A test device for simulating soft rock disintegration under stress-moisture cycle coupling

Abstract

This invention provides an experimental apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling, comprising a confining pressure loading module, an axial loading module, and a wet-dry cycle module. The invention achieves simultaneous application of confining pressure and overlying stress to the soft rock sample through the test chamber and the axial loading module, simulating the actual stress state of the bank slope rock mass. The wet-dry cycle module performs periodic humidification and drying treatment on the sample, reproducing the alternating wet and dry environment of the drawdown zone, thereby realizing indoor simulation of the soft rock collapse process under the coupled action of stress field and wet-dry environment. This invention can accurately test the collapse law and deterioration characteristics of soft rock under complex working conditions, providing experimental basis and technical support for the long-term stability evaluation and engineering protection of soft rock bank slopes in the drawdown zone. The apparatus has a reasonable structure and strong controllability of working conditions, providing a reliable experimental platform for in-depth understanding of the soft rock collapse mechanism in the drawdown zone, and has significant academic research value and engineering application prospects.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, specifically to an experimental device for simulating soft rock collapse under stress-wet-dry cycle coupling. Background Technology

[0002] Soft rock is widely distributed in nature, and its mechanical properties are extremely sensitive to environmental changes. Especially in slope engineering, tunnel engineering, and hydraulic engineering, soft rock is often subjected to complex geostress environments and periodic wet-dry cycles. Traditional testing devices mostly only consider wet-dry cycles or stress loading factors individually, making it difficult to accurately reflect the impact of the coupling of stress and seepage fields on the soft rock disintegration process in actual engineering projects. Therefore, developing an experimental device capable of simultaneously simulating confining pressure, overlying stress, and the coupled effects of wet-dry cycles is of great significance for revealing the soft rock disintegration mechanism and assessing engineering stability. Summary of the Invention

[0003] This application provides a test device for simulating soft rock collapse under stress-wet-dry cycle coupling. It integrates a confining pressure loading test module, an axial loading module, and a wet-dry cycle module, which can simultaneously realize the coupled simulation of confining pressure, overlying stress, and wet-dry cycle, thus overcoming the limitations of single-factor simulation in existing technologies and reproducing the real stress environment of soft rock slopes.

[0004] The objective of this invention is achieved as follows: An experimental device for simulating soft rock collapse under stress-wet-dry cycle coupling includes a confining pressure loading test module, an axial loading module, and a wet-dry cycle module; The confining pressure loading test module includes a test box mounted on a fixed frame. The test box has a flexible confining pressure transfer sleeve distributed longitudinally inside. The flexible confining pressure transfer sleeve has a first cavity inside. The test box and the flexible confining pressure transfer sleeve form a sealed second cavity. The loading interface and the unloading interface on the wall of the second cavity are respectively connected to the hydraulic control system. The axial loading module includes a pressure-stabilizing axial pressurizing unit installed on the top of the flexible confining pressure transmission sleeve. The pressure-stabilizing axial pressurizing unit is connected to the loading column, and the loading column is provided with a tailwater channel communicating with the first cavity. During operation, the pressure-stabilizing axial pressurizing unit outputs downward pressure, and the pressure is applied to the top of the rock sample fitted in the first cavity after passing through the loading column. The dry-wet cycle module includes a pressure-adjustable water supply system. The bottom of the flexible confining pressure transmission sleeve is detachably mounted with a support. The support is provided with a water inlet communicating with the first cavity. The water inlet is connected to the pressure-adjustable water supply system through a water supply and drainage pipe. The water supply and drainage pipe is provided with a drain outlet, and the drain outlet is provided with a drain switch. Furthermore, it also includes a top permeable stone, an upper filter paper, a bottom permeable stone, and a lower filter paper; During operation, the top permeable stone and the upper filter paper are placed sequentially from top to bottom between the loading column and the rock sample, while the lower filter paper and the bottom permeable stone are placed sequentially from top to bottom between the rock sample and the support.

[0005] Furthermore, the support is provided with a conical chamber that is larger at the top and smaller at the bottom. The water inlet is connected to the first chamber through the conical chamber, and the bottom permeable stone is adapted to and installed in the conical chamber.

[0006] Furthermore, the pressure-stabilizing axial pressurization unit is a hydraulic cylinder, and the loading column is connected to the moving end of the hydraulic cylinder.

[0007] Furthermore, the pressure-adjustable water supply system includes a water storage tank connected to the water inlet via the water supply and drainage pipe. The water storage tank is equipped with a water inlet connected to an external water source and a pressure interface connected to an external pressure instrument.

[0008] A test method for an experimental apparatus simulating soft rock collapse under stress-wet-dry cycle coupling includes the following steps: S1. Sample loading: Remove the support, load the rock sample into the flexible confining pressure transfer sleeve, and reinstall the support. Then, install the test chamber on the fixed frame and connect the water inlet to the water supply system. S2. Pressurization: Oil is injected into the second chamber through the hydraulic control system. After it is full, the pressure is slowly increased in stages. The increased oil pressure in the second chamber acts on the flexible confining pressure transmission sleeve and is transmitted to the rock sample inside it to achieve the application of confining pressure. After the confining pressure reaches the target value and stabilizes, the output pressure of the pressure-stabilizing axial pressurization unit is adjusted to slowly apply axial pressure to the rock sample in stages until the set overburden stress value is reached and the pressure is stabilized. S3. Humidification: Based on the actual working conditions of the bank slope, set the water supply pressure of the adjustable water supply system and inject water into the first chamber to simulate the water pressure environment corresponding to the actual water depth. During the water injection process, ensure that the drain switch is kept closed. When the tailwater flow rate in the tailwater channel is stable, the pore water pressure inside the rock sample reaches a stable state. Determine the humidification time based on the actual engineering conditions of the bank slope. S4. Drying: Turn off the pressure-adjustable water supply system and stop the water supply. Open the drain switch. The water in the first chamber will be discharged from the drain outlet, thus drying the rock sample. The drying time should be determined according to the actual engineering needs. S5. Cycle: Based on the actual engineering requirements of the bank slope, repeat the above S3 wetting step and S4 drying step to complete the stress-wet-dry cycle coupling test a set number of times. S6. Sampling and Evaluation: After the required number of cyclic tests are completed and the rock sample is stable, the axial pressure is slowly withdrawn, and the oil pressure in the second chamber is slowly reduced by controlling the hydraulic control system. After the axial pressure and confining pressure are completely removed, the support is removed, the rock sample is taken out and its disintegration is collected, and finally the disintegration characteristics of the rock sample are systematically evaluated.

[0009] The present invention has the following beneficial effects: 1. This invention integrates confining pressure loading, axial loading, and wet-dry cycle systems, which can simultaneously realize the coupled simulation of confining pressure, overlying stress, and wet-dry cycle, solving the limitations of single-factor simulation in existing technologies and reproducing the real stress environment of soft rock slopes.

[0010] 2. This invention uses a flexible confining pressure transfer sleeve, which applies hydraulic pressure evenly to the side of the rock sample, avoiding stress concentration caused by rigid loading. This allows for a more accurate simulation of the uniform stress environment of natural rock masses, ensuring the reliability and repeatability of the test loading.

[0011] 3. The present invention sets a permeable stone and filter paper combination structure at both ends of the rock sample, which not only ensures water seepage and stress transmission, but also effectively intercepts the fine debris generated by disintegration, prevents pipeline blockage and rock sample quality loss, and ensures the continuity and data accuracy of multiple wet and dry cycle tests.

[0012] 4. In this invention, both confining pressure and axial pressure are applied in stages and slowly to avoid non-targeted damage to the rock sample due to sudden pressure changes. After the test, the pressure is also released slowly to facilitate the complete collection of disintegration products and provide reliable samples for subsequent evaluation of disintegration characteristics (such as disintegration rate, particle size analysis, etc.).

[0013] 5. This invention is suitable for various soft rock test scenarios. By adjusting the confining pressure, axial pressure, and wet-dry cycle parameters, it can simulate different actual working conditions, overcome the problem of limited applicability of existing technologies, and has both scientific research value and engineering application value, with broad prospects for promotion. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Figure 1 A schematic diagram of the structure of an experimental device for simulating soft rock collapse under stress-wet-dry cycle coupling provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of the test chamber provided in an embodiment of the present invention; Figure 3 The test chamber provided in this embodiment of the invention is shown in a cross-sectional view of the working state of the wet-dry cycle module; In the diagram: 1. Fixed frame; 2. Test chamber; 2a. Upper base plate; 2b. Lower base plate; 3. Flexible confining pressure transfer sleeve; 3a. First cavity; 3b. Second cavity; 3b1. Loading interface; 3b2. Pressure relief interface; 3c. Upper interface; 3d. Lower interface; 4. Pressure-stabilizing axial pressurization unit; 5. Loading column; 5a. Tailwater channel; 5b. Tailwater pipe; 6. Rock sample; 7. Support seat; 7a. Water inlet; 7b. Conical chamber; 8. Water supply and drainage pipe; 8a. Drainage outlet; 8b. Drainage switch; 9. Top permeable stone; 10. Upper filter paper; 11. Bottom permeable stone; 12. Lower filter paper; 13. Water storage tank; 13a. Water inlet; 13a1. Air pressure interface; 20. Hydraulic control system. Detailed Implementation

[0016] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0017] To achieve the above-mentioned technical features, the objective of this invention is as follows: Example 1: See appendix Figure 1-3An experimental device for simulating soft rock collapse under stress-wet-dry cycle coupling includes a confining pressure loading test module, an axial loading module, and a wet-dry cycle module. The confining pressure loading test module includes a test chamber 2 mounted on a fixed frame 1. The test chamber 2 has a flexible confining pressure transfer sleeve 3 distributed longitudinally inside. The upper bottom plate 2a and lower bottom plate 2b of the test chamber 2 are connected to the upper interface 3c and lower interface 3d of the flexible confining pressure transfer sleeve 3, respectively. The flexible confining pressure transfer sleeve 3 has a first cavity 3a inside. The upper interface 3c and lower interface 3d of the flexible confining pressure transfer sleeve 3 are connected to the test chamber 2. All connection points of the test chamber 2 are equipped with sealing wing rings to ensure the overall structure is sealed. The test chamber 2 and the flexible confining pressure transmission sleeve 3 form a sealed second cavity 3b. The loading interface 3b1 and the pressure relief interface 3b2 on the wall of the second cavity 3b are respectively connected to the hydraulic control system 20. The axial loading module includes a pressure-stabilizing axial pressurizing unit 4 installed on the top of the flexible confining pressure transmission sleeve 3. The pressure-stabilizing axial pressurizing unit 4 is connected to the loading column 5, and the loading column 5 is located between the pressure-stabilizing axial pressurizing unit 4 and the flexible confining pressure transmission sleeve 3. The test chamber 2 and the loading column 5 form a sealed connection. The loading column 5 is equipped with a tailwater channel 5a that communicates with the first cavity 3a, and the tailwater channel 5a is connected to the tailwater pipe 5b. The wet-dry circulation module includes a pressure-adjustable water supply system. The bottom of the flexible confining pressure transmission sleeve 3 is detachably equipped with a support 7. The support 7 is equipped with a water inlet 7a that communicates with the first cavity 3a. The water inlet 7a is connected to the pressure-adjustable water supply system through a water supply and drainage pipe 8. The water supply and drainage pipe 8 is equipped with a drain outlet 8a, and the drain outlet 8a is equipped with a drain switch 8b. During operation, the rock sample 6 is pre-placed in the flexible confining pressure transmission sleeve 3. Pressurized water is injected into the flexible confining pressure transmission sleeve 3 through the pressure-adjustable water supply system to simulate the water pressure environment generated under the action of near-shore water depth. By opening a tailwater channel in the loading column, the tailwater overflowing from the top of the flexible confining pressure transmission sleeve 3 can be transported to the tailwater pipe 5b, so that the rock sample 6 is kept continuously moist and the internal pore water is ensured to circulate, thereby simulating the internal pore water seepage characteristics of the slope rock mass under immersion conditions. The hydraulic control system 20 gradually pressurizes the hydraulic oil in the second chamber 3b in stages. The increased internal oil pressure acts on the flexible confining pressure transmission sleeve 3 and is transmitted to the rock sample 6 inside, thus applying confining pressure. A downward pressure is output through the pressure-stabilized axial pressurization unit 4, and this pressure, after passing through the loading column 5, acts on the top of the rock sample 6 fitted inside the first chamber 3a, simulating the overburden stress generated by the rock mass of an actual slope due to the rock strata's own weight or external loads. This invention integrates the confining pressure loading test module, the axial loading module, and the wet-dry cycle module, enabling simultaneous coupled simulation of confining pressure, overburden stress, and wet-dry cycles. This overcomes the limitations of existing single-factor simulations and reproduces the true stress environment of soft rock slopes.

[0018] As one implementation method, this embodiment also includes a top permeable stone 9, an upper filter paper 10, a bottom permeable stone 11, and a lower filter paper 12. During operation, the top permeable stone 9 and the upper filter paper 10 are placed sequentially from top to bottom between the loading column 5 and the rock sample 6, which can realize the effective transmission of water flow and axial stress, and also prevent the rock sample from disintegrating and falling off. The lower filter paper 12 and the bottom permeable stone 11 are placed sequentially from top to bottom between the rock sample 6 and the support seat 7, which can ensure the flow of water, form a stable structural support for the rock sample, and prevent the loss of rock sample debris.

[0019] In one embodiment, the support 7 has a conical chamber 7b that is wider at the top and narrower at the bottom. The water inlet 7a is connected to the first cavity 3a through the conical chamber 7b. The bottom permeable stone 11 is adapted to and installed in the conical chamber 7b. The conical chamber and the bottom permeable stone of the conical structure are designed to ensure that the water flow is evenly diffused into the second cavity 3b.

[0020] In one implementation method, in this embodiment, the pressure-stabilizing axial pressurization unit 4 is a hydraulic cylinder, and the loading column 5 is connected to the moving end of the hydraulic cylinder. During operation, a constant downward pressure is output through the hydraulic cylinder and transmitted through the loading column to act on the rock sample 6 inside the flexible confining pressure transmission sleeve 3, so as to simulate the overburden stress generated by the actual slope rock mass due to the self-weight of the rock strata or external loads.

[0021] In one implementation method, the pressure-adjustable water supply system includes a water storage tank 13 connected to a water inlet 7a via a water supply and drainage pipe 8. The water storage tank 13 is equipped with a water inlet 13a connected to an external water source and a pressure interface 13b connected to an external pressure instrument. During humidification of the sample: the water inlet 13a1 is opened, the drainage switch 8b is closed, and water is injected into the water storage tank 13. Once the water volume in the tank meets the experimental requirements, the water inlet 13a1 is closed. The pressure interface 13b is then connected to the external pressure instrument, and the inside of the water storage tank 13 is pressurized according to the actual working conditions of the bank slope to simulate the water pressure environment corresponding to the actual water depth. When the tailwater flow rate in the tailwater pipe 5b stabilizes, the pore water pressure inside the rock sample 6 in the flexible confining pressure transmission sleeve 3 reaches a stable state. The humidification duration is determined based on the actual engineering conditions of the bank slope. During the drying process of the sample: pause the application of air pressure inside the water storage tank 13, and after the pressure inside the tank is reduced to normal pressure, open the drain switch 8a to drain the remaining water in the water storage tank 13; apply air pressure to the inside of the water storage tank 13 again, and the air flows through the drain outlet and generates negative pressure in the pipeline. The negative pressure absorbs the residual moisture inside the rock sample 6 to accelerate the drying of the rock sample.

[0022] Example 2: A test method for a model test device simulating the unloading and tunneling process of tunnel excavation includes the following steps: S1. Sample loading: Remove the support 7, and load the top permeable stone 9, the upper filter paper 10, and the rock sample 9 to be tested for stress-wet-dry cycle coupling into the flexible confining pressure transfer sleeve 3 from top to bottom; after loading the bottom permeable stone 11 and the lower filter paper 12 into the support 7, put the support 7 back into the test chamber 2 to ensure a stable connection; install the loaded test chamber 2 on the fixed frame 1 and connect it to the water supply system via the water inlet 7a. S2, Pressurization: Oil is injected into the second chamber 3b through the hydraulic control system 20. After it is full, the pressure is slowly increased in stages. The increased oil pressure in the second chamber 3b acts on the flexible confining pressure transmission sleeve 3 and is transmitted to the rock sample 6 inside it to achieve the application of confining pressure. After the confining pressure reaches the target value and stabilizes, the output pressure of the pressure-stabilizing axial pressurization unit 4 is adjusted to slowly apply axial pressure to the rock sample 6 in stages until the set overburden stress value is reached and the pressure is stabilized. S3. Humidification: Connect the water inlet 13a to an external water source, open the water inlet switch 13a1 to fill the water tank 13 with water, and ensure that the drain switch 8b remains closed during the water filling process; after the water volume in the water tank 13 meets the test requirements, close the water inlet switch 13a1; connect the air pressure interface 13b to an external air pressure instrument, and pressurize the inside of the water tank 13 according to the actual working conditions of the bank slope to simulate the water pressure environment corresponding to the actual water depth; when the tailwater flow rate in the tailwater pipe 5b is stable, it indicates that the pore water pressure inside the rock sample 6 has reached a stable state, and the wetting time is determined according to the actual engineering conditions of the bank slope. S4. Drying: Stop applying air pressure to the inside of water storage tank 13. After the pressure inside the tank is reduced to normal pressure, open the drain switch 8b to drain the remaining water in water storage tank 310. Apply air pressure to the inside of water storage tank 13 again. Air flows through the drain port 8a and generates negative pressure in the pipeline. The negative pressure absorbs the residual moisture inside rock sample 6, thus drying the rock sample. Determine the drying time according to the actual engineering needs. S5. Cycle: Based on the actual engineering requirements of the bank slope, repeat the above S3 wetting step and S4 drying step to complete the stress-wet-dry cycle coupling test a set number of times. S6. Sampling and Evaluation: After the required number of cyclic tests are completed and the rock sample 6 is stable, the axial pressure is slowly withdrawn, and at the same time, the oil pressure in the second chamber 3b is slowly reduced by controlling the hydraulic control system 20. After the axial pressure and confining pressure are completely removed, the support seat 7 is opened, the rock sample 6 is taken out and its disintegration is collected, and finally the disintegration characteristics of the rock sample 6 are systematically evaluated.

[0023] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A test apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling, characterized in that: Includes a confining pressure loading test module, an axial loading module, and a wet-dry cycle module; The confining pressure loading test module includes a test box mounted on a fixed frame. The test box has a flexible confining pressure transfer sleeve distributed longitudinally inside. The flexible confining pressure transfer sleeve has a first cavity inside. The test box and the flexible confining pressure transfer sleeve form a sealed second cavity. The loading interface and the unloading interface on the wall of the second cavity are respectively connected to the hydraulic control system. The axial loading module includes a pressure-stabilizing axial pressurizing unit installed on the top of the flexible confining pressure transmission sleeve. The pressure-stabilizing axial pressurizing unit is connected to the loading column, and the loading column is provided with a tailwater channel communicating with the first cavity. During operation, the pressure-stabilizing axial pressurizing unit outputs downward pressure, and the pressure is applied to the top of the rock sample fitted in the first cavity after passing through the loading column. The dry-wet cycle module includes a pressure-adjustable water supply system. The bottom of the flexible confining pressure transmission sleeve is detachably mounted with a support. The support is provided with a water inlet communicating with the first cavity. The water inlet is connected to the pressure-adjustable water supply system through a water supply and drainage pipe. The water supply and drainage pipe is provided with a drain outlet, and the drain outlet is provided with a drain switch.

2. The experimental apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling as described in claim 1, characterized in that: It also includes a top permeable stone, an upper filter paper, a bottom permeable stone, and a lower filter paper; During operation, the top permeable stone and the upper filter paper are placed sequentially from top to bottom between the loading column and the rock sample, while the lower filter paper and the bottom permeable stone are placed sequentially from top to bottom between the rock sample and the support.

3. The experimental apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling as described in claim 2, characterized in that: The support base is provided with a conical cavity that is larger at the top and smaller at the bottom. The water inlet is connected to the first cavity through the conical cavity. The bottom permeable stone is adapted to the conical cavity and installed therein.

4. The experimental apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling as described in claim 1, characterized in that: The pressure-stabilizing axial pressurization unit is a hydraulic cylinder, and the loading column is connected to the moving end of the hydraulic cylinder.

5. The experimental apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling as described in claim 1, characterized in that: The pressure-adjustable water supply system includes a water storage tank connected to the water inlet via the water supply and drainage pipe. The water storage tank is equipped with a water inlet connected to an external water source and a pressure interface connected to an external pressure instrument.

6. The test method for the test apparatus for simulating soft rock collapse under stress-wet-dry cycle coupling according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Sample loading: Remove the support, load the rock sample into the flexible confining pressure transfer sleeve, and reinstall the support. Then, install the test chamber on the fixed frame and connect the water inlet to the water supply system. S2. Pressurization: Oil is injected into the second chamber through the hydraulic control system. After it is full, the pressure is slowly increased in stages. The increased oil pressure in the second chamber acts on the flexible confining pressure transmission sleeve and is transmitted to the rock sample inside it to achieve the application of confining pressure. After the confining pressure reaches the target value and stabilizes, the output pressure of the pressure-stabilizing axial pressurization unit is adjusted to slowly apply axial pressure to the rock sample in stages until the set overburden stress value is reached and the pressure is stabilized. S3. Humidification: Based on the actual working conditions of the bank slope, set the water supply pressure of the adjustable water supply system and inject water into the first chamber to simulate the water pressure environment corresponding to the actual water depth. During the water injection process, ensure that the drain switch is kept closed. When the tailwater flow rate in the tailwater channel is stable, the pore water pressure inside the rock sample reaches a stable state. Determine the humidification time based on the actual engineering conditions of the bank slope. S4. Drying: Turn off the pressure-adjustable water supply system and stop the water supply. Open the drain switch. The water in the first chamber will be discharged from the drain outlet, thus drying the rock sample. The drying time should be determined according to the actual engineering needs. S5. Cycle: Based on the actual engineering requirements of the bank slope, repeat the above S3 wetting step and S4 drying step to complete the stress-wet-dry cycle coupling test a set number of times. S6. Sampling and Evaluation: After the required number of cyclic tests are completed and the rock sample is stable, the axial pressure is slowly withdrawn, and the oil pressure in the second chamber is slowly reduced by controlling the hydraulic control system. After the axial pressure and confining pressure are completely removed, the support is removed, the rock sample is taken out and its disintegration is collected, and finally the disintegration characteristics of the rock sample are systematically evaluated.

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