; The normal loading force range of the servo hydraulic loading device is 10kN-500kN. The servo hydraulic loading device has a built-in multi-point force sensor to monitor the uniformity of normal loading in real time to avoid eccentric loading. The normal loading system is equipped with a closed-loop control function for the loading force, which can apply a constant normal force and normal strain.

[0013] Preferably, the data acquisition control system is used to collect shear test process parameters in real time and process and output the data; The data acquisition control system includes: force sensor, displacement sensor, pore pressure sensor and data processing module; The force sensor is installed in the servo hydraulic loading device, the displacement sensor is installed on the shear loading guide rail, and the shear displacement parameters of the shear loading drive device are monitored in real time. The pore pressure sensor is installed on the embedded porous pressure plate in the modular sample container, and the force sensor, displacement sensor, and pore pressure sensor are all connected to the data processing module through digital signal lines; The data processing module has a built-in embedded AI algorithm to collect and process shear force, normal force, displacement and pore pressure parameters in real time to generate shear strength curves, yield points and residual strength test results; The data supports multiple output methods, including real-time display, wireless transmission to the cloud, and USB interface storage.

[0014] Preferably, the base is connected to the reaction structure frame through anchor bolts, the reaction structure frame includes a reaction beam, a connecting longitudinal beam and a connecting cross beam, the reaction beam, the connecting longitudinal beam and the connecting cross beam are all connected by anchor bolts, 1 cm thick steel plates are installed on both sides of the outer wall of the reaction structure frame, reaction pads are fixedly installed on the inner wall side of the steel plate, and a shear loading drive device is installed on the outer wall side of the reaction pad.

[0015] Preferably, the modular sample container is installed in a shear box, a cover plate is fixedly installed on the top of the outer wall of the shear box, a transverse movable guide rail is fixedly installed on the top of the outer wall of the cover plate, a sliding plate group is movably installed in the transverse movable guide rail, a pressure plate is fixedly installed on the top of the outer wall of the sliding plate group, and a servo hydraulic loading device is fixedly installed on the top of the outer wall of the pressure plate.

[0016] Preferably, the servo hydraulic loading device is against the bottom of the outer wall of the reaction beam, the reaction beam plays a reaction force limiting role on the servo hydraulic loading device, and the reaction force pad plays a reaction force limiting role on the shear loading drive device.

[0017] Preferably, a shear loading guide rail is fixedly installed on the side of the inner wall of the shear box, and the shear loading drive device uses a horizontal jack to push the shear cutter head along the shear loading guide rail.

[0018] Preferably, an automatic centering device is fixedly installed on the top of the outer wall of the base, and the automatic centering device includes a centering guide rail driven by a stepper motor. The centering guide rail is fixedly installed on the bottom of the outer wall of the shear box and can adjust the initial position of the modular sample container so that the shear loading direction is consistent with the center line direction of the sample.

[0019] Preferably, the modular sample container is provided with a constant temperature and humidity system, including an embedded heating element, a cooling element and a humidity controller, which can control the sample temperature between -20°C and 80°C and maintain the humidity within the range of 10%-100%, so as to simulate the mechanical properties of the samples under different climates.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention realizes the function of uniformly applying normal force during the shearing process by installing a base, a protection system and a normal loading system, solves the problem of the influence of eccentricity error on the test results during the shearing process, and improves the accuracy and stability of the shearing test; 2. The present invention realizes the reaction force limiting and stabilizing effect on the shear tester by installing a reaction force structure frame and an anti-seismic vibration reduction component, thereby preventing the tester from being affected by vibration, ensuring the stability of the shearing process, and avoiding parameter errors caused by inadequate shearing; 3. The present invention realizes the function of simulating soil under different climatic conditions by installing a constant temperature and humidity system, solves the problem of studying the mechanical properties of soil under different temperature and humidity environments in indoor research, and improves the environmental adaptability of the test; 4. The present invention realizes the real-time monitoring and processing function of the test parameters by installing an automatic centering device and a data acquisition control system, and dynamically adjusts the loading process according to the experiment, thereby solving the hysteresis and accuracy problems of data acquisition and analysis, and improving the intelligence level and test accuracy of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a front view structural schematic diagram of the present invention; Figure 2 It is a schematic diagram of the reaction force structure frame of the present invention; Figure 3 It is a schematic diagram of the test process of the present invention.

[0022] In the figure: 1. reaction beam; 2. connecting longitudinal beam; 3. connecting cross beam; 4. anchor bolt; 5. shear box; 6. sliding plate group; 7. pressure plate; 8. jack; 9. reaction pad; 10. cover plate; 11. servo hydraulic loading device. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] See also Figure 1 , Figure 2 and Figure 3 , an embodiment provided by the present invention: a large-scale direct shear tester for indoor use in geotechnical engineering, comprising a sample container system, a shear loading system, a data acquisition control system and a base protection system, wherein the sample container system is formed by splicing a plurality of modular sample containers, the modular sample containers are connected by detachable connecting buckles, a replaceable lining plate is provided inside the container for adjusting the size and interface conditions of the sample container, and an embedded porous pressure plate is provided at the bottom of the container for measuring the change of pore pressure during the seepage process of the sample; The base and protection system include: a base, an anti-vibration damping component and a transparent protective cover, which are used to observe the test process and protect the operator. The outer wall of the base is provided with an anti-vibration damping component, which includes: a shock-absorbing pad and a reaction pad 9. The bottom of the outer wall of the base is fixedly installed with a shock-absorbing pad. The shear loading system is connected and installed in the reaction structure frame through the reaction pad 9. A transparent observation window is provided on one side of the modular sample container, and the transparent observation window is used to observe the shear band evolution process inside the sample through a camera; A shear loading system is fixedly installed on the side of the outer wall of the container, and the shear loading system is used to apply constant speed and constant force shear loading to the sample; The shear loading system includes: a shear loading drive device and a shear loading guide rail. The shear loading drive device is powered by a servo motor. The speed of the shear loading system is precisely adjusted within the range of 0.001mm / min-10mm / min, and the shear deformation is monitored by a displacement sensor. The shear loading system supports bidirectional loading and is used to study the strength attenuation characteristics and residual strength changes of soil under multi-cycle shear conditions; A normal loading system is movably installed on the top of the outer wall of the container; The normal loading system comprises: a servo hydraulic loading device 11 and a loading sensor unit; The servo hydraulic loading device 11 is used to apply an adjustable normal pressure, and the loading sensor unit is used to monitor the normal force value; The normal loading force range of the servo hydraulic loading device 11 is 10kN-500kN. The servo hydraulic loading device 11 has a built-in multi-point force sensor to monitor the uniformity of the normal loading in real time to avoid eccentric loading. The normal loading system is equipped with a closed-loop control function for loading force, which can apply constant normal force and normal strain; Furthermore, according to the test requirements, a suitable modular sample container is selected, and multiple modules are spliced ​​into a complete sample container through detachable connection buckles. The required replaceable lining plate, such as wear-resistant steel plate or sandpaper friction surface, is installed on the inner wall of the container, and the interface conditions of the sample container are adjusted, such as convenient friction characteristics. A porous pressure plate is embedded in the bottom of the inner wall of the container, and an external pressure sensor and flow regulating device are connected to record the pore pressure data during the seepage process; Prepare geotechnical samples, such as sand, clay or soft rock samples, with the size matching the inner cavity of the container, place the sample in the modular sample container, ensure that it is in close contact with the inner liner to avoid gaps affecting the experimental accuracy, start the normal loading system, apply initial normal pressure through the servo hydraulic device, monitor the uniformity of normal loading through the loading sensor unit, adjust the servo hydraulic loading device 11 to avoid uneven sample and deformation caused by eccentric loading, and set the loading path (constant normal force or normal strain mode) according to the test requirements; Start the shear loading system, set the shear loading rate to 2mm / min, and use the servo motor to drive the shear guide to move, thereby applying shear stress to the sample. The shear loading system collects displacement sensor data in real time to monitor the shear deformation. If the test requires cyclic shearing, adjust the servo motor to reverse direction to apply bidirectional loading, and study the strength attenuation and residual strength change of the sample under cyclic shearing conditions. The camera records the shear band evolution process inside the sample through a transparent observation window. Combined with the real-time monitoring results of the data acquisition system (shear force, displacement, pore pressure, etc.), the shear behavior and seepage characteristics of the sample are evaluated. The data processing system generates a shear stress-strain curve and analyzes parameters such as yield point, peak strength and residual strength. The test is terminated when the set shear deformation or force value is reached, the normal pressure and shear force are released, the sample is taken out of the container, and the residue in the modular sample container is cleaned.

[0027] See also Figure 1 , Figure 2 and Figure 3 , an embodiment provided by the present invention: a large direct shear tester for indoor use in geotechnical engineering, wherein the data acquisition control system is used to collect shear test process parameters in real time, and process and output the data; The data acquisition control system includes: force sensor, displacement sensor, pore pressure sensor and data processing module; The force sensor is installed in the servo hydraulic loading device 11, the displacement sensor is installed on the shear loading guide rail to monitor the shear displacement parameters of the shear loading drive device in real time, and the pore pressure sensor is installed on the embedded porous pressure plate in the modular sample container, and the force sensor, displacement sensor, and pore pressure sensor are all connected to the data processing module through digital signal lines; The data processing module has a built-in embedded AI algorithm to collect and process shear force, normal force, displacement and pore pressure parameters in real time to generate shear strength curves, yield points and residual strength test results; Data supports multiple output methods, including real-time display, wireless transmission to the cloud, and USB interface storage; Furthermore, after the test is started, each sensor starts working. The force sensor records the normal force value applied by the servo hydraulic loading device 11 in real time. The displacement sensor continuously monitors the displacement change of the shear loading guide rail and calculates the shear deformation. The pore pressure sensor monitors the seepage pore pressure in the porous pressure plate. Each sensor transmits the collected data to the data processing module through a digital signal line. The data collection frequency is 100Hz to ensure real-time recording of high dynamic change processes. The RNN neural network algorithm in the data processing module performs denoising and filtering on raw data such as force, displacement and pore pressure to improve data quality, calculate shear stress and shear strain in real time, and generate shear stress-strain curves; dynamically identify key parameters such as the yield point, peak strength and residual strength of the sample during the test loading process, analyze the dynamic changes of pore pressure, and evaluate the coupling relationship between the permeability characteristics and mechanical behavior of the sample in combination with shear data; The real-time display system presents key parameters such as shear force, normal force, displacement and pore pressure in the form of graphs on the experimental console, allowing operators to intuitively observe the progress of the test and parameter changes; if the AI ​​algorithm detects an abnormality, such as a sudden drop in shear force, an abnormal increase in displacement or an abnormal increase in pore pressure, the system will issue an alarm and automatically suspend the test to avoid equipment damage.

[0028] See also Figure 1 , Figure 2 and Figure 3 , an embodiment provided by the present invention: a large direct shear tester for indoor use in geotechnical engineering, the base is connected to a reaction structure frame through an anchor bolt 4, the reaction structure frame includes a reaction beam 1, a connecting longitudinal beam 2 and a connecting cross beam 3, the reaction beam 1, the connecting longitudinal beam 2 and the connecting cross beam 3 are all connected through the anchor bolt 4, 1 cm thick steel plates are installed on both sides of the outer wall of the reaction structure frame, reaction pads 9 are fixedly installed on the inner wall side of the steel plate, and a shear loading drive device is installed on the outer wall side of the reaction pad 9; The modular sample container is installed in the shear box 5, a cover plate 10 is fixedly installed on the top of the outer wall of the shear box 5, a transverse moving guide rail is fixedly installed on the top of the outer wall of the cover plate 10, a sliding plate group 6 is movably installed in the transverse moving guide rail, a pressure plate 7 is fixedly installed on the top of the outer wall of the sliding plate group 6, and a servo hydraulic loading device 11 is fixedly installed on the top of the outer wall of the pressure plate 7; The servo hydraulic loading device 11 is against the bottom of the outer wall of the reaction beam 1, the reaction beam 1 plays a reaction force limiting role on the servo hydraulic loading device 11, and the reaction pad 9 plays a reaction force limiting role on the shear loading drive device; The inner wall side of the shear box 5 is fixedly mounted with a shear loading guide rail, and the shear loading drive device uses a horizontal jack 8 to push the shear cutter head along the shear loading guide rail; Further, the base is fixedly connected to the base platform of the reaction structure frame by anchor bolts 4 to ensure that the reaction structure has sufficient stability and rigidity during the test. The function of the reaction pad 9 is to provide a stable reaction support for the shear loading drive device to prevent deviation during the loading process. The container is installed in the shear box 5 to ensure that the shear and normal forces can be transmitted between the container and the reaction structure frame. A cover plate 10 is fixedly installed on the top of the outer wall of the shear box 5 to prevent the sample from overflowing or accidentally damaged during the test. A lateral moving guide rail is installed on the top of the outer wall of the cover plate 10. The sliding plate group 6 moves in the lateral direction through the guide rail. A pressure plate 7 is installed on the sliding plate group 6 to evenly distribute the normal force. The servo hydraulic loading device 11 is against the bottom of the outer wall of the reaction beam 1. The reaction beam 1 plays a limiting role here to ensure the stability of the loading direction during the loading process. The function of the reaction beam 1 is to transmit the normal force from the servo hydraulic loading device 11 to the base through the reaction structure frame to ensure that the reaction force during the loading process can be fully absorbed to avoid deformation or failure of the equipment. The reaction pad 9 is connected to the shear loading drive device to ensure that the loading force of the shear loading drive device can be accurately transmitted to the sample through the reaction limit effect; The shear loading drive device pushes the shear to the end along the shear loading guide rail through the horizontal jack 8, and gradually increases the shear force. During the shear loading process, the contact surface between the shear cutter head and the sample slides relative to each other, resulting in shear deformation. The data acquisition system monitors parameters such as shear force, displacement and pore pressure in real time. The shear loading drive device gradually applies shear force according to the set loading rate until the sample reaches the yield point or failure point, and the system automatically stops loading. During the shear loading process, the sample experienced a process from elastic deformation to yield stage. As the shear force continued to increase, shear bands appeared in the sample and began to be locally damaged. The data processing module stimulated the dynamic changes of shear force, displacement changes and pore pressure in real time to generate test data such as shear strength curve, yield point and residual strength.

[0029] See also Figure 1 , Figure 2 and Figure 3 , an embodiment provided by the present invention: a large direct shear tester for indoor use in geotechnical engineering, wherein an automatic centering device is fixedly installed on the top of the outer wall of the base, and the automatic centering device includes a centering guide rail driven by a stepping motor, and the centering guide rail is fixedly installed on the bottom of the outer wall of the shear box 5, and can adjust the initial position of the modular sample container so that the shear loading direction is consistent with the center line direction of the sample; Furthermore, before the test begins, the operator places the modular sample container in the shear box 5 and starts the automatic centering device. The stepper motor controls the centering guide rail to move smoothly and accurately adjust the sample container to the preset initial position. The system feeds back the actual position of the sample container through the sensor, automatically calibrates and ensures that the center of the container is consistent with the shear loading direction. The stepper motor achieves fine-tuning of the modular sample container through precise stepping control, so that the center line of the sample is aligned with the shear loading direction. During each adjustment process, the system detects the centering accuracy through infrared monitoring technology and makes further fine-tuning based on real-time feedback until the required centering accuracy requirements are met. After the automatic centering is completed, the system will display the container centering status and notify the operator that the sample container is ready for loading. At this time, the automatic centering device will lock the centering guide rail position to ensure stability during the loading process.

[0030] See also Figure 1 , Figure 2 and Figure 3 , an embodiment provided by the present invention: a large direct shear tester for indoor use in geotechnical engineering, wherein a constant temperature and humidity system is arranged in the modular sample container, including an embedded heating element, a cooling element and a humidity controller, which can control the sample temperature between -20°C and 80°C, and maintain the humidity within the range of 10%-100%, so as to simulate the mechanical properties of the sample under different climates; Furthermore, the constant temperature and humidity system consists of an embedded heating element, a cooling element, and a humidity controller. The heating element is used to increase the temperature, the cooling element is used to reduce the temperature, and the humidity controller controls the humidity by automatically adjusting the humidification or dehumidification device. The system is able to control the temperature of the specimen within the range of -20°C to 80°C, and maintain the humidity between 10%-100% to simulate the effects of different climatic conditions on the mechanical properties of geotechnical specimens. Before the test begins, the operator can set the required test temperature and humidity conditions through the control panel or data acquisition system. The system will automatically adjust according to the set temperature and humidity, and remain stable until the specimen reaches the set conditions; During the operation of the system, the embedded heating and cooling elements will automatically work according to the difference between the current temperature of the sample and the set value. The system monitors the sample temperature in real time through the temperature sensor, and adjusts the heating or cooling intensity through the control system to ensure the stability of the temperature. The humidity controller also detects the humidity changes around the sample through the humidity sensor, and automatically adjusts the humidification or dehumidification function according to the demand to maintain the humidity within the set range of 10%-100%; During the test, the data acquisition system will record and display the temperature and humidity changes of the sample in real time. The operator can check the current environmental conditions of the sample through the control system to ensure that the temperature and humidity of the sample meet the experimental requirements. If the temperature or humidity exceeds the preset range, the system will automatically alarm and make adjustments to ensure the reliability of the test data. The constant temperature and humidity system can be used to simulate various extreme climate conditions, such as the behavior of rock and soil samples in high temperature and high humidity or low temperature and low humidity environments. This is very important for studying the shear strength, deformation characteristics and failure modes of soil in different climates. For example, if a cold environment (frozen soil behavior at low temperatures) is simulated, the constant temperature and humidity system will set the temperature to -20°C and keep the humidity at a low level to observe the shear characteristics of the sample in this environment; if a humid environment (such as tropical areas) is simulated, the system will set the temperature to a higher value and adjust the humidity to reflect the mechanical behavior of the soil in a high temperature and humid environment; During the actual shear test, the constant temperature and humidity system continues to operate to ensure that the sample is kept at the set temperature and humidity conditions during the loading process. At the beginning of the test, the operator starts the shear loading system, and the system applies shear force according to the preset loading rate; at the same time, the constant temperature and humidity system continuously monitors the temperature and humidity conditions to ensure that the experimental environment remains stable, and automatically adjusts to avoid adverse effects on the sample due to changes in the external environment.

[0031] Working principle: The core of this tester is the shear loading system. The servo motor provides power and controls the shear loading system to accurately apply shear force at a predetermined loading rate (0.001mm / min-10mm / min). A shearing action is generated between the shearing knife head installed on the shear loading guide and the sample container, gradually increasing the shear stress until the sample is sheared or reaches the set conditions. The system monitors the shear displacement in real time and adjusts the loading process according to the sensor data to ensure the uniformity and stability of the shear force application. The normal loading system applies normal pressure through a servo hydraulic device and monitors the change of normal force through a loading sensor. Through a precise force control system, it can apply normal loads from 10 kN to 500 kN to the specimen and automatically adjust the loading method according to the change of force to ensure uniform application of normal force throughout the test. The system has built-in multi-point force sensors that can detect the uniformity of normal force in real time to avoid eccentric loading and ensure the accuracy and stability of the loading process. The constant temperature and humidity system controls the temperature and humidity of the sample environment through the combined action of heating elements, cooling elements and humidity controllers. The system can adjust the temperature of the sample to a range of -20°C to 80°C and maintain the humidity in the range of 10% to 100%, simulating the impact of different climatic conditions on the mechanical properties of soil. The system monitors the temperature and humidity of the sample in real time, and adjusts the heating, cooling or humidification equipment through feedback control to ensure that the test conditions always meet the set standards.

[0032] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A large direct shear tester for indoor geotechnical engineering, comprising a sample container system, a shear loading system, a data acquisition control system and a base protection system, characterized in that: The sample container system is composed of a plurality of modular sample containers, which are connected by detachable connecting buckles. A replaceable liner is provided inside the container to adjust the size and interface conditions of the sample container. An embedded porous pressure plate is provided at the bottom of the container to measure the pore pressure change during the sample seepage process. The base and protection system comprises: a base, an anti-vibration damping component and a transparent protective cover, which is used to observe the test process and protect the operator; the outer wall of the base is provided with an anti-vibration damping component, which comprises: a shock-absorbing pad and a reaction pad (9); the shock-absorbing pad is fixedly installed at the bottom of the outer wall of the base; the shear loading system is connected and installed in the reaction structure frame through the reaction pad (9); A transparent observation window is provided on one side of the modular sample container, and the transparent observation window is used to observe the shear band evolution process inside the sample through a camera.

2. A large-scale direct shear tester for indoor geotechnical engineering according to claim 1, characterized in that: A shear loading system is fixedly installed on the side of the outer wall of the container, and the shear loading system is used to apply constant speed and constant force shear loading to the sample; The shear loading system includes: a shear loading drive device and a shear loading guide rail. The shear loading drive device is powered by a servo motor. The speed of the shear loading system is precisely adjusted within the range of 0.001mm / min-10mm / min, and the shear deformation is monitored by a displacement sensor. The shear loading system supports bidirectional loading and is used to study the strength attenuation characteristics and residual strength changes of soil under multi-cycle shear conditions.

3. A large-scale direct shear tester for indoor use in geotechnical engineering according to claim 1, characterized in that: A normal loading system is movably installed on the top of the outer wall of the container; The normal loading system comprises: a servo hydraulic loading device (11) and a loading sensor unit; The servo hydraulic loading device (11) is used to apply an adjustable normal pressure, and the loading sensor unit is used to monitor the normal force value; The normal loading force range of the servo hydraulic loading device (11) is 10 kN-500 kN. The servo hydraulic loading device (11) has a built-in multi-point force sensor to monitor the uniformity of the normal loading in real time to avoid eccentric loading. The normal loading system is equipped with a closed-loop control function for the loading force, which can apply a constant normal force and normal strain.

4. A large-scale direct shear tester for indoor use in geotechnical engineering according to claim 1, characterized in that: The data acquisition control system is used to collect shear test process parameters in real time and process and output the data; The data acquisition control system includes: force sensor, displacement sensor, pore pressure sensor and data processing module; The force sensor is installed in the servo hydraulic loading device (11), the displacement sensor is installed on the shear loading guide rail to monitor the shear displacement parameters of the shear loading drive device in real time, the pore pressure sensor is installed on the embedded porous pressure plate in the modular sample container, and the force sensor, the displacement sensor, and the pore pressure sensor are all connected to the data processing module through a digital signal line; The data processing module has a built-in embedded AI algorithm to collect and process shear force, normal force, displacement and pore pressure parameters in real time to generate shear strength curves, yield points and residual strength test results; The data supports multiple output methods, including real-time display, wireless transmission to the cloud, and USB interface storage.

5. A large direct shear tester for indoor use in geotechnical engineering according to claim 1, characterized in that: The base is connected to the reaction structure frame via anchor bolts (4); the reaction structure frame comprises a reaction beam (1), a connecting longitudinal beam (2) and a connecting transverse beam (3); the reaction beam (1), the connecting longitudinal beam (2) and the connecting transverse beam (3) are all connected via anchor bolts (4); 1 cm thick steel plates are installed on both sides of the outer wall of the reaction structure frame; reaction pads (9) are fixedly installed on the side of the inner wall of the steel plates; and a shear loading drive device is installed on the side of the outer wall of the reaction pads (9).

6. A large-scale direct shear tester for indoor use in geotechnical engineering according to claim 1, characterized in that: The modular sample container is installed in a shear box (5), a cover plate (10) is fixedly installed on the top of the outer wall of the shear box (5), a transverse movable guide rail is fixedly installed on the top of the outer wall of the cover plate (10), a sliding plate group (6) is movably installed in the transverse movable guide rail, a pressure plate (7) is fixedly installed on the top of the outer wall of the sliding plate group (6), and a servo hydraulic loading device (11) is fixedly installed on the top of the outer wall of the pressure plate (7).

7. A large-scale direct shear tester for indoor use in geotechnical engineering according to claim 3, characterized in that: The servo hydraulic loading device (11) abuts against the bottom of the outer wall of the reaction beam (1); the reaction beam (1) plays a reaction force limiting role on the servo hydraulic loading device (11); and the reaction force pad (9) plays a reaction force limiting role on the shear loading drive device.

8. A large-scale direct shear tester for indoor use in geotechnical engineering according to claim 6, characterized in that: A shear loading guide rail is fixedly mounted on the inner wall side of the shear box (5), and the shear loading drive device uses a horizontal jack (8) to push the shearing cutter head along the shear loading guide rail.

9. A large-scale direct shear tester for indoor use in geotechnical engineering according to claim 1, characterized in that: An automatic centering device is fixedly mounted on the top of the outer wall of the base. The automatic centering device comprises a centering guide rail driven by a stepping motor. The centering guide rail is fixedly mounted on the bottom of the outer wall of the shear box (5) and can adjust the initial position of the modular sample container so that the shear loading direction is consistent with the center line direction of the sample.

10. A large-scale direct shear tester for indoor geotechnical engineering according to claim 1, characterized in that: The modular sample container is equipped with a constant temperature and humidity system, including an embedded heating element, a cooling element and a humidity controller, which can control the sample temperature between -20°C and 80°C and maintain the humidity within the range of 10%-100%, so as to simulate the mechanical properties of the samples under different climates.

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