A triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines

Abstract

This invention discloses a triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines, belonging to the field of stress simulation technology for pumped-storage water storage tunnels in abandoned mines. The method includes: firstly, preparing a rock sample and conducting a uniaxial compression test to obtain the maximum destructive load; installing another rock sample in a true triaxial dynamic loading system and applying preload for fastening; applying the maximum principal stress, intermediate principal stress, and minimum principal stress to the rock sample respectively; keeping the triaxial principal stress constant, applying unilateral dynamic water pressure to the rock sample, and simultaneously applying a dynamic load to the rock sample through an impact transmission rod; finally, observing and recording the obtained stress-strain curve data, stress-time curve data, stress-time curve data, and water pressure-time curve data, and conducting analysis based on the recorded curve data and theoretical knowledge of those skilled in the art. This invention can more realistically simulate the actual state of pumped-storage water storage tunnels in abandoned mines.

Description

Technical Field

[0001] This invention relates to the field of stress simulation technology for pumped-storage water storage tunnels in abandoned mines, specifically to a three-dimensional stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines. Background Technology

[0002] With the demands of energy structure transformation and sustainable development, pumped storage, as an important energy storage technology, is playing an increasingly vital role in energy systems. Abandoned mines, due to their abundant underground space and stable geological conditions, have become potential application sites for pumped storage projects. By converting abandoned mines into pumped storage power stations, not only can idle resources be effectively utilized, but the pressure on traditional energy supply can also be alleviated, and the stability and dispatch flexibility of the power system can be improved. Therefore, pumped storage projects in abandoned mines have broad application prospects in the future energy industry.

[0003] In the design and construction of pumped-storage water storage tunnels in abandoned mines, the triaxial stress state borne by the tunnel plays a crucial role in its structural stability and watertightness. The triaxial stress state of the water storage tunnel is mainly influenced by the combined effects of the geostress field of the surrounding rock mass, water pressure, and the excavation stress of the mine itself. Therefore, accurately simulating the triaxial stress state within the tunnel, especially the interaction between water pressure and the rock mass, is essential for assessing the tunnel's stability and design rationality. Although existing technologies employ various rock mechanics testing methods, they often cannot accurately predict the mechanical behavior and failure modes of the rock during the water storage process because they cannot fully simulate the complex water-rock-force interactions within abandoned mine water storage tunnels.

[0004] This shows that the existing technology needs further improvement. Summary of the Invention

[0005] The purpose of this invention is to provide a triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines. This method can reproduce the complex triaxial stress state in the tunnel under laboratory conditions, and can more realistically simulate the actual state of pumped-storage water storage tunnels in abandoned mines.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines includes the following steps:

[0008] a. Prepare cubic specimens as rock samples and conduct uniaxial compression tests on the rock samples to obtain the maximum destructive load of the rock samples;

[0009] b. Install another rock sample in the true triaxial dynamic loading system. The true triaxial dynamic loading system includes a workbench, a main frame, a confining chamber, a vertical loading unit, a horizontal loading unit, a longitudinal loading unit, a lifting device, and a feeding and discharging platform. The vertical loading unit includes an impact transmission rod. The longitudinal loading unit includes a front loading cylinder, a rear loading cylinder, a front loading head, and a rear loading head. The front loading head and the rear loading head are both arranged opposite each other in the confining chamber via a longitudinal loading rod. The front loading cylinder and the rear loading cylinder are symmetrically arranged on the front and rear sides of the main frame via a rotating arm, and apply static loads to the front loading head and the rear loading head synchronously, respectively.

[0010] A square groove is provided on the end face of the front loading head, and a water channel is provided inside the longitudinal loading rod connected to the front loading head. The water channel is connected to a water supply device for providing high-pressure water into the groove.

[0011] c. Apply a preload to the rock sample located in the true triaxial dynamic loading system to fix it; then apply the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3 to the rock sample through the vertical loading unit, the horizontal loading unit, and the longitudinal loading unit, respectively; during the initial loading process, the maximum principal stress σ1 and the intermediate principal stress σ2 are 50% of the maximum failure load described in step a; the minimum principal stress σ3 is 10% of the maximum failure load described in step a; after the loading stabilizes, the maximum principal stress σ1 is adjusted to 80% of the maximum failure load described in step a;

[0012] d. Keeping the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3 unchanged, apply unilateral dynamic water pressure to the rock sample through the aforementioned pre-loading head, and simultaneously apply dynamic load to the rock sample through the impact force transmission rod;

[0013] e. Observe and record the stress-strain curve data, stress-time curve data, stress-time curve data and water pressure-time curve data obtained when the rock sample in the true triaxial dynamic loading system has been destroyed, and observe the failure mode of the rock sample.

[0014] f. Combining theoretical knowledge, we obtain the damage intensity and damage mode of the surrounding rock of abandoned mine pumping and energy storage tunnels at different depths and water pressures.

[0015] In the above-mentioned triaxial stress simulation method applicable to pumping and storage tunnels in abandoned mines, the rock sample in step a has a size of 150mm×150mm×150mm.

[0016] The above-mentioned triaxial stress simulation method applicable to pumping and storage water storage tunnels in abandoned mines, in step b, the vertical loading unit further includes an impact load cylinder, a top loading cylinder, and a top loading head. The impact load cylinder is vertically set at the center of the top of the main frame. There are multiple top loading cylinders. All top loading cylinders are regularly arranged around the impact load cylinder. The execution ends of each top loading cylinder are fixedly connected by a force-gathering block.

[0017] The top loading head is set on the upper side of the confining pressure chamber via a vertical loading rod. The impact transmission rod is coaxially arranged inside the vertical loading rod. The force-gathering block applies a static load to the top loading head via the vertical loading rod. The impact load cylinder applies an impact load to the top loading head via the impact transmission rod, which applies true triaxial stress.

[0018] In the above-mentioned triaxial stress simulation method applicable to pumped storage and water storage tunnels in abandoned mines, in step c, a preload of 10kN is first applied to the rock sample in the Z-axis direction through a vertical loading unit; then, preloads of 10kN are applied to the rock sample in the X-axis direction and Y-axis direction through a longitudinal loading unit and a transverse loading unit, respectively.

[0019] In the above-mentioned triaxial stress simulation method applicable to pumped storage and water storage tunnels in abandoned mines, in step d, the dynamic load applied to the rock sample by the impact transmission rod is 5% of the maximum destructive load in step a.

[0020] In the above-mentioned triaxial stress simulation method applicable to pumped storage and water storage tunnels in abandoned mines, step e is used to determine whether the rock sample is damaged by the stress-strain curve and the water pressure-time change.

[0021] The above-mentioned triaxial stress simulation method, applicable to pumped-storage water storage tunnels in abandoned mines, indicates that the rock sample has been damaged when the maximum principal stress value in the stress-strain curve drops or the water pressure value changes abruptly.

[0022] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0023] The present invention provides a triaxial stress simulation method applicable to pumping and storage tunnels in abandoned mines. Compared with traditional indoor uniaxial crush tests and conventional triaxial crush tests, it can more realistically reflect the stress path during the actual water storage process in the storage tunnel. Compared with true triaxial creep tests, it can greatly reduce the number of test specimens, thereby obtaining more test data in the same amount of time.

[0024] This invention provides a triaxial stress simulation method applicable to pumping and storage tunnels in abandoned mines. By keeping the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3 constant, a unilateral dynamic water pressure is applied to the rock sample through a front loading head, while a dynamic load is applied to the rock sample through an impact force transmission rod. This method can more realistically reflect the stress environment during the actual water storage process in the tunnel. It allows for understanding the triaxial stress state under actual working conditions in a laboratory environment, providing a certain reference for the mechanical behavior and failure mode of rocks under actual working conditions. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 This is a flowchart of a three-dimensional stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines, according to the present invention.

[0027] Figure 2 This is a schematic diagram of the uniaxial compressive force direction of the rock sample of this invention;

[0028] Figure 3 This is a schematic diagram of the triaxial stress on the rock sample of this invention;

[0029] Figure 4 This is a uniaxial compression curve of the rock sample of this invention;

[0030] Figure 5 This is a schematic diagram of the true triaxial seepage disturbance loading stress path of the rock sample of this invention;

[0031] Figure 6 This is a true triaxial seepage disturbance loading stress-time curve of the rock sample of this invention;

[0032] Figure 7 This is a true triaxial seepage disturbance loading water pressure-time curve of the standard rock sample of the present invention;

[0033] Figure 8 This is a perspective view of the combined structure of the confining pressure chamber and related parts of the present invention;

[0034] Figure 9 for Figure 8 Vertical sectional view of the composite structure;

[0035] In the picture:

[0036] 1. Top cover, 2. Clamping flap, 3. Clamping clamp, 4. Square base plate, 5. Stroke cylinder, 6. Impact transmission rod, 7. Vertical loading rod, 8. Horizontal loading rod, 9. Longitudinal loading rod, 10. Return spring, 11. Annular limiting part, 12. Base, 13. Cylinder body, 14. Positioning column, 15. Top loading head, 16. Front loading head, 17. Rear loading head, 18. Waterway, 19. Rock sample, 20. Square groove. Detailed Implementation

[0037] This invention proposes a triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0038] The true triaxial dynamic loading system required by this invention includes a worktable, a main frame, a confining pressure chamber, a vertical loading unit, a horizontal loading unit, a longitudinal loading unit, a lifting device, and a feeding / discharging platform; combined with Figure 8 and Figure 9 As shown, this invention mainly introduces the structure of the confining pressure chamber and its related components.

[0039] The confining chamber is set on the workbench via a liftable linear transfer mechanism. Specifically, the confining chamber includes a base 12, a cylindrical body 13, and a top cover 1. The base 12 is fixed to the upper surface of the linear transfer mechanism and has a frustum-shaped structure. The cylindrical body 13 is a cylindrical structure with openings at both ends and is vertically positioned above the base 12. The upper end of the cylindrical body 13 is fixedly and sealed to the top cover 1, and the lower end of the cylindrical body 13 is sealed to the base 12 and fixedly connected to the base 12 via a clamping assembly.

[0040] The confining pressure chamber is connected to the water supply device through a pipeline. After the confining pressure chamber is filled with high-pressure water, rock sample 19 can simulate a uniaxial loading test under the action of dynamic and static confining pressure.

[0041] The clamping assembly includes four clips 2 and four clamps 3. Each clip 2 is a 1 / 4 arc shape with a groove on the inner side. The four clips 2 are spliced ​​together to form a ring, which is clamped at the connection between the base 12 and the lower end of the cylinder 13. The clamp 3 is sleeved on the outside of the four clips 2. The clamping force of the clamp 3 tightens the four clips 2, fixing the lower end of the cylinder 13 to the base 12.

[0042] The vertical loading unit includes an impact load cylinder, a top loading cylinder, a top loading head 15, and an impact transmission rod 6. The impact load cylinder is vertically fixedly installed at the center of the top of the main frame. There are four top loading cylinders 52, which are vertically and regularly arranged around the impact load cylinder. Both the impact load cylinder and the top loading cylinder are supplied with oil and returned by a hydraulic station.

[0043] The top loading head 15 is installed on the upper side of the confining pressure chamber via a vertical loading rod 7. The vertical loading rod 7 has an impact transmission rod 6 arranged coaxially with it. The impact transmission rod 6 slides with the vertical loading rod 7 outside it. The impact load cylinder 51 applies an impact load to the top loading head 15 through the impact transmission rod 6. In turn, the top loading head 15 applies a vertical static load to the rock sample 19, and the impact transmission rod 6 applies a vertical impact load to the rock sample 19 through the top loading head 15.

[0044] The lateral loading unit includes loading cylinders, a left loading head, and a right loading head located on the left and right sides. The left and right loading cylinders are symmetrically fixed on the left and right sides of the main frame. Both the left and right loading cylinders are supplied with oil and returned by a hydraulic station.

[0045] Both the left and right loading heads are positioned opposite each other inside the confining pressure chamber via a transverse loading rod 8. Specifically, the two transverse loading rods 8 are coaxially aligned and pass through the left and right walls of the confining pressure chamber, with each transverse loading rod 8 slidingly engaging with the side walls of the confining pressure chamber along its axial direction. The opposite sides of the left and right loading heads are fixedly connected to the opposite ends of the two transverse loading rods 8. The two transverse loading rods 8 are located at one end outside the confining pressure chamber and are respectively inserted into the two transverse external loading heads at the ends of the transverse force transmission rods. The left and right loading cylinders drive the two transverse external loading heads to move synchronously relative to each other, thereby applying transverse loading to the rock sample 19 by driving the left and right loading heads to move synchronously relative to each other via the transverse loading rods 8.

[0046] The vertical loading unit includes an impact transmission rod, and the longitudinal loading unit includes a front loading cylinder, a rear loading cylinder, a front loading head 16, and a rear loading head 17. The front loading head 16 and the rear loading head 17 are both arranged opposite each other in the confining chamber via a longitudinal loading rod 9. The front loading cylinder and the rear loading cylinder are symmetrically arranged on the front and rear sides of the main frame via a rotating arm, and apply static loads to the front loading head and the rear loading head synchronously, respectively.

[0047] A square groove 20 is provided on the end face of the front loading head, and a water channel 18 is provided inside the longitudinal loading rod connected to the front loading head. The water channel is connected to a water supply device for providing high-pressure water to the groove.

[0048] The positioning pin 14 is vertically fixed to the center of the bottom of the square base plate 4, and its lower end can be inserted into the positioning hole to fix the square base plate 4 to the worktable. Four stroke cylinders 5 are respectively installed on the upper surface of the four corners of the square base plate 4. The four stroke cylinders 5 drive the four rollers to be housed inside the square base plate 4. The square base plate 4 descends until its bottom is in contact with the surface of the worktable, the positioning pin is located in the positioning hole of the worktable, and the square base plate 4 is fixed to the worktable.

[0049] Each of the two transverse loading rods 8 and the two longitudinal loading rods 9 is fitted with a return spring 10. All return springs 10 are located on the outside of the confining pressure chamber. Both the transverse loading rods 8 and the longitudinal loading rods 9 are provided with annular limiting parts 11 to limit the return springs 10. In the unloaded state, the return springs 10 drive the corresponding transverse loading rod 8 or longitudinal loading rod 9 to move outwards, separating the left loading head, right loading head, front loading head, and rear loading head from the rock sample. Before placing the rock sample inside the confining pressure chamber, the left loading head, right loading head, front loading head, and rear loading head are in an outward-expanding state, facilitating the placement of the rock sample inside the confining pressure chamber. The rock sample used in this invention is a cubic specimen.

[0050] The following is a detailed description of the triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines.

[0051] A triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines, such as... Figure 1 As shown, the specific steps include:

[0052] The first step is to prepare several rock samples of the same shape and size, which are cubic in shape. Natural rock samples are obtained from the engineering site and processed into cubic shapes through drilling, cutting and grinding. The specifications of the rock samples are 150mm×150mm×150mm. The length error of the rock samples does not exceed 0.1mm. The allowable deviation of the unevenness of the two ends of the rock samples is ±0.02mm. Rocks with similar wave velocities are selected as test samples using an acoustic detection system. If necessary, the loading direction can be identified by marking the rock samples, such as the loading in the X-axis, Y-axis and Z-axis directions involved in this invention.

[0053] The second step is to select one of the rock samples and perform a uniaxial compression test on it (e.g., ...). Figure 2 As shown in the figure, the maximum failure load was obtained to provide a reference for subsequent loading. The obtained uniaxial compressive stress-strain curve is shown in the figure. Figure 4 As shown.

[0054] Third step: Select another rock sample and install it in the confining pressure chamber, applying preload to fix the rock sample; the loading method is as follows. Figure 3 As shown, Figure 3 In the figure, σd and σs represent the dynamic load and dynamic water pressure, respectively. The loading path is as follows: Figure 5 As shown, the rock sample is a regular cube to ensure it can undergo a true triaxial test. The cubic rock sample is fixed with a preload of 10 kN.

[0055] like Figure 3As shown, true triaxial stresses σ1, σ2, and σ3 were independently applied to cubic rock samples, where σ1 is the maximum principal stress, σ2 is the intermediate principal stress, and σ3 is the minimum principal stress. σ1, σ2, and σ3 were applied to 50% of the initial principal stress level. Using a stress loading control method, the cubic rock samples were simultaneously and independently loaded with true triaxial stresses σ1, σ2, and σ3 according to the loading method recommended in the "Code for True Triaxial Testing of Rocks" until all three stresses reached the set initial principal stress level.

[0056] Step 4: Keep the intermediate principal stress σ2 unchanged, and apply the maximum principal stress σ1 until the maximum principal stress σ1 reaches the set maximum principal stress level; use the stress loading control method to apply the maximum principal stress σ1 at the same loading rate as in Step 3 until the set maximum principal stress level is reached; where the set maximum principal stress level is 80% of the maximum failure load of the rock sample measured in Step 2.

[0057] Step 5: Keeping the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3 unchanged, apply a suitable unilateral dynamic water pressure to the rock sample through the front loading head (e.g., sinusoidal loading, with a trough of 0.1 MPa, a peak of 2 MPa, and a frequency of 0.01 Hz) (which can be changed according to experimental needs). At the same time as applying the water pressure, apply a dynamic load to the rock sample using an impact transmission rod (e.g., sinusoidal loading, with a trough of 0, a peak of 5% of the maximum failure load of the rock sample obtained in Step 2, and a frequency of 5 Hz) (which can be changed according to experimental needs).

[0058] Step 6: Observe and record the stress-strain curve data obtained during the experiment. Determine whether stress-strain curves, strain-time curves, and hydrostatic test curve data are needed based on the research situation. The stress-time curve data can quickly show the true triaxial strength of the test, the strain-time curve data is helpful for the actual deformation and failure in engineering, the stress-strain curve data can reflect the overall mechanical properties of the tested rock, and the hydrostatic test curve can reflect the changes in internal fractures of the rock.

[0059] The test ends when the rock sample in the true triaxial dynamic loading system has been damaged, and the failure mode of the rock sample is observed; preferably, the failure of the rock sample is determined by observing the stress-strain curve and the change in water pressure over time.

[0060] Step 7: Combining theoretical knowledge, we obtain the damage intensity and damage mode of the surrounding rock of abandoned mine pumping and energy storage tunnels at different depths and water pressures.

[0061] The loading path and the resulting stress-time curve of cyclic loading in this embodiment are as follows: Figure 6 As shown in the figure, the water pressure-time curve is as follows: Figure 7 As shown.

[0062] In summary, this invention can realistically simulate the stress process of the surrounding rock during the water storage process in abandoned mine water storage tunnels. Although this invention focuses on abandoned mines, as is known to those skilled in the art, it can also be applied to other similar scenarios (such as underground reservoirs, tunnel surrounding rock, etc.) or different geological conditions.

[0063] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0064] Those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection of the claims of this application.

Claims

1. A triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines, characterized in that, The steps are as follows: a. Prepare cubic specimens as rock samples and conduct uniaxial compression tests on the rock samples to obtain the maximum destructive load of the rock samples; b. Install another rock sample in the true triaxial dynamic loading system. The true triaxial dynamic loading system includes a workbench, a main frame, a confining chamber, a vertical loading unit, a horizontal loading unit, a longitudinal loading unit, a lifting device, and a feeding and discharging platform. The vertical loading unit includes an impact transmission rod. The longitudinal loading unit includes a front loading cylinder, a rear loading cylinder, a front loading head, and a rear loading head. The front loading head and the rear loading head are both arranged opposite each other in the confining chamber via a longitudinal loading rod. The front loading cylinder and the rear loading cylinder are symmetrically arranged on the front and rear sides of the main frame via a rotating arm, and apply static loads to the front loading head and the rear loading head synchronously, respectively. A square groove is provided on the end face of the front loading head, and a water channel is provided inside the longitudinal loading rod connected to the front loading head. The water channel is connected to a water supply device for providing high-pressure water into the groove. c. Apply a preload to the rock sample located in the true triaxial dynamic loading system to fix it; then apply the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3 to the rock sample through the vertical loading unit, the horizontal loading unit, and the longitudinal loading unit, respectively; during the initial loading process, the maximum principal stress σ1 and the intermediate principal stress σ2 are 50% of the maximum failure load described in step a; the minimum principal stress σ3 is 10% of the maximum failure load described in step a; after the loading stabilizes, the maximum principal stress σ1 is adjusted to 80% of the maximum failure load described in step a; d. Keeping the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3 unchanged, apply unilateral dynamic water pressure to the rock sample through the aforementioned pre-loading head, and simultaneously apply dynamic load to the rock sample through the impact force transmission rod; e. Observe and record the stress-strain curve data, stress-time curve data, stress-time curve data and water pressure-time curve data obtained when the rock sample in the true triaxial dynamic loading system has been destroyed, and observe the failure mode of the rock sample. f. Combining theoretical knowledge, we obtain the damage intensity and damage mode of the surrounding rock of abandoned mine pumping and energy storage tunnels at different depths and water pressures.

2. The triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines according to claim 1, characterized in that: In step a, the rock sample has dimensions of 150mm × 150mm × 150mm.

3. The triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines according to claim 1, characterized in that: In step b, the vertical loading unit also includes an impact load cylinder, a top loading cylinder, and a top loading head. The impact load cylinder is vertically set at the center of the top of the main frame. There are multiple top loading cylinders, and all the top loading cylinders are regularly arranged around the impact load cylinder. The execution ends of each top loading cylinder are fixedly connected by a force-gathering block. The top loading head is set on the upper side of the confining pressure chamber via a vertical loading rod. The impact transmission rod is coaxially arranged inside the vertical loading rod. The force-gathering block applies a static load to the top loading head via the vertical loading rod. The impact load cylinder applies an impact load to the top loading head via the impact transmission rod, which applies true triaxial stress.

4. The triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines according to claim 1, characterized in that: In step c, a preload of 10 kN is first applied to the rock sample in the Z-axis direction through the vertical loading unit; then, a preload of 10 kN is applied to the rock sample in the X-axis direction and the Y-axis direction through the longitudinal loading unit and the transverse loading unit, respectively.

5. The triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines according to claim 1, characterized in that: In step d, the dynamic load applied to the rock sample by the impact transmission rod is 5% of the maximum destructive load in step a.

6. The triaxial stress simulation method applicable to pumped-storage water storage tunnels in abandoned mines according to claim 1, characterized in that: In step e, the rock sample is determined to be damaged by the stress-strain curve and the water pressure-time change.

7. A triaxial stress simulation method for pumped-storage water storage tunnels in abandoned mines according to claim 6, characterized in that: When the maximum principal stress value in the stress-strain curve drops or the water pressure value changes abruptly, it indicates that the rock sample has been destroyed.

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