A hierarchical controllable rockburst simulation test device and test method

Abstract

The present invention relates to a hierarchical controllable rockburst simulation test device and a test method, belonging to the field of geotechnical engineering technology. The device comprises a test frame, a test platform and a concave loading slot. The test platform is liftably arranged at the lower part of the test frame, the concave loading slot is placed on the test platform, a test model is placed in the concave loading slot, a loading plate is placed on the top of the test model, a loading pressure head is fixedly connected to the top of the test frame, a multi-layer through-hole is arranged at intervals along the axial direction of the loading pressure head on the side surface of the loading pressure head, each layer has two symmetrical through-holes, and the through-holes are used to accommodate positioning blocks that can enter and exit the through-holes; the lower end of the loading pressure head is penetrated by the small-diameter end of a conical spring; a rotating rod is provided inside the loading pressure head, and a plurality of cams are arranged at intervals along the axial direction of the rotating rod; the test method using the device can realize the release of the spring deformation component in stages, simulate the staged release of ground stress when rockburst occurs continuously for multiple times, and realize the simulation of the physical conditions of continuous rockburst in the laboratory.

Description

Technical Field

[0001] The present invention belongs to the field of geotechnical engineering technology, relates to the study of rock burst occurrence law, and particularly relates to a hierarchical controllable rock burst simulation test device and a test method. Background Art

[0002] Rockbursts are a common dynamic destructive phenomenon during the construction of deep underground projects. It is generally believed that when the high elastic strain energy accumulated in the rock mass exceeds the energy consumed by rock failure, the equilibrium of the rock structure is disrupted. The excess energy causes the rock to explode, causing rock fragments to break off and break out of the rock mass. Minor rockbursts only cause the shedding of rock fragments without ejection. Severe rockbursts can have a magnitude of 4 to 6 and typically last for days or months. Rockbursts often cause severe damage to the excavation face, equipment damage, and casualties, making them a global challenge in underground rock engineering and rock mechanics.

[0003] The rock mechanics community generally believes that the causes of rockbursts are: first, high in-situ stress within the rock mass, which exceeds the rock's inherent strength; second, rock has high brittleness and elasticity; and third, when underground engineering construction disrupts the equilibrium of the rock mass, this accumulated energy is suddenly released, leading to rock failure and ejection. In other words, high in-situ stress, hard rock, and unloading are the primary causes of rockbursts.

[0004] To explore the laws governing rockburst occurrence and development, many researchers at home and abroad have conducted research using geomechanical model tests and developed a number of rockburst loading systems. For example, Patent Application No. 2013104259114 discloses a simplified rockburst simulation test system for deep tunnels, overcoming the insufficient elastic energy replenishment found in previous spring-loading and oil-gas composite loading systems. Patent Application No. 2013103362550 addresses the inability of previous test systems to simulate the actual boundary conditions of a rockburst by proposing a true triaxial rockburst physical simulation test system. Patent Application No. 201710322478X addresses the inability of previous test systems to simulate the "rapid unloading" that occurs before a rockburst by proposing a method using disc springs as elastic loading elements. However, it should be noted that rockbursts can persist for days or even months at a working face, resulting in staged and discontinuous stress release. Model tests addressing this situation have yet to be conducted. Therefore, the development of a rockburst simulation test device capable of staged and controlled stress release is crucial. Summary of the Invention

[0005] The purpose of the present invention is to provide a hierarchical controllable rockburst simulation test device and test method, which can truly simulate the hierarchical release of stress when a rockburst occurs.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a hierarchical controllable rock burst simulation test device, including a test frame, a test platform and a concave loading slot, the test platform is arranged at the lower part of the test frame in a liftable manner, the concave loading slot is placed on the test platform, the test model is placed in the concave loading slot, the test model is provided with a chamber, and a loading plate is placed on the top of the test model. A hollow cylindrical loading pressure head is fixedly connected to the top of the test frame, and multiple layers of through holes are arranged on the side of the loading pressure head along its axial direction. Each layer has two symmetrical through holes, and the through holes are used to accommodate energy. A positioning block that can enter and exit the through hole; the lower end of the loading pressure head is inserted into the small diameter end of the conical spring, the large diameter end of the conical spring is supported on the loading plate, and the inner diameter of the small diameter end of the conical spring matches the outer diameter of the loading pressure head; a rotating rod is provided inside the loading pressure head, the upper end of the rotating rod is connected to the rotating mechanism on the upper part of the test frame, and a plurality of cams are arranged on the rotating rod along its axial direction, and the plurality of cams have unequal installation angles. As the rotating rod rotates, the protrusions and recesses on the cam successively contact the positioning block to drive the positioning block to extend or retract into the corresponding through hole.

[0007] Furthermore, a magnet is provided at the inner end of the positioning block, and the magnet can be adsorbed on the raised portion and the recessed portion of the cam.

[0008] Furthermore, the inner end and the outer end of the positioning block are both tapered.

[0009] Furthermore, the cam has two protrusions, which are symmetrically arranged and located at both ends of the cam in the radial direction, and the recessed portion is between the two protrusions.

[0010] Furthermore, the space between the inner wall of the concave loading tank and the test model is filled with expansion cement.

[0011] Furthermore, the two ends of the chamber pass through the opposite side walls of the test model.

[0012] Furthermore, the test platform is connected to the lower part of the test frame through loading bolts, and the loading bolts drive the test platform to rise and fall vertically.

[0013] The present invention also proposes a hierarchical controllable rockburst simulation test method, which uses the above-mentioned hierarchical controllable rockburst simulation test device and includes the following steps:

[0014] The first step is to place the test model into a matching concave loading tank, fill the gap between the test model and the concave loading tank with expansion cement, and place it on the test platform after the expansion cement solidifies.

[0015] The second step is to secure the loading head to the upper portion of the test frame, install a positioning block and cam on the loading head and rotating rod, respectively. A conical spring is placed under the loading head, and the small-diameter end of the conical spring is crimped onto the positioning block at the bottom of the loading head. The test platform is then raised to compress the conical spring until the preset load is reached.

[0016] The third step is to start the rotating mechanism and turn the rotating rod to drive the positioning block to expand and contract in the through hole, thereby realizing the gradual reset of the compressed conical spring and the graded release of the elastic force. After the different levels of elastic force are released, the bursting of the test model is observed.

[0017] Furthermore, in the second step, the positions of the positioning blocks and cams on the loading head and the rotating rod are adjusted according to the magnitude of the graded release load to simulate the probability and degree of rock burst under different release loads.

[0018] Furthermore, in the third step, by adjusting the rotation speed of the rotating mechanism, the effects of different load release intervals and frequencies on the probability and severity of rock burst are simulated.

[0019] The beneficial effects of the present invention are as follows: the present invention aims to explore solutions to the problems of long duration, high frequency and unclear occurrence patterns of rock bursts in underground engineering rock masses. Based on the geomechanical model test method, a conical spring is used as a loading element, and the rotating rod controls the in and out of the positioning block through a cam, so as to realize the release of the spring deformation component in stages, simulating the staged release of ground stress when rock bursts occur continuously for many times, and simulating the physical conditions for the continuous occurrence of rock bursts in the laboratory. At the same time, the present invention can also adjust the stiffness of the conical spring sheet, the frequency and size of the released ground stress, etc. according to the strength of the test model, so as to meet the research on the laws of rock bursts at different burial depths. The device of the present invention has a simple structure and convenient test operation, which is conducive to the development of rock burst engineering tests and theories. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the simulation test device of the present invention;

[0021] Figure 2 Schematic diagram of the structure of the rotating rod of the present invention;

[0022] Figure 3 Schematic diagram of the structure of the cam in the present invention;

[0023] Markings in the figure: 1, test frame, 10, motor, 11, output shaft, 12, upper platform, 13, lower platform, 14, column, 15, fixing bolt II, 16, test model;

[0024] 2. Concave loading trough, 20. Expansive cement;

[0025] 3. Test platform, 30. Loading bolts;

[0026] 4. Chamber, 5. Loading plate, 6. Conical spring;

[0027] 7. Loading head, 70. Through hole, 71. Positioning block, 72. Magnet; P1. First positioning block, P2. Second positioning block, P3. Third positioning block, P4. Fourth positioning block, P5. Fifth positioning block, P6. Sixth positioning block, P7. Seventh positioning block;

[0028] 8. Fixing bolt I;

[0029] 9. Rotating rod, 90. Cam, 901. Protrusion, 902. Recess, 91. Key, 92. Pin; 90A. Lower cam, 90B. Middle cam, 90C. Upper cam. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but they are not intended to limit the invention in any way.

[0031] Example 1

[0032] Refer to the attached Figure 1 As shown, a hierarchical controllable rock burst simulation test device includes a test model 16, a test frame 1 and a loading device.

[0033] The test frame 1 includes an upper support platform 12, a lower support platform 13 and a plurality of columns 14 connecting the upper support platform 12 and the lower support platform 13. Fixing bolts II15 are installed on the columns 14 at the upper and lower sides of the upper support platform 12 and the upper and lower sides of the lower support platform 13 to achieve the connection between the upper support platform 12, the lower support platform 13 and the columns 14, providing an installation platform for structures such as the test model 16 and the loading device.

[0034] A test platform 3 is provided above the lower platform 13, and the bottom of the test platform 3 is connected to the lower platform 13 via a loading bolt 30. The upper end of the loading bolt 30 is rotatably connected to the lower surface of the test platform 3, and the loading bolt 30 is threadedly connected to the lower platform 13. The height of the test platform 3 relative to the lower platform 13 can be adjusted by rotating the loading bolt 30. The rotational connection between the loading bolt 30 and the test platform 3 can be achieved in the following ways: a bearing is embedded in the test platform 3, and the loading bolt 30 is connected to the bearing to achieve a rotational connection; or, a rotating disk is provided at the end of the loading bolt 30, and a groove is provided on the lower surface of the test platform 3, and the rotating disk is axially limited in the groove and can rotate to achieve a rotational connection; or other rotational connection methods that can be axially limited in the prior art are adopted.

[0035] The test platform 3 is equipped with a concave loading tank 2, with an open top. The test model 16 is placed within the tank, and the gap between the test model 16 and the concave loading tank 2 is filled with expansive cement 20. The test model 16 is formed by solidifying a mixture of gypsum and diatomaceous earth. A chamber 4 of a predetermined shape is excavated in its center, with both ends of the chamber 4 penetrating the opposite walls of the test model 16. A loading plate 5 is placed on top of the test model 16. The dimensions of the loading plate 5 match those of the top of the test model 16 to prevent the expansive cement 20 surrounding the test model 16 from interfering with the loading effect of the loading plate 5 on the test model 16.

[0036] By adjusting the size of the gap between the test model 16 and the concave loading tank 2 and the water-cement ratio of the expansive cement 20, different ground stress load conditions can be simulated and loading of different confining pressures can be achieved.

[0037] A conical spring 6 is placed on the loading plate 5 to simulate the phased release of ground stress during repeated rockbursts. One axial end of the conical spring 6 has a larger diameter, while the other has a smaller diameter. The larger diameter end of the conical spring 6 can be placed on the loading plate 5, or it can be fixed. Because it is axially compressed, no lateral load is generated, preventing lateral deflection. Therefore, a simple fixing method such as screws or clips can be used.

[0038] The upper platform 12 of the test stand 1 is provided with a loading pressure head 7 located directly above the test platform 3. The loading pressure head 7 is a hollow tube structure, the upper end of which is connected to the lower surface of the upper platform 12 by a fixing bolt I, and the lower end extends from the small diameter end of the conical spring 6 into the conical spring 6, and the outer diameter of the loading pressure head 7 is consistent with the inner diameter of the small diameter end of the conical spring 6, so that the conical spring 6 can slide along the outer circular surface of the loading pressure head 7 when the elastic force is released after compression.

[0039] The side of the loading ram 7 is provided with multiple layers of through holes spaced apart along its axial direction. Each layer includes two symmetrical through holes 70, which are radial holes and have a certain width. Each through hole 70 is provided with a positioning block 71 that can enter and exit the through hole 70 radially along the loading ram 7. The positioning blocks 71 are tapered at both ends facing the outside and inside of the through hole 70, and a magnet 72 is provided at the inner end of the positioning block 71. The magnet 72 can be coated on the end of the positioning block 71 or embedded within the positioning block 71.

[0040] The interior of the loading head 7 is provided with a vertical rotating rod 9, on which a plurality of cams 90 are distributed along its axial direction. The height of the cams 90 corresponds to the positioning blocks 71. Specifically, each cam 90 corresponds to two positioning blocks 71 of a layer, or according to the test requirements, the number of cams 90 is less than the number of layers of through holes 70, and the cams 90 correspond to the positioning blocks 71 of the corresponding layer. The structure of the cams 90 is as follows: Figure 3As shown, the cam 90 is a double semicircular cam having two protrusions 901. The two protrusions 901 are symmetrically arranged at the radial ends of the cam 90. A recessed portion 902 is located between the two protrusions 901. That is, the two protrusions 901 and the two recessed portions 902 are alternately arranged along the circumferential direction. The distance between the apexes of the two protrusions 901 is greater than the distance between the concave points of the two recessed portions 902. The cam 90 is fixed to the rotating rod 9 by a pin 92. When the cam 90 rotates with the rotating rod 9, when the protrusion 901 of the cam 90 contacts the positioning block 71, the positioning block 71 is pushed out of the through hole 70. When the protrusion 901 of the cam 90 leaves the positioning block 71, the magnet 72 at the inner end of the positioning block 71 is adsorbed on the cam 90 and moves along the contour of the cam 90 to the recessed portion 902 of the cam 90, and then the positioning block 71 gradually retracts into the through hole 70. In this way, as the rotating rod 9 rotates, the positioning block 71 moves back and forth in the through hole 70 and enters and exits the through hole 70. The significance of the positioning block 71 entering and exiting the through hole 70 is that, after the positioning block 71 extends out of the through hole 70, it can block the small-diameter end of the compressed conical spring 6, so that the conical spring 6 maintains a certain amount of compression; after the positioning block 71 retracts into the through hole 70, it can release the obstruction of the small-diameter end of the conical spring 6, so that the compressed conical spring 6 can release a certain elastic force.

[0041] The rotation of the rotating rod 9 is driven by a rotating mechanism provided on the test stand 1, and the rotating mechanism is an electric motor 10. The output shaft 11 of the electric motor 10 and the upper end of the rotating rod 9 are connected by a key 91 and a keyway. The upper end of the rotating rod 9 is provided with a key 91 required for transmission, and the corresponding keyway is provided in the mounting hole on the end face of the output shaft 11. The key and keyway can also be interchanged and can also play a transmission role. In other embodiments, a coupling or the like can be used to realize power transmission between the motor 10 and the rotating rod 9.

[0042] In this device, the height of the test platform 3 can be adjusted by the loading bolt 30 , thereby compressing the conical spring 6 to generate elastic force, which reacts on the loading plate 5 and the test model 16 , thereby achieving loading of the test model 16 .

[0043] The principle analysis of this device to simulate the staged release of ground stress when rock bursts occur repeatedly is as follows: Figure 2As shown, 7 layers of through holes are provided on the loading pressure head (not shown in the figure), and a positioning block 71 is provided in each layer of through holes. The positioning block 71 of the bottom layer is defined as the first positioning block P1. From bottom to top, the positioning blocks 71 of the 7 layers are the first positioning block P1, the second positioning block P2...the seventh positioning block P7; three cams 90 are provided on the rotating rod 9 from bottom to top, namely the lower cam 90A, the middle cam 90B and the upper cam 90C, and the lower cam 90A, the middle cam 90B and the upper cam 90C correspond to the first positioning block P1, the fifth positioning block P5 and the seventh positioning block P7 respectively. Block P7; the distance between the lower cam 90A and the middle cam 90B is S1, and the distance between the middle cam 90B and the upper cam 90C is S2; the lower cam 90A, the middle cam 90B and the upper cam 90C have different installation angles on the rotating rod 9, and the upper cam 90C and the lower cam 90A have the same installation angle and are perpendicular to the installation angle of the middle cam 90B. In this way, the first positioning block P1 and the seventh positioning block P7 are pushed out of the through hole 70 by the corresponding lower cam 90A and upper cam 90C, and the fifth positioning block P5 is retracted into the through hole 70. At this time, the small diameter end of the conical spring 6 is extended. The first positioning block P1 of the through hole 70 is blocked. By adjusting the loading bolt 30 below the test platform 3, the height position of the test platform 3 and the test model 16 thereon is adjusted, so that the conical spring 6 is further compressed, thereby adjusting the load on the test model 16; when the rotating rod 9 rotates 90°, the protrusion 901 of the lower cam 90A leaves the first positioning block P1, and the first positioning block P1 retracts into the through hole 70, releasing the obstruction to the conical spring 6, and the compressed conical spring 6 releases its elastic force. At the same time, the protrusion 901 of the middle cam 90B rotates to the position of the fifth positioning block P5, and the fifth positioning block is rotated. Block P5 pushes out of through-hole 70, re-blocking conical spring 6. During this process, the small-diameter end of conical spring 6 moves upward by a distance S1. Since conical spring 6 has a smaller diameter at the upper end and a larger diameter at the lower end, the first positioning block P1, which previously blocked the small-diameter end of conical spring 6, no longer blocks the upward return of conical spring 6 after extending out of through-hole 70. As rotating rod 9 rotates another 90°, the protrusion 901 of middle cam 90B leaves fifth positioning block P5, and upper cam 90C pushes seventh positioning block P7 out of through-hole 70, releasing the elastic force of conical spring 6 again and moving it upward by a distance S2. Therefore, according to this principle, the rotating rod 9, driven by motor 10, drives positioning block 71 along through-hole 70 via cam 90 to reciprocate. The movement of positioning block 71 determines the amount of deformation recovery of conical spring 6, thereby achieving a staged release of the elastic force of conical spring 6, simulating the staged release of ground stress during repeated rockbursts.

[0044] In the present invention, the number of cams 90 , the installation height on the rotating rod 9 , and the installation angle of the cams 90 can be adjusted according to the need for the positioning block 71 to move in and out.

[0045] Example 2

[0046] The hierarchical controllable rockburst simulation test method using the hierarchical controllable rockburst simulation test device described in Example 1 includes the following steps:

[0047] Step 1: Prepare a concave loading tank 2 that matches the size of the test model 16. A chamber 4 is reserved in the center of the test model 16, penetrating its two opposite side walls. The test model 16 is placed in the concave loading tank 2, ensuring that the chamber 4 is parallel to the bottom wall of the concave loading tank 2. The gap between the test model 16 and the concave loading tank 2 is filled with expansive cement 20. After the expansive cement 20 cures, the test model 16 is placed on the test platform 3.

[0048] Step 2: Fix the loading head 7 to the upper platform 12, install the positioning block 71 and the cam 90 on the loading head 7 and the rotating rod 9, respectively; trap the conical spring 6 at the bottom of the loading head 7, and press the small-diameter end of the top of the conical spring 6 onto the positioning block 71 at the bottom of the loading head 7; adjust the loading bolt 30 and raise the test platform 3 to compress the conical spring 6 until the predetermined load is reached;

[0049] Step three, start the motor 10, rotate the rotating rod 9, drive the positioning block 71 to expand and contract in the through hole 70, thereby realizing the gradual reset of the compressed conical spring 6 and releasing the elastic force in stages. After the elastic force at different levels is released, observe the bursting of the test model.

[0050] It should be noted that:

[0051] (1) In step 2, the positions of the positioning block 71 and the cam 90 on the loading head 7 and the rotating rod 9 are adjusted according to the magnitude of the graded release load to simulate the probability and degree of rock burst under different release loads.

[0052] (2) In step 2, the predetermined load can be obtained by calculating the spring's elastic coefficient and the spring compression. Figure 1 、 2 As shown, for example, by adjusting the loading bolt 30 and raising the test platform 3, the conical spring 6 reaches a length of L when it just contacts the first positioning block P1. By further tightening the loading bolt 30 and raising the test platform 3, the conical spring 6 is compressed. When the length of the conical spring 6 reaches L1, the compression amount of the conical spring 6 is L2, where L2 = L - L1. Assuming the elastic constant of the conical spring 6 is represented by K, the elastic load F at this point is F = K × L2, which is the predetermined load. Therefore, after setting the predetermined load before loading, the change in the compressed length of the conical spring 6 can be used to determine whether the predetermined load has been reached.

[0053] (3) In step 3, the speed of the motor 10 is adjusted to simulate the effects of different load release intervals and frequencies on the probability and severity of rock burst.

[0054] (4) In step 3, the test model 16 can be taken out from the concave loading tank 2 to observe the bursting of the test model 16, or an endoscopic camera can be set in the concave loading tank 2 for observation.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation methods of the present invention can be modified or replaced with equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A hierarchical controllable rockburst simulation test device, comprising a test frame, a test platform, and a concave loading tank. The test platform is escalably disposed at the bottom of the test frame. The concave loading tank is placed on the test platform. A test model is placed in the concave loading tank. The test model has a chamber inside. A loading plate is placed on top of the test model. The device is characterized by: A hollow cylindrical loading pressure head is fixedly connected to the top of the test frame, and a plurality of through holes are arranged on the side of the loading pressure head along its axial direction, each layer has two symmetrical through holes, and the through holes are used to accommodate positioning blocks that can enter and exit the through holes; the lower end of the loading pressure head is passed through the small diameter end of the conical spring, and the large diameter end of the conical spring is supported on the loading plate, and the inner diameter of the small diameter end of the conical spring coincides with the outer diameter of the loading pressure head; a rotating rod is provided inside the loading pressure head, and the upper end of the rotating rod is connected to the rotating mechanism on the upper part of the test frame, and a plurality of cams are arranged on the rotating rod along its axial direction, and the cam has two protrusions, which are symmetrically arranged and located at the radial ends of the cam, and a recessed portion is provided between the two protruding portions; the plurality of cams have unequal installation angles. As the rotating rod rotates, when the protrusion on the cam contacts the positioning block, the positioning block is pushed out of the through hole, and when the recessed portion on the cam contacts the positioning block, the positioning block is retracted into the through hole.

2. A hierarchical controllable rockburst simulation test device according to claim 1, characterized in that: The inner end of the positioning block is provided with a magnet, and the magnet can be adsorbed on the protruding portion and the recessed portion of the cam.

3. The hierarchical controllable rockburst simulation test device according to claim 1, characterized in that: The inner end and the outer end of the positioning block are both tapered.

4. The hierarchical controllable rockburst simulation test device according to claim 1, characterized in that: Expansive cement is filled between the inner wall of the concave loading tank and the test model.

5. The hierarchical controllable rockburst simulation test device according to claim 1, characterized in that: The two ends of the chamber pass through the opposite side walls of the test model.

6. The hierarchical controllable rockburst simulation test device according to claim 1, characterized in that: The test platform is connected to the lower part of the test frame through loading bolts, and the loading bolts drive the test platform to rise and fall vertically.

7. A hierarchical controllable rockburst simulation test method, characterized by: The method is carried out using the hierarchical controllable rockburst simulation test device according to any one of claims 1 to 6, and comprises the following steps: The first step is to place the test model into a matching concave loading tank, fill the gap between the test model and the concave loading tank with expansion cement, and place it on the test platform after the expansion cement solidifies. The second step is to secure the loading head to the upper portion of the test frame, install a positioning block and cam on the loading head and rotating rod, respectively. A conical spring is placed under the loading head, and the small-diameter end of the conical spring is crimped onto the positioning block at the bottom of the loading head. The test platform is then raised to compress the conical spring until the preset load is reached. The third step is to start the rotating mechanism and turn the rotating rod to drive the positioning block to expand and contract in the through hole, thereby realizing the gradual reset of the compressed conical spring and the graded release of the elastic force. After the different levels of elastic force are released, the bursting of the test model is observed.

8. The hierarchical controllable rockburst simulation test method according to claim 7, characterized in that: In the second step, the positions of the positioning blocks and cams on the loading head and rotating rod are adjusted according to the size of the graded release load to simulate the probability and degree of rock burst under different release loads.

9. The hierarchical controllable rockburst simulation test method according to claim 7, characterized in that: In the third step, by adjusting the rotation speed of the rotating mechanism, the effects of different load release intervals and frequencies on the probability and severity of rock burst are simulated.

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