Multifunctional device for testing compressive and shearing performance of large-diameter gravel and use method thereof

Abstract

This invention discloses a multifunctional device and method for testing the compressive and shear properties of large-diameter crushed stone. The multifunctional device includes an experimental platform, a reaction frame structure positioned above the experimental platform, a vertical loading mechanism and a horizontal loading mechanism mounted on the experimental platform and the reaction frame structure, and a test device box placed on the experimental platform. Large-diameter crushed stone ballast material is placed in the test device box. Vertical forces are applied to it through the vertical loading mechanism, and shear forces are applied through the horizontal loading mechanism, conducting direct shear tests, vertical stiffness tests, and / or triaxial tests to test the compressive and shear properties of the large-diameter crushed stone ballast material. Overall, this invention, by integrating multiple functions and advantages, can provide more accurate and effective evaluation information to complete the mechanical property testing of large-diameter crushed stone ballast material, successfully overcoming the problems and limitations of existing ballast material mechanical property testing devices, and has good practical value.

Description

TECHNICAL FIELD

[0001] The present application relates to a multifunctional device for testing the compressive and shear resistance of large-diameter crushed stone and a method of use. BACKGROUND

[0002] Large-diameter crushed stone ballast plays an important role in ballast track structure. It has high compressive strength and can withstand the pressure exerted by the rail and train load, maintaining the stability of the track. At the same time, it can make the ballast have a certain elasticity, absorbing and dispersing the impact force generated by the load when the train passes, reducing the wear and tear of the track and rail by the train, and prolonging the service life. In addition, large-diameter crushed stone ballast can uniformly disperse the load of the rail and the sleeper, reducing local stress concentration and preventing the sleeper from sinking and deforming, improving the stability and carrying capacity of the track. Furthermore, large-diameter crushed stone ballast generally has good drainage performance, can quickly drain rainwater and groundwater, prevent the accumulation of water in the ballast bed and softening, maintain the stability of the railway line, and has good durability, can withstand frequent train operation and load for a long time, reduce the settlement and deformation of the ballast bed, and maintain the flatness and geometric stability of the track. Therefore, understanding the performance characteristics of large-diameter crushed stone ballast is of great significance for the design and maintenance of railway tracks.

[0003] Typically, crushed stone ballast under train loads must withstand loads from multiple directions, including shear and vertical forces, resulting in varying degrees of deformation and damage. Generally, the failure of crushed stone ballast is primarily caused by shear failure, while also being affected by vertical stress. Therefore, effectively testing the compressive and shear strength of crushed stone ballast to ensure that the compressive and shear strength of the ballast material meets the strength requirements in railway crushed stone ballast specifications is paramount to ensuring track safety. However, commonly used conventional soil mechanics instruments are mainly used for testing the mechanical properties of fine-grained materials such as soil and rock; however, large-diameter crushed stone ballast has a larger particle size and higher shear strength, which is significantly different from fine-grained materials. Therefore, conventional soil mechanics instruments are not suitable for testing large-diameter crushed stone ballast materials. First, conventional soil mechanics instruments are designed for materials with smaller particles, while large-diameter crushed stone ballast particles are too large and may not be suitable for the instrument's testing setup and size. Second, large-diameter crushed stone ballast has high shear strength, and the testing range of conventional soil mechanics instruments may not meet its requirements because they are designed for lower-strength, fine-grained materials. Third, large-diameter crushed stone ballast particles have fewer contact points and irregular particle arrangement, which does not perfectly match the testing assumptions and models of conventional soil mechanics instruments. Furthermore, conventional soil mechanics instruments are typically designed for laboratory environments and small samples, while in actual railway track beds, the scale and actual stress conditions of crushed stone ballast far exceed the capabilities of these instruments. Therefore, to effectively test the mechanical properties of large-diameter crushed stone ballast, it is necessary to design and develop a testing device specifically for this material to address issues related to particle size, shear strength, and particle arrangement, and to ensure the accuracy and reliability of the test results.

[0004] Existing technologies for testing the mechanical properties of self-made large-diameter crushed stone ballast materials also suffer from numerous problems, such as complex operation procedures, difficulty in installation and disassembly, limited functionality, and significant errors in test results. For example, Chinese patent CN104833585B discloses a device for testing the compressive strength of railway crushed stone ballast. This device only provides a horizontal loading mechanism for testing the compressive strength of the ballast, and the pressure applied is solely from this horizontal loading mechanism. In reality, railway crushed stone ballast under train loads must withstand loads from multiple directions, including shear force and vertical force, requiring direct shear tests, vertical stiffness tests, and triaxial tests, which this device clearly cannot perform simultaneously. Another example is a portable rock direct shear apparatus disclosed in Chinese patent CN218412094U. In this apparatus, the sample shearing and vertical pressure device are in direct contact, which increases frictional resistance and component wear during the sliding of the horizontal loading device, leading to significant errors in the test results. Most importantly, when using different devices to conduct direct shear tests, vertical stiffness tests, and triaxial tests on large-diameter crushed stone ballast materials, the process is not only cumbersome, but also the structural differences between different testing devices, such as the size and shape of the specimens in different testing devices, may affect the distribution of stress and deformation, resulting in errors in the results obtained by each device when testing the mechanical properties of the same specimen.

[0005] Therefore, how to effectively test the mechanical properties of large-diameter crushed stone ballast and ensure the accuracy and reliability of the test results remains an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the problems existing in current devices for testing the mechanical properties of large-diameter crushed stone ballast materials, this invention provides a multifunctional device and method for testing the compressive and shear properties of large-diameter crushed stone. It effectively integrates direct shear, vertical compression, and triaxial testing into a single design, facilitating convenient assembly, reducing experimental errors, and ensuring the accuracy of test results. The specific technical solution is as follows:

[0007] First, the present invention provides a multifunctional device for testing the compressive and shear properties of large-diameter crushed stone, including an experimental platform, a reaction frame structure set above the experimental platform, a vertical loading mechanism and a horizontal loading mechanism installed on the experimental platform and the reaction frame structure, and a test device box placed on the experimental platform.

[0008] Large-diameter crushed stone ballast material is placed in a testing device box. Vertical force is applied to it through the vertical loading mechanism, and shear force is applied to it through the horizontal loading mechanism. Direct shear test, vertical stiffness test and / or triaxial test are carried out to test the compressive and shear properties of the large-diameter crushed stone ballast material.

[0009] The aforementioned multifunctional device for testing the compressive and shear properties of large-diameter crushed stone includes a reaction frame structure comprising two support columns set at both ends of the experimental platform and a reaction frame beam erected on the upper ends of the two support columns and horizontally positioned above the experimental platform.

[0010] The bottom end of the supporting column is fixedly connected to the ground by large bolts, and the upper side is provided with a crossbeam through hole.

[0011] The two ends of the reaction frame beam are inserted into the beam through holes at the upper ends of the two supporting columns and welded to fix them.

[0012] The aforementioned multifunctional device for testing the compressive and shear properties of large-diameter crushed stone includes a vertical loading mechanism that is hoisted onto the reaction frame beam via a hoisting base. The mechanism includes a vertical loader for providing vertical loading power and a first hydraulic jack for performing vertical loading.

[0013] The hoisting base includes several long bolts, an upper clamping plate, and a lower clamping plate; the width of the upper clamping plate and the lower clamping plate is greater than the width of the reaction frame beam, and the two are clamped and fixed to the upper and lower sides of the reaction frame beam by the long bolts.

[0014] The lower clamp plate is provided with mounting holes for hoisting the vertical loader. The first hydraulic jack is located at the front end of the vertical loader and applies a vertical force to the large-diameter crushed stone ballast material below it under the action of the vertical loader.

[0015] The aforementioned multifunctional device for testing the compressive and shear properties of large-diameter crushed stone includes a horizontal loading mechanism mounted on an experimental platform via a support base. The horizontal loading mechanism includes a horizontal loader for providing horizontal loading power and a second hydraulic jack for performing horizontal loading.

[0016] The support base is located at one end of the experimental platform and close to the support column of the reaction frame structure. It includes a support steel leg and a horizontal base. The support steel leg is fixed on the platform surface of the experimental platform, and the horizontal base is horizontally placed on the upper end of the support steel leg. The two are connected and fixed in a T-shape.

[0017] The horizontal loader is installed inside the horizontal base, and the second hydraulic jack is located at the front end of the horizontal loader. Under the action of the horizontal loader, it applies a horizontal shear force to the large-diameter crushed stone ballast material directly in front of it.

[0018] The aforementioned multifunctional device for testing the compressive and shear strength of large-diameter crushed stone includes a direct shear test chamber, a vertical compression test chamber, and a triaxial test chamber; wherein:

[0019] The direct shear test box includes a first shear box and a second shear box. The first shear box has no bottom and the second shear box has no lid. The two are stacked one on top of the other, and the side length of the first shear box at the top is smaller than the side length of the second shear box at the bottom.

[0020] The direct shear test box also includes a cover plate, a horizontal loading plate, and several rollers; the cover plate is placed on the large-diameter crushed stone ballast material inside the first shear box; the horizontal loading plate is located on the cover plate and its area is smaller than that of the cover plate; the rollers are located between the cover plate and the horizontal loading plate; a vertical force is applied to the horizontal loading plate, and a horizontal shear force is applied to one side of the first shear box facing the support column to perform a direct shear test;

[0021] The vertical pressure test box includes a vertical pressure sample box body and a simulated sleeper; the cross-section of the vertical pressure sample box body is approximately the cross-section of the first shear box in the direct shear test box, and its height is approximately twice that of the first shear box; the simulated sleeper is embedded in large-particle-size crushed stone ballast material within the vertical pressure sample box body to simulate the structure of a real railway sleeper; a vertical force is applied to the simulated sleeper to perform the vertical pressure test;

[0022] The triaxial test box includes a triaxial sample box body, a simulated sleeper, and a simulated rail. The triaxial sample box body is similar to the vertical pressure sample box body. The simulated sleeper is embedded in the large-particle-size crushed stone ballast material within the triaxial sample box body. The simulated rail is installed on the simulated sleeper to simulate the structure of a real railway line. Vertical forces are applied to the simulated rail, and horizontal shear forces are applied to the two sides of the triaxial sample box body facing the supporting column to perform triaxial testing.

[0023] The aforementioned multifunctional device for testing the compressive and shear strength of large-diameter crushed stone also includes a test monitoring system, which includes a pressure monitoring module, a displacement monitoring module, and an information acquisition, processing, and control center.

[0024] The pressure monitoring module includes a vertical pressure sensor and a horizontal pressure sensor. The vertical pressure sensor is used to detect the vertical force applied to the large-diameter crushed stone ballast material, and the horizontal pressure sensor is used to detect the horizontal shear force applied to the large-diameter crushed stone ballast material.

[0025] The displacement monitoring module includes a vertical displacement sensor and a horizontal displacement sensor. The vertical displacement sensor is used to detect the compressive settlement of large-diameter crushed stone ballast material under vertical force, and the horizontal displacement sensor is used to detect the relative displacement of large-diameter crushed stone ballast material under horizontal shear force in direct shear test and triaxial test.

[0026] The information acquisition and processing control center includes a data acquisition unit and a monitoring and control center. The data acquisition unit is used to collect detection information from vertical pressure sensors, horizontal pressure sensors, vertical displacement sensors, and horizontal displacement sensors and transmit it to the monitoring and control center. The monitoring and control center is used to receive the information collected by the data acquisition unit, monitor data changes in real time, and complete data recording, storage, and control the conduct of experiments.

[0027] The aforementioned multifunctional device for testing the compressive and shear strength of large-diameter crushed stone has a vertical pressure sensor installed between the lower clamping plate and the vertical loader, located directly above the vertical loader, and connected to the data acquisition unit via a data transmission interface.

[0028] The horizontal pressure sensor is installed in the horizontal base of the horizontal loading mechanism, located at the rear end of the horizontal loader, and is connected to the data acquisition device through a data transmission interface;

[0029] Both the vertical displacement sensor and the horizontal displacement sensor include a sensor body and a sensing element; wherein...

[0030] The sensor body of the vertical displacement sensor is mounted on the sensor bracket and is at the same height as the upper edge of the direct shear test box, the vertical pressure test box and the triaxial test box. In the direct shear test, its sensing element is set on the cover plate inside the first shear box. In the vertical stiffness test and the triaxial test, its sensing element is set on the simulated sleeper.

[0031] The sensor body of the horizontal displacement sensor is mounted on the platform of the experimental platform. In the direct shear test, its sensing element is set on the side of the first shear box facing the supporting column. In the triaxial test, its sensing element is set on the side of the triaxial test box facing the supporting column.

[0032] The aforementioned multifunctional device was used to conduct a direct shear test on the large-diameter crushed stone ballast material to be tested, specifically including the following steps:

[0033] 1-1) Sample loading: Place the second shear box at the designated position on the experimental platform. Fill the second shear box with the large-diameter crushed stone ballast material to be tested in layers until it is full. Stack the first shear box on top of the large-diameter crushed stone ballast material in the second shear box. Then fill the remaining large-diameter crushed stone ballast material to be tested into the first shear box in layers. Perform compaction and pressure treatment to compact the large-diameter crushed stone ballast material to be tested.

[0034] 1-2) Covering: Place the cover plate on the compacted large-diameter crushed stone ballast material, then place the roller on the cover plate, and finally place the horizontal loading plate on the roller.

[0035] 1-3) Install the vertical loading mechanism: Use long bolts to clamp the upper and lower clamping plates onto the reaction frame beam. Use fasteners to assemble the vertical pressure sensor, vertical loader, and first hydraulic jack in that order. The vertical pressure sensor is connected to the lower clamping plate and hoisted into the middle of the reaction frame beam. The first hydraulic jack of the vertical loading mechanism is directly opposite the horizontal loading plate on the first shear box.

[0036] 1-4) Install the horizontal loading mechanism: Use fasteners to install the horizontal pressure sensor, horizontal loader, and second hydraulic jack in the horizontal base in that order, and install it on the experimental platform through supporting steel legs; the second hydraulic jack of the horizontal loading mechanism faces one side of the second shear box facing the reaction frame structure support column;

[0037] 1-5) Install displacement sensors: Install the sensor bodies of two vertical displacement sensors on separate sensor brackets, and set their sensing elements at both ends of the cover plate inside the first shear box; install the sensor body of a horizontal displacement sensor on the experimental platform and opposite to the horizontal loading mechanism, and set its sensing element on the other side of the second shear box opposite to the second hydraulic jack.

[0038] 1-6) Install the data acquisition unit: Connect the vertical pressure sensor, horizontal pressure sensor, vertical displacement sensor, and horizontal displacement sensor to the data acquisition unit, and connect the data acquisition unit to the monitoring and control center;

[0039] 1-7) Pre-compression judgment: When all equipment is properly installed and connected, apply a certain vertical force to the horizontal loading plate through the vertical loading mechanism to compact and compact the large-diameter crushed stone ballast material to be tested, and observe the data acquisition device and monitoring and control center to determine whether the device can operate normally.

[0040] 1-8) Direct shear test: After confirming that the instrument can operate normally, control the vertical loading mechanism to continue to apply external loads until the vertical load reaches the predetermined pressure value. After the pressure stabilizes, start the horizontal loading mechanism to apply horizontal shear force to the first shear box. At the same time, control the horizontal shear force through the monitoring and control center. When the horizontal shear force can no longer be increased or the data collected by the data acquisition device reaches the required value, stop all load pressurization and the test ends.

[0041] 1-9) Shear resistance performance analysis: By monitoring and controlling the data recorded by the control center, the relationship curve between the horizontal shear force and the shear displacement of the first shear box under the set vertical pressure can be obtained, and the shear resistance performance of the large-diameter crushed stone ballast material to be tested can be further analyzed.

[0042] The aforementioned multifunctional device was used to conduct a vertical stiffness test on the large-diameter crushed stone ballast material to be tested, specifically including the following steps:

[0043] 2-1) Sample loading: Place the vertical pressure sample loading box body at the designated position on the experimental platform, and fill the large-diameter crushed stone ballast material to be tested into the box in an orderly manner according to the layers. Whenever the large-diameter crushed stone ballast material to be tested is filled to a certain depth, it is manually tamped and pressure is applied to compact the large-diameter crushed stone ballast material to be tested.

[0044] 2-2) Sleeper embedding: During the sample loading process, when the remaining height inside the box is close to half the height of the simulated sleeper, place the simulated sleeper in the center of the vertical pressure sample loading box body, and continue to fill in the remaining large-diameter crushed stone ballast material to be tested until the ballast fills the iron box.

[0045] 2-3) Install the vertical loading mechanism: Use long bolts to clamp the upper and lower clamps onto the reaction frame beam. Use fasteners to combine the vertical pressure sensor, vertical loader and first hydraulic jack in sequence. The vertical pressure sensor is connected to the lower clamp and hoisted in the middle of the reaction frame beam. The first hydraulic jack of the vertical loading mechanism is directly opposite the simulated sleeper in the vertical pressure sample box body.

[0046] 2-4) Install displacement sensors: Install the sensor bodies of the two vertical displacement sensors on separate sensor brackets, and set their sensing elements on the simulated sleepers respectively;

[0047] 2-5) Install the data acquisition unit: Connect both the vertical pressure sensor and the vertical displacement sensor to the data acquisition unit, and connect the data acquisition unit to the monitoring and control center;

[0048] 2-6) Pre-compression judgment: When all equipment is properly installed and connected, apply a certain vertical force to the simulated sleeper through the vertical loading mechanism to compact the large-diameter crushed stone ballast material to be tested, and observe the data acquisition device and monitoring and control center to determine whether the device can operate normally.

[0049] 2-7) Vertical pressure test: After confirming that the instrument can operate normally, control the vertical loading mechanism to continue to apply external load, stabilize the vertical pressure through the vertical pressure sensor, and monitor the vertical displacement and pressure in real time through the monitoring and control center. When the vertical pressure can no longer be increased or the vertical pressure collected by the data acquisition device reaches the required value, stop all load pressurization and the test ends.

[0050] 2-8) Vertical stiffness analysis: The vertical pressure-displacement relationship curve can be obtained by monitoring and controlling the data recorded by the control center. The section with a relatively stable slope is the vertical stiffness of the large-diameter crushed stone ballast material to be tested.

[0051] The aforementioned multifunctional device was used to conduct triaxial tests on the large-diameter crushed stone ballast material to be tested, specifically including the following steps:

[0052] 3-1) Sample loading: Place the triaxial sample loading box body at the designated position on the experimental platform. Fill the box with the large-diameter crushed stone ballast material to be tested in layers. When the large-diameter crushed stone ballast material to be tested is filled to a certain depth, manually tamp it down and apply pressure to compact the large-diameter crushed stone ballast material to be tested.

[0053] 3-2) Sleeper and rail embedding: During the sample loading process, when the remaining height inside the box is close to half the height of the simulated sleeper, place the simulated sleeper in the center of the three-axis sample loading box body, continue to fill in the remaining large-diameter crushed stone ballast material to be tested until the ballast fills the iron box, and then install the simulated rail on the simulated sleeper.

[0054] 3-3) Install the vertical loading mechanism: Use long bolts to clamp the upper and lower clamps onto the reaction frame beam. Use fasteners to combine the vertical pressure sensor, vertical loader and first hydraulic jack in sequence. The vertical pressure sensor is connected to the lower clamp and hoisted in the middle of the reaction frame beam. The first hydraulic jack of the loading mechanism is directly opposite the simulated rail in the three-axis sample box body.

[0055] 3-4) Install the horizontal loading mechanism: Use fasteners to combine the two horizontal pressure sensors, two horizontal loaders and two second hydraulic jacks in the order of horizontal pressure sensors, horizontal loaders and second hydraulic jacks, and install them at both ends of the experimental platform through supporting steel legs. The two second hydraulic jacks of the two horizontal loading mechanisms face the two sides of the triaxial test box facing the reaction frame structure support column.

[0056] 3-5) Install displacement sensors: Install the sensor bodies of the two vertical displacement sensors on separate sensor brackets, and set their sensing elements on the simulated sleepers; install the sensor bodies of the two horizontal displacement sensors on the experimental platform on both sides of the triaxial test box, and set their sensing elements on the two sides of the triaxial test box facing the reaction frame support column.

[0057] 3-6) Install the data acquisition unit: Connect the vertical pressure sensor, horizontal pressure sensor, vertical displacement sensor, and horizontal displacement sensor to the data acquisition unit, and connect the data acquisition unit to the monitoring and control center;

[0058] 3-7) Pre-compression judgment: When all equipment is properly installed and connected, a certain vertical force is applied to the simulated rail through the vertical loading mechanism to compact the large-diameter crushed stone ballast material to be tested, and the data acquisition device and monitoring and control center are observed to determine whether the device can operate normally.

[0059] 3-8) Triaxial test: After confirming that the instrument can operate normally, control the vertical loading mechanism to continue to apply vertical load, and at the same time apply horizontal shear force to the triaxial test box through two horizontal loading mechanisms respectively. The vertical displacement sensor and the horizontal displacement sensor detect the relevant displacement data in real time. When the data obtained by the data acquisition device reaches the required value, stop all load pressurization.

[0060] 3-9) Compression and shear performance analysis: By monitoring the data recorded by the control center, relevant curves can be obtained, and the required triaxial test results can be obtained. The test ends.

[0061] The beneficial effects of this invention are as follows:

[0062] Compared with existing devices for testing the mechanical properties of ballast materials, the device of the present invention has at least the following advantages:

[0063] 1) Multifunctionality: The device of this invention has both a vertical loading mechanism and a horizontal loading mechanism, which can simultaneously apply vertical force and horizontal shear force to the particle size crushed stone ballast material. It realizes the compressive and shear performance test of particle size crushed stone ballast material under the influence of vertical stress, covering a variety of experimental evaluations such as direct shear test, vertical stiffness test and triaxial test, providing more comprehensive, accurate and effective detection and evaluation information for the mechanical properties of particle size crushed stone ballast material.

[0064] 2) Reduced friction: In the direct shear device box of this invention, the moving parts are connected by ball bearings or rollers, effectively reducing the friction between the parts and minimizing damage during operation. It also significantly reduces the resistance of the horizontal loading device during testing, providing effective labor savings while protecting the testing equipment and extending its service life.

[0065] 3) Stability and reliability: Unlike other testing instruments, this device is not easily disturbed. It is fixed to the laboratory's own solid foundation with bolts. All test equipment is placed on the fixed reaction frame structure, which has high stability and greatly reduces the influence of external factors on the test.

[0066] 4) Flexibility and versatility: The device of this invention can be freely combined according to test requirements. In the configuration of the test device, the reaction frame structure is retained and the corresponding device box for the required test is selected for assembly, which improves the efficiency of test preparation and facilitates quick entry into the formal test, and helps to save the time spent installing the loading device. At the same time, it is not limited to completing one type of mechanical property test of the specimen. This device can complete a variety of different mechanical property index tests. Moreover, the device boxes selected by this multifunctional testing device are almost the same size, which effectively controls the number of specimens when conducting multiple tests on the specimens, ensuring that all tests are completed in one loading mode, and effectively reducing unnecessary errors caused by frequent device changes.

[0067] 5) Simple operation and real-time monitoring: The device of this invention can be directly assembled from the reaction frame structure and the test device box. The usage of each component is simple, easy to learn and use. It has the characteristics of simple structure, simple operation, time saving and clear force transmission. The data acquisition device is connected to an external control console to monitor data changes in real time, control the gradual increase of pressure in the test loading device, ensure stable changes in data during the test, and effectively improve the authenticity of the test results.

[0068] In summary, the device of the present invention, by integrating multiple functions and advantages, can provide more accurate and effective evaluation information to complete the mechanical property testing of large-particle-size crushed stone ballast materials, and successfully overcomes the problems and limitations of existing devices for testing the mechanical properties of ballast materials. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the multifunctional device for testing the compressive and shear strength of large-diameter crushed stone according to the present invention.

[0070] Figure 2 This is a schematic diagram of the vertical loading mechanism structure of the present invention;

[0071] Figure 3 This is a schematic diagram of the lifting base structure of the vertical loading mechanism of the present invention;

[0072] Figure 4 This is a schematic diagram of the device structure for conducting a direct shear test using the present invention;

[0073] Figure 5 This is a schematic diagram of the structure of the vertical stiffness testing device using the present invention;

[0074] Figure 6 Photos of a vertical stress test conducted using the vertical stiffness testing device of this invention;

[0075] Figure 7 This is a schematic diagram of the triaxial testing device using the present invention.

[0076] In the diagram: 1. Experimental platform; 2. Reaction frame structure; 21. Support column; 22. Reaction frame beam; 3. Vertical loading mechanism; 31. Lifting base; 311. Long bolt; 312. Upper clamping plate; 313. Lower clamping plate; 32. Vertical loader; 33. First hydraulic jack; 4. Horizontal loading mechanism; 41. Mounting support; 411. Supporting steel leg; 412. Horizontal base; 42. Horizontal loader; 43. Second hydraulic jack; 5. Test device box; 51. Straight shear test box; 511. First shear Box; 512, Second shear box; 513, Cover plate; 514, Horizontal loading plate; 515, Roller; 52, Vertical pressure test box; 521, Vertical pressure sample box body; 53, Triaxial test box; 531, Triaxial sample box body; 6, Simulated sleeper; 7, Simulated rail; 8, Pressure monitoring module; 81, Vertical pressure sensor; 82, Horizontal pressure sensor; 9, Displacement monitoring module; 91, Vertical displacement sensor; 92, Horizontal displacement sensor; 10, Data acquisition unit; 11, On the sensor bracket. Detailed Implementation

[0077] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are merely preferred embodiments of the present invention, and not all embodiments, nor are they intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications or equivalent variations based on the disclosed technical content. However, any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention's technical solution shall still fall within the protection scope of the present invention's technical solution.

[0078] Example 1

[0079] This embodiment describes a multifunctional device for testing the compressive and shear strength of large-diameter crushed stone, such as... Figure 1 As shown, the test includes an experimental platform 1, a reaction frame structure 2 set above the experimental platform 1, a vertical loading mechanism 3 and a horizontal loading mechanism 4 installed on the experimental platform 1 and the reaction frame structure 2, and a test device box 5 placed on the experimental platform 1. The large-diameter crushed stone ballast material is placed in the test device box 5. Vertical force is applied to it by the vertical loading mechanism 3, and shear force is applied to it by the horizontal loading mechanism 4. Direct shear test, vertical stiffness test and / or triaxial test are carried out to test the compressive and shear properties of the large-diameter crushed stone ballast material.

[0080] Specifically, in this embodiment, the reaction frame structure 2 includes two supporting columns 21 set at both ends of the experimental platform 1 and a reaction frame beam 22 erected on the upper end of the two supporting columns 21 and horizontally arranged above the experimental platform 1; the bottom end of the supporting column 21 is fixedly connected to the ground by large bolts, and the upper side of the column is provided with a beam through hole; the two ends of the reaction frame beam 22 are inserted into the beam through holes at the upper end of the two supporting columns 21 and welded and fixed.

[0081] The vertical loading mechanism 3 is hoisted onto the reaction frame beam 22 via the hoisting base 31. It includes a vertical loader 32 for providing vertical loading power and a first hydraulic jack 33 for performing vertical loading. The vertical loader 32 is a hydraulic loader, which can be purchased on the market, such as a dual-circuit manual hydraulic pump (model CP-700S). The hoisting base 31 includes a long bolt 311, an upper clamping plate 312, and a lower clamping plate 313. The width of the upper clamping plate 312 and the lower clamping plate 313 is greater than the width of the reaction frame beam 22. The long bolt 311 clamps and fixes the two plates to the upper and lower sides of the reaction frame beam 22. The lower clamping plate 313 is provided with mounting holes for hoisting. The first hydraulic jack 33 is located at the front end of the vertical loader 32 and extends and retracts under the action of the vertical loader 32. When not in operation, the first hydraulic jack 33 is usually retracted inside the vertical loader 32. When pressurized during operation, it is pushed out to apply a vertical force to the large-diameter crushed stone ballast material below it.

[0082] like Figure 2 and Figure 3 As shown, the vertical loading mechanism 3 is suspended from the middle of the reaction frame beam 22 via a lifting base 31. The upper clamping plate 312 and the lower clamping plate 313 of the lifting base 31 are connected and clamped to the reaction frame beam 22 by bolts 311. This design allows the clamping position of the upper clamping plate 312 and the lower clamping plate 313 on the reaction frame beam 22 to be adjustable, thereby allowing the position of the vertical loading mechanism 3 to be adjusted to meet different experimental needs.

[0083] The horizontal loading mechanism 4 is mounted on the test bench 1 via a support base 41. It includes a horizontal loader 42 for providing horizontal loading power and a second hydraulic jack 43 for performing horizontal loading. The hydraulic loader is commercially available and can be a dual-circuit manual hydraulic pump (model CP-700S) of the same type as the vertical loader 32. The support base 41 is located at one end of the test platform 1 and near the support column 21 of the reaction frame structure 2. It includes a support leg 411 and a horizontal base 412. The support leg 411 is fixed to the test platform 1, and the horizontal base 412 is horizontally positioned above the support leg 411, with the two connected in a T-shape. The horizontal loader 42 is located within the horizontal base 412, and the second hydraulic jack 43 is located at the front end of the horizontal loader 42. Its working principle is the same as the first hydraulic jack 33; it extends and retracts under the action of the horizontal loader 42, applying a horizontal shear force to the large-diameter crushed stone ballast material directly in front of the loader.

[0084] In this embodiment, the test device box 5 includes three types of device boxes: a direct shear test box 51, a vertical pressure test box 52, and a triaxial test box 53. The direct shear test box 51 includes a first shear box 511 and a second shear box 512. The first shear box 511 has no bottom, and the second shear box 512 has no lid. They are stacked one on top of the other, with the side length of the upper first shear box 511 being smaller than the side length of the lower second shear box 512, particularly in length. This ensures that the first shear box 511 and the second shear box 512 can be displaced under the action of the horizontal loading mechanism 4, making it suitable for direct shear testing. Furthermore, in this embodiment, the second shear box 512 has limiting baffle structures on its front and rear sides to facilitate the stacking of the first shear box 511 and prevent lateral displacement when a horizontal shear force is subsequently applied. The direct shear test box 51 also includes a cover plate 513, a horizontal loading plate 514, and several rollers 515; the cover plate 513 is placed over the large-diameter crushed stone ballast material inside the first shear box 511; the horizontal loading plate 514 is located above the cover plate 513, and its area is smaller than that of the cover plate 513; the rollers 515 are located between the cover plate 513 and the horizontal loading plate 514; a vertical force is applied to the horizontal loading plate 514, and a horizontal shear force is applied to one side of the first shear box 511 facing the support column 21 to perform a direct shear test.

[0085] The vertical pressure test box 52 includes a vertical pressure sample box body 521 and a simulated sleeper 6; the cross-section of the vertical pressure sample box body 521 is approximately the cross-section of the first shear box 511 in the direct shear test box 51, and its height is approximately twice that of the first shear box 511; the simulated sleeper 6 is embedded in large-diameter crushed stone ballast material within the vertical pressure sample box body 521 to simulate the structure of a real railway sleeper; a vertical force is applied to the simulated sleeper 6 to perform a vertical pressure test.

[0086] The triaxial test box 53 includes a triaxial sample box body 531, a simulated sleeper 6, and a simulated rail 7. The triaxial sample box body 531 is similar to the vertical pressure sample box body 521. The simulated sleeper 6 is embedded in large-particle-size crushed stone ballast material within the triaxial sample box body 531. The simulated rail 7 is installed on the simulated sleeper 6 to simulate the structure of a real railway line. Vertical forces are applied to the simulated rail 7 and transmitted to the crushed stone ballast material to be tested. Horizontal shear forces are applied to the two sides of the triaxial sample box body 531 facing the supporting column 21 and transmitted to the crushed stone ballast material to be tested, thus performing triaxial triaxial testing.

[0087] The multifunctional device for testing the compressive and shear properties of large-diameter crushed stone described in this embodiment also includes a testing and monitoring system. This system comprises a pressure monitoring module 8, a displacement monitoring module 9, and an information acquisition, processing, and control center. The pressure monitoring module 8 includes a vertical pressure sensor 81 and a horizontal pressure sensor 82. The vertical pressure sensor 81 detects the vertical force applied to the large-diameter crushed stone ballast material, and the horizontal pressure sensor 82 detects the horizontal shear force applied to the large-diameter crushed stone ballast material. The displacement monitoring module 9 includes a vertical displacement sensor 91 and a horizontal displacement sensor 92. The vertical displacement sensor 91 detects the compressive settlement of the large-diameter crushed stone ballast material under vertical force, and the horizontal displacement sensor 92 detects the relative displacement of the large-diameter crushed stone ballast material under horizontal shear force during direct shear and triaxial tests. In this embodiment, both the vertical pressure sensor 81 and the horizontal pressure sensor 82 are spoke-type tension / compression sensors (TJH-4B), which are equipped with a data transmission interface connected to the data acquisition unit 10. Both the vertical displacement sensor 91 and the horizontal displacement sensor 92 are universal magnetic bases (WCZ-6A). The information acquisition and processing control center includes the data acquisition unit 10 and a monitoring control center. The data acquisition unit 10 collects the detection information from the vertical pressure sensor 81, the horizontal pressure sensor 82, the vertical displacement sensor 91, and the horizontal displacement sensor 92 and transmits it to the monitoring control center. The monitoring control center receives the information collected by the data acquisition unit 10, monitors data changes in real time, and completes data recording, storage, and control of the experiment.

[0088] Specifically, in this embodiment, the vertical pressure sensor 81 is disposed between the lower clamping plate 313 and the vertical loader 32, and is located directly above the vertical loader 32. The vertical pressure sensor 81 is directly connected to the lower clamping plate 313, and the vertical loader 32 is installed below it by fasteners. The horizontal pressure sensor 82 is disposed in the horizontal base 412 of the horizontal loading mechanism 4, and is connected to the data acquisition device 10 through a data transmission interface. Both the vertical displacement sensor 91 and the horizontal displacement sensor 92 include a sensor body and a sensing element. The sensor body of the vertical displacement sensor 91 is mounted on a sensor bracket 11, at the same height as the upper edge of the direct shear test box 51, the vertical pressure test box 52, and the triaxial test box 53. In the direct shear test, its sensing element is located on the cover plate 513 inside the first shear box 511; in the vertical stiffness test and the triaxial test, its sensing element is located on the simulated sleeper 6. The sensor body of the horizontal displacement sensor 92 is mounted on the platform 1 of the experimental platform. In the direct shear test, its sensing element is located on the side of the first shear box 511 facing the supporting column 21; in the triaxial test, its sensing element is located on the side of the triaxial test box 53 facing the supporting column 21.

[0089] Example 2

[0090] This embodiment uses the multifunctional device described in Embodiment 1 to test the shear resistance of large-diameter crushed stone, specifically to conduct a direct shear test on the large-diameter crushed stone ballast material to be tested using the aforementioned multifunctional device. The device is as follows: Figure 4 As shown, the specific steps include the following:

[0091] 1-1) Sample Loading: Place the second shear box 512 at the designated position on the experimental platform 1. Fill the second shear box 512 with the large-diameter crushed stone ballast material to be tested in layers until it is full. Stack the first shear box 511 on top of the large-diameter crushed stone ballast material in the second shear box 512. Then, fill the remaining large-diameter crushed stone ballast material to be tested into the first shear box 511 in layers, and perform tamping and pressure treatment to compact the large-diameter crushed stone ballast material to be tested. In this invention, the steps of sample loading, installing the vertical loading mechanism, installing the horizontal loading mechanism, and installing the displacement sensor do not have a specific order. Generally, the step of installing the vertical loading mechanism precedes the sample loading step. Therefore, the pressure treatment can be achieved through the vertical loading mechanism.

[0092] 1-2) Covering: Place the cover plate 513 on the compacted large-diameter crushed stone ballast material, then install the roller 515 on the cover plate 513, and finally place the horizontal loading plate 514 on the roller 515.

[0093] 1-3) Install the vertical loading mechanism: Install the vertical pressure sensor 81 on the lower clamping plate 313, and then use fasteners to combine the vertical loader 32 and the first hydraulic jack 33 to form the vertical loading mechanism 3, and suspend it in the middle of the reaction frame beam 22 by the vertical pressure sensor 81. The first hydraulic jack 33 is directly facing the horizontal loading plate 514 on the first shear box 511.

[0094] 1-4) Install the horizontal loading mechanism: Install the horizontal pressure sensor 82 in the horizontal base 412 of the horizontal loading mechanism 4, and assemble the horizontal loading mechanism 4 by combining the horizontal pressure sensor 82, the horizontal loader 42 and the second hydraulic jack 43 in the order of fasteners. The horizontal loading mechanism 4 is fixedly installed on the table surface of the experimental platform 1 by the supporting steel leg 411. The second hydraulic jack 43 faces the side of the second shear box 512 facing the support column 21 of the reaction frame structure 2.

[0095] 1-5) Install displacement sensors: Install the sensor bodies of two vertical displacement sensors 91 on the independent sensor brackets 11 respectively, and set their sensing elements at both ends of the cover plate 513 inside the first shear box 511; install the sensor body of a horizontal displacement sensor 92 on the experimental platform 1 and opposite to the horizontal loading mechanism 4, and set its sensing element on the other side of the second shear box 512 opposite to the second hydraulic top 43.

[0096] 1-6) Install the data acquisition unit: Connect the vertical pressure sensor 81, the horizontal pressure sensor 82, the vertical displacement sensor 91, and the horizontal displacement sensor 92 to the data acquisition unit 10, and connect the data acquisition unit to the monitoring and control center.

[0097] 1-7) Pre-compression judgment: When all equipment is properly installed and connected, apply a certain vertical force to the horizontal loading plate 514 through the vertical loading mechanism 3 to compact and compact the large-diameter crushed stone ballast material to be tested, and observe the data acquisition device 10 and the monitoring and control center to determine whether the device can operate normally.

[0098] 1-8) Direct shear test: After confirming that the instrument can operate normally, control the vertical loading mechanism 3 to continue to apply external load so that the vertical load reaches the predetermined pressure value. After the pressure stabilizes, start the horizontal loading mechanism 4 to apply horizontal shear force to the first shear box 511. At the same time, control the horizontal shear force through the monitoring and control center. When the horizontal shear force can no longer be increased or the data collected by the data acquisition device 10 reaches the required value, stop all load pressurization and the test ends.

[0099] 1-9) Shear resistance performance analysis: By monitoring and controlling the data recorded by the control center, the relationship curve between the horizontal shear force and the shear displacement of the first shear box 511 under the set vertical pressure can be obtained, and the shear resistance performance of the large-diameter crushed stone ballast material to be tested can be further analyzed.

[0100] Example 3

[0101] This embodiment uses the multifunctional device described in Embodiment 1 to test the compressive strength of large-diameter crushed stone, specifically to conduct a vertical stiffness test on the large-diameter crushed stone ballast material to be tested. The device is as follows: Figure 5 and Figure 6 As shown, the specific steps include the following:

[0102] 2-1) Sample loading: Place the vertical pressure sample loading box body 521 at the designated position on the experimental platform 1, and fill the large-diameter crushed stone ballast material to be tested into the box in an orderly manner according to the layers. Whenever the large-diameter crushed stone ballast material to be tested is filled to a depth of 5-10cm, it is manually tamped and pressure is applied (which can be achieved through a vertical loading mechanism) to compact the large-diameter crushed stone ballast material to be tested.

[0103] 2-2) Sleeper embedding: During the sample loading process, when the remaining height inside the box is close to half the height of the simulated sleeper 6, place the simulated sleeper 6 in the center of the vertical pressure sample loading box body 521, and continue to fill in the remaining large-diameter crushed stone ballast material to be tested until the ballast fills the iron box.

[0104] 2-3) Install the vertical loading mechanism: Install the vertical pressure sensor 81 on the lower clamping plate 313, and then use fasteners to assemble the vertical pressure sensor 81, the vertical loader 32 and the first hydraulic jack 33 in that order to hoist the vertical loading mechanism 3 to the middle of the reaction frame beam 22. The first hydraulic jack 33 is directly opposite the simulated sleeper 6 in the vertical pressure sample box body 521.

[0105] 2-4) Install displacement sensors: Install the sensor bodies of the two vertical displacement sensors 91 on the independent sensor brackets 11 respectively, and set their sensing elements on the simulated sleepers 6 respectively.

[0106] 2-5) Install the data acquisition unit: Connect the vertical pressure sensor 81 and the vertical displacement sensor 91 to the data acquisition unit 10, and connect the data acquisition unit to the monitoring and control center;

[0107] 2-6) Pre-compression judgment: When all equipment is properly installed and connected, a certain vertical force is applied to the simulated sleeper 6 through the vertical loading mechanism 3 to compact the large-diameter crushed stone ballast material to be tested, and the data acquisition device 10 and the monitoring and control center are observed to determine whether the device can operate normally.

[0108] 2-7) Vertical pressure test: After confirming that the instrument can operate normally, control the vertical loading mechanism 3 to continue to apply external force load, stabilize the vertical pressure through the vertical pressure sensor 81, and monitor the vertical displacement and pressure in real time through the monitoring and control center. When the vertical pressure can no longer be increased or the vertical pressure collected by the data acquisition device 10 reaches the required value, stop all load pressurization and the test ends.

[0109] 2-8) Vertical stiffness analysis: The vertical pressure-displacement relationship curve can be obtained by monitoring and controlling the data recorded by the control center. The section with a relatively stable slope is the vertical stiffness of the large-diameter crushed stone ballast material to be tested.

[0110] Example 4

[0111] This embodiment describes a method for testing the compressive and shear strength of large-diameter crushed stone using the multifunctional device described in Embodiment 1. Specifically, it uses the multifunctional device to perform triaxial tests on the large-diameter crushed stone ballast material to be tested. The device is as follows: Figure 7 As shown, the specific steps include the following:

[0112] 3-1) Sample loading: Place the triaxial sample loading box body 531 at the designated position on the experimental platform 1, and fill the large-diameter crushed stone ballast material to be tested into the box in an orderly manner according to the layers. When the large-diameter crushed stone ballast material to be tested is filled to a depth of 5-10cm, it is manually tamped and pressure is applied (which can be achieved through a vertical loading mechanism) to compact the large-diameter crushed stone ballast material to be tested.

[0113] 3-2) Sleeper and rail embedding: During the sample loading process, when the remaining height inside the box is close to half the height of the simulated sleeper 6, place the simulated sleeper 6 in the center of the three-axis sample loading box body 531, continue to fill in the remaining large-diameter crushed stone ballast material to be tested until the ballast fills the iron box, and then install the simulated rail 7 on the simulated sleeper 6.

[0114] 3-3) Install the vertical loading mechanism: Install the vertical pressure sensor 81 on the lower clamping plate 313, and then use fasteners to assemble the vertical pressure sensor 81, the vertical loader 32 and the first hydraulic jack 33 in that order to hoist the vertical loading mechanism 3 to the middle of the reaction frame beam 22. The first hydraulic jack 33 is directly opposite the simulated rail 7 in the three-axis sample box body 531.

[0115] 3-4) Install the horizontal loading mechanism: Install the two horizontal pressure sensors 82 in the horizontal base 412 of the two horizontal loading mechanisms 4 respectively. Assemble the horizontal loading mechanism 4 by combining the horizontal pressure sensor 82, the horizontal loader 42 and the second hydraulic jack 43 in the order of fasteners. And fix them on the platform of the experimental platform 1 respectively by supporting steel legs 411. The two second hydraulic jacks 43 face the two sides of the triaxial test box 53 facing the support column 21 of the reaction frame structure 2.

[0116] 3-5) Install displacement sensors: Install the sensor bodies of the two vertical displacement sensors 91 on the independent sensor brackets 11 respectively, and set their sensing elements on the simulated sleepers 6 respectively; install the sensor bodies of the two horizontal displacement sensors 92 on the experimental platform 1 on both sides of the triaxial test box 53, and set their sensing elements on the two sides of the triaxial test box 53 facing the support column 21 of the reaction frame structure 2 respectively.

[0117] 3-6) Install the data acquisition unit: Connect the vertical pressure sensor 81, the horizontal pressure sensor 82, the vertical displacement sensor 91, and the horizontal displacement sensor 92 to the data acquisition unit 10, and connect the data acquisition unit to the monitoring and control center.

[0118] 3-7) Pre-compression judgment: When all equipment is properly installed and connected, a certain vertical force is applied to the simulated rail 7 through the vertical loading mechanism 3 to compact the large-diameter crushed stone ballast material to be tested, and the data acquisition device 10 and monitoring and control center are observed to determine whether the device can operate normally.

[0119] 3-8) Triaxial test: After confirming that the instrument can operate normally, control the vertical loading mechanism 3 to continue to apply the vertical load, and at the same time apply the horizontal shear force to the triaxial test box 53 through the two horizontal loading mechanisms 4 respectively. The vertical displacement sensor 91 and the horizontal displacement sensor 92 detect the relevant displacement data in real time. When the data obtained by the data acquisition unit 10 reaches the required value, stop all load pressurization.

[0120] 3-9) Compression and shear performance analysis: By monitoring the data recorded by the control center, relevant curves can be obtained, and the required triaxial test results can be obtained. The test ends.

[0121] Compared with existing devices for testing the mechanical properties of ballast materials, the device of the present invention has at least the following advantages:

[0122] 1) Multifunctionality: The device of this invention has both a vertical loading mechanism and a horizontal loading mechanism, which can simultaneously apply vertical force and horizontal shear force to the particle size crushed stone ballast material. It realizes the compressive and shear performance test of particle size crushed stone ballast material under the influence of vertical stress, covering a variety of experimental evaluations such as direct shear test, vertical stiffness test and triaxial test, providing more comprehensive, accurate and effective detection and evaluation information for the mechanical properties of particle size crushed stone ballast material.

[0123] 2) Reduced friction: In the direct shear device box of this invention, the moving parts are connected by ball bearings or rollers, effectively reducing the friction between the parts and minimizing damage during operation. It also significantly reduces the resistance of the horizontal loading device during testing, providing effective labor savings while protecting the testing equipment and extending its service life.

[0124] 3) Stability and reliability: Unlike other testing instruments, this device is not easily disturbed. It is fixed to the laboratory's own solid foundation with bolts. All test equipment is placed on the fixed reaction frame structure, which has high stability and greatly reduces the influence of external factors on the test.

[0125] 4) Flexibility and versatility: The device of this invention can be freely combined according to test requirements. In the configuration of the test device, the reaction frame structure is retained and the corresponding device box for the required test is selected for assembly, which improves the efficiency of test preparation and facilitates quick entry into the formal test, and helps to save the time spent installing the loading device. At the same time, it is not limited to completing one type of mechanical property test of the specimen. This device can complete a variety of different mechanical property index tests. Moreover, the device boxes selected by this multifunctional testing device are almost the same size, which effectively controls the number of specimens when conducting multiple tests on the specimens, ensuring that all tests are completed in one loading mode, and effectively reducing unnecessary errors caused by frequent device changes.

[0126] 5) Simple operation and real-time monitoring: The device of this invention can be directly assembled from the reaction frame structure and the test device box. The usage of each component is simple, easy to learn and use. It has the characteristics of simple structure, simple operation, time saving and clear force transmission. The data acquisition device is connected to an external control console to monitor data changes in real time, control the gradual increase of pressure in the test loading device, ensure stable changes in data during the test, and effectively improve the authenticity of the test results.

[0127] Overall, the device of the present invention, by integrating multiple functions and advantages, can provide more accurate and effective evaluation information to complete the mechanical property testing of large-particle-size crushed stone ballast materials, and successfully overcomes the problems and limitations of existing devices for testing the mechanical properties of ballast materials.

[0128] 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 implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and not restrictive in all respects. Furthermore, it should be understood that although this specification describes embodiments, it does not encompass only one technical solution. This descriptive method is merely for clarity, and those skilled in the art should consider the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A multifunctional device for testing the compressive and shear strength of large-diameter crushed stone, characterized in that: It includes an experimental platform (1), a reaction frame structure (2) set above the experimental platform (1), a vertical loading mechanism (3) and a horizontal loading mechanism (4) installed on the experimental platform (1) and the reaction frame structure (2), and a test device box (5) placed on the experimental platform (1). The reaction frame structure (2) includes two support columns (21) set at both ends of the experimental platform (1) and a reaction frame beam (22) erected on the upper end of the two support columns (21) and horizontally set above the experimental platform (1). The bottom end of the support column (21) is fixedly connected to the ground by large bolts, and the upper side of the column is provided with a crossbeam through hole. The two ends of the reaction frame crossbeam (22) are inserted into the crossbeam through holes at the upper ends of the two support columns (21) and welded and fixed. The test device box (5) includes a direct shear test box (51), a vertical pressure test box (52), and a triaxial test box (53); wherein: The straight shear test box (51) includes a first shear box (511) and a second shear box (512). The first shear box (511) has no bottom and the second shear box (512) has no lid. The two are stacked one on top of the other, and the side length of the first shear box (511) at the top is smaller than the side length of the second shear box (512) at the bottom. The direct shear test box (51) also includes a cover plate (513), a horizontal loading plate (514), and several rollers (515); the cover plate (513) is placed on the large-diameter crushed stone ballast material inside the first shear box (511); the horizontal loading plate (514) is located above the cover plate (513) and its area is smaller than that of the cover plate (513); the rollers (515) are located between the cover plate (513) and the horizontal loading plate (514); the vertical force is applied to the horizontal loading plate (514), and the horizontal shear force is applied to one side of the first shear box (511) facing the support column (21) to perform the direct shear test; The vertical pressure test box (52) includes a vertical pressure sample box body (521) and a simulated sleeper (6); the cross-section of the vertical pressure sample box body (521) is approximately the same as the cross-section of the first shear box (511) in the direct shear test box (51), and its height is approximately twice that of the first shear box (511); the simulated sleeper (6) is embedded in large-diameter crushed stone ballast material in the vertical pressure sample box body (521) to simulate the structure of a real railway sleeper; vertical force is applied to the simulated sleeper (6) to conduct a vertical pressure test; The triaxial test box (53) includes a triaxial sample box body (531), a simulated sleeper (6), and a simulated rail (7); the triaxial sample box body (531) is similar to the vertical pressure sample box body (521), the simulated sleeper (6) is embedded in the large-particle-size crushed stone ballast material in the triaxial sample box body (531), and the simulated rail (7) is installed on the simulated sleeper (6) to simulate the structure of a real railway line; the vertical force is applied to the simulated rail (7), and the horizontal shear force is applied to the two sides of the triaxial sample box body (531) facing the support column (21) to perform triaxial testing; Large-diameter crushed stone ballast material is placed in the test device box (5). Vertical force is applied to it by the vertical loading mechanism (3), and shear force is applied to it by the horizontal loading mechanism (4). Direct shear test, vertical stiffness test and / or triaxial test are carried out to test the compressive and shear properties of the large-diameter crushed stone ballast material.

2. The multifunctional device for testing the compressive and shear strength of large-diameter crushed stone according to claim 1, characterized in that: The vertical loading mechanism (3) is hoisted on the reaction frame beam (22) via a hoisting base (31), which includes a vertical loader (32) for providing vertical loading power and a first hydraulic jack (33) for performing vertical loading. The hoisting base (31) includes several long bolts (311), an upper clamping plate (312), and a lower clamping plate (313); the width of the upper clamping plate (312) and the lower clamping plate (313) is greater than the width of the reaction frame beam (22), and the two are clamped and fixed to the upper and lower sides of the reaction frame beam (22) by the long bolts (311); The lower clamping plate (313) is provided with mounting holes for hoisting the vertical loader (32). The first hydraulic jack (33) is located at the front end of the vertical loader (32) and applies a vertical force to the large-diameter crushed stone ballast material below it under the action of the vertical loader (32).

3. The multifunctional device for testing the compressive and shear strength of large-diameter crushed stone according to claim 2, characterized in that: The horizontal loading mechanism (4) is mounted on the experimental platform (1) via a support base (41), and includes a horizontal loader (42) for providing horizontal loading power and a second hydraulic jack (43) for performing horizontal loading. The support base (41) is located at one end of the experimental platform (1) and close to the support column (21) of the reaction frame structure (2). It includes a support steel leg (411) and a horizontal base (412). The support steel leg (411) is fixed on the platform of the experimental platform (1), and the horizontal base (412) is horizontally arranged on the upper end of the support steel leg (411). The two are connected and fixed in a T-shape. The horizontal loader (42) is set inside the horizontal base (412), and the second hydraulic jack (43) is located at the front end of the horizontal loader (42). Under the action of the horizontal loader (42), it applies a horizontal shear force to the large-diameter crushed stone ballast material directly in front of it.

4. The multifunctional device for testing the compressive and shear properties of large-diameter crushed stone according to claim 3, characterized in that: The device also includes a test and monitoring system, which includes a pressure monitoring module (8), a displacement monitoring module (9), and an information acquisition and processing control center; The pressure monitoring module (8) includes a vertical pressure sensor (81) and a horizontal pressure sensor (82). The vertical pressure sensor (81) is used to detect the vertical force applied to the large-diameter crushed stone ballast material, and the horizontal pressure sensor (82) is used to detect the horizontal shear force applied to the large-diameter crushed stone ballast material. The displacement monitoring module (9) includes a vertical displacement sensor (91) and a horizontal displacement sensor (92). The vertical displacement sensor (91) is used to detect the compressive settlement of large-diameter crushed stone ballast material under vertical force. The horizontal displacement sensor (92) is used to detect the relative displacement of large-diameter crushed stone ballast material under horizontal shear force in direct shear test and triaxial test. The information acquisition and processing control center includes a data acquisition unit (10) and a monitoring and control center. The data acquisition unit (10) is used to acquire the detection information of the vertical pressure sensor (81), the horizontal pressure sensor (82), the vertical displacement sensor (91), and the horizontal displacement sensor (92) and transmit it to the monitoring and control center. The monitoring and control center is used to receive the information collected by the data acquisition unit (10), monitor the data changes in real time, and complete the data recording, storage, and control of the experiment.

5. The multifunctional device for testing the compressive and shear strength of large-diameter crushed stone according to claim 4, characterized in that: The vertical pressure sensor (81) is located between the lower clamping plate (313) and the vertical loader (32), directly above the vertical loader (32), and is connected to the data acquisition unit (10) through a data transmission interface. The horizontal pressure sensor (82) is installed in the horizontal base (412) of the horizontal loading mechanism (4), located at the rear end of the horizontal loader (42), and connected to the data acquisition unit (10) through the data transmission interface; Both the vertical displacement sensor (91) and the horizontal displacement sensor (92) include a sensor body and a sensing element; wherein, The sensor body of the vertical displacement sensor (91) is mounted on the sensor bracket (11) and is at the same height as the upper edge of the direct shear test box (51), the vertical pressure test box (52) and the triaxial test box (53); in the direct shear test, its sensing element is set on the cover plate (513) inside the first shear box (511); in the vertical stiffness test and the triaxial test, its sensing element is set on the simulated sleeper (6); The sensor body of the horizontal displacement sensor (92) is installed on the table of the experimental platform (1). In the direct shear test, its sensing element is set on the side of the first shear box (511) facing the support column (21). In the triaxial test, its sensing element is set on the side of the triaxial test box (53) facing the support column (21).

6. A method for testing the shear resistance of large-diameter crushed stone using the multifunctional device described in claim 5, characterized in that: The direct shear test of the large-diameter crushed stone ballast material to be tested using the multifunctional device described in claim 5 specifically includes the following steps: 1-1) Sample loading: Place the second shear box (512) at the designated position on the experimental platform (1), and fill the large-diameter crushed stone ballast material to be tested into the second shear box (512) in an orderly manner according to the layers until it is full; stack the first shear box (511) on the large-diameter crushed stone ballast material in the second shear box (512), and then fill the remaining large-diameter crushed stone ballast material to be tested into the first shear box (511) in an orderly manner according to the layers, and perform tamping and pressure treatment to compact the large-diameter crushed stone ballast material to be tested; 1-2) Covering: Place the cover plate (513) on the compacted large-diameter crushed stone ballast material, then place the roller (515) on the cover plate (513), and finally place the horizontal loading plate (514) on the roller (515). 1-3) Install the vertical loading mechanism: Use long bolts (311) to clamp the upper clamping plate (312) and the lower clamping plate (313) onto the reaction frame beam (22). Use fasteners to combine the vertical pressure sensor (81), the vertical loader (32) and the first hydraulic jack (33) in that order, and connect the vertical pressure sensor (81) to the lower clamping plate (313) to suspend it in the middle of the reaction frame beam (22). The first hydraulic jack (33) of the vertical loading mechanism (3) is directly facing the horizontal loading plate (514) on the first shear box (511). 1-4) Install the horizontal loading mechanism: The horizontal pressure sensor (82), the horizontal loader (42), and the second hydraulic jack (43) are assembled in the horizontal base (412) using fasteners in that order, and are installed on the platform of the experimental platform (1) by supporting steel legs (411); the second hydraulic jack (43) of the horizontal loading mechanism (4) faces the second shear box (512) on one side facing the support column (21) of the reaction frame structure (2); 1-5) Install displacement sensors: Install the sensor bodies of two vertical displacement sensors (91) on separate sensor brackets (11), and set their sensing elements at both ends of the cover plate (513) inside the first shear box (511); install the sensor body of a horizontal displacement sensor (92) on the experimental platform (1) and opposite to the horizontal loading mechanism (4), and set its sensing element on the other side of the second shear box (512) opposite to the second hydraulic top (43); 1-6) Install the data acquisition unit: Connect the vertical pressure sensor (81), horizontal pressure sensor (82), vertical displacement sensor (91) and horizontal displacement sensor (92) to the data acquisition unit (10), and connect the data acquisition unit to the monitoring and control center; 1-7) Pre-compression judgment: When all equipment is properly installed and connected, apply a certain vertical force to the horizontal loading plate (514) through the vertical loading mechanism (3) to compact and compact the large-diameter crushed stone ballast material to be tested, and observe the data acquisition device (10) and monitoring and control center to judge whether the device can operate normally; 1-8) Direct shear test: After confirming that the instrument can operate normally, control the vertical loading mechanism (3) to continue to apply external load so that the vertical load reaches the predetermined pressure value. After the pressure stabilizes, start the horizontal loading mechanism (4) to apply horizontal shear force to the first shear box (511). At the same time, control the horizontal shear force through the monitoring and control center. When the horizontal shear force can no longer be increased or the data collected by the data acquisition device (10) reaches the required value, stop all load pressurization and the test ends. 1-9) Shear resistance performance analysis: By monitoring and controlling the data recorded by the control center, the relationship curve between the horizontal shear force under the set vertical pressure and the shear displacement of the first shear box (511) can be obtained, and the shear resistance performance of the large-diameter crushed stone ballast material to be tested can be further analyzed.

7. A method for testing the compressive strength of large-diameter crushed stone using the multifunctional device described in claim 5, characterized in that: The vertical stiffness test of the large-diameter crushed stone ballast material to be tested using the multifunctional device described in claim 5 specifically includes the following steps: 2-1) Sample loading: Place the vertical pressure sample loading box body (521) at the designated position on the experimental platform (1), and fill the large-diameter crushed stone ballast material to be tested into the box in an orderly manner according to the layers. Whenever the large-diameter crushed stone ballast material to be tested is filled to a certain depth, it is manually tamped and pressure is applied to compact the large-diameter crushed stone ballast material to be tested. 2-2) Sleeper embedding: During the sample loading process, when the remaining height inside the box is close to half the height of the simulated sleeper (6), the simulated sleeper (6) is placed in the center of the vertical pressure sample loading box body (521), and the remaining large-diameter crushed stone ballast material to be tested is continued to be filled until the ballast fills the iron box. 2-3) Install the vertical loading mechanism: Use long bolts (311) to clamp the upper clamping plate (312) and the lower clamping plate (313) onto the reaction frame beam (22). Use fasteners to combine the vertical pressure sensor (81), the vertical loader (32) and the first hydraulic jack (33) in that order. The vertical pressure sensor (81) is connected to the lower clamping plate (313) and hoisted in the middle of the reaction frame beam (22). The first hydraulic jack (33) of the vertical loading mechanism (3) is directly opposite the simulated sleeper (6) in the vertical pressure sample box body (521). 2-4) Install displacement sensors: Install the sensor bodies of the two vertical displacement sensors (91) on the independent sensor brackets (11) respectively, and set their sensing elements on the simulated sleepers (6); 2-5) Install the data acquisition unit: Connect the vertical pressure sensor (81) and the vertical displacement sensor (91) to the data acquisition unit (10), and connect the data acquisition unit to the monitoring and control center; 2-6) Pre-compression judgment: When all equipment is properly installed and connected, a certain vertical force is applied to the simulated sleeper (6) through the vertical loading mechanism (3) to compact the large-diameter crushed stone ballast material to be tested, and the data acquisition device (10) and monitoring and control center are observed to determine whether the device can operate normally. 2-7) Vertical pressure test: After confirming that the instrument can operate normally, control the vertical loading mechanism (3) to continue to apply external force load, stabilize the vertical pressure through the vertical pressure sensor (81), and monitor the vertical displacement and pressure in real time through the monitoring and control center. When the vertical pressure can no longer be increased or the vertical pressure collected by the data acquisition device (10) reaches the required value, stop all load pressurization and the test ends. 2-8) Vertical stiffness analysis: The vertical pressure-displacement relationship curve can be obtained by monitoring and controlling the data recorded by the control center. The section with a relatively stable slope is the vertical stiffness of the large-diameter crushed stone ballast material to be tested.

8. A method for testing the compressive and shear strength of large-diameter crushed stone using the multifunctional device described in claim 5, characterized in that: The triaxial test of the large-diameter crushed stone ballast material to be tested using the multifunctional device described in claim 5 specifically includes the following steps: 3-1) Sample loading: Place the triaxial sample loading box body (531) at the designated position on the experimental platform (1), and fill the large-diameter crushed stone ballast material to be tested into the box in an orderly manner according to the layers. Whenever the large-diameter crushed stone ballast material to be tested is filled to a certain depth, it is manually tamped and pressure is applied to compact the large-diameter crushed stone ballast material to be tested. 3-2) Sleeper and rail embedding: During the sample loading process, when the remaining height inside the box is close to half the height of the simulated sleeper (6), place the simulated sleeper (6) in the center of the three-axis sample loading box body (531), continue to fill in the remaining large-diameter crushed stone ballast material to be tested until the ballast fills the iron box, and then install the simulated rail (7) on the simulated sleeper (6); 3-3) Install the vertical loading mechanism: Use long bolts (311) to clamp the upper clamping plate (312) and the lower clamping plate (313) onto the reaction frame beam (22). Use fasteners to combine the vertical pressure sensor (81), the vertical loader (32) and the first hydraulic jack (33) in that order. The vertical pressure sensor (81) is connected to the lower clamping plate (313) and hoisted in the middle of the reaction frame beam (22). The first hydraulic jack (33) of the loading mechanism (3) is directly opposite the simulated rail (7) in the three-axis sample box body (531). 3-4) Install the horizontal loading mechanism: Use fasteners to combine the two horizontal pressure sensors (82), the two horizontal loaders (42) and the two second hydraulic jacks (43) in the order of horizontal pressure sensor (82), horizontal loader (42) and second hydraulic jack (43), and install them at both ends of the experimental platform (1) respectively by supporting steel legs (411). The two second hydraulic jacks (43) of the two horizontal loading mechanisms (4) face the two sides of the triaxial test box (53) facing the reaction frame structure (2) support column (21); 3-5) Install displacement sensors: Install the sensor bodies of the two vertical displacement sensors (91) on the independent sensor brackets (11) respectively, and set their sensing elements on the simulated sleepers (6); install the sensor bodies of the two horizontal displacement sensors (92) on the experimental platform (1) on both sides of the triaxial test box (53), and set their sensing elements on the two sides of the triaxial test box (53) facing the support column (21) of the reaction frame structure (2); 3-6) Install the data acquisition unit: Connect the vertical pressure sensor (81), horizontal pressure sensor (82), vertical displacement sensor (91) and horizontal displacement sensor (92) to the data acquisition unit (10), and connect the data acquisition unit to the monitoring and control center; 3-7) Pre-compression judgment: When all equipment is properly installed and connected, a certain vertical force is applied to the simulated rail (7) through the vertical loading mechanism (3) to compact the large-diameter crushed stone ballast material to be tested, and observe the data acquisition device (10) and monitoring and control center to determine whether the device can operate normally; 3-8) Triaxial test: After confirming that the instrument can operate normally, control the vertical loading mechanism (3) to continue to apply the vertical load, and at the same time apply the horizontal shear force to the triaxial test box (53) through the two horizontal loading mechanisms (4). The vertical displacement sensor (91) and the horizontal displacement sensor (92) detect the relevant displacement data in real time. When the data obtained by the data acquisition device (10) reaches the required value, stop all load pressurization. 3-9) Compression and shear performance analysis: By monitoring the data recorded by the control center, relevant curves can be obtained, and the required triaxial test results can be obtained. The test ends.

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