Dynamic characterization test system and method for degradation of rock mass in hydro-fluctuation zone

Abstract

The invention belongs to the technical field of geotechnical tests, and particularly discloses a dynamic characterization test system and method for degradation of rock mass in a hydro-fluctuation zone, and the system comprises a nuclear magnetic resonance tester, a nuclear magnetic core holder, a stress loading system, a fluid injection system, a solution collection system and a data processing system; the nuclear magnetic core holder comprises a cover body, an isolation plate, a shell, a heating belt, a gasket and a base, wherein the cover body and the base are detachably arranged at the upper end and the lower end of the shell respectively; the top of the cover body is connected with an oil inlet pipe, one side of the base is connected with a liquid outlet pipe, the two sides of the shell wrap the heating belt, one side of the shell is connected with the liquid inlet pipe, the isolation plate and the gasket are arranged in the shell, and the shell is used for containing a rock core. According to the invention, the dynamic influence rule of the dry-wet cycle effect on the rock mass pore-permeability characteristic under the conditions of stress loading and flowing water can be directly obtained.

Description

Technical Field

[0001] The invention relates to the technical field of rock and soil testing, and in particular to a dynamic characterization test system and method for rock mass degradation in a drawdown zone. Background Art

[0002] During the normal operation of a reservoir, a drawdown zone is formed along the shore of the reservoir due to the periodic fluctuation of the water level. For example, in the Three Gorges Reservoir, the water level in front of the reservoir dam is 175-145-175 meters, forming a drawdown zone about 600 kilometers long and 30 meters high on both sides. However, under the influence of the periodic fluctuation of the water level, the rock mass in the drawdown zone will experience physical, chemical and biological weathering degradation, which will weaken the rock structure and reduce its strength, further causing geological disasters and posing a threat to the stability of the reservoir bank and the safe operation of the reservoir. Therefore, the degradation simulation and dynamic characterization of the rock mass in the drawdown zone are of great practical significance for the prediction of rock mass degradation and the prevention and control of geological disasters on the reservoir bank.

[0003] The degradation of rock mass in the drawdown zone is the result of the combined action of multiple factors, among which the dry-wet cycle and scouring and dissolution of water on the rock mass are important causes of its degradation. In this process, the rock mass is subject to the combined action of the static and dynamic water pressures of the river water. At the same time, the load of the overlying rock strata on the bank of the reservoir on the drawdown zone will also accelerate the degradation process of the rock mass, thus forming landslide and collapse disasters. Therefore, the simulation of rock mass degradation in the drawdown zone needs to comprehensively consider the combined action of the stress of the overlying rock strata and the dynamic water pressure of the river scouring.

[0004] Chinese patent application CN112903467A discloses a test device and method for rock damage under dry-wet cycle coupled confining pressure. The device includes a test box, an isolation plate, a pressurizing device, and a water supply tank, which can realize dry-wet cycle action on the rock while applying confining pressure.

[0005] Chinese patent application CN221860439U discloses a test device for simulating the influence of different water-rock effects on the rock structure surface in the drawdown zone. The device includes an electric oven, a sliding water tank, and a water pump, which can simulate the degradation process of the rock structure surface under the combined action of different water-rock effects.

[0006] Chinese patent application CN105181507A discloses a device for simulating the scouring effect of water flow on the rock mass of the reservoir bank slope. The device includes a test chamber and a spiral agitator shaft arranged in the test chamber. It can simulate the effects of reservoir water scouring and water level rise and fall on the rock mass in the drawdown zone under natural conditions.

[0007] The main problems with the existing technology are: 1. The test device can only meet the dry-wet cycle operation of the rock mass under the single factor of stress loading or dynamic water pressure; 2. The rock degradation degree test and the dry-wet cycle operation require the rock specimens to be taken out many times, which is cumbersome and easy to cause damage to the specimens. In addition, during the conventional rock degradation test, the specimens are not subject to external stress and cannot truly reflect the rock degradation conditions in the on-site environment. Summary of the invention

[0008] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a test system and method for dynamic characterization of rock degradation in a drawdown zone, which can truly simulate the dry-wet cycle process of rock in a drawdown zone under the combined action of stress loading and dynamic water pressure, and can directly and dynamically characterize the degree of degradation of rock in the dry-wet cycle process under stress loading conditions without taking out the test specimens for individual testing.

[0009] In order to achieve the above object, the present invention adopts the following technical scheme:

[0010] In a first aspect, the present invention provides a dynamic characterization test system for rock mass degradation in a drawdown zone, characterized in that it comprises a nuclear magnetic resonance tester, a nuclear magnetic core holder, a stress loading system, a fluid injection system, a solution collection system, and a data processing system;

[0011] The nuclear magnetic core holder comprises a cover, an isolation plate, a shell, a heating belt, a gasket and a base; wherein the cover and the base are detachably provided at the upper and lower ends of the shell respectively; the top of the cover is connected to the oil inlet pipe, one side of the base is connected to the liquid outlet pipe, the two sides of the shell are wrapped with the heating belt, one side of the shell is connected to the liquid inlet pipe, the isolation plate and the gasket are provided inside the shell, and the shell is used to place the core;

[0012] The nuclear magnetic resonance tester is used to obtain core nuclear magnetic signals to calculate core pore parameters;

[0013] The stress loading system is used to apply stress to the core;

[0014] The fluid injection system is used to inject fluid into the nuclear magnetic core holder in a constant pressure or constant flow mode, thereby simulating the effect of dynamic water pressure;

[0015] The solution collection system is used to collect the aqueous solution during the flushing process;

[0016] The data processing system is connected to the nuclear magnetic resonance tester and is used for real-time acquisition of core nuclear magnetic resonance signals and data processing during the test process to achieve dynamic characterization of the corresponding rock mass degradation.

[0017] Preferably, in the above-mentioned dynamic characterization test system for rock degradation in the drawdown zone, the stress loading system includes a stress loading control system and a hydraulic pump; the hydraulic pump is used to inject pressure medium into the nuclear magnetic core clamp, and push the isolation plate through the pressure medium to simulate the load effect of the overlying rock formation; the stress loading control system is connected to the hydraulic pump, and the stress loading control system is used to control the pressure output of the hydraulic pump, one side of the hydraulic pump is connected to the oil inlet pipe to form an oil inlet pipeline, and the oil inlet pipeline is connected with a first pressure gauge and a first check valve for monitoring and switching the pressure of the hydraulic pump.

[0018] Preferably, in the above-mentioned dynamic characterization test system for rock degradation in the drawdown zone, the fluid injection system includes a liquid booster pump and an air compressor; wherein, one side of the liquid booster pump and the air compressor are connected with a liquid inlet pipe to form a liquid inlet pipeline, and the liquid inlet pipeline is connected with a second check valve, a second pressure gauge, a third check valve and a fourth check valve for monitoring and switching the pressure of the liquid booster pump and the air compressor.

[0019] Preferably, in the above-mentioned dynamic characterization test system for rock degradation in the drawdown zone, the solution collection system includes a liquid collection container, a flow meter, a sealed intermediate container and a vacuum pump; wherein the liquid collection container, the flow meter, the sealed intermediate container and the vacuum pump are all connected to a liquid outlet pipe to form a liquid outlet pipeline, and the liquid outlet pipeline is simultaneously connected to a fifth check valve and a sixth check valve for controlling the direction of water flow toward the liquid collection container or the sealed intermediate container.

[0020] Preferably, in the above-mentioned dynamic characterization test system for rock degradation in the drawdown zone, the data processing system includes a nuclear magnetic signal acquisition system and a nuclear magnetic resonance instrument control and data processing system that are interconnected; wherein the nuclear magnetic signal acquisition system is connected to the nuclear magnetic resonance tester.

[0021] In a second aspect, the present invention provides a dynamic characterization test method for rock mass degradation in a drawdown zone, based on the dynamic characterization test system for rock mass degradation in a drawdown zone described in the first aspect, the method comprising:

[0022] The dried core is fixedly mounted in the nuclear magnetic core holder, and the nuclear magnetic core holder is placed on the nuclear magnetic resonance tester;

[0023] Connect the stress loading system to the oil inlet pipe of the core holder, and apply a set stress to the core through the stress loading system;

[0024] Connect the fluid injection system to the inlet pipe of the core holder, connect the solution collection system to the outlet pipe, perform a flushing process, and obtain the relaxation time T2 spectrum of the rock;

[0025] Repeat multiple flushing processes until the relaxation time T2 spectrum of the rock no longer changes, and obtain the nuclear magnetic porosity φ of the rock sample to be tested by calibrating the correlation between the nuclear magnetic signal and the porosity;

[0026] The heating belt is heated to the set temperature, and air is pressed into the clamp by an air compressor until the wet core is completely dried. Multiple flushing processes are performed until the relaxation time T2 spectrum of the rock no longer changes. The relaxation time T2 spectrum of dry and wet rocks is used to dynamically characterize the rock degradation process.

[0027] Preferably, in the above-mentioned test method for dynamic characterization of rock degradation in the drawdown zone, the flushing process includes: after the stress is stabilized, injecting constant flow / constant pressure water into the core holder to flush the rock, and using a liquid collection container to collect the water, stopping the injection of water after the set flushing time, using an intermediate container and a vacuum pump to evacuate the residual water in the cavity part of the holder except the core, and performing a nuclear magnetic resonance test on the wet core after emptying to obtain a relaxation time T2 spectrum of the rock, and the relaxation time T2 spectrum of the rock is used to characterize the situation of water entering pores of different apertures in the core.

[0028] Preferably, in the above-mentioned dynamic characterization test method for rock mass degradation in the drawdown zone, the relaxation time T2 spectrum of the rock is obtained by the following formula: there is a one-to-one functional relationship between the relaxation time T2 and the pore radius:

[0029]

[0030] In the formula, F s is the pore geometry factor, ρ2 is the surface relaxation rate, and r is the pore radius.

[0031] Preferably, in the above-mentioned dynamic characterization test method for rock mass degradation in the drawdown zone, the nuclear magnetic porosity φ of the rock sample to be tested is obtained by the following formula:

[0032]

[0033] Where φ and φ0 represent the porosity and initial porosity of the core, respectively; k and k0 represent the permeability and initial permeability of the core, respectively.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. It can simulate the dry-wet cycle process of rock mass in the drawdown zone under the combined action of stress loading and dynamic water pressure.

[0036] 2. It can directly and dynamically characterize the degree of rock degradation during the dry-wet cycle process under stress loading conditions without taking out the specimens for separate testing. It can provide guidance for the prediction of rock degradation in the drawdown zone of the reservoir bank and the prevention and control of geological disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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 or the description of the prior art 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 the structures shown in these drawings without paying creative work.

[0038] Figure 1 A structural diagram of a dynamic characterization test system for rock mass degradation in a drawdown zone provided in an embodiment of the present invention.

[0039] Figure 2 A structural diagram of a nuclear magnetic core holder in a dynamic characterization test system for rock mass degradation in a drawdown zone provided in an embodiment of the present invention.

[0040] Figure 3 A flow chart of a dynamic characterization test method for rock mass degradation in a drawdown zone provided in an embodiment of the present invention.

[0041] Description of reference numerals:

[0042] 1-Nuclear magnetic resonance tester, 2-stress loading control system, 3-oil hydraulic pump, 4-first pressure gauge, 5-first check valve, 6-cover, 7-isolation plate, 8-core, 9-shell, 10-heating belt, 11-gasket, 12-base, 13-liquid booster pump, 14-second check valve, 15-second pressure gauge, 16-third check valve, 17-air compressor, 18-fourth check valve, 19-flow meter, 20-fifth check valve, 21-sixth check valve, 22-sealed intermediate container, 23-vacuum pump, 24-liquid collection container, 25-Nuclear magnetic resonance signal acquisition system, 26-Nuclear magnetic resonance instrument control and data processing system, 27-oil inlet pipe, 28-liquid inlet pipe, 29-liquid outlet pipe. DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0044] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] The present invention will now be further described with reference to the accompanying drawings.

[0047] Embodiment 1:

[0048] The embodiment of the present invention provides a dynamic characterization test system for rock degradation in a drawdown zone, which can be applied to the field of rock degradation prediction and geological disaster prevention in the drawdown zone of a reservoir bank, so as to directly obtain the dynamic influence of dry-wet cycles on the pore-permeability characteristics of the rock mass under stress loading and dynamic water conditions.

[0049] See also Figure 1 As shown, the dynamic characterization test system for rock degradation in the drawdown zone includes a nuclear magnetic resonance tester 1, a nuclear magnetic core holder, a stress loading system, a fluid injection system, a solution collection system, and a data processing system. The nuclear magnetic resonance tester 1 is used to obtain the nuclear magnetic signal of the core to calculate the core pore parameters; the nuclear magnetic core holder is used to clamp and fix the core; the stress loading system is used to apply stress to the core; the fluid injection system is used to inject the fluid into the nuclear magnetic core holder in a constant pressure or constant flow mode to simulate the dynamic water pressure; the solution collection system is used to collect the aqueous solution during the flushing process; the data processing system is connected to the nuclear magnetic resonance tester, and is used to collect the core nuclear magnetic signal and data processing in real time during the test process to achieve the dynamic characterization of the corresponding rock degradation.

[0050] Specifically, see Figure 1 and Figure 2As shown, the nuclear magnetic core holder includes a cover 6, an isolation plate 7, a shell 9, a heating belt 10, a gasket 11, and a base 12, all of which are made of non-magnetic materials and are the main places for rock dry-wet cycle process and nuclear magnetic signal collection. Among them, the cover 6 and the base 12 are both detachable, the top of the cover 6 is connected to an oil inlet pipe 27, the right side of the base 12 is connected to a liquid outlet pipe 29, the shell 9 is wrapped with heating belts 10 on both sides, and the left side is connected to a liquid inlet pipe 28. The core 8 is placed inside the holder, the top of which is an isolation plate 7, and the bottom is a gasket 11. The nuclear magnetic resonance tester 1 is mainly used to obtain the nuclear magnetic signal of the core to calculate the core pore parameters.

[0051] The stress loading system includes a stress loading control system 2 and a hydraulic pump 3. The main function of this part is to apply stress to the core 8. The hydraulic pump 3 is used to inject fluorine oil into the nuclear magnetic core holder to simulate the overburden load by pushing the isolation plate 7. The stress loading control system 2 is connected to the hydraulic pump 3. The stress loading control system 2 is mainly used to control the pressure output of the hydraulic pump 3. The right side of the hydraulic pump 3 is connected to the oil inlet pipe 27. The first pressure gauge 4 and the first check valve 5 are connected to the oil inlet pipe, which are mainly used to monitor and switch the pressure of the hydraulic pump 3.

[0052] The fluid injection system includes a liquid booster pump 13 and an air compressor 17. The liquid booster pump 13 is mainly used to inject water into the nuclear magnetic core holder at a constant pressure or constant flow mode to simulate the effect of dynamic water pressure. The air compressor 17 is mainly used to inject air to simulate the drying process of the wet core 8. The right side of the liquid booster pump 13 and the left side of the air compressor 17 are both connected to a liquid inlet pipe 28. The second check valve 14, the second pressure gauge 15, the third check valve 16, and the fourth check valve 18 are connected to the liquid inlet pipeline, which are mainly used for monitoring and switching the pressure of the liquid booster pump 13 and the air compressor 17.

[0053] The solution collection system includes a liquid collection container 24, a flow meter 19, a sealed intermediate container 22 and a vacuum pump 23. The liquid collection container 24 is mainly used to collect the aqueous solution during the water flow flushing process. The flow meter 19 is mainly used to monitor the water flow rate. The sealed intermediate container 22 is connected to the vacuum pump 23 and is mainly used to extract the residual water flow in the cavity part of the nuclear magnetic core clamp except the core 8. The sealed intermediate container 22 is mainly used to prevent the water flow from directly entering the vacuum pump 23. Each component in the solution collection system, namely the liquid collection container 24, the flow meter 19, the sealed intermediate container 22 and the vacuum pump 23, is connected by a liquid outlet pipe 29. The fifth check valve 20 and the sixth check valve 21 are also connected to the liquid outlet pipe, which are mainly used to control the direction of the water flow to the liquid collection container 24 or the sealed intermediate container 22.

[0054] The data processing system includes a nuclear magnetic resonance signal acquisition system 25 and a nuclear magnetic resonance instrument control and data processing system 26, which are mainly used for real-time acquisition of nuclear magnetic resonance signals of the core 8 and data processing during the test process to achieve dynamic characterization of the corresponding rock mass degradation.

[0055] Embodiment 2:

[0056] The embodiment of the present invention provides a dynamic characterization test method for rock mass degradation in a drawdown zone. The dynamic characterization test method for rock mass degradation in a drawdown zone is based on the dynamic characterization test device for rock mass degradation in a drawdown zone as described in Example 1. Figure 3 As shown in FIG. 1 , the dynamic characterization test method for rock mass degradation in the drawdown zone is performed by the following steps:

[0057] Step 1: install the completely dried core 8 in a nuclear magnetic resonance core holder, and place the core holder on a nuclear magnetic resonance tester platform 1.

[0058] Step 2: Connect the stress loading system to the oil inlet pipe 27 of the core holder, and apply a set stress to the core 8 through the stress loading system.

[0059] Step 3, connect the fluid injection system to the liquid inlet pipe 28 of the core clamp, connect the solution collection system to the liquid outlet pipe 29, and after the stress is stabilized, use the liquid booster pump 13 to inject constant flow / constant pressure water into the core clamp to flush the rock mass, and use the liquid collection container 24 to collect the water.

[0060] Step 4: After 20 minutes of flushing, stop injecting water, use the intermediate container 22 and the vacuum pump 23 to drain the residual water in the cavity of the holder except the core, and conduct nuclear magnetic resonance testing on the wet core after draining to obtain the relaxation time T2 spectrum of the rock at this time, so as to obtain the situation of water entering pores of different apertures in the core. This process is mainly obtained through the following formula, and there is a one-to-one corresponding functional relationship between the relaxation time T2 and the pore radius:

[0061]

[0062] Where F s is the pore geometry factor. For spherical pores, F s =3, the surface relaxation rate ρ2 can be approximately regarded as a constant, r is the pore radius, T2 is proportional to r, so the relaxation time T2 spectrum can be converted into a curve of the relationship between the pore radius and the distribution frequency.

[0063] Step 5, after the NMR test is completed, repeat steps 3 and 4 to obtain the water infiltration inside the core pores during the next flushing process (flushing for 20 minutes).

[0064] Step 6, repeat steps 3 to 5 until the core T2 spectrum no longer changes, that is, the core is considered to be completely saturated with water. Since the integral area of ​​the T2 spectrum is proportional to the hydrogen content of the fluid in the core pores, the correlation between the nuclear magnetic signal and the porosity can be obtained by calibration to obtain the nuclear magnetic porosity φ of the rock sample to be tested. Porosity and permeability conform to the cubic law, so the permeability of the core can be obtained by the following formula:

[0065]

[0066] Where φ and φ0 represent the porosity and initial porosity of the core, respectively; k and k0 represent the permeability and initial permeability of the core, respectively.

[0067] Step 7, after obtaining the core porosity and permeability, the heating belt 10 is heated to 100 degrees Celsius, and the air compressor 17 presses air into the holder until the wet core is completely dried.

[0068] Steps 3 to 7 are the dynamic characterization process of rock mass degradation under one dry-wet cycle. By repeating steps 3 to 7, the dynamic change law of rock mass pore-permeability characteristics under multiple dry-wet cycles can be obtained, thereby revealing the mechanism of rock mass degradation.

[0069] In a specific embodiment, a dynamic characterization test of rock mass degradation in the drawdown zone is conducted under the combined action of stress loading axial pressure = 3MPa and dynamic water pressure water pressure = 0.3MPa, and the specific implementation steps are as follows:

[0070] Install the completely dried core in the nuclear magnetic core holder, open the first check valve, use the hydraulic pump to apply the set axial pressure of 3MPa to the core, open the second check valve, the fourth check valve and the fifth check valve, and use the liquid booster pump to inject water to flush the core for 20 minutes, where the dynamic water pressure is set to 0.3MPa. The water flow is collected by the liquid collection container during this process. After flushing the core for 20 minutes, close the second check valve, the fourth check valve and the fifth check valve, open the sixth check valve, and start the vacuum pump to empty the residual water flow in the holder. After emptying, use the nuclear magnetic resonance tester to carry out nuclear magnetic resonance testing on the wet core to obtain the relaxation time T2 spectrum of the rock, and use the relationship function between the relaxation time T2 and the pore radius to obtain the situation of water entering the pores of different apertures in the core. After the nuclear magnetic resonance test, close the sixth check valve, open the second check valve, the fourth check valve and the fifth check valve, and continue to carry out the next stage of core flushing (flushing time is 20 minutes) and the test of emptying the residual water flow in the clamp, and obtain the core relaxation time T2 spectrum in each flushing stage until the core T2 spectrum no longer changes, and calculate the porosity and permeability of the core. After obtaining the core porosity and permeability parameters, raise the heating belt to 100 degrees Celsius, close the second check valve and the fifth check valve, open the third check valve, the fourth check valve and the sixth check valve, and press air into the clamp until the core is completely dry. The above operation process is the dynamic characterization process of rock degradation under a dry-wet cycle. Repeating the above experimental operation process can obtain the dynamic change law of the rock mass pore-permeability characteristics under the second to fifth dry-wet cycles, thereby revealing the rock mass degradation mechanism.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of the claims and specification of the present invention.

Claims

1. A dynamic characterization test system for rock mass degradation in a drawdown zone, characterized in that: Including nuclear magnetic resonance tester, nuclear magnetic core holder, stress loading system, fluid injection system, solution collection system and data processing system; The nuclear magnetic core holder comprises a cover, an isolation plate, a shell, a heating belt, a gasket and a base; wherein the cover and the base are detachably provided at the upper and lower ends of the shell respectively; the top of the cover is connected to the oil inlet pipe, one side of the base is connected to the liquid outlet pipe, the two sides of the shell are wrapped with the heating belt, one side of the shell is connected to the liquid inlet pipe, the isolation plate and the gasket are provided inside the shell, and the shell is used to place the core; The nuclear magnetic resonance tester is used to obtain core nuclear magnetic signals to calculate core pore parameters; The stress loading system is used to apply stress to the core; The fluid injection system is used to inject fluid into the nuclear magnetic core holder in a constant pressure or constant flow mode, thereby simulating the effect of dynamic water pressure; The solution collection system is used to collect the aqueous solution during the flushing process; The data processing system is connected to the nuclear magnetic resonance tester and is used for real-time acquisition of core nuclear magnetic resonance signals and data processing during the test process to achieve dynamic characterization of the corresponding rock mass degradation.

2. The dynamic characterization test system for rock mass degradation in the drawdown zone according to claim 1 is characterized in that: The stress loading system includes a stress loading control system and an oil pressure pump; the oil pressure pump is used to inject a pressure medium into the nuclear magnetic core holder, and push the isolation plate through the pressure medium to simulate the load effect of the overlying rock formation; The stress loading control system is connected to the oil pressure pump, and the stress loading control system is used to control the pressure output of the oil pressure pump. One side of the oil pressure pump is connected to the oil inlet pipe to form an oil inlet pipeline. The oil inlet pipeline is connected with a first pressure gauge and a first check valve for monitoring and switching the oil pressure of the oil pressure pump.

3. The dynamic characterization test system for rock mass degradation in the drawdown zone according to claim 1 is characterized in that: The fluid injection system includes a liquid booster pump and an air compressor; wherein, one side of the liquid booster pump and the air compressor are connected to a liquid inlet pipe to form a liquid inlet pipeline, and the liquid inlet pipeline is connected to a second check valve, a second pressure gauge, a third check valve and a fourth check valve for monitoring and switching the pressure of the liquid booster pump and the air compressor.

4. The dynamic characterization test system for rock mass degradation in the drawdown zone according to claim 1 is characterized in that: The solution collection system includes a liquid collection container, a flow meter, a sealed intermediate container and a vacuum pump; wherein the liquid collection container, the flow meter, the sealed intermediate container and the vacuum pump are all connected to a liquid outlet pipe to form a liquid outlet pipeline, and the liquid outlet pipeline is simultaneously connected to a fifth check valve and a sixth check valve for controlling the direction of water flow toward the liquid collection container or the sealed intermediate container.

5. The dynamic characterization test system for rock mass degradation in drawdown zone according to claim 1 is characterized in that: The data processing system includes a nuclear magnetic signal acquisition system and a nuclear magnetic resonance instrument control and data processing system which are interconnected; wherein the nuclear magnetic signal acquisition system is connected to the nuclear magnetic resonance tester.

6. A dynamic characterization test method for rock mass degradation in a drawdown zone, based on the dynamic characterization test system for rock mass degradation in a drawdown zone according to any one of claims 1 to 5, characterized in that: The method comprises: The dried core is fixedly mounted in the nuclear magnetic core holder, and the nuclear magnetic core holder is placed on the nuclear magnetic resonance tester; Connect the stress loading system to the oil inlet pipe of the core holder, and apply a set stress to the core through the stress loading system; Connect the fluid injection system to the inlet pipe of the core holder, connect the solution collection system to the outlet pipe, perform a flushing process, and obtain the relaxation time T2 spectrum of the rock; Repeat multiple flushing processes until the relaxation time T2 spectrum of the rock no longer changes, and obtain the nuclear magnetic porosity φ of the rock sample to be tested by calibrating the correlation between the nuclear magnetic signal and the porosity; The heating belt is heated to the set temperature, and air is pressed into the clamp by an air compressor until the wet core is completely dried. Multiple flushing processes are performed until the relaxation time T2 spectrum of the rock no longer changes. The relaxation time T2 spectrum of dry and wet rocks is used to dynamically characterize the rock degradation process.

7. The dynamic characterization test method for rock mass degradation in a drawdown zone according to claim 6 is characterized in that: The flushing process includes: after the stress is stabilized, injecting a constant flow / constant pressure water flow into the core holder to flush the rock mass, and using a liquid collection container to collect the water flow, stopping the injection of water flow after the set flushing time, using an intermediate container and a vacuum pump to empty the residual water flow in the cavity part of the holder except the core, and performing a nuclear magnetic resonance test on the wet core after emptying to obtain a relaxation time T2 spectrum of the rock, and the relaxation time T2 spectrum of the rock is used to characterize the situation of water entering pores of different apertures in the core.

8. The dynamic characterization test method for rock mass degradation in a drawdown zone according to claim 7 is characterized in that: The relaxation time T2 spectrum of rock is obtained by the following formula: There is a one-to-one functional relationship between relaxation time T2 and pore radius: In the formula, F s is the pore geometry factor, ρ2 is the surface relaxation rate, and r is the pore radius.

9. The dynamic characterization test method for rock mass degradation in a drawdown zone according to claim 6 is characterized in that: The nuclear magnetic porosity φ of the rock sample to be tested is obtained by the following formula: Where φ and φ0 represent the porosity and initial porosity of the core, respectively; k and k0 represent the permeability and initial permeability of the core, respectively.

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