Jointed rock impact shear test device capable of realizing constant normal stiffness

Abstract

The invention discloses a jointed rock impact shear test device capable of realizing constant normal stiffness, which comprises a bracket, a sample table and a lifting device are mounted on the bracket, the sample table is used for placing a sample, and a constraint assembly is arranged on the outer side of the sample; a drop hammer assembly is mounted on the lifting device, the lifting device is used for adjusting the height of the drop hammer assembly, and the drop hammer assembly corresponds to the sample table; a laser displacement sensor is arranged below the sample and is used for recording the displacement of the sample in real time; a high-speed camera and a digital speckle collector are arranged on the outer side of the support and correspond to the sample, the high-speed camera is used for recording the form change of the sample in the impact shearing process, and the digital speckle collector is used for recording the deformation field change of the sample in the impact shearing process. The constant normal rigidity condition during impact shearing can be realized, the normal force change is quicker and more sensitive, and the device is more suitable for the impact shearing test of jointed rocks.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic shear mechanical characteristics testing of deep jointed rocks, and in particular to a jointed rock impact shear testing device capable of achieving constant normal stiffness. Background Art

[0002] With the development of the national economy, many major projects such as transportation, water conservancy and hydropower are developing towards the west and deep underground. Large underground caverns such as transportation tunnels and hydraulic tunnels are inevitably built in unfavorable geological areas with strong tectonic activities and highly developed joints and fissures. During the life cycle of deep underground projects, strong mining disturbances such as blasting disturbances, dynamic disturbances such as far-field seismic waves and rock bursts often cause changes in the stress state and mechanical properties of joint surfaces in a metastable state, which may induce dynamic instability and damage of joint surfaces. Accurately understanding the mechanical response characteristics of rock joint surfaces under dynamic disturbances and their activation instability mechanism is crucial to the safety and stability of deep engineering.

[0003] Most of the current jointed rock impact shear test devices use servo hydraulics or a combination of pneumatics and hydraulics to provide dynamic shear loads. The shear rate provided by this method is low, and it is difficult to simulate the dynamic loads caused by rock bursts and blasting construction in engineering. In addition, as the normal displacement of the shear joint increases, the surrounding rock mass will exert a constraint force in the opposite direction of the shear displacement to prevent it from continuing to deform. At this time, the greater the normal displacement, the greater the constraint force, and the greater the normal stress applied to the joint surface. Therefore, in indoor tests, the constant normal stress boundary condition can no longer meet the requirements.

[0004] In summary, there is an urgent need for a jointed rock impact shear test device that can achieve constant normal stiffness conditions and provide a high shear rate. Summary of the invention

[0005] The purpose of the present invention is to provide a jointed rock impact shear test device capable of achieving constant normal stiffness, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above-mentioned purpose, the present invention provides a jointed rock impact shear test device capable of achieving constant normal stiffness, comprising a bracket, a sample table and a lifting device are installed on the bracket, the sample table is used to place the sample, and a constraint assembly is arranged on the outside of the sample; a drop hammer assembly is installed on the lifting device, the lifting device is used to adjust the height of the drop hammer assembly, and the drop hammer assembly is arranged corresponding to the sample table; a laser displacement sensor is placed below the sample, and the laser displacement sensor is used to record the displacement of the sample in real time; a high-speed camera and a digital speckle collector are arranged on the outside of the bracket, and both the high-speed camera and the digital speckle collector are arranged corresponding to the sample, the high-speed camera is used to record the morphological changes of the sample during the impact shear process, and the digital speckle collector is used to record the deformation field changes of the sample during the impact shear process.

[0007] Preferably, the bracket includes a base, on which two main frames are fixedly mounted, a crossbeam is installed between the tops of the two main frames, and the lifting device is installed on the crossbeam; the sample table is arranged at the top of the base, and the two main frames are respectively arranged on both sides of the sample table.

[0008] Preferably, the drop hammer assembly includes a hammer head, the top end of which is detachably mounted on the bottom of the lifting device, a plurality of weights are sleeved on the top of the hammer head, and a pressure sensor is installed between the hammer head and the weights.

[0009] Preferably, a drop weight slide rail is provided at the bottom of the lifting device, and the weight is slidably sleeved on the drop weight slide rail.

[0010] Preferably, the constraint assembly includes two oppositely arranged bearing plates, the specimen is arranged between the two bearing plates, a round steel tie rod is connected between the two bearing plates, both ends of the round steel tie rod are threadedly connected with nuts, and the specimen is clamped and fixed by the bearing plates, the nuts and the round steel tie rod.

[0011] Preferably, a pad is placed on top of the sample.

[0012] Preferably, the sample stage comprises two platforms that are arranged opposite to each other, a gap is provided between the two platforms, and the laser displacement sensor is placed in the gap between the two platforms.

[0013] Preferably, pads are provided at the top ends of the two platforms, and the sample is placed on the two pads through the restraint assembly.

[0014] Preferably, both ends of the top surface of the cushion block are provided with limiting ridges, and a plurality of wear-reducing rods are provided on the top of the cushion block, and the wear-reducing rods are arranged parallel to the limiting ridges.

[0015] Preferably, a protective cover is provided on the outside of the sample, the protective cover is a transparent structure, and the protective cover is placed on the top of the base.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] The jointed rock impact shear test device that can achieve constant normal stiffness provided by the present invention, the sample is fixed by a constraint assembly, and the gravitational potential energy is converted into kinetic energy by the free fall of the drop hammer assembly, thereby generating impact shear on the sample. The present invention can achieve a constant normal stiffness condition during impact shearing. Compared with the normal stiffness achieved by electro-hydraulic servo control, the present invention can provide a constant normal stiffness condition in real time, and the normal force changes more quickly and sensitively, and is more suitable for impact shear tests of jointed rocks.

[0018] The present invention can implement impact shear tests under constant normal stiffness conditions on various types of jointed rocks, and can be used to explore the mechanical properties of jointed rocks under high-rate shear under constant normal stiffness. It has important scientific significance and engineering value for understanding the instability and failure mechanism of rock joint surfaces and the disaster-causing mechanism of strong dynamic geological disasters such as earthquakes and rock bursts. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a structural schematic diagram of the jointed rock impact shear test device of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the constraint component of the present invention;

[0022] Figure 3 It is a schematic diagram of the connection between the weight and the drop weight slide rail of the present invention;

[0023] Figure 4 This is a positional relationship diagram of the wear-reducing rod and the cushion block of the present invention;

[0024] In the figure: 1. Main frame; 2. Protective cover; 3. Sample table; 4. Weight; 5. Hammer head; 6. Drop hammer slide rail; 7. Lifting device; 8. High-speed camera; 9. Laser displacement sensor; 10. Pressure sensor; 11. Digital speckle collector; 12. Round steel pull rod; 13. Load-bearing plate; 14. Pad; 15. Pad; 16. Wear-reducing rod. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0026] like Figures 1 to 4 As shown, the present invention provides a jointed rock impact shear test device capable of achieving constant normal stiffness, comprising a bracket, on which a sample table 3 and a lifting device 7 are installed, the sample table 3 is used to place the sample, and a constraint assembly is arranged on the outside of the sample; a drop hammer assembly is installed on the lifting device 7, and the lifting device 7 is used to adjust the height of the drop hammer assembly, and the drop hammer assembly is arranged corresponding to the sample table 3; a laser displacement sensor 9 is placed below the sample, and the laser displacement sensor 9 is used to record the displacement of the sample in real time; a high-speed camera 8 and a digital speckle collector 11 are arranged on the outside of the bracket, and the high-speed camera 8 and the digital speckle collector 11 are both arranged corresponding to the sample, the high-speed camera 8 is used to record the morphological changes of the sample during the impact shear process, and the digital speckle collector 11 is used to record the deformation field changes of the sample during the impact shear process.

[0027] The sample of the present invention is fixed by a restraint assembly, and the gravitational potential energy is converted into kinetic energy by the free fall of the drop hammer assembly, thereby generating impact shear on the sample. The present invention can implement impact shear tests under constant normal stiffness conditions for various types of jointed rocks, and has important scientific significance and engineering value for understanding the instability and failure mechanism of rock joint surfaces and the disaster-causing mechanism of strong dynamic geological disasters such as earthquakes and rock bursts.

[0028] According to a further optimized solution, the bracket includes a base, on which two main frames 1 are fixedly mounted, a crossbeam is installed between the tops of the two main frames 1, and a lifting device 7 is installed on the crossbeam; the sample table 3 is arranged at the top of the base, and the two main frames 1 are respectively arranged on both sides of the sample table 3.

[0029] According to a further optimized solution, the drop hammer assembly includes a hammer head 5 , the top end of the hammer head 5 is detachably mounted on the bottom of the lifting device 7 , a plurality of weights 4 are sleeved on the top of the hammer head 5 , and a pressure sensor 10 is installed between the hammer head 5 and the weights 4 .

[0030] By changing the number of weights 4, the mass of the hammer assembly is controlled to control the impact force of the hammer head 5 when it impacts the sample, and by changing the initial height of release, the impact speed of the hammer head 5 when it impacts the sample is controlled. Therefore, the present invention can perform impact shear tests with different impact forces and different impact speeds on the sample by changing parameters. When the sample is impacted and sheared, the pressure sensor 10 on the upper part of the hammer head 5 measures and records the impact force generated.

[0031] To further optimize the solution, a drop-hammer slide rail 6 is provided at the bottom of the lifting device 7, and the weight 4 is slidably sleeved on the drop-hammer slide rail 6. The hammer head 5 can fall freely along the drop-hammer slide rail 6, and under the action of the drop-hammer slide rail 6, the hammer head 5 can accurately impact the jointed rock sample.

[0032] A further optimized solution is that the constraint assembly includes two relatively arranged bearing plates 13, the sample is arranged between the two bearing plates 13, a round steel tie rod 12 is connected between the two bearing plates 13, both ends of the round steel tie rod 12 are threadedly connected with nuts, and the sample is clamped and fixed by the bearing plates 13, nuts and round steel tie rods 12.

[0033] The real-time constant normal stiffness condition is achieved through the normal constraint of the round steel tie rod 12. When the jointed rock produces shear expansion, the round steel tie rod 12 will produce a tensile effect, and tensile stress will be generated in the round steel tie rod 12, thereby increasing the constraint force of the round steel tie rod 12 on the rock sample, thereby achieving the constant normal stiffness condition.

[0034] Furthermore, the round steel tie rods 12 with different tensile stiffnesses are replaced to achieve different constant normal stiffnesses.

[0035] To further optimize the solution, a pad 14 is placed on the top of the sample to prevent the sample from breaking under the impact force.

[0036] According to a further optimized solution, the sample stage 3 includes two platforms that are arranged opposite to each other, a gap is provided between the two platforms, and the laser displacement sensor 9 is placed in the gap between the two platforms.

[0037] The sample platform 3 is divided into two parts, a left part and a right part, with a space reserved in the middle to ensure that the sample can generate sufficient shear displacement.

[0038] According to a further optimized solution, pads 15 are provided at the top of the two platforms, and the samples are placed on the two pads 15 through a restraining assembly.

[0039] According to a further optimization scheme, both ends of the top surface of the cushion block 15 are provided with limiting ridges, and a plurality of wear-reducing rods 16 are provided on the top of the cushion block 15 , and the wear-reducing rods 16 are arranged parallel to the limiting ridges.

[0040] The friction reducing rod 16 can reduce the friction between the jointed rock sample and the pad 15 during the shearing process, ensuring that the sample is always under a constant normal stiffness condition.

[0041] To further optimize the solution, a protective cover 2 is provided on the outside of the sample to provide protection. The protective cover 2 is a transparent structure and is placed on the top of the base.

[0042] The impact shear test device for jointed rock that can achieve constant normal stiffness provided by the present invention, when working, firstly, the sample is placed between two bearing plates 13, and the sample is fixed by a round steel tie rod 12 and nuts at both ends. The cushion block 15 is placed at a designated position above the sample table 3, and then the fixed sample is placed on the cushion block 15, and the laser displacement sensor 9 is placed under the sample to record the displacement of the sample in real time, and the high-speed camera 8 and the digital speckle collector 11 are aimed at the sample, and the morphological changes and deformation field change characteristics of the sample during the impact shear process are respectively recorded in real time. Then the protective cover 2 is closed to play a protective role, and the lifting device 7 lifts the drop hammer assembly to the designated position with the main frame 1 as support, and then releases the hammer assembly, and the hammer assembly falls freely along the drop hammer slide rail 6. Since the free fall of the hammer assembly converts the gravitational potential energy into kinetic energy, when the hammer head 5 contacts the pad 14, it will produce impact shear on the sample, and the pad 14 can prevent the sample from being broken under the action of the impact force. When the sample is impact sheared, the pressure sensor 10 on the hammer head 5 measures and records the impact force generated, and the laser displacement sensor 9, the high-speed camera 8, and the digital speckle collector 11 respectively record the shear displacement, morphological changes, and deformation field change characteristics of the jointed rock sample during the impact shear process in real time.

[0043] The present invention can complete impact shear tests on various types of jointed rocks under constant normal stiffness, and can be used to explore the mechanical properties of jointed rocks under high-rate shear under constant normal stiffness. It has important scientific significance and engineering value for understanding the instability and failure mechanism of rock joint surfaces and the disaster-causing mechanism of strong dynamic geological disasters such as earthquakes and rock bursts.

[0044] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A jointed rock impact shear test device capable of achieving constant normal stiffness, characterized in that: The invention comprises a support, on which a sample platform (3) and a lifting device (7) are installed. The sample platform (3) is used to place the sample, and a constraint component is arranged on the outside of the sample; a drop hammer component is installed on the lifting device (7), and the lifting device (7) is used to adjust the height of the drop hammer component, and the drop hammer component is arranged corresponding to the sample platform (3); a laser displacement sensor (9) is placed below the sample, and the laser displacement sensor (9) is used to record the displacement of the sample in real time; a high-speed camera (8) and a digital speckle collector (11) are arranged on the outside of the support, and the high-speed camera (8) and the digital speckle collector (11) are both arranged corresponding to the sample, and the high-speed camera (8) is used to record the morphological changes of the sample during the impact shearing process, and the digital speckle collector (11) is used to record the deformation field changes of the sample during the impact shearing process.

2. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 1, characterized in that: The bracket comprises a base, on which two main frames (1) are fixedly mounted, a crossbeam is mounted between the tops of the two main frames (1), and the lifting device (7) is mounted on the crossbeam; the sample table (3) is arranged at the top of the base, and the two main frames (1) are respectively arranged on both sides of the sample table (3).

3. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 1, characterized in that: The drop hammer assembly comprises a hammer head (5), the top end of which is detachably mounted on the bottom of the lifting device (7), a plurality of weights (4) are sleeved on the top of the hammer head (5), and a pressure sensor (10) is installed between the hammer head (5) and the weights (4).

4. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 3, characterized in that: A drop-weight slide rail (6) is provided at the bottom of the lifting device (7), and the weight (4) is slidably sleeved on the drop-weight slide rail (6).

5. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 1, characterized in that: The constraint assembly comprises two oppositely arranged bearing plates (13), the sample is arranged between the two bearing plates (13), a round steel tie rod (12) is connected between the two bearing plates (13), both ends of the round steel tie rod (12) are threadedly connected with nuts, and the sample is clamped and fixed by the bearing plates (13), the nuts and the round steel tie rod (12).

6. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 1, characterized in that: A backing plate (14) is placed on top of the sample.

7. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 1, characterized in that: The sample platform (3) comprises two platforms arranged opposite to each other, a gap is arranged between the two platforms, and the laser displacement sensor (9) is placed in the gap between the two platforms.

8. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 7, characterized in that: The top ends of the two platforms are both provided with cushion blocks (15), and the sample is placed on the two cushion blocks (15) through the restraining assembly.

9. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 8, characterized in that: Both ends of the top surface of the cushion block (15) are provided with limiting ridges, and a plurality of wear-reducing rods (16) are provided on the top of the cushion block (15), and the wear-reducing rods (16) are arranged parallel to the limiting ridges.

10. The jointed rock impact shear test device capable of achieving constant normal stiffness according to claim 2, characterized in that: A protective cover (2) is arranged on the outside of the sample, the protective cover (2) is a transparent structure, and the protective cover (2) is placed on the top of the base.

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