Shear sample preparation device based on triaxial test system and sample testing method

Abstract

The present application relates to the field of rock material performance testing, especially a shear sample preparation device based on a triaxial test system and a sample testing method, aiming at the problems of inconvenient shear sample preparation and insufficient tightness of the combination of concrete and rock test blocks in the prior art, the present application proposes the following scheme, which comprises a forming mechanism, the forming mechanism comprises a mounting seat, a placing disc fixed on the top surface of the mounting seat and a mold sleeved on the outer periphery of the placing disc, the mold is formed by a first annular sheet and a second annular sheet in a semicylindrical structure, the top surface of the mounting seat is also provided with a driving piece for driving the first annular sheet and the second annular sheet to open and close, and the top surface of the placing disc is fixed with a placing table for placing rock test blocks. Thus, the integrated and convenient preparation of the rock and concrete combined sample is realized, at the same time, the prepared sample is subjected to mechanical property testing under a complex stress path based on a triaxial test system, and test data reflecting the internal structure change of the sample are obtained.

Description

Technical Field

[0001] This invention relates to the field of rock material performance testing, and in particular to a shear specimen preparation device and a specimen testing method based on a triaxial testing system. Background Technology

[0002] With the acceleration of urbanization and the expansion of resource development into deeper areas in my country, the scale of underground space continues to grow. More and more underground projects face the challenges of multiple factors, including high temperatures, seepage, stress, and chemical erosion. The control of rock mass structural surfaces (such as joints and faults) and fracture networks on project stability under complex geological conditions is becoming increasingly prominent. Studies show that the morphology, orientation, and spacing of structural surfaces not only directly determine the shear strength, deformation modulus, and permeability of the rock mass, but also induce major disasters such as water inrush, sand inrush, and surrounding rock instability through dynamic coupling between different physical fields. Conducting systematic research on the mechanical response of rock structural surfaces under complex conditions is of significant theoretical and practical importance for constructing multi-scale, multi-physics field coupled analysis models, optimizing underground engineering design and construction schemes, and improving disaster prevention and control capabilities. It is also a key technological support for achieving green development of deep resources and safe utilization of urban underground space.

[0003] To advance relevant theoretical development and achieve breakthroughs in engineering applications, accurately acquiring experimental data that truly reflects the mechanical behavior of structural surfaces under complex environments is crucial. Therefore, the preparation and testing of high-quality rock-concrete composite specimens are fundamental for obtaining key parameters and validating numerical models. However, current conventional methods for preparing rock-concrete composite specimens for shear tests have significant limitations. Existing technologies often rely on specialized molds, which are cumbersome to assemble and disassemble, and provide poor fixation of the rock specimens, easily leading to specimen displacement during pouring and affecting the geometric accuracy of the specimens. Furthermore, ensuring uniform concrete distribution during pouring often results in internal porosity and defects, weakening the bond between the concrete and rock interfaces and directly impacting the accuracy and reliability of subsequent shear test results. To overcome these preparation challenges, this paper proposes an integrated specimen preparation device and corresponding testing method based on a triaxial testing system. Summary of the Invention

[0004] The shear specimen preparation device and specimen testing method based on the triaxial testing system proposed in this invention solve the problems of inconvenient shear specimen preparation and insufficient bonding between concrete and rock specimens in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A shear specimen preparation device and a specimen testing method based on a triaxial testing system, including:

[0007] The forming mechanism includes a mounting base, a placement plate fixed on the top surface of the mounting base, and a mold sleeved on the outer periphery of the placement plate. The mold is formed by a first annular piece and a second annular piece with a semi-cylindrical structure. The top surface of the mounting base is also equipped with a driving component for driving the first annular piece and the second annular piece to open and close. The top surface of the placement plate is fixed with a placement platform for placing rock test blocks.

[0008] A pressing mechanism, which is mounted on the second annular plate and used to fix the rock test block placed on the placement platform;

[0009] A compaction mechanism is installed on the top inner wall of the mounting base and is used to tap the mounting base to compact the concrete when concrete is poured into the mold. The compaction mechanism includes multiple swing arms hinged to the top inner wall of the mounting base and a transmission assembly for driving the multiple swing arms to tap the top surface of the mounting base in sequence.

[0010] The feeding mechanism includes a toothed disc rotatably connected to the top of a first annular plate, a feeding hopper mounted on the top of the toothed disc, and a reciprocating drive assembly mounted on a mounting base for driving the toothed disc to reciprocate around the center of rotation of the disc shaft. A discharge hole communicating with the discharge port at the bottom of the hopper is provided at a position off-center on the top surface of the toothed disc. The reciprocating drive assembly cooperates with the transmission assembly to drive the reciprocating drive assembly to run while compacting the material.

[0011] The above technical solution enables the integrated and convenient preparation of rock-concrete bonded specimens, ensuring the rock blocks are firmly fixed and have high molding precision. Furthermore, the prepared specimens are sealed using a sealing device, and mechanical property tests are conducted under complex stress paths using a triaxial testing system to obtain test data reflecting changes in the internal structure of the specimens. Analysis of this data extracts structural parameters characterizing the evolution of the specimen's internal structure. This invention, through the aforementioned integrated specimen preparation device, achieves a complete process integration from specimen molding and sealing loading to data analysis, significantly improving the reliability and experimental efficiency of studying the mechanical behavior of rock materials under complex stress states. It has broad application prospects in rock mechanics testing and related engineering technologies.

[0012] As a further improvement to the above solution, the placement platform has a semi-circular structure, and the outer periphery of the placement platform matches the inner ring of the second annular piece. The top surface of the placement platform is parallel to the top surface of the placement tray, and there is a height difference between the top surface of the placement platform and the top surface of the placement tray.

[0013] As a further improvement to the above solution, the driving component includes two fixing plates respectively fixed on both sides of the top surface of the mounting base and a telescopic component mounted on the fixing plates. Mounting blocks are fixed on the outer periphery of both the first annular plate and the second annular plate. The output ends of the telescopic components on the two fixing plates are respectively fixedly connected to the mounting blocks on the first annular plate and the second annular plate.

[0014] As a further improvement to the above solution, the transmission assembly includes a rotating shaft rotatably connected to the inner wall of the top of the mounting base, a lifting block fixed to the outer periphery of the rotating shaft, and a servo motor installed inside the mounting base for driving the rotating shaft to rotate. The lifting block has a right-angled triangular structure with its inclined surface facing upward. Multiple swing arms are distributed in a ring around the rotating shaft. A return spring is installed on the top surface of the swing arm near the rotating shaft at the hinge point between the swing arm and the mounting base. The other end of the return spring is fixed to the inner wall of the top of the mounting base to make the swing arm tilted. The end of the swing arm away from the rotating shaft is on top and fixed with a striking hammer that abuts against the inner wall of the top of the mounting base. The lower end of the swing arm is rotatably connected to a wheel coaxially arranged with it. The wheel cooperates with the lifting block to lift it upward when the lifting block passes the wheel.

[0015] As a further improvement to the above solution, the reciprocating drive assembly includes a drive shaft that rotates axially on the outer periphery of the first annular plate, a drive gear fixed to the top of the drive shaft and meshing with the gear plate, and a linkage installed inside the mounting base for driving the drive shaft to reciprocate when the shaft rotates.

[0016] As a further improvement to the above solution, the top of the mounting base is provided with a connecting groove communicating with its interior. The bottom of the drive shaft extends through the connecting groove into the interior of the mounting base and is fixed with a linkage gear coaxially arranged therewith. The linkage component includes a cam sleeved on the outer circumference of the rotating shaft, a movable rack mounted on the inner wall of the mounting base by an elastic element, a drive screw rotatably connected to the interior of the mounting base along the width direction of the mounting base, and a linkage rack threadedly sleeved on the outer circumference of the drive screw. The movable rack is arranged along the length direction of the mounting base and located below the drive screw. A fixed gear that meshes with the movable rack is sleeved on the outer circumference of the drive screw. The linkage rack meshes with the linkage gear, and the top surface of the linkage rack slides against the interior of the top of the mounting base. A roller that abuts against the outer circumference of the cam is installed at one end of the movable rack.

[0017] As a further improvement to the above solution, the elastic element includes a fixed cylinder fixed to the inner wall of the mounting base and a buffer spring disposed inside the fixed cylinder. One end of the spring is fixedly connected to the inner wall of the fixed cylinder, and one end of the movable rack extends into the fixed cylinder and is fixedly connected to the other end of the buffer spring. The outer periphery of the movable rack is movably sleeved with a plurality of limiting sleeves fixedly connected to the inner wall of the top of the mounting base.

[0018] As a further improvement to the above solution, the second annular piece has an installation groove on its outer periphery arranged along its axial direction. The pressing mechanism includes a fixed sleeve that is slidably installed in the installation groove, a threaded pressure rod that is movably sleeved inside the fixed sleeve, and a threaded sleeve that is threaded around the outer periphery of the threaded pressure rod. One end of the threaded pressure rod extends to the inner side of the second annular piece and is fixed with a side rod arranged along its axial direction. The threaded sleeve is located on the outer side of the second annular piece and is rotatably connected to one end of the fixed sleeve. The outer periphery of the threaded sleeve is threaded with a plurality of L-shaped locking bolts, and one end of the locking bolts abuts against the outer periphery of the second annular piece.

[0019] The test method for shear specimens based on a triaxial testing system includes the following steps:

[0020] S1. Rock specimen preparation: Select a target specimen with a semi-cylindrical structure, cut it off at the bottom, and smooth the cross section to obtain a rock specimen.

[0021] S2. Concrete sample preparation: Place the prepared rock sample on the placement platform in the mold and fix it with the pressing mechanism. Then, inject the prepared concrete sample into the other half of the space in the mold, and make the height of the top surface of the final concrete and the top height of the rock sample have a difference in height that is the same as the bottom part of the rock sample.

[0022] S3. Complete the sample. After the concrete has cured, take out the sample and smooth the top of the concrete sample. Then, use supplementary blocks to fill in the bottom of the rock block and the top of the concrete sample to finally obtain a complete sample.

[0023] S4. Sample sealing: The complete sample is sealed, and the sealed sample is placed on a triaxial testing machine to perform shear tests on the sample under different conditions.

[0024] S5. Saturate the sample. After evacuating the sample, saturate it using conventional methods or by applying water pressure at both ends.

[0025] S6. Shear test: Apply confining pressure, temperature and water pressure to the sample, and load the sample by displacement or force control.

[0026] S7. Microscopic experimental testing: Microscopic experimental testing is conducted on the sample or crack surface before the experiment, during the experiment (specific loading stage), and after the experiment. Finally, the experimental results are analyzed in combination with the changes in microstructure before and after the experiment.

[0027] As a further improvement to the above solution, the supplementary block can be selected from one of polyurethane foam, rubber, foamed concrete, and sponge material.

[0028] Through the above technical solution, the material has certain elasticity and compressive strength, and good compatibility with rock and concrete, thus avoiding the impact of test results on the test results due to the destruction of the supplementary block itself during the test process.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. Through the coordinated operation of the molding mechanism, pressing mechanism, vibration compaction mechanism and feeding mechanism, the integrated preparation of rock-concrete bonded specimens is realized. The mold is easy to open and close, and the rock specimen is firmly fixed, effectively solving the problems of inconvenient specimen preparation and low molding accuracy in the existing technology.

[0031] 2. The vibration compaction mechanism uses a servo motor to drive multiple swing arms to strike the mounting base in sequence, generating continuous and uniform vibration. This can significantly reduce the internal porosity of the concrete and improve the bonding tightness between the concrete and the rock specimen. At the same time, the reciprocating drive component and the transmission component are linked to drive the gear plate to rotate back and forth, so that the concrete falls evenly into the mold, further improving the molding quality of the specimen.

[0032] 3. The sample testing method and process are standardized, forming a complete testing system from rock block preparation, concrete pouring, sample completion, sealing treatment to shear testing and microscopic analysis. This ensures the accuracy and reliability of the test results and provides a scientific and effective experimental means for studying the mechanical response of rock mass structures under complex geological conditions. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure after the first and second annular plates are opened;

[0035] Figure 3 This is a schematic diagram of the pressing mechanism;

[0036] Figure 4 This is a schematic diagram of the gear-disc contact structure.

[0037] Figure 5 This is a schematic diagram of the structure of the inner wall of the top of the mounting base;

[0038] Figure 6 This is a structural schematic diagram of the vibration damping mechanism and the reciprocating drive assembly;

[0039] Figure 7 A schematic diagram of the structure of the moving groove on the top surface of the mounting base;

[0040] Figure 8 This is a schematic diagram of the complete sample.

[0041] Explanation of key symbols:

[0042] 1. Mounting base; 2. First annular plate; 3. Second annular plate; 4. Connecting groove; 5. Telescopic component; 6. Fixing plate; 7. Drive shaft; 8. Drive gear; 9. Hopper; 10. Drop hole; 11. Threaded pressure rod; 12. Placement plate; 13. Sealing ring; 14. Placement platform; 15. Side rod; 16. Mounting groove; 17. Gear plate; 18. Screw sleeve; 19. Drive screw; 20. Servo motor; 21. Swing arm; 22. Linkage rack; 23. Linkage gear; 24. Movable rack; 25. Limit sleeve; 26. Fixing cylinder; 27. Striking hammer; 28. Return spring; 29. ​​Rotary wheel; 30. Lifting block; 31. Rotating shaft; 32. Cam; 33. Roller; 34. Fixed gear; 35. Buffer spring; 36. Mounting block; 37. Fixing sleeve; 38. Locking bolt. Detailed Implementation

[0043] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0044] Example 1:

[0045] Please combine Figure 1 - Figure 8 The shear specimen preparation device based on the triaxial testing system in this embodiment includes:

[0046] The forming mechanism includes a mounting base 1, a placement plate 12 fixed to the top surface of the mounting base 1, and a mold sleeved around the outer periphery of the placement plate 12. The mold is formed by a first annular piece 2 and a second annular piece 3 with a semi-cylindrical structure. A driving component for opening and closing the first annular piece 2 and the second annular piece 3 is also mounted on the top surface of the mounting base 1. A placement platform 14 for placing rock test blocks is fixed to the top surface of the placement plate 12. The placement platform 14 has a semi-circular structure, and its outer periphery matches the inner ring of the second annular piece 3. The top surface of the placement platform 14 is parallel to the top surface of the placement tray 12, and there is a height difference between the top surface of the placement platform 14 and the top surface of the placement tray 12. The setting of this height difference is coordinated with the subsequent sample completion steps to ensure that the final formed complete sample is a standard cylindrical structure, which meets the testing requirements of the triaxial testing machine. The top surface of the placement tray 12 has an annular groove, and a sealing ring 13 is installed in the groove. The inner ring of the sealing ring 13 fits against the outer circumference of the bottom of the mold to enhance the sealing between the mold and the placement tray 12 and prevent grout leakage when pouring concrete.

[0047] The pressing mechanism is installed on the second annular plate 3 and used to fix the rock test block placed on the placement platform 14. The second annular plate 3 has an installation groove 16 on its outer periphery along its axial direction. The pressing mechanism includes a fixed sleeve 37 slidably installed in the installation groove 16, a threaded pressure rod 11 movably sleeved inside the fixed sleeve 37, and a threaded sleeve 18 threadedly sleeved on the outer periphery of the threaded pressure rod 11. Both long sides of the installation groove 16 have limiting grooves along their length direction. Both sides of the fixed sleeve 37 are fixed with limiting blocks. One end of each limiting block extends into the two limiting grooves and slides therein, thereby restricting the stable up and down movement of the fixed sleeve 37 in the installation groove 16.

[0048] One end of the threaded pressure rod 11 extends to the inner side of the second annular plate 3 and is fixed with a side rod 15 arranged axially thereon. The threaded sleeve 18 is located on the outer side of the second annular plate 3 and is rotatably connected to one end of the fixed sleeve 37. The outer circumference of the threaded sleeve 18 is threaded with multiple L-shaped locking bolts 38, and one end of the locking bolts 38 abuts against the outer circumference of the second annular plate 3. By rotating the threaded sleeve 18, the threaded pressure rod 11 can be driven to move axially, thereby driving the side rod 15 to press or loosen the rock test block. The fixed sleeve 37 can slide along the mounting groove 16 to facilitate the adjustment of the pressure material. The position of the mechanism is adapted to rock blocks of different sizes; the locking bolt 38 is used to fix the threaded sleeve 18 and the second annular plate 3 relative to each other to prevent the threaded pressure rod 11 from loosening during the sample preparation process and to ensure the reliability of the rock block fixation. After the threaded pressure rod 11 is pressed against the top surface of the rock block and the side rod 15 is pressed against the outer wall of the rock block away from the second annular plate 3, the locking bolt 38, which is not directly opposite the mounting groove 16, is tightened. The static friction between the locking bolt and the outer wall of the second annular plate 3 is used to lock the pressing mechanism to prevent the rock block from loosening.

[0049] A compaction mechanism is installed on the top inner wall of the mounting base 1 and is used to tap the mounting base 1 to compact the concrete when concrete is poured into the mold. The compaction mechanism includes multiple swing arms 21 hinged to the bottom inner wall of the mounting base 1 and a transmission assembly for driving the multiple swing arms 21 to tap the bottom surface of the mounting base 1 in sequence. The transmission assembly includes a rotating shaft 31 rotatably connected to the top inner wall of the mounting base 1, a lifting block 30 fixed to the outer periphery of the rotating shaft 31, and a servo motor 20 installed inside the mounting base 1 to drive the rotating shaft 31 to rotate. The lifting block 30 has a right-angled triangular structure with its inclined surface facing upward. The multiple swing arms 21 are distributed in a ring around the rotating shaft 31. A return spring 28 is installed on the top surface of the end of the swing arm 21 near the rotating shaft 31 at the hinge point with the mounting base 1. The other end of the return spring 28 is fixed to the top inner wall of the mounting base 1 so that the swing arm 21 is in an inclined state. The arm 21, with its end away from the rotating shaft 31, is fixed at the top and has a striking hammer 27 that abuts against the inner wall of the top of the mounting base 1. The lower end of the arm 21 is rotatably connected to a rotating wheel 29 coaxially arranged with it. The rotating wheel 29 cooperates with the lifting block 30 to lift the lifting block 30 upward as it passes the rotating wheel 29. The rotating shaft 31 rotates at a constant speed under the drive of the servo motor 20, causing the lifting block 30 to rotate synchronously. When the inclined surface of the lifting block 30 contacts the rotating wheel 29, the lower end of the arm 21 is gradually lifted upward, causing the arm 21 to rotate around the hinge point, and the striking hammer 27 moves away from the inner wall of the top of the mounting base 1. When the lifting block 30 disengages from the rotating wheel 29, the arm 21 quickly returns to its original position under the elastic restoring force of the return spring 28, and the striking hammer 27 violently strikes the inner wall of the top of the mounting base 1, generating vibration and transmitting it to the mold to achieve concrete compaction. Multiple swing arms 21 are arranged in a ring and cooperate with lifting blocks 30 in sequence to achieve a continuous and uniform tapping and compaction effect, effectively reducing the internal pores of concrete.

[0050] In this embodiment, the driving component includes two fixing plates 6 fixed on both sides of the top surface of the mounting base 1 and a telescopic component 5 mounted on the fixing plates 6. Mounting blocks 36 are fixed on the outer periphery of the first annular piece 2 and the second annular piece 3. The output ends of the telescopic components 5 on the two fixing plates 6 are respectively fixed to the mounting blocks 36 on the first annular piece 2 and the second annular piece 3. The telescopic component 5 is one of an electric telescopic rod, a hydraulic cylinder or a pneumatic cylinder. Through the telescopic movement of the telescopic component 5, the first annular piece 2 and the second annular piece 3 can be driven to move closer or further away from each other, so as to realize the rapid opening and closing of the mold and improve the sample loading and unloading efficiency.

[0051] The implementation principle of this embodiment is as follows: First, the first annular plate 2 is opened by the driving component, and the prepared rock test block is placed on the placement platform 14. Then, the pressing mechanism is adjusted, and the rock test block is firmly fixed by the arc-shaped pressing block. Then, the driving component is controlled to drive the first annular plate 2 to reset, and it is closed with the second annular plate 3 to form a complete mold. The sealing ring 13 and the sealing gasket achieve sealing. The servo motor 20 is started to drive the rotating shaft 31 to rotate. The lifting block 30 rotates with the rotating shaft 31 and contacts the rotating wheel 29 on each swing arm 21 in sequence, lifting the end of the swing arm 21 away from the rotating shaft 31 upward. After the lifting block 30 rotates past the rotating wheel 29, the swing arm 21 falls back quickly under the action of the return spring 28. The hammer 27 strikes the bottom surface of the mounting base 1 to generate vibration, thereby achieving the compaction of the concrete.

[0052] Example 2:

[0053] Combination Figure 1 , Figure 2 and Figure 4 - Figure 7 This embodiment, based on embodiment 1, further improves upon the following: it also includes a feeding mechanism, comprising a geared disc 17 rotatably connected to the top of the first annular plate 2, a feeding hopper 9 mounted on the top of the geared disc 17, and a reciprocating drive assembly mounted on the mounting base 1 for driving the geared disc 17 to reciprocate around the axis of the placement disc 12. A discharge hole 10, communicating with the bottom outlet of the hopper 9, is provided on the top surface of the geared disc 17 at a position offset from its center. The reciprocating drive assembly cooperates with the transmission assembly to drive the reciprocating drive assembly while compacting the material. The reciprocating drive assembly includes a feeding mechanism along the first annular plate 2. A drive shaft 7, which rotates axially on the outer periphery of an annular plate 2, a drive gear 8 fixed on the top of the drive shaft 7 and meshing with a gear disc 17, and a linkage installed inside the mounting base 1 to drive the drive shaft 7 to reciprocate when the rotating shaft 31 rotates, convert the rotational motion of the rotating shaft 31 into the reciprocating rotation of the drive shaft 7, which in turn drives the drive gear 8 to reciprocate. Since the drive gear 8 meshes with the gear disc 17, it ultimately drives the gear disc 17 to reciprocate around the axis of the placement disc 12, so that the concrete in the feed hopper 9 falls evenly into different positions in the mold through the discharge hole 10.

[0054] The top of the mounting base 1 has a connecting groove 4 communicating with its interior. The bottom of the drive shaft 7 extends through the connecting groove 4 into the interior of the mounting base 1 and is fixed with a linkage gear 23 coaxially arranged therewith. The linkage components include a cam 32 sleeved on the outer periphery of the rotating shaft 31, a movable rack 24 mounted on the inner wall of the mounting base 1 by an elastic element, a drive screw 19 rotatably connected to the interior of the mounting base 1 along the width direction of the mounting base 1, and a linkage rack 22 threadedly sleeved on the outer periphery of the drive screw 19. The movable rack 24 is arranged along the length direction of the mounting base 1 and located below the drive screw 19. A fixed gear 34 that meshes with the movable rack 24 is sleeved on the outer periphery of the drive screw 19. The movable rack 24 meshes with the linkage gear 23, and the top surface of the linkage rack 22 slides against the inside of the top of the mounting base 1. One end of the movable rack 24 is equipped with a roller 33 that abuts against the outer periphery of the cam 32. When the rotating shaft 31 rotates, it drives the cam 32 to rotate synchronously. The cam 32 pushes the movable rack 24 to reciprocate along the length direction through the roller 33. The movable rack 24 meshes with the fixed gear 34, driving the fixed gear 34 to drive the transmission screw 19 to alternately rotate forward and backward. The forward and reverse rotation of the transmission screw 19 is converted into the reciprocating linear motion of the linkage rack 22. The linkage rack 22 meshes with the linkage gear 23, thereby driving the transmission shaft 7 to rotate reciprocally, realizing the reciprocating rotation of the gear disk 17. This linkage structure can drive the vibration mechanism and the feeding mechanism simultaneously with only one servo motor 20, simplifying the device structure, realizing the synchronous operation of vibration and uniform feeding, and improving the quality and efficiency of sample preparation.

[0055] The elastic element includes a fixed cylinder 26 fixed to the inner wall of the mounting base 1 and a buffer spring 35 disposed inside the fixed cylinder 26. One end of the spring is fixedly connected to the inner wall of the fixed cylinder 26, and one end of the movable rack 24 extends into the fixed cylinder 26 and is fixedly connected to the other end of the buffer spring 35. Multiple limiting sleeves 25 fixedly connected to the top inner wall of the mounting base 1 are movably sleeved on the outer periphery of the movable rack 24. The buffer spring 35 provides elastic restoring force for the reciprocating motion of the movable rack 24, ensuring that the movable rack 24 is always in close contact with the cam 32. The limiting sleeves 25 limit the movement direction of the movable rack 24 to prevent it from deviating during the movement, thus ensuring the stability and accuracy of the transmission.

[0056] The implementation principle of this embodiment is as follows: When adding concrete, the prepared concrete is poured into the feed hopper 9. The concrete falls into the mold through the discharge hole 10. While the rotating shaft 31 rotates, it drives the cam 32 to rotate. The cam 32 drives the movable rack 24 to move back and forth. The movable rack 24 drives the fixed gear 34 and the transmission screw 19 to rotate back and forth. The transmission screw 19 drives the linkage rack 22 to move back and forth. The linkage rack 22 drives the linkage gear 23, the transmission shaft 7 and the transmission gear 8 to rotate back and forth, which in turn drives the gear plate 17 to rotate back and forth. The discharge hole 10 moves with the gear plate 17, so that the concrete is evenly distributed in the space of the mold where no rock test block is placed, thus completing the concrete pouring.

[0057] Example 3:

[0058] Combination Figure 1 - Figure 8 This embodiment, based on Embodiments 1 and 2, further improves upon the following: the test method for shear specimens based on a triaxial testing system includes the following steps:

[0059] S1. Rock specimen preparation: Select a rock of the same uniform texture and without obvious natural defects as the initial specimen. Process it into a cylindrical structure. Place the initial specimen on the Brazilian splitting test device and split it into two semi-circular solid structures of the same size. One of the solid structures is used as the target specimen. The fracture surface formed by it is the natural fracture surface. After cutting it off at the bottom, the cross section is smoothed to obtain the rock specimen. The cutting height is determined according to the position of the shear surface required for the test, usually 1 / 3-1 / 2 of the specimen height. After smoothing, apply butter or petroleum jelly to reduce friction. After application, let it stand for 5-10 minutes to ensure stable adhesion.

[0060] S2. Concrete sample preparation: Place the prepared rock sample on the placement platform in the mold and fix it with the pressing mechanism. Then, inject the prepared concrete sample into the other half of the space in the mold, and make the height of the top surface of the final concrete and the top height of the rock sample have a difference in height that is the same as the bottom part of the rock sample.

[0061] S3. Complete the sample. After the concrete has cured, take out the sample and smooth the top of the concrete sample. Then, use supplementary blocks to fill in the bottom of the rock block and the top of the concrete sample to finally obtain a complete sample.

[0062] S4. Sample sealing: Seal the complete sample and place the sealed sample on a triaxial testing machine to perform shear tests under different conditions. The sealing is done in two stages. For the first sealing, place the sample between the upper and lower pressure heads and wrap it with a high-temperature and corrosion-resistant heat-shrinkable sleeve. For the second sealing, install a fluororubber sealing ring at the connection between the upper and lower pressure heads and the heat-shrinkable sleeve, and then tighten it with a stainless steel ferrule and bolts.

[0063] S5. To saturate the sample, first evacuate the sample to a vacuum, then introduce deionized water or test chemical fluid, and gradually apply back pressure. The back pressure loading rate can be selected as 0.01-0.3 MPa / min, so that the fluid can fully penetrate into the sample and maintain the back pressure stable after saturation.

[0064] S6. Shear test: Place the sealed and qualified specimen into the pressure chamber of the triaxial testing machine, connect the confining pressure, temperature, water pressure and back pressure control system, apply confining pressure, temperature and water pressure to the specimen to make the specimen reach a consolidation state, and when loading the consolidated specimen, the loading method can be selected according to the test requirements, such as displacement loading, stress loading, cyclic loading and unloading, staged loading, long-term creep loading or long-term creep relaxation loading, and the shear test can be carried out with different stress paths under different confining pressure, temperature, back pressure and chemical conditions.

[0065] S7. Microscopic Experimental Testing: Microscopic experimental testing is conducted on the sample or fracture surface before, during (specific loading stage), and after the experiment to obtain test data representing changes in the internal structure of the sample. Microscopic experimental testing includes CT, SEM, MIP, and gas adsorption on the processed rock sample; CT scanning and DIC 3D reconstruction on the fracture surface of the rock sample. Finally, the collected macroscopic test data (load, displacement, stress, strain, flow rate, pressure, etc.) and microscopic test data (CT images, SEM images, porosity, specific surface area, deformation field, etc.) are comprehensively processed and analyzed. The shear strength parameters (cohesion c, internal friction angle φ), deformation modulus (elastic modulus E, Poisson's ratio μ), permeability coefficient k, and other structural parameters of the fracture surface are calculated from the macroscopic data. Combined with the microscopic data, the development, expansion, and connection mechanisms of internal fractures in the sample are revealed, establishing the correlation between macroscopic mechanical and permeability properties and microscopic structural changes, thereby comprehensively understanding the mechanical response and permeability characteristics of rock structural surfaces under complex conditions.

[0066] The supplementary blocks can be selected from one of the following materials: polyurethane foam, rubber, foamed concrete, and sponge.

[0067] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A shear specimen preparation device based on a triaxial testing system, characterized in that, include: The forming mechanism includes a mounting base (1), a placement plate (12) fixed on the top surface of the mounting base (1), and a mold sleeved on the outer periphery of the placement plate (12). The mold is formed by a first annular piece (2) and a second annular piece (3) with a semi-cylindrical structure. The top surface of the mounting base (1) is also equipped with a driving component for driving the opening and closing of the first annular piece (2) and the second annular piece (3). The top surface of the placement plate (12) is fixed with a placement platform (14) for placing rock test blocks. A pressing mechanism, which is mounted on the second annular plate (3) and used to fix the rock test block placed on the placement platform (14); A compaction mechanism is installed on the top inner wall of the mounting base (1) and is used to tap the mounting base (1) to compact the concrete when pouring concrete into the mold. The compaction mechanism includes a plurality of swing arms (21) hinged to the top inner wall of the mounting base (1) and a transmission assembly for driving the plurality of swing arms (21) to tap the top surface of the mounting base (1) in sequence. The feeding mechanism includes a toothed disc (17) rotatably connected to the top of the first annular plate (2), a feeding hopper (9) mounted on the top of the toothed disc (17), and a reciprocating drive assembly mounted on the mounting base (1) for driving the toothed disc (17) to reciprocate around the axis of the placement disc (12). A discharge hole (10) communicating with the bottom discharge port of the hopper (9) is provided at a position off-center from the top surface of the toothed disc (17). The reciprocating drive assembly cooperates with the transmission assembly to drive the reciprocating drive assembly to run while compacting the material.

2. The shear specimen preparation device based on a triaxial testing system according to claim 1, characterized in that, The placement platform (14) has a semi-circular structure, and the outer periphery of the placement platform (14) matches the inner circle of the second annular piece (3). The top surface of the placement platform (14) is parallel to the top surface of the placement plate (12), and there is a height difference between the top surface of the placement platform (14) and the top surface of the placement plate (12).

3. The shear specimen preparation device based on a triaxial testing system according to claim 1, characterized in that, The driving component includes two fixing plates (6) fixed on both sides of the top surface of the mounting base (1) and a telescopic component (5) mounted on the fixing plate (6). Mounting blocks (36) are fixed on the outer periphery of the first annular piece (2) and the second annular piece (3). The output ends of the telescopic components (5) on the two fixing plates (6) are respectively fixed to the mounting blocks (36) on the first annular piece (2) and the second annular piece (3).

4. The shear specimen preparation device based on a triaxial testing system according to claim 1, characterized in that, The transmission assembly includes a rotating shaft (31) rotatably connected to the inner wall of the top of the mounting base (1), a lifting block (30) fixed to the outer periphery of the rotating shaft (31), and a servo motor (20) installed inside the mounting base (1) to drive the rotating shaft (31) to rotate. The lifting block (30) is a right-angled triangular structure with its inclined surface facing upward. Multiple swing arms (21) are arranged in a ring around the rotating shaft (31). The top surface of the swing arm (21) near the hinge point of the mounting base (1) is equipped with a... A return spring is provided, with the other end of the return spring fixed to the inner wall of the top of the mounting base (1) so that the swing arm (21) is tilted. The end of the swing arm (21) away from the pivot (31) is fixed with a hammer (27) that abuts against the inner wall of the top of the mounting base (1). The lower end of the swing arm (21) is rotatably connected to a wheel (29) coaxially arranged with it. The wheel (29) cooperates with the lifting block (30) to lift it upward when the lifting block (30) passes the wheel (29).

5. The shear specimen preparation device based on a triaxial testing system according to claim 4, characterized in that, The reciprocating drive assembly includes a drive shaft (7) that rotates on its outer periphery in the axial direction of the first annular plate (2), a drive gear (8) fixed on the top of the drive shaft (7) and meshing with the gear plate (17), and a linkage installed inside the mounting base (1) for driving the drive shaft (7) to reciprocate when the rotating shaft (31) rotates.

6. The shear specimen preparation device based on a triaxial testing system according to claim 5, characterized in that, The top of the mounting base (1) is provided with a connecting groove (4) communicating with its interior. The bottom of the drive shaft (7) extends through the connecting groove (4) into the interior of the mounting base (1) and is fixed with a linkage gear (23) coaxially arranged therewith. The linkage component includes a cam (32) sleeved on the outer circumference of the rotating shaft (31), a movable rack (24) mounted on the inner wall of the mounting base (1) by an elastic element, a drive screw (19) rotatably connected to the interior of the mounting base (1) along the width direction of the mounting base (1), and a threaded drive screw (19) sleeved on the drive screw. A linkage rack (22) is attached to the outer periphery of the rod (19), and a movable rack (24) is set along the length direction of the mounting base (1) and located below the transmission screw (19). A fixed gear (34) that meshes with the movable rack (24) is sleeved on the outer periphery of the transmission screw (19). The linkage rack (22) meshes with the linkage gear (23), and the top surface of the linkage rack (22) slides against the inside of the top of the mounting base (1). A roller (33) that abuts against the outer periphery of the cam (32) is installed at one end of the movable rack (24).

7. The shear specimen preparation device based on a triaxial testing system according to claim 6, characterized in that, The elastic element includes a fixed cylinder (26) fixed on the inner wall of the mounting base (1) and a buffer spring (35) disposed in the fixed cylinder (26). One end of the spring is fixed to the inner wall of the fixed cylinder (26), and one end of the movable rack (24) extends into the fixed cylinder (26) and is fixed to the other end of the buffer spring (35). The outer periphery of the movable rack (24) is movably sleeved with a plurality of limiting sleeves (25) fixed to the top inner wall of the mounting base (1).

8. The shear specimen preparation device based on a triaxial testing system according to claim 1, characterized in that, The second annular piece (3) has an installation groove (16) arranged along its axial direction on its outer periphery. The pressing mechanism includes a fixed sleeve (37) slidably installed in the installation groove (16), a threaded pressure rod (11) movably sleeved inside the fixed sleeve (37), and a threaded sleeve (18) threadedly sleeved on the outer periphery of the threaded pressure rod (11). One end of the threaded pressure rod (11) extends to the inner side of the second annular piece (3) and is fixed with a side rod (15) arranged along its axial direction. The threaded sleeve (18) is located outside the second annular piece (3) and is rotatably connected to one end of the fixed sleeve (37). The outer periphery of the threaded sleeve (18) is threadedly connected with a plurality of L-shaped locking bolts (38), and one end of the locking bolts (38) abuts against the outer periphery of the second annular piece (3).

9. A testing method applicable to specimens prepared by the shear specimen preparation apparatus based on a triaxial testing system as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Rock specimen preparation: Select a target specimen with a semi-cylindrical structure, cut it off at the bottom, and smooth the cross section to obtain a rock specimen. S2. Concrete sample preparation: Place the prepared rock sample on the placement platform in the mold and fix it with the pressing mechanism. Then, inject the prepared concrete sample into the other half of the space in the mold, and make the height of the top surface of the final concrete and the top height of the rock sample have a difference in height that is the same as the bottom part of the rock sample. S3. Complete the sample. After the concrete has cured, take out the sample, smooth the top of the concrete sample, and then use supplementary blocks to complete the bottom of the rock block and the top of the concrete sample to finally obtain a complete sample. S4. Sample sealing: The complete sample is sealed, and the sealed sample is placed on a triaxial testing machine to perform shear tests on the sample under different conditions. S5. Saturate the sample. After evacuating the sample, saturate the sample using conventional methods or by applying water pressure at both ends. S6. Shear test: Apply confining pressure, temperature and water pressure to the sample, and load the sample by displacement or force control. S7. Microscopic experimental testing: Microscopic experimental testing is conducted on the sample or crack surface before the experiment, during the experiment (specific loading stage), and after the experiment. Finally, the experimental results are analyzed in combination with the changes in microstructure before and after the experiment.

10. The shear specimen preparation device and specimen testing method based on a triaxial testing system according to claim 9, characterized in that, The supplementary block can be selected from one of polyurethane foam, rubber, foamed concrete, or sponge material.

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