Rockfill particle cyclic shear test system and test method

Abstract

The invention discloses a rock-fill particle cyclic shear test system and test method, and relates to the technical field of shear tests, the rock-fill particle cyclic shear test system comprises a test frame, a shear box assembly, a vertical loading device, a horizontal shear device and a data acquisition system. By adopting a rolling shaft structure, friction interference can be reduced, constant vertical stress can be accurately applied by combining the synergistic effect of a high-precision hydraulic pusher and a force transmission plate in the vertical loading device, and the horizontal shearing device can be used for shearing a workpiece through a second hydraulic pusher and a third hydraulic pusher. Dynamic simulation of a horizontal cyclic shear load under a complex stress path is realized, mechanical response of a rockfill body in an actual working condition is completely restored, a data acquisition system integrates a three-dimensional shear force sensor, a laser displacement sensor and a high-speed camera unit, a stress-displacement evolution process and particle motion mesoscopic characteristics can be synchronously captured, and the mechanical response of the rockfill body in the actual working condition is completely restored. And multi-dimensional coupling analysis can be realized in cooperation with a data processing terminal.

Description

Technical Field

[0001] The present invention relates to the technical field of shear testing, and in particular to a rockfill particle cyclic shear testing system and a testing method. Background Art

[0002] Rockfill bodies, including earth-rock dams, roadbed fills, and slope protection structures, are typical aggregates of granular materials. Their mechanical properties directly affect the long-term stability and safety of engineering structures. Under the action of cyclic loads such as earthquakes and traffic vibrations, the contact force chain between rockfill particles will undergo dynamic reconstruction, leading to weakened shear strength, particle crushing and cumulative deformation, and thus causing structural instability.

[0003] The defects of existing shear test technology are:

[0004] 1. Patent document US20180031457A1 discloses a shear test apparatus and test method for rock mass discontinuities under constant stiffness conditions. However, the shear test apparatus described in the aforementioned document only supports a single waveform with a narrow frequency range, making it difficult to simulate multi-directional coupled cyclic loads in actual working conditions such as earthquakes and landslides. This results in a significant deviation between the test stress path and the actual scenario.

[0005] 2. Patent document US20170284911A1 discloses an integrated shear device for rock structural surfaces and a rock structural surface shear test method. However, the shear device described in the aforementioned document has a technical problem of being unable to dynamically adjust the restraining force, resulting in lateral deviation or instability of the specimen during cyclic shearing.

[0006] 3. Patent document JPS566819A discloses a shear force testing method and equipment for two soil quality platforms. However, the platform in the aforementioned document uses a fixed force transmission mechanism, which cannot achieve dynamic switching of compression-shear combined loads. The force transmission component is difficult to disassemble and lacks an emergency unlocking device. Resetting test parameters is time-consuming and has poor flexibility.

[0007] 4. Patent document CN109374438B discloses a rock shear test system. However, the device in the above document is unable to adjust stress in real time according to particle crushing, and the data acquisition system only obtains macroscopic mechanical parameters. There is a lack of cross-scale fusion of high-speed camera and discrete element simulation, resulting in insufficient technical problems such as insufficient analysis of microscopic mechanisms such as particle motion trajectory and energy dissipation. Summary of the Invention

[0008] The object of the present invention is to provide a rockfill particle cyclic shear test system and test method to solve the technical problems raised in the above background technology.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a rockfill particle cyclic shear test system, comprising a test frame and a shear box assembly, a vertical loading device, a horizontal shear device, and a data acquisition system; a shear box assembly is mounted on the top of the test frame, the shear box assembly comprising a base and a shear box; an adjustment assembly is provided in the middle of the top of the base, the top of the adjustment assembly is movably connected to the shear box, and the adjustment assembly is used to ensure friction when the shear box moves;

[0010] The vertical loading device includes a first hydraulic pusher provided on a bracket above the base and a first force transmission plate provided on the top of the shear box, and the output end of the first hydraulic pusher is fixedly connected to the top of the first force transmission plate, for applying a preset vertical stress to the rockfill sample;

[0011] The horizontal shear device includes a second hydraulic pusher provided on both sides of the shear box and a third hydraulic pusher provided on both sides of the front end of the base, and the second hydraulic pusher is fixedly connected to both sides of the top of the base, and the outer wall of the third hydraulic pusher is embedded in the test frame for applying horizontal cyclic shear load;

[0012] The data acquisition system includes a three-dimensional shear force sensor, a laser displacement sensor, a high-speed camera unit and a data processing terminal connected to the sensor signals, which is used to collect and process test data in real time. The three-dimensional shear force sensor is embedded in the bottom of the shear box, and the laser displacement sensor is set in the test frame and aligned with the marking point on the side wall of the shear box.

[0013] Preferably, the adjustment component includes a groove, and the groove is arranged in the middle of the top of the base, and a plurality of rollers are installed on the inner wall of the groove through a rotating shaft, and the top of the roller is movably connected to the bottom of the shear box, and a group of limit plates are arranged above the groove, and the outer walls of the limit plates are movably connected to the bottom of the front and back of the shear box respectively, and a first hydraulic cylinder is provided on both sides of one end of the limit plate, and the bottom of the first hydraulic cylinder is fixedly connected to the top of the base for constraining the lateral displacement of the shear box.

[0014] Preferably, the first hydraulic pusher integrates a high-precision pressure sensor and is electrically connected to the data processing terminal. The maximum loading capacity of the first hydraulic pusher is 500kN, and the loading frequency range is 0.01-10Hz. The second hydraulic pusher and the third hydraulic pusher can generate a sinusoidal wave or square wave composite waveform load with an amplitude of 0-200mm and a frequency of 0.1-10Hz.

[0015] Preferably, through holes are provided on both sides of the shear box, and the inner wall of the through hole is movably connected to the second force transmission plate, a connecting sleeve is installed on one side of the second force transmission plate, and the inner wall of the connecting sleeve is movably connected to the outer wall of the second hydraulic pusher, and a group of limiting grooves are provided on the inner wall of the connecting sleeve, and the interior of the limiting groove is movably connected to a pressure spring, one end of the pressure spring is movably connected to a limiting block, and the tail end of the outer wall of the limiting block is arranged on the inner wall of the limiting groove, the front end of the outer wall is arranged inside the limiting hole, and the limiting hole is arranged on the outer wall of the output end of the second hydraulic pusher, a pull rod is installed at one end of the limiting block, and the other end of the pull rod passes through the interior of the limiting groove and is installed with a pull ring.

[0016] Preferably, second hydraulic cylinders are embedded and installed on the top and bottom of both sides of the outer wall of the second force transmission plate, the output end of the second hydraulic cylinder is installed inside the fixing groove, and the fixing groove is opened on the inner wall of the through hole.

[0017] Preferably, the high-speed camera unit includes two industrial cameras, and the industrial cameras are set in the test frame with a frame rate of 10,000 fps and equipped with a particle image velocimetry and analysis module for capturing the movement trajectory of rockfill particles and generating a velocity field distribution map.

[0018] Preferably, a rockfill particle cyclic shear test method is characterized by comprising the following steps:

[0019] Step S1, sample preparation: filling the rockfill particles into the shear box according to the preset gradation and controlling the density;

[0020] Step S2, system initialization: start the data acquisition system, calibrate the three-dimensional shear force sensor, laser displacement sensor and high-speed camera unit;

[0021] Step S3, applying vertical stress: applying a preset vertical stress to the first force transmission plate through the first hydraulic pusher, and dynamically adjusting it through the closed-loop feedback system;

[0022] Step S4, applying a horizontal cyclic shear load: synchronously driving the second hydraulic pusher and the third hydraulic pusher to generate a composite waveform load, causing the shear box to reciprocate along the adjustment assembly;

[0023] Step S5, data acquisition and processing: a shear stress-displacement curve is obtained by a three-dimensional shear force sensor, a laser displacement sensor measures the displacement of the shear box, a high-speed camera unit records particle motion images, and a data processing terminal analyzes the particle breakage rate, friction coefficient, and shear modulus.

[0024] Preferably, in step S3, the preset vertical stress is 100 kPa-2 MPa, the loading rate is 0.1-5 kN / s, and the vertical stress is dynamically adjusted according to the particle crushing situation during the test, and the adjustment range does not exceed ±20% of the initial value.

[0025] Preferably, in step S4, the waveform of the horizontal cyclic shear load includes a superposition of a sine wave and a square wave, an amplitude of 50-200 mm, a frequency of 0.1-5 Hz, and a number of cycles ≥1000 times.

[0026] Preferably, in step S5, the data processing terminal extracts particle displacement field data through particle image velocimetry, and generates a particle contact force chain network and an energy dissipation distribution diagram in combination with discrete element numerical simulation.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention utilizes a roller structure to reduce friction interference. Combined with the synergistic effect of the high-precision hydraulic pusher and force transfer plate in the vertical loading device, it can precisely apply constant vertical stress. The horizontal shear device, through the second and third hydraulic pushers, achieves dynamic simulation of horizontal cyclic shear loads under complex stress paths, fully reproducing the mechanical response of the rockfill under actual working conditions. The data acquisition system integrates a three-dimensional shear force sensor, a laser displacement sensor, and a high-speed camera unit to simultaneously capture the stress-displacement evolution process and the microscopic characteristics of particle motion. Combined with a data processing terminal, it enables multi-dimensional coupled analysis. This system provides an efficient experimental platform for studying the strength attenuation, particle breakage, and long-term stability of rockfill materials.

[0029] 2. This invention utilizes multiple sets of rollers mounted via rotating shafts within the groove at the top of the base, replacing traditional sliding friction with rolling friction. This significantly reduces the resistance to movement of the shear box and ensures uniform force during the shearing process. A limit plate, additionally positioned above the groove, is flexibly connected to the bottom of the shear box. Combined with the dynamic constraints of the first hydraulic cylinders on either side, this precisely suppresses lateral deflection of the shear box under cyclic loading, maintaining the specimen in a pure shear deformation state. This preserves the degree of freedom in the shear direction while actively controlling boundary conditions through hydraulic pressure, effectively simulating the boundary constraint effects of a rockfill during a real shearing process while avoiding test data distortion caused by lateral instability. This provides a high-fidelity experimental environment for revealing the microscopic mechanical behaviors of granular materials, such as the evolution of contact force chains and the formation mechanism of shear bands, further enhancing the system's engineering applicability in simulating complex stress paths.

[0030] 3. The present invention employs an embedded slide rail structure to install a second force transmission plate within the lateral through-hole of the shear box. This force transmission assembly forms an axial linkage mechanism with the second hydraulic pusher via a connecting sleeve. A limiting groove, a pressure spring, and a limiting block, in conjunction with an external pull rod and a pull ring, form an emergency unlocking device, significantly improving equipment maintenance efficiency and the convenience of resetting test parameters. Simultaneously, the symmetrical double-acting second hydraulic cylinders arranged on both sides of the force transmission plate and the fixed grooves jointly construct a bidirectional dynamic constraint system. This system enables fine-tuning of the lateral displacement of the shear box. By disengaging the output end of the second hydraulic cylinder from the fixed groove, the system can be switched to an active pressure mechanism, directly applying dynamic compression-shear combined loads to the rockfill specimen via the second force transmission plate, thereby expanding the equipment's multi-condition testing capabilities.

[0031] 4. This invention utilizes a wide-range vertical stress loading system of 100 kPa-2 MPa, combined with an adjustable rate of 0.1-5 kN / s and a ±20% dynamic compensation strategy, to effectively simulate the stress redistribution effect of rockfill bodies affected by particle crushing during geological activities. Furthermore, a composite shear path combining sine and square waves with an amplitude of 50-200 mm, a frequency of 0.1-5 Hz, and a cycle of ≥1000 times is introduced. Through three-way hydraulic coordinated drive, complex shear scenarios such as seismic waves and intermittent landslides are accurately reproduced. During the test, a 10,000 fps high-speed camera unit synchronously captures particle motion trajectories. Combined with the cross-scale fusion of a particle image velocimetry module and discrete element numerical simulation, a full-dimensional correlation database of particle displacement field, contact force chain network, and energy dissipation distribution is constructed. This provides an innovative research paradigm with both engineering applicability and scientific depth for optimizing the seismic performance of rockfill dams and establishing a multi-scale early warning model for landslide hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a three-dimensional schematic diagram of the overall structure of the present invention;

[0033] Figure 2 This is a schematic diagram of the base structure of the present invention;

[0034] Figure 3 Schematic diagram of the through-hole structure of the present invention;

[0035] Figure 4 For the present invention Figure 3 Schematic diagram of the structure at A in the middle;

[0036] Figure 5 Schematic diagram of the structure of the three-dimensional shear force sensor of the present invention;

[0037] Figure 6 This is a schematic diagram of the shear test system process structure of the present invention;

[0038] Figure 7 It is a schematic diagram of the workflow structure of the present invention.

[0039] In the figure: 1. Test frame; 2. Shear box assembly; 3. Vertical loading device; 4. Horizontal shear device; 6. Data acquisition system; 7. Base; 8. Shear box; 9. First hydraulic pusher; 10. First force transmission plate; 11. Second hydraulic pusher; 12. Third hydraulic pusher; 13. Three-dimensional shear force sensor; 14. Laser displacement sensor; 15. High-speed camera unit; 16. Data processing terminal; 17. Groove; 18. Roller; 19. Limit plate; 20. First hydraulic cylinder; 22. High-precision pressure sensor; 23. Through hole; 24. Second force transmission plate; 25. Connecting sleeve; 26. Limiting groove; 27. Pressure spring; 28. Limiting block; 29. ​​Limiting hole; 30. Second hydraulic cylinder; 31. Fixing groove; 32. Industrial camera; 33. Analysis module; 34. Pull rod; 35. Pull ring. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," "the other end," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "connected," etc., should be understood in a broad sense. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; it may refer to a mechanical connection or an electrical connection; it may refer to a direct connection or an indirect connection through an intermediate medium; it may refer to internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0043] Example 1: Please refer to Figure 1 、 Figure 5 and Figure 6The present invention provides an embodiment of a rockfill particle cyclic shear test system, comprising a test frame 1, a shear box assembly 2, a vertical loading device 3, a horizontal shear device 4, and a data acquisition system 6. The shear box assembly 2 is mounted on the top of the test frame 1. The shear box assembly 2 comprises a base 7 and a shear box 8. An adjustment assembly is provided in the middle of the top of the base 7. The shear box 8 is movably connected to the top of the adjustment assembly. The adjustment assembly is used to ensure friction when the shear box 8 moves.

[0044] The vertical loading device 3 includes a first hydraulic pusher 9 provided above the base 7 and a first force transmission plate 10 provided on the top of the shear box 8. The output end of the first hydraulic pusher 9 is fixedly connected to the top of the first force transmission plate 10, and is used to apply a preset vertical stress to the rockfill specimen.

[0045] The horizontal shear device 4 includes a second hydraulic pusher 11 provided on both sides of the shear box 8 and a third hydraulic pusher 12 provided on both sides of the front end of the base 7. The second hydraulic pusher 11 is fixedly connected to both sides of the top of the base 7, and the outer wall of the third hydraulic pusher 12 is embedded in the test frame 1 for applying horizontal cyclic shear load.

[0046] The data acquisition system 6 includes a three-dimensional shear force sensor 13, a laser displacement sensor 14, a high-speed camera unit 15, and a data processing terminal 16 connected to the sensor signals, and is used to collect and process the test data in real time. The three-dimensional shear force sensor 13 is embedded in the bottom of the shear box 8, and the laser displacement sensor 14 is set in the test frame 1 and aligned with the marking point on the side wall of the shear box 8;

[0047] Furthermore, the shear box assembly 2 is conducive to reducing friction interference by adopting a roller 18 structure. Combined with the synergistic effect of the high-precision hydraulic pusher and the force transmission plate in the vertical loading device 3, constant vertical stress can be accurately applied. The horizontal shear device 4 realizes the dynamic simulation of horizontal cyclic shear load under complex stress path through the second hydraulic pusher 11 and the third hydraulic pusher 12, and completely restores the mechanical response of the rockfill under actual working conditions. The data acquisition system 6 integrates a three-dimensional shear force sensor 13, a laser displacement sensor 14 and a high-speed camera unit 15, which can synchronously capture the stress-displacement evolution process and the microscopic characteristics of particle movement. In conjunction with the data processing terminal 16, multi-dimensional coupling analysis can be realized. The system provides an efficient experimental platform for the study of strength attenuation, particle crushing and long-term stability of rockfill materials, and has important application value in engineering fields such as seismic design of earth-rock dams and landslide prevention.

[0048] Example 2: Please refer to Figure 1 and Figure 2, an embodiment provided by the present invention: the adjustment component includes a groove 17, and the groove 17 is arranged in the middle of the top of the base 7, the inner wall of the groove 17 is installed with a plurality of rollers 18 through a rotating shaft, and the top of the roller 18 is movably connected to the bottom of the shear box 8, a group of limit plates 19 are provided above the groove 17, and the outer walls of the limit plates 19 are movably connected to the bottom of the front and back sides of the shear box 8, a first hydraulic cylinder 20 is provided on both sides of one end of the limit plate 19, and the bottom of the first hydraulic cylinder 20 is fixedly connected to the top of the base 7, for restricting the lateral displacement of the shear box 8;

[0049] Furthermore, multiple sets of rollers 18 are installed through the rotating shaft inside the groove 17 on the top of the base 7, replacing traditional sliding friction with rolling friction, greatly reducing the movement resistance of the shear box 8 and ensuring uniform force during the shearing process. The limit plate 19 added above the groove 17 is movably connected to the bottom of the shear box 8. Combined with the dynamic constraints of the first hydraulic cylinders 20 on both sides, the lateral displacement of the shear box 8 under cyclic load can be accurately suppressed to maintain the pure shear deformation state of the specimen. It not only retains the degree of freedom in the shear direction, but also actively controls the boundary conditions through hydraulic pressure, effectively simulating the boundary constraint effect of the rockfill in the actual shear process, while avoiding the distortion of the test data caused by lateral instability, providing a high-fidelity test environment for revealing the microscopic mechanical behaviors such as the evolution of the contact force chain and the shear band formation mechanism of granular materials, and further enhancing the engineering applicability of the system in the simulation of complex stress paths.

[0050] Example 3: Please refer to Figure 6 In one embodiment of the present invention, the first hydraulic pusher 9 integrates a high-precision pressure sensor 22 and is electrically connected to the data processing terminal 16. The first hydraulic pusher 9 has a maximum loading capacity of 500 kN and a loading frequency range of 0.01-10 Hz. The second hydraulic pusher 11 and the third hydraulic pusher 12 can generate a sine wave or square wave composite waveform load with an amplitude of 0-200 mm and a frequency of 0.1-10 Hz.

[0051] Furthermore, by integrating a high-precision pressure sensor 22 into the first hydraulic thruster 9 and forming a closed-loop feedback loop with the data processing terminal 16, real-time and precise control of a 500 kN vertical load can be achieved within an ultra-wide frequency band of 0.01-10 Hz. This can simulate the long-term creep characteristics of the rockfill and reproduce the transient response under high-frequency shocks such as earthquakes. The second and third hydraulic thrusters 11 and 12 of the horizontal shearing device 4 use composite waveform loading technology. By outputting sine waves or square waves with amplitudes of 0-200 mm within the 0.1-10 Hz frequency band, or their combined waveforms, they can accurately construct the complex cyclic shear paths that the rockfill undergoes in actual engineering.

[0052] Example 4: Please refer to Figure 1 、 Figure 2 、 Figure 3and Figure 4 , an embodiment provided by the present invention: through holes 23 are opened on both sides of the shear box 8, the inner wall of the through hole 23 is movably connected with the second force transmission plate 24, a connecting sleeve 25 is installed on one side of the second force transmission plate 24, and the inner wall of the connecting sleeve 25 is movably connected to the outer wall of the second hydraulic pusher 11, and a group of limiting grooves 26 are opened on the inner wall of the connecting sleeve 25, and a pressure spring 27 is movably connected inside the limiting groove 26, and one end of the pressure spring 27 is movably connected to a limiting block 28, and the tail end of the outer wall of the limiting block 28 is arranged on the inner wall of the limiting groove 26, and the front end of the outer wall is arranged inside the limiting hole 29, and the limiting hole 29 is arranged on the outer wall of the output end of the second hydraulic pusher 11, one end of the limiting block 28 is installed with a pull rod 34, and the other end of the pull rod 34 passes through the limiting groove 26 and is installed with a pull ring 35;

[0053] The second hydraulic cylinder 30 is mounted on the top and bottom of both sides of the outer wall of the second force transmission plate 24. The output end of the second hydraulic cylinder 30 is installed inside the fixing groove 31, and the fixing groove 31 is opened on the inner wall of the through hole 23.

[0054] Furthermore, a second force transmission plate 24 is installed in the lateral through hole 23 of the shear box 8 using an embedded slide structure. The force transmission assembly forms an axial linkage mechanism with the second hydraulic pusher 11 through the connecting sleeve 25. Then, through the limiting groove 26, the pressure spring 27 and the limiting block 28, in conjunction with the external pull rod 34 and the pull ring 35, an emergency unlocking device is formed, which significantly improves the equipment maintenance efficiency and the convenience of resetting the test parameters. At the same time, the symmetrical double-acting second hydraulic cylinder 30 and the fixed groove 31 arranged on both sides of the force transmission plate jointly construct a bidirectional dynamic constraint system. This system can realize fine adjustment of the lateral displacement of the shear box 8, and can also be switched to an active pressure mechanism by disengaging the output end of the second hydraulic cylinder 30 from the fixed groove 31, thereby switching to an active pressure mechanism, and directly applying dynamic compression-shear composite load to the rockfill specimen through the second force transmission plate 24, which is conducive to expanding the multi-condition testing capability of the equipment.

[0055] Example 5: Please refer to Figure 5 and Figure 6 In one embodiment of the present invention, the high-speed camera unit 15 includes two industrial cameras 32, which are arranged in the test frame 1 and have a frame rate of 10,000 fps. The industrial cameras 32 are equipped with a particle image velocity measurement and analysis module 33 for capturing the motion trajectory of rockfill particles and generating a velocity field distribution map.

[0056] Furthermore, two 10,000fps ultra-high frame rate industrial cameras 32 are symmetrically arranged on the inner wall of the test frame 1. Combined with an adaptive light source system, the transient evolution of particle displacement, rotation and contact separation during the shearing process can be accurately captured. The integrated particle image velocimetry and analysis module 33 converts massive image sequences into a particle group motion trajectory database through a sub-pixel displacement tracking algorithm, and reconstructs three-dimensional velocity field and strain field distribution cloud maps, quantitatively revealing microscopic mechanisms such as the dynamic reorganization of the internal force chain network of the rockfill body and the initiation and expansion of shear bands. This not only breaks through the "black box" limitations of traditional macroscopic mechanical testing, but its millisecond-level time resolution and micron-level spatial positioning accuracy can also synchronously correlate the macroscopic stress-strain response with the particle-scale kinematic characteristics, providing direct experimental evidence for the establishment of a constitutive model that considers the coupling of multiple factors such as particle breakage and contact friction, significantly improving the scientific nature and engineering guidance value of research on the nonlinear mechanical properties of materials in the fields of seismic design of rockfill dams and landslide disaster warning.

[0057] Example 6: Please refer to Figure 6 and Figure 7 An embodiment of the present invention provides a method for cyclic shear testing of rockfill particles, comprising the following steps:

[0058] Step S1, sample preparation: filling the rockfill particles into the shear box 8 according to the preset gradation and controlling the density;

[0059] Step S2, system initialization: start the data acquisition system 6, calibrate the three-dimensional shear force sensor 13, the laser displacement sensor 14 and the high-speed camera unit 15;

[0060] Step S3, applying vertical stress: applying a preset vertical stress to the first force transmission plate 10 through the first hydraulic pusher 9, and dynamically adjusting it through the closed-loop feedback system;

[0061] Step S4, applying a horizontal cyclic shear load: synchronously driving the second hydraulic pusher 11 and the third hydraulic pusher 12 to generate a composite waveform load, causing the shear box 8 to reciprocate along the adjustment assembly;

[0062] Step S5, data acquisition and processing: a shear stress-displacement curve is obtained by a three-dimensional shear force sensor 13, a laser displacement sensor 14 measures the displacement of the shear box 8, a high-speed camera unit 15 records particle motion images, and a data processing terminal 16 analyzes the particle breakage rate, friction coefficient, and shear modulus;

[0063] In step S3, the vertical stress is preset to 100 kPa-2 MPa, the loading rate is 0.1-5 kN / s, and the vertical stress is dynamically adjusted according to the particle breakage during the test, with the adjustment range not exceeding ±20% of the initial value;

[0064] In step S4, the waveform of the horizontal cyclic shear load includes a superposition of a sine wave and a square wave, with an amplitude of 50-200 mm, a frequency of 0.1-5 Hz, and a number of cycles ≥ 1000 times;

[0065] In step S5, the data processing terminal 16 extracts the particle displacement field data through the particle image velocimetry module and generates the particle contact force chain network and energy dissipation distribution diagram in combination with discrete element numerical simulation;

[0066] Furthermore, by adopting a 100kPa-2MPa wide-range vertical stress loading system, combined with an adjustable rate of 0.1-5kN / s and a ±20% dynamic compensation strategy, the stress redistribution effect of rockfill bodies affected by particle crushing during geological activities was effectively simulated. A composite shear path consisting of a superposition of sine waves and square waves was then introduced with an amplitude of 50-200mm, a frequency of 0.1-5Hz, and a cycle of ≥1000 times. Complex shear scenarios such as seismic waves and intermittent landslides were accurately reproduced through three-way hydraulic collaborative drive. During the test, a 10,000fps high-speed camera unit15 synchronously captured the particle motion trajectory. Combined with the cross-scale fusion of the particle image velocimetry module and discrete element numerical simulation, a full-dimensional correlation database of particle displacement field, contact force chain network, and energy dissipation distribution was constructed, which is conducive to providing an innovative research paradigm with both engineering applicability and scientific depth for the optimization of the seismic performance of rockfill dams and the establishment of a multi-scale early warning model for landslide disasters.

[0067] Working principle: The use of roller 18 structure is conducive to reducing friction interference. Combined with the synergistic effect of the high-precision hydraulic pusher and the force transmission plate in the vertical loading device 3, constant vertical stress can be accurately applied. The horizontal shear device 4 realizes the dynamic simulation of horizontal cyclic shear load under complex stress path through the second hydraulic pusher 11 and the third hydraulic pusher 12, and completely restores the mechanical response of the rockfill body in actual working conditions. The data acquisition system 6 integrates a three-dimensional shear force sensor 13, a laser displacement sensor 14 and a high-speed camera unit 15, which can synchronously capture the stress-displacement evolution process and the microscopic characteristics of particle movement. In conjunction with the data processing terminal 16, multi-dimensional coupling analysis can be achieved. The system provides an efficient experimental platform for the study of strength attenuation, particle crushing and long-term stability of rockfill materials, and has important application value in engineering fields such as seismic design of earth-rock dams and landslide prevention. Multiple sets of rollers 18 are installed through the rotating shaft inside the groove 17 on the top of the base 7, and rolling friction replaces traditional sliding friction, which greatly reduces the movement resistance of the shear box 8 and ensures uniform force during the shearing process. The additional upper limit plate 19 is movably connected to the bottom of the shear box 8. Combined with the dynamic constraints of the first hydraulic cylinders 20 on both sides, it can accurately suppress the lateral displacement of the shear box 8 under cyclic loads and maintain the pure shear deformation state of the specimen. It not only retains the degree of freedom in the shear direction, but also actively controls the boundary conditions through hydraulic pressure, effectively simulating the boundary constraint effect of the rockfill in the actual shear process, while avoiding the distortion of the test data caused by lateral instability. It provides a high-fidelity test environment for revealing the micromechanical behavior of granular materials, such as the evolution of the contact force chain and the formation mechanism of shear bands, and further enhances the engineering applicability of the system in complex stress path simulation. By integrating a high-precision pressure sensor 22 with the data processing terminal 16 through closed-loop feedback, the first hydraulic pusher 9 can achieve real-time and precise control of the 500kN vertical load within the ultra-wide frequency band of 0.01-10Hz, which can not only simulate the long-term creep characteristics of the rockfill, but also reproduce the transient response under high-frequency impacts such as earthquakes. The second hydraulic pusher 11 and the third hydraulic pusher 12 of the horizontal shear device 4 adopt composite waveform loading technology.The output of sine waves or square waves with an amplitude of 0-200mm and their combined waveforms in the 1-10Hz frequency band can accurately construct the complex cyclic shear path experienced by the rockfill body in actual engineering. The second force transmission plate 24 is installed in the lateral through hole 23 of the shear box 8 using an embedded slide rail structure. The force transmission component forms an axial linkage mechanism with the second hydraulic pusher 11 through the connecting sleeve 25, and then forms an emergency unlocking device through the limiting groove 26, the pressure spring 27 and the limiting block 28, in conjunction with the external pull rod 34 and the pull ring 35, which significantly improves the equipment maintenance efficiency and the convenience of resetting the test parameters. At the same time, the symmetrical double-acting second hydraulic cylinder 30 and the fixed groove 31 on both sides of the force transmission plate jointly construct a bidirectional dynamic constraint system, which can achieve The shear box 8 can also be fine-tuned in lateral displacement by disengaging the output end of the second hydraulic cylinder 30 from the fixed groove 31, thereby switching to an active pressure mechanism, and directly applying dynamic compression-shear composite load to the rockfill specimen through the second force transmission plate 24, thereby facilitating the expansion of the equipment's multi-condition testing capabilities. Two 10,000fps ultra-high frame rate industrial cameras 32 are symmetrically arranged on the inner wall of the test frame 1, combined with an adaptive light source system, which can accurately capture the transient evolution of particle displacement, rotation, and contact separation during the shearing process. The integrated particle image velocimetry and analysis module 33 converts massive image sequences into a particle group motion trajectory database through a sub-pixel displacement tracking algorithm, and reconstructs a three-dimensional velocity field and strain field distribution cloud map, quantitatively revealing the particle group's motion trajectory. The dynamic reorganization of the force chain network inside the rockfill body, the initiation and expansion of shear bands and other microscopic mechanisms have not only broken through the "black box" limitation of traditional macroscopic mechanical testing, but its millisecond time resolution and micron-level spatial positioning accuracy can more synchronously correlate the macroscopic stress-strain response with the particle-scale kinematic characteristics, providing direct experimental evidence for the establishment of a constitutive model that considers the coupling of multiple factors such as particle crushing and contact friction, and significantly improving the scientific nature and engineering guidance value of the study of nonlinear mechanical properties of materials in the fields of seismic design of rockfill dams and landslide disaster warning. By adopting a 100kPa-2MPa wide-range vertical stress loading system, combined with an adjustable rate of 0.1-5kN / s and a ±20% dynamic compensation strategy, it can effectively simulate the rockfill body in geological activity. The stress redistribution effect caused by particle crushing during motion was investigated. A composite shear path consisting of a superposition of sine and square waves was introduced, with an amplitude of 50-200 mm, a frequency of 0.1-5 Hz, and a cycle of 1,000 or more. Through three-way hydraulic synergy, complex shear scenarios such as seismic waves and intermittent landslides were accurately reproduced. During the test, a 10,000 fps high-speed camera unit15 simultaneously captured the particle motion trajectory. Combined with the cross-scale fusion of the particle image velocimetry module and discrete element numerical simulation, a full-dimensional correlation database of particle displacement field, contact force chain network, and energy dissipation distribution was constructed. This provides an innovative research paradigm with both engineering applicability and scientific depth for optimizing the seismic performance of rockfill dams and establishing a multi-scale early warning model for landslide hazards.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A rockfill particle cyclic shear test system, comprising a test frame (1), a shear box assembly (2), a vertical loading device (3), a horizontal shear device (4), and a data acquisition system (6), characterized in that: A shear box assembly (2) is installed on the top of the test frame (1), and the shear box assembly (2) includes a base (7) and a shear box (8). An adjustment assembly is provided in the middle of the top of the base (7), and the top of the adjustment assembly is movably connected to the shear box (8). The adjustment assembly is used to ensure friction when the shear box (8) moves. The vertical loading device (3) comprises a first hydraulic pusher (9) arranged on a bracket above the base (7) and a first force transmission plate (10) arranged on the top of the shear box (8), and the output end of the first hydraulic pusher (9) is fixedly connected to the top of the first force transmission plate (10), and is used to apply a preset vertical stress to the rockfill sample; The horizontal shearing device (4) comprises a second hydraulic pusher (11) provided on both sides of the shear box (8) and a third hydraulic pusher (12) provided on both sides of the front end of the base (7), wherein the second hydraulic pusher (11) is fixedly connected to both sides of the top of the base (7), and the outer wall of the third hydraulic pusher (12) is embedded in the test frame (1) for applying a horizontal cyclic shear load; The data acquisition system (6) includes a three-dimensional shear force sensor (13), a laser displacement sensor (14), a high-speed camera unit (15), and a data processing terminal (16) connected to the signals of each sensor, and is used to collect and process test data in real time. The three-dimensional shear force sensor (13) is embedded in the bottom of the shear box (8), and the laser displacement sensor (14) is set in the test frame (1) and aligned with the marking point on the side wall of the shear box (8).

2. The rockfill particle cyclic shear test system according to claim 1, characterized in that: The adjustment component includes a groove (17), and the groove (17) is arranged in the middle of the top of the base (7), the inner wall of the groove (17) is installed with a plurality of rollers (18) through a rotating shaft, and the top of the roller (18) is movably connected to the bottom of the shear box (8), a group of limit plates (19) are arranged above the groove (17), and the outer walls of the limit plates (19) are movably connected to the bottom of the front and back sides of the shear box (8), a first hydraulic cylinder (20) is provided on both sides of one end of the limit plate (19), and the bottom of the first hydraulic cylinder (20) is fixedly connected to the top of the base (7) for constraining the lateral displacement of the shear box (8).

3. The rockfill particle cyclic shear test system according to claim 1, characterized in that: The first hydraulic pusher (9) is integrated with a high-precision pressure sensor (22) and is electrically connected to a data processing terminal (16). The first hydraulic pusher (9) has a maximum loading capacity of 500 kN and a loading frequency range of 0.01-10 Hz. The second hydraulic pusher (11) and the third hydraulic pusher (12) are capable of generating a sinusoidal or square wave composite waveform load with an amplitude of 0-200 mm and a frequency of 0.1-10 Hz.

4. The rockfill particle cyclic shear test system according to claim 1, characterized in that: The shear box (8) is provided with through holes (23) on both sides, and the inner wall of the through hole (23) is movably connected to the second force transmission plate (24), and a connecting sleeve (25) is installed on one side of the second force transmission plate (24), and the inner wall of the connecting sleeve (25) is movably connected to the outer wall of the second hydraulic pusher (11), and a group of limiting grooves (26) are provided on the inner wall of the connecting sleeve (25), and the interior of the limiting groove (26) is movably connected to a pressure spring (27), and one end of the pressure spring (27) is movably connected to a limiting block (28), and the tail end of the outer wall of the limiting block (28) is arranged on the inner wall of the limiting groove (26), and the front end of the outer wall is arranged inside the limiting hole (29), and the limiting hole (29) is arranged on the outer wall of the output end of the second hydraulic pusher (11), and a pull rod (34) is installed on one end of the limiting block (28), and the other end of the pull rod (34) passes through the interior of the limiting groove (26) and is installed with a pull ring (35).

5. The rockfill particle cyclic shear test system according to claim 4, characterized in that: A second hydraulic cylinder (30) is embedded and installed at the top and bottom of both sides of the outer wall of the second force transmission plate (24), and the output end of the second hydraulic cylinder (30) is installed inside the fixing groove (31), and the fixing groove (31) is opened on the inner wall of the through hole (23).

6. The rockfill particle cyclic shear test system according to claim 1, characterized in that: The high-speed camera unit (15) includes two industrial cameras (32), which are arranged in the test frame (1) with a frame rate of 10,000 fps and equipped with a particle image velocity measurement and analysis module (33) for capturing the movement trajectory of rockfill particles and generating a velocity field distribution diagram.

7. A cyclic shear test method for rockfill particles, applicable to a cyclic shear test system for rockfill particles according to claims 1-6, characterized in that: The following steps are involved: Step S1, sample preparation: filling the rockfill particles into the shear box (8) according to the preset gradation and controlling the density; Step S2, system initialization: start the data acquisition system (6), calibrate the three-dimensional shear force sensor (13), the laser displacement sensor (14) and the high-speed camera unit (15); Step S3, applying vertical stress: applying a preset vertical stress to the first force transmission plate (10) through the first hydraulic pusher (9), and dynamically adjusting it through a closed-loop feedback system; Step S4, applying a horizontal cyclic shear load: synchronously driving the second hydraulic pusher (11) and the third hydraulic pusher (12) to generate a composite waveform load, causing the shear box (8) to reciprocate along the adjustment assembly; Step S5, data acquisition and processing: a shear stress-displacement curve is obtained by a three-dimensional shear force sensor (13), a laser displacement sensor (14) measures the displacement of the shear box (8), a high-speed camera unit (15) records particle motion images, and a data processing terminal (16) analyzes the particle breakage rate, friction coefficient, and shear modulus.

8. The rockfill particle cyclic shear test method according to claim 7, characterized in that: In step S3, the preset vertical stress is 100 kPa-2 MPa, the loading rate is 0.1-5 kN / s, and the vertical stress is dynamically adjusted according to the particle crushing situation during the test, and the adjustment range does not exceed ±20% of the initial value.

9. The rockfill particle cyclic shear test method according to claim 7, characterized in that: In step S4, the waveform of the horizontal cyclic shear load includes a superposition of a sine wave and a square wave, an amplitude of 50-200 mm, a frequency of 0.1-5 Hz, and a number of cycles ≥1000 times.

10. The rockfill particle cyclic shear test method according to claim 7, characterized in that: In step S5, the data processing terminal (16) extracts the particle displacement field data by particle image velocimetry, and generates the particle contact force chain network and energy dissipation distribution diagram by combining discrete element numerical simulation.

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