Rock aging degradation monitoring device and method under stress-temperature-seepage coupling

Abstract

The invention discloses a stress-temperature-seepage coupled rock aging degradation monitoring device and method.The device comprises a three-way stress loading assembly, a temperature control assembly and a seepage control assembly, the three-way stress loading assembly is used for applying axial stress and confining pressure, the temperature control assembly is used for adjusting the heating temperature, and the seepage control assembly is used for controlling seepage; the seepage control assembly is used for applying seepage pressure. The method comprises the following steps: acquiring a correction coefficient; the monitoring device is assembled, and the original porosity and the original density of the rock sample are tested; and carrying out three-dimensional stress, temperature and seepage coupling on the rock sample, calculating the porosity and density of the rock sample at different times through a corrected formula, and finally obtaining the change relation of the porosity, density and deterioration degree of the rock sample along with time under the three-dimensional stress-temperature-seepage coupling. According to the invention, the coupling influence of stress, temperature and seepage field is considered at the same time, and the aging degradation process of the rock in a complex environment is comprehensively reflected.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock deterioration simulation and monitoring, and particularly relates to a device and method for monitoring rock aging deterioration under stress-temperature-seepage coupling. Background Technique

[0002] As a key material in multiple fields such as underground engineering, oil exploitation, and geothermal development, the long-term stability of rock is affected by multiple environmental factors. Especially under conditions such as groundwater level change, temperature fluctuation, and stress loading, rock often bears the combined action of three-dimensional stress, temperature, seepage, etc. These factors interact with each other and jointly affect the mechanical properties and stability of rock. The failure of rock is usually caused by the combined action of multiple factors. For example, thermal expansion caused by temperature change, crack propagation caused by stress change, pore change caused by seepage pressure, etc. These factors are intertwined, resulting in the expansion of microcracks inside the rock and the decline of mechanical properties.

[0003] The research on the internal deterioration mechanism of rock under the coupling action of stress-seepage-temperature is one of the current research hotspots in the field of rock mechanics. Temperature change can change the internal stress distribution of rock through thermal expansion, thereby affecting the mechanical properties of rock. At the same time, the change of seepage water pressure can apply additional stress to the rock and change the crack propagation behavior of the rock. And the redistribution of internal stress in the rock will further affect the change of the seepage path, thus forming a complex three-dimensional stress-seepage-temperature coupling process. This multi-field coupling effect will lead to the deterioration of rock being highly nonlinear and complex, making it particularly difficult to predict the rock deterioration process.

[0004] Most traditional rock damage detection methods focus on the action of a single factor. For example, it is only carried out on rock under a certain stress or temperature state, and the aging deterioration process of rock cannot be obtained. Existing rock damage detection methods, such as crack propagation experiments based on stress-temperature field conditions, although they can reveal the rock damage evolution under a certain specific field condition, cannot comprehensively obtain the aging deterioration effect of rock under the coupling action of multiple environmental factors. Another example is based on strain gauge or stress sensor technology, which usually can only monitor the mechanical response on the surface of the rock and is difficult to accurately capture the microscopic pore evolution and aging deterioration process inside the rock.

[0005] As a high-precision non-destructive testing method, ultrasonic technology can detect the density, pore changes, etc. inside materials by measuring parameters such as the acoustic wave propagation velocity and attenuation coefficient. However, the current application of ultrasonic waves in a multi-field coupling environment is still in the initial exploration stage, and there is still a lack of monitoring technology for rock aging deterioration that can simultaneously consider the coupling effects of stress, temperature, and seepage. Most traditional ultrasonic monitoring methods focus on the detection of rock damage under the action of a single stress or temperature field, and there is no systematic solution for the monitoring of rock deterioration under multi-field coupling. Therefore, it is urgent to develop a monitoring device and method for rock aging deterioration under stress-temperature-seepage coupling to accurately monitor the aging deterioration process of rocks under multi-field coupling in real time, laying a foundation for studying the complex deterioration mechanism of rocks under multi-field coupling conditions.

[0006] The invention patent with the application publication number CN108426782A discloses an ultrasonic monitoring device for rock damage evolution under multi-field coupling. The device includes a stress loading unit, a water-vapor generating unit, and a water-vapor circulation unit; the stress loading unit includes an upper pressure head, a lower pressure head, and an oil cylinder. Ultrasonic transmitting probes and ultrasonic receiving probes are respectively arranged on the upper and lower pressure heads. Hydraulic oil enters the oil cylinder to drive the upper and lower pressure heads to apply axial pressure to the rock specimen; the water-vapor generating unit includes a solution bottle filled with chemical solution and a heater at the bottom; the water-vapor circulation unit includes an intake pipeline and a return pipeline. One end of the intake pipeline is connected to the solution bottle and the other end is connected to the closed cover, and one end of the return pipeline is connected to the solution bottle and the other end is connected to the closed cover; the water-vapor generating unit generates water-vapor with a set humidity and temperature, and the influence of different humidity and temperature changes on the rock specimen is realized through the water-vapor circulation unit, and different chemical solutions can be replaced. The monitoring method includes the following steps: during the uniaxial compression process, the propagation wave velocity of ultrasonic waves in the rock specimen is measured at regular intervals, and the damage degree of the rock is defined by the wave velocity. This technical solution has the following defects: (1) Only axial stress is applied to the rock specimen, lacking confining pressure, which does not conform to the triaxial stress state of underground rocks; (2) There is no seepage field, that is, the influence of seepage pressure on rock damage deterioration is not considered. However, in reality, seepage is one of the important factors affecting the long-term stability of rocks. Seepage pressure will cause pore changes in rocks and change the crack propagation behavior of rocks. If the role of the seepage field is not considered, it does not conform to the real situation and the monitoring results are inaccurate; (3) During the monitoring process, only the propagation wave velocity of ultrasonic waves in the rock specimen is used to evaluate the damage degree of the rock, which is only a macroscopic monitoring. The mesoscopic changes such as pores and internal structures of the rock are not considered, and the deterioration degree cannot be directly obtained, and the monitoring results are inaccurate. Summary of the Invention

[0007] To solve the problems existing in the prior art, the present invention provides a monitoring device for rock aging deterioration under stress-temperature-seepage coupling. The monitoring device includes a triaxial stress loading component, a temperature control component, a seepage control component, and a computer control system. The triaxial stress loading component is used to apply axial stress to the top and bottom surfaces of the rock specimen respectively, and confining pressure to the side surface of the rock specimen. The temperature control component is used to adjust the heating temperature of the rock specimen. The seepage control component is used to apply seepage pressure to the rock specimen. The computer control system is used to control the axial pressure, confining pressure, and heating temperature.

[0008] Preferably, the triaxial stress loading component includes a sealed box, an oil cylinder, a connecting shaft, an upper platen base, a lower platen base, an upper platen, a lower platen, an ultrasonic transmitting probe, an ultrasonic receiving probe, a first oil tank, a second oil tank, a first oil pump, a second oil pump, a first oil pressure gauge, a second oil pressure gauge, a first oil pipe, and a second oil pipe.

[0009] In any of the above solutions, preferably, the sealed box is cylindrical and made of stainless steel. Upper platen jacks and lower platen jacks are respectively opened at the central parts of the top and bottom surfaces of the sealed box, and the inside of the sealed box is a hydraulic chamber. The oil cylinder is arranged above the top surface of the sealed box, and a connecting shaft jack is opened at the central part of the top surface of the oil cylinder.

[0010] In any of the above solutions, preferably, the upper platen and the lower platen are cylindrical with equal diameters and made of stainless steel. The upper platen and the lower platen are respectively inserted vertically into the sealed box through the upper platen jack and the lower platen jack, and the rock specimen is placed between the upper platen and the lower platen. The rock specimen is cylindrical, and the diameter of the rock specimen is smaller than the diameters of the upper platen and the lower platen.

[0011] The ultrasonic transmitting probe and the ultrasonic receiving probe are respectively embedded at the central parts of the upper platen near its lower surface and the lower platen near its upper surface. First water flow channels and second water flow channels are respectively arranged inside the upper platen and the lower platen.

[0012] In any of the above solutions, preferably, the upper platen base and the lower platen base are respectively connected to the upper platen and the lower platen. The upper platen base is located inside the oil cylinder. One end of the connecting shaft is connected to the upper platen, and the other end is connected to the oil cylinder through the connecting shaft jack. The lower platen base is located at the bottom of the sealed box.

[0013] The central axes of the sealed box, the oil cylinder, the upper platen, the lower platen, the upper platen base, the lower platen base, the connecting shaft, and the rock specimen are located on the same vertical line.

[0014] Preferably, in any of the above solutions, the first fuel tank is communicated with the oil cylinder through the first oil pipe, and the first oil pressure pump and the first oil pressure gauge are arranged on the first oil pipe. The first oil pressure pump is connected to the computer control system through a circuit. The second fuel tank is communicated with the hydraulic chamber through the second oil pipe, and the second oil pressure pump and the second oil pressure gauge are arranged on the second oil pipe. The second oil pressure pump is connected to the computer control system through a circuit.

[0015] Preferably, in any of the above solutions, the temperature control component includes a heater, a heating pipe, and a thermometer. The heater is connected to the heating pipe through a wire. The heating pipe is arranged in the hydraulic chamber. The thermometer is arranged at the output end of the heater. The heater is connected to the computer control system through a circuit.

[0016] Preferably, in any of the above solutions, the seepage control component includes a first water tank, a second water tank, a first water pipe, a second water pipe, a first pressure control valve, and a second pressure control valve. The first water tank is communicated with the first water flow channel through the first water pipe, and the first pressure control valve is arranged on the first water pipe. The second water tank is communicated with the second water flow channel through the second water pipe, and the second pressure control valve is arranged on the second water pipe.

[0017] The present invention also provides a method for monitoring the rock aging deterioration under stress-temperature-seepage coupling. Using the monitoring device for rock aging deterioration under stress-temperature-seepage coupling described in any of the above items, it includes the following steps in sequence: Step 1: Assemble each component of the monitoring device and a rock specimen together according to the designed connection relationship, and check the monitoring device to ensure that the monitoring device has good sealing performance. Step 2: Obtain the correction coefficient. The specific operation is as follows: First, in the state of not applying triaxial stress, emit ultrasonic waves to the rock specimen through the computer control system, and collect the time from the ultrasonic wave emitting probe emitting ultrasonic waves to the ultrasonic wave receiving probe receiving ultrasonic waves, and then calculate the propagation wave speed of ultrasonic waves in the rock specimen. Then, turn on the triaxial stress loading component to apply triaxial stress to the rock specimen. After the triaxial stress is stable, emit ultrasonic waves to the rock specimen through the computer control system, and collect the time from the ultrasonic wave emitting probe emitting ultrasonic waves to the ultrasonic wave receiving probe receiving ultrasonic waves, and then calculate the propagation wave speed of ultrasonic waves in the rock specimen. Finally, take the ratio of the propagation wave speed of ultrasonic waves in the rock specimen under the state of applying triaxial stress to the propagation wave speed of ultrasonic waves in the rock specimen under the state of not applying triaxial stress as the correction coefficient. After the operation of obtaining the correction coefficient is completed, take out the rock specimen from the monitoring device. Step 3: Assemble each component of the monitoring device and another rock specimen according to the designed connection relationship, and inspect the monitoring device to ensure it has good airtightness; Step 4: Before subjecting the rock specimen to triaxial stress, temperature, and seepage coupling, emit ultrasonic waves to the rock specimen through the computer control system, and collect the time from when the ultrasonic wave is emitted by the ultrasonic wave transmitting probe to when it is received by the ultrasonic wave receiving probe, and then calculate the original propagation wave velocity of the ultrasonic wave in the rock specimen; calculate the original porosity and original density of the rock specimen through the time-average formula and volume-weighted formula respectively; Step 5: Subject the rock specimen to triaxial stress, temperature, and seepage coupling. The specific operation is as follows: First, turn on the seepage control component to apply seepage pressure to the rock specimen. After the seepage pressure is stable, simultaneously turn on the triaxial stress loading component and the temperature control component to apply triaxial stress and heat to the rock specimen respectively. After the triaxial stress, temperature, and seepage pressure all reach the set values and remain stable, the coupling is completed; Step 6: Under the condition of keeping the triaxial stress, temperature, and seepage pressure unchanged, measure the propagation wave velocity of ultrasonic waves in the rock specimen every certain time interval. At the same time, calculate the porosity and density of the rock specimen at this time through the modified time-average formula and volume-weighted formula respectively, and take the ratio of the porosity at this time to the original porosity as the parameter of the deterioration degree of the rock specimen at this time, and then obtain the variation of the porosity, density, and deterioration degree of the rock specimen with time at a series of different times, and finally obtain the variation relationship of the porosity, density, and deterioration degree of the rock specimen with time under triaxial stress-temperature-seepage coupling.

[0018] In Step 1 and Step 3, the rock specimen is obtained by coring from the underground rock core, with its surface intact, undamaged, and internal structure complete; the diameter of the rock specimen is 50 mm and the height is 100 mm.

[0019] In Step 2, triaxial stress is applied to the rock specimen according to the triaxial stress situation at the site where the rock specimen is cored; the correction coefficient formula is , where: ——Correction coefficient, dimensionless; ——The propagation wave velocity of ultrasonic waves in the rock specimen in the state without applying triaxial stress, m / s; ——The propagation wave velocity of ultrasonic waves in the rock specimen in the state of applying triaxial stress, m / s.

[0020] The propagation wave velocity of ultrasonic waves in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time.

[0021] In Step 4, the time-averaging formula is , where: —— The original porosity of the rock sample, dimensionless; —— The original propagation wave velocity of ultrasonic waves in the rock sample, m / s; —— The propagation wave velocity of ultrasonic waves in the skeletal minerals, m / s; —— The propagation wave velocity of ultrasonic waves in the pore fluid, m / s.

[0022] The propagation wave velocity of ultrasonic waves in the rock sample is equal to the ratio of the height of the rock sample to the propagation time.

[0023] The volume-weighting formula is , where: —— The original density of the rock sample, g / cm 3 ; —— The density of the skeletal minerals, g / cm 3 ; —— The density of the pore fluid, g / cm 3 ; —— The original porosity of the rock sample, dimensionless.

[0024] In Step 6, the modified time-averaging formula is , where: —— The porosity of the rock sample at different times, dimensionless; —— The propagation wave velocity of ultrasonic waves in the rock sample at different times, m / s; —— The propagation wave velocity of ultrasonic waves in the skeletal minerals, m / s; —— The propagation wave velocity of ultrasonic waves in the pore fluid, m / s; —— The correction coefficient, dimensionless.

[0025] The propagation wave velocity of ultrasonic waves in the rock sample is equal to the ratio of the height of the rock sample to the propagation time.

[0026] The modified volume-weighting formula is , where: —— The density of the rock sample at different times, g / cm 3 ; —— Density of the skeletal mineral, g / cm 3 ; —— Density of the pore fluid, g / cm 3 ; —— Porosity of the rock specimen at different times, dimensionless; —— Correction factor, dimensionless.

[0027] The deterioration degree of the rock specimen is , where: —— Deterioration degree of the rock specimen, dimensionless; —— Porosity of the rock specimen at different times, dimensionless; —— Original porosity of the rock specimen, dimensionless.

[0028] The series of changes of the porosity, density, and deterioration degree of the rock specimen with time at different times, the porosity is expressed as , the density is expressed as , and the deterioration degree is expressed as , .

[0029] In the present invention, the heater, heating pipe, thermometer, fuel tank, oil pump, oil pipe, oil pressure gauge, water tank, water pipe, pressure control valve, computer control system, etc. used are all traditional equipment or instruments, and there are no special requirements for the model and structure. The computer control system includes a computer, a control panel, a switch, an interface, etc., and has functions such as data processing and storage.

[0030] The rock specimen can be placed into the sealed box through the upper punch hole or the lower punch hole. For example, in actual operation, the lower punch can be inserted into the sealed box first, and a lower punch base is set at the bottom of the lower punch. Then, the rock specimen is inserted into the sealed box through the upper punch hole, and the rock specimen is vertically dropped onto the top surface of the lower punch. Then, the upper punch is inserted into the sealed box so that the rock specimen is located between the upper punch and the lower punch.

[0031] After the components of the monitoring device and the rock specimen are assembled together, a good sealing state needs to be achieved, and sealing rings, gaskets or other sealing materials need to be used for sealing treatment at the connection parts or the parts with gaps of each component.

[0032] The propagation wave velocity of ultrasonic waves in the skeletal mineral and the pore fluid is a fixed value, and the densities of the skeletal mineral and the pore fluid are also fixed values, and these fixed values can be determined according to the rock type.

[0033] The stress-temperature-seepage coupling rock aging deterioration monitoring device and method of the present invention have the following beneficial effects: It can conduct comprehensive monitoring under multi-field coupling, taking into account the comprehensive effects of various factors such as triaxial stress, temperature, and seepage, comprehensively reflecting the deterioration process of rocks in complex environments, and providing more comprehensive data support than traditional single-field monitoring. The high sensitivity and real-time nature of ultrasonic technology enable it to be effectively monitored at the initial stage of rock damage, thus providing an accurate basis for the safety assessment of engineering. The computer control system can automatically adjust the working parameters of each unit and issue a warning when the damage reaches the preset threshold, ensuring the safety of rock engineering.

[0034] The present invention can simultaneously simulate the multi-field coupling effects of triaxial stress, temperature, and seepage, providing a comprehensive deterioration monitoring platform for rocks. The combined action of triaxial stress, temperature, and seepage makes the deterioration process of rocks more complex. Traditional single-field monitoring methods cannot effectively capture these complex dynamic changes, while the present invention can accurately monitor the deterioration state of rocks under multi-field coupling conditions. By accurately measuring the aging deterioration situation inside the rock (microscopic monitoring), the present invention can predict the deterioration risk of rocks under the coupling conditions of triaxial stress, temperature, and seepage, and take corresponding protective measures in advance. The present invention can adjust the triaxial stress, temperature, and seepage conditions in real time during the experiment and synchronously conduct ultrasonic monitoring, providing dynamic rock aging deterioration data, which enables researchers to accurately observe the aging deterioration process of rocks in a multi-field coupling environment and ensure the reliability and timeliness of experimental data.

[0035] The present invention introduces a correction coefficient when calculating the porosity and density of rocks. Due to the action of triaxial stress, the pore channels inside the rock are compressed, and the skeleton density and seepage channels of the rock are affected. Therefore, a correction coefficient is introduced to make the monitoring results more accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 FIG. is a schematic diagram of the overall structure of the monitoring device in a preferred embodiment of the stress-temperature-seepage coupling rock aging deterioration monitoring device and method according to the present invention; Figure 2 For Figure 1 FIG. is a schematic diagram of the structure of the triaxial stress loading component in the illustrated embodiment; Figure 3 For Figure 1 FIG. is a schematic diagram of the structure of the temperature control component in the illustrated embodiment; Figure 4 For Figure 1 FIG. is a schematic diagram of the structure of the seepage control component in the illustrated embodiment; Figure 5 FIG. is a physical photograph of the rock specimens used in the embodiment and the comparative example; Figure 6 The relationship between the porosity of the rock specimens in the examples and comparative examples and time. Figure 7 The relationship between the density of the rock specimens in the examples and comparative examples and time. Figure 8 The relationship between the deterioration degree of the rock specimens in the examples and comparative examples and time. Figure 9 The internal structure state of the rock specimen in the example after 24-hour aging deterioration. Figure 10 The internal structure state of the rock specimen in the comparative example after 24-hour aging deterioration.

[0037] Description of the markings in the figure: 1 - Triaxial stress loading assembly, 101 - Sealing box, 102 - Oil cylinder, 103 - Connecting shaft, 104 - Upper platen base, 105 - Lower platen base, 106 - Upper platen, 107 - Lower platen, 108 - Ultrasonic transmitting probe, 109 - Ultrasonic receiving probe, 110 - First oil tank, 111 - Second oil tank, 112 - First oil pump, 113 - Second oil pump, 114 - First oil pressure gauge, 115 - Second oil pressure gauge, 116 - First oil pipe, 117 - Second oil pipe, 118 - Hydraulic chamber, 119 - First water flow channel, 120 - Second water flow channel; 2 - Temperature control assembly, 201 - Heater, 202 - Heating pipe, 203 - Thermometer; 3 - Seepage control assembly, 301 - First water tank, 302 - Second water tank, 303 - First water pipe, 304 - Second water pipe, 305 - First pressure control valve, 306 - Second pressure control valve; 4 - Computer control system; 5 - Rock specimen. Detailed implementation manners

[0038] In order to further understand the content of the present invention, the present invention will be elaborated in detail below in combination with specific embodiments.

[0039] As Figures 1-4 shown, according to a preferred embodiment of the rock aging deterioration monitoring device under stress-temperature-seepage coupling of the present invention, the monitoring device includes a triaxial stress loading assembly 1, a temperature control assembly 2, a seepage control assembly 3 and a computer control system 4. The triaxial stress loading assembly 1 is used to apply axial stress to the top and bottom surfaces of the rock specimen 5 respectively and confining pressure to the side surface of the rock specimen 5. The temperature control assembly 2 is used to adjust the heating temperature of the rock specimen 5. The seepage control assembly 3 is used to apply seepage pressure to the rock specimen 5. The computer control system 4 is used to control the axial pressure, confining pressure and heating temperature.

[0040] The three-way stress loading assembly 1 includes a sealing box 101, an oil cylinder 102, a connecting shaft 103, an upper platen base 104, a lower platen base 105, an upper platen 106, a lower platen 107, an ultrasonic transmitting probe 108, an ultrasonic receiving probe 109, a first oil tank 110, a second oil tank 111, a first oil pump 112, a second oil pump 113, a first oil pressure gauge 114, a second oil pressure gauge 115, a first oil pipe 116, and a second oil pipe 117.

[0041] The sealing box 101 is cylindrical and made of stainless steel. An upper platen insertion hole and a lower platen insertion hole are respectively opened at the central parts of the top surface and the bottom surface of the sealing box 101. The inside of the sealing box 101 is a hydraulic chamber 118. The oil cylinder 102 is arranged above the top surface of the sealing box 101, and a connecting shaft insertion hole is opened at the central part of the top surface of the oil cylinder 102.

[0042] The upper platen 106 and the lower platen 107 are cylindrical with equal diameters and made of stainless steel. The upper platen 106 and the lower platen 107 are respectively vertically inserted into the sealing box 101 through the upper platen insertion hole and the lower platen insertion hole. The rock specimen 5 is placed between the upper platen 106 and the lower platen 107. The rock specimen 5 is cylindrical, and the diameter of the rock specimen 5 is smaller than the diameters of the upper platen 106 and the lower platen 107.

[0043] The ultrasonic transmitting probe 108 and the ultrasonic receiving probe 109 are respectively embedded at the central parts of the upper platen 106 near its lower surface and the lower platen 107 near its upper surface. First water flow channels 119 and second water flow channels 120 are respectively arranged inside the upper platen 106 and the lower platen 107.

[0044] The upper platen base 104 and the lower platen base 105 are respectively connected to the upper platen 106 and the lower platen 107. The upper platen base 104 is located inside the oil cylinder 102. One end of the connecting shaft 103 is connected to the upper platen 106, and the other end is connected to the oil cylinder 102 through the connecting shaft insertion hole. The lower platen base 105 is located at the bottom of the sealing box 101.

[0045] The central axes of the sealing box 101, the oil cylinder 102, the upper platen 106, the lower platen 107, the upper platen base 104, the lower platen base 105, the connecting shaft 103, and the rock specimen 5 are located on the same vertical line.

[0046] The first fuel tank 110 is communicated with the oil cylinder 102 through the first oil pipe 116. The first oil pressure pump 112 and the first oil pressure gauge 114 are arranged on the first oil pipe 116. The first oil pressure pump 112 is connected to the computer control system 4 through a circuit. The second fuel tank 111 is communicated with the hydraulic chamber 118 through the second oil pipe 117. The second oil pressure pump 113 and the second oil pressure gauge 115 are arranged on the second oil pipe 117. The second oil pressure pump 113 is connected to the computer control system 4 through a circuit.

[0047] The temperature control component 2 includes a heater 201, a heating pipe 202, and a thermometer 203. The heater 201 is connected to the heating pipe 202 through a wire. The heating pipe 202 is arranged in the hydraulic chamber 118. The thermometer 203 is arranged at the output end of the heater 201. The heater 201 is connected to the computer control system 4 through a circuit.

[0048] The seepage control component 3 includes a first water tank 301, a second water tank 302, a first water pipe 303, a second water pipe 304, a first pressure control valve 305, and a second pressure control valve 306. The first water tank 301 is communicated with the first water flow channel 119 through the first water pipe 303. The first pressure control valve 305 is arranged on the first water pipe 303. The second water tank 302 is communicated with the second water flow channel 120 through the second water pipe 304. The second pressure control valve 306 is arranged on the second water pipe 304.

[0049] This embodiment also provides a method for monitoring the rock aging deterioration under the coupling of stress-temperature-seepage. Using the above-mentioned device for monitoring the rock aging deterioration under the coupling of stress-temperature-seepage, it includes the following steps in sequence: Step 1: Assemble each component of the monitoring device and a rock specimen together according to the designed connection relationship, and check the monitoring device to ensure that the monitoring device has good airtightness. Step 2: Obtain the correction coefficient. The specific operation is as follows: First, in the state without applying triaxial stress, use the computer control system to emit ultrasonic waves to the rock specimen, and collect the time from the ultrasonic wave emitter emitting ultrasonic waves to the ultrasonic wave receiver receiving ultrasonic waves, and then calculate the propagation wave speed of ultrasonic waves in the rock specimen. Then, turn on the triaxial stress loading component to apply triaxial stress to the rock specimen. After the triaxial stress is stable, use the computer control system to emit ultrasonic waves to the rock specimen, and collect the time from the ultrasonic wave emitter emitting ultrasonic waves to the ultrasonic wave receiver receiving ultrasonic waves, and then calculate the propagation wave speed of ultrasonic waves in the rock specimen. Finally, take the ratio of the propagation wave speed of ultrasonic waves in the rock specimen under the state of applying triaxial stress to the propagation wave speed of ultrasonic waves in the rock specimen under the state of not applying triaxial stress as the correction coefficient. After the operation of obtaining the correction coefficient is completed, take out the rock specimen from the monitoring device; Step 3: Assemble each component of the monitoring device and another rock specimen together according to the designed connection relationship, and check the monitoring device to ensure that the monitoring device has good sealing performance; Step 4: Before applying the triaxial stress, temperature, and seepage coupling action to the rock specimen, use the computer control system to emit ultrasonic waves to the rock specimen, and collect the time from the ultrasonic wave emitter emitting ultrasonic waves to the ultrasonic wave receiver receiving ultrasonic waves, and then calculate the original propagation wave speed of ultrasonic waves in the rock specimen. Calculate the original porosity and original density of the rock specimen through the time-averaging formula and the volume-weighting formula respectively; Step 5: Apply the triaxial stress, temperature, and seepage coupling action to the rock specimen. The specific operation is as follows: First, turn on the seepage control component to apply seepage pressure to the rock specimen. After the seepage pressure is stable, turn on the triaxial stress loading component and the temperature control component at the same time, and apply triaxial stress and heat to the rock specimen respectively. After the triaxial stress, temperature, and seepage pressure all reach the set values and remain unchanged, the coupling action is completed; Step 6: Under the condition of keeping the triaxial stress, temperature, and seepage pressure unchanged, measure the propagation wave speed of ultrasonic waves in the rock specimen every certain time interval. At the same time, calculate the porosity and density of the rock specimen at this time through the corrected time-averaging formula and the volume-weighting formula respectively, and take the ratio of the porosity at this time to the original porosity as the parameter of the degradation degree of the rock specimen at this time, and then obtain the change of the porosity, density, and degradation degree of the rock specimen with time at a series of different times. Finally, obtain the change relationship of the porosity, density, and degradation degree of the rock specimen with time under the triaxial stress-temperature-seepage coupling;

[0050] In Step 1 and Step 3, the rock specimen is obtained by drilling from the underground core, and its surface is intact, undamaged and the internal structure is complete; the diameter of the rock specimen is 50 mm and the height is 100 mm.

[0051] In Step 2, triaxial stresses are applied to the rock specimen according to the triaxial stress conditions at the site where the cored rock specimen is located. The correction factor formula is , where: ——Correction factor, dimensionless; ——Propagation wave velocity of ultrasonic wave in the rock specimen under the state of no triaxial stress applied, m / s; ——Propagation wave velocity of ultrasonic wave in the rock specimen under the state of triaxial stress applied, m / s.

[0052] The propagation wave velocity of ultrasonic wave in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time.

[0053] In Step 4, the time-averaging formula is , where: ——Original porosity of the rock specimen, dimensionless; ——Original propagation wave velocity of ultrasonic wave in the rock specimen, m / s; ——Propagation wave velocity of ultrasonic wave in the skeletal mineral, m / s; ——Propagation wave velocity of ultrasonic wave in the pore fluid, m / s.

[0054] The propagation wave velocity of ultrasonic wave in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time.

[0055] The volume-weighting formula is , where: ——Original density of the rock specimen, g / cm 3 ; ——Density of the skeletal mineral, g / cm 3 ; ——Density of the pore fluid, g / cm 3 ; ——Original porosity of the rock specimen, dimensionless.

[0056] In Step 6, the corrected time-averaging formula is , where: ——Porosity of the rock specimen at different times, dimensionless; ——Wave velocity of ultrasonic wave in rock specimen at different times, m / s; ——Wave velocity of ultrasonic wave in skeletal minerals, m / s; ——Wave velocity of ultrasonic wave in pore fluid, m / s; ——Correction coefficient, dimensionless.

[0057] The wave velocity of ultrasonic wave in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time.

[0058] The corrected volume weighted formula is , where: ——Density of rock specimen at different times, g / cm 3 ; ——Density of skeletal minerals, g / cm 3 ; ——Density of pore fluid, g / cm 3 ; ——Porosity of rock specimen at different times, dimensionless; ——Correction coefficient, dimensionless.

[0059] The deterioration degree of the rock specimen is , where: ——Deterioration degree of rock specimen, dimensionless; ——Porosity of rock specimen at different times, dimensionless; ——Original porosity of rock specimen, dimensionless.

[0060] The series change situations of porosity, density and deterioration degree of rock specimen at different times with time, porosity is expressed as , density is expressed as , deterioration degree is expressed as \[ .

[0061] In this embodiment, the heater, heating pipe, thermometer, oil tank, oil pump, oil pipe, oil pressure gauge, water tank, water pipe, pressure control valve, computer control system, etc. used are all traditional equipment or instruments, and there are no special requirements for the model and structure. The computer control system includes a computer, a control panel, a switch, an interface, etc., and has functions such as data processing and storage.

[0062] The rock specimen can be placed into the sealed box through the upper platen jack or the lower platen jack. In actual operation of this embodiment, first insert the lower platen into the sealed box, and a lower platen base is provided at the bottom of the lower platen. Then insert the rock specimen into the sealed box through the upper platen jack, and make the rock specimen vertically fall on the top surface of the lower platen. Then insert the upper platen into the sealed box so that the rock specimen is located between the upper platen and the lower platen.

[0063] After all components of the monitoring device and the rock specimen are assembled together, a good sealing state needs to be achieved. Sealing treatment should be carried out at the connection parts or the parts with gaps of each component using sealing rings, gaskets or other sealing materials. The propagation wave velocity of ultrasonic waves in the skeletal minerals and pore fluids is a fixed value, and the densities of the skeletal minerals and pore fluids are also fixed values, and these fixed values can be determined according to the rock types.

[0064] The rock aging deterioration monitoring device and method under stress-temperature-seepage coupling of this embodiment have the following beneficial effects: (1) Considering the comprehensive effects of various factors such as triaxial stress, temperature and seepage at the same time, it comprehensively reflects the deterioration process of rocks in complex environments. (2) It can simultaneously simulate the multi-field coupling effects of triaxial stress, temperature and seepage, provide a comprehensive deterioration monitoring platform for rocks, and predict the deterioration risk of rocks under the coupling conditions of triaxial stress, temperature and seepage by accurately measuring the aging deterioration situation inside the rocks (microscopic monitoring), and take corresponding protective measures in advance. (3) It can adjust the triaxial stress, temperature and seepage conditions in real time during the experiment and synchronously conduct ultrasonic monitoring, and can provide dynamic rock aging deterioration data. (4) A correction coefficient is introduced when calculating the rock porosity and density. Due to the action of triaxial stress, the pore channels inside the rock are compacted, and the skeletal density and seepage channels of the rock are affected, so a correction coefficient is introduced, thereby making the monitoring results more accurate and reliable.

[0065] In this embodiment, = 3268 m / s, = 3921.6 m / s, and the calculated correction coefficient = 1.2; = 4500 m / s, = 1501 m / s, = 3260 m / s, and the original porosity of the rock specimen is calculated as = 0.181; = 2.65 g / cm 3 、 = 0.191 g / cm 3 , and the original density of the rock specimen is calculated as = 2.794 g / cm 3 .

[0066] In this embodiment, under the combined action of triaxial stress (axial compression in the upper and lower directions, confining pressure), temperature (50°C), and seepage pressure, the propagation wave velocity of ultrasonic waves in the rock specimen is measured every 1 hour within 24 hours. Then, the porosity, density, and deterioration degree of the rock specimen at the corresponding time are calculated respectively through the corrected time-averaging formula and volume-weighting formula, so as to obtain the variation relationships of porosity, density, and deterioration degree of the rock specimen with time under the coupling of triaxial stress-temperature-seepage.

[0067] The following design is a comparative example: The test is carried out using traditional test equipment and test methods. Only axial stress in the upper and lower directions is applied to the rock specimen, without applying confining pressure or seepage pressure; no correction coefficient is introduced, that is, the time-averaging formula and volume-weighting formula are not corrected, so the calculated porosity, density, deterioration degree, etc. of the rock specimen are also uncorrected results; the size, test temperature, test period, test time interval, etc. of the rock specimen are the same as those in the embodiment of the present invention; the propagation wave velocities of ultrasonic waves in the skeletal minerals and pore fluids, the densities of the skeletal minerals and pore fluids, etc. are the same as those in the embodiment of the present invention; finally, the variation relationships of porosity, density, and deterioration degree of the rock specimen with time under only axial stress are obtained.

[0068] The physical photos of the rock specimens used in the above-mentioned embodiment and comparative example are as Figure 5 shown; the variation relationships of porosity, density, and deterioration degree of the rock specimens in the above-mentioned embodiment and comparative example with time are respectively as Figure 6 、 Figure 7 、 Figure 8 shown; the internal structural states of the rock specimens in the above-mentioned embodiment and comparative example after 24 hours of aging deterioration are respectively as Figure 9 、 Figure 10 shown.

[0069] From Figures 6-8 the comparison results, it can be seen that the variation relationships of porosity, density, and deterioration degree of the rock specimen measured by using the monitoring device and monitoring method of this embodiment are closer to the actual situation, and the test results are more accurate and reliable. Comparing Figure 9 and Figure 10 it can be seen that after 24 hours of aging deterioration, the internal structure of the rock specimen in this embodiment is compact and has fewer pores, while the rock specimen in the comparative example has more pores after 24 hours of aging deterioration.

[0070] Special note: Many parameters are involved in the technical solution of the present invention. It is necessary to comprehensively consider the synergistic effects among various parameters to obtain the beneficial effects and remarkable progress of the present invention. Moreover, the value ranges of various parameters in the technical solution are obtained through a large number of experiments. For each parameter and the mutual combination of various parameters, the inventor has recorded a large amount of experimental data. Due to space limitations, the specific experimental data are not disclosed here.

[0071] It is not difficult for those skilled in the art to understand that the rock aging deterioration monitoring device and method under stress-temperature-seepage coupling of the present invention include any combination of the above-mentioned inventive content and specific implementation parts of the specification of the present invention and each part shown in the drawings. Due to space limitations and to make the specification concise, the various solutions formed by these combinations are not described one by one. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A monitoring device for rock aging deterioration under stress-temperature-seepage coupling, characterized in that: The monitoring device includes a triaxial stress loading component, a temperature control component, a seepage control component, and a computer control system. The triaxial stress loading component is used to apply axial stress to the top and bottom surfaces of the rock specimen respectively, and confining pressure to the side surface of the rock specimen. The temperature control component is used to adjust the heating temperature of the rock specimen. The seepage control component is used to apply seepage pressure to the rock specimen. The computer control system is used to control the axial pressure, confining pressure, and heating temperature.

2. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 1, wherein: The triaxial stress loading component includes a sealed box, an oil cylinder, a connecting shaft, an upper platen base, a lower platen base, an upper platen, a lower platen, an ultrasonic transmitting probe, an ultrasonic receiving probe, a first oil tank, a second oil tank, a first oil pump, a second oil pump, a first oil pressure gauge, a second oil pressure gauge, a first oil pipe, and a second oil pipe.

3. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 2, characterized in that: The sealed box is cylindrical and made of stainless steel. An upper platen socket and a lower platen socket are respectively opened at the central parts of the top and bottom surfaces of the sealed box. The interior of the sealed box is a hydraulic chamber. The oil cylinder is arranged above the top surface of the sealed box, and a connecting shaft socket is opened at the central part of the top surface of the oil cylinder.

4. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 3, characterized in that: The upper platen and the lower platen are cylindrical with equal diameters and made of stainless steel. The upper platen and the lower platen are respectively inserted vertically into the sealed box through the upper platen socket and the lower platen socket. The rock specimen is placed between the upper platen and the lower platen. The rock specimen is cylindrical, and the diameter of the rock specimen is smaller than the diameters of the upper platen and the lower platen. The ultrasonic transmitting probe and the ultrasonic receiving probe are respectively embedded at the central parts near the lower surface of the upper platen and near the upper surface of the lower platen. A first water flow channel and a second water flow channel are respectively arranged inside the upper platen and the lower platen.

5. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 4, characterized in that: The upper platen base and the lower platen base are respectively connected to the upper platen and the lower platen. The upper platen base is located inside the oil cylinder. One end of the connecting shaft is connected to the upper platen, and the other end is connected to the oil cylinder through the connecting shaft socket. The lower platen base is located at the bottom of the sealed box. The central axes of the sealed box, the oil cylinder, the upper platen, the lower platen, the upper platen base, the lower platen base, the connecting shaft, and the rock specimen are located on the same vertical line.

6. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 5, characterized in that: The first oil tank is communicated with the oil cylinder through the first oil pipe. The first oil pump and the first oil pressure gauge are arranged on the first oil pipe. The first oil pump is connected to the computer control system through a circuit. The second oil tank is communicated with the hydraulic chamber through the second oil pipe. The second oil pump and the second oil pressure gauge are arranged on the second oil pipe. The second oil pump is connected to the computer control system through a circuit.

7. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 6, characterized in that: The temperature control component includes a heater, a heating pipe, and a thermometer. The heater is connected to the heating pipe through a wire. The heating pipe is arranged inside the hydraulic chamber. The thermometer is arranged at the output end of the heater. The heater is connected to the computer control system through a circuit.

8. The rock aging deterioration monitoring device under stress-temperature-seepage coupling according to claim 7, characterized in that: The seepage control component includes a first water tank, a second water tank, a first water pipe, a second water pipe, a first pressure control valve, and a second pressure control valve. The first water tank is communicated with the first water flow channel through the first water pipe, and the first pressure control valve is arranged on the first water pipe. The second water tank is communicated with the second water flow channel through the second water pipe, and the second pressure control valve is arranged on the second water pipe.

9. A method for monitoring the aging deterioration of rock under the coupling of stress-temperature-seepage, characterized in that: When using the rock time-dependent deterioration monitoring device under stress-temperature-seepage coupling according to any one of claims 1-8, it includes the following steps in sequence. Step 1: Assemble each component of the monitoring device and a rock specimen together according to the designed connection relationship, and check the monitoring device to ensure that the monitoring device has good sealing performance. Step 2: Obtain the correction coefficient. The specific operation is as follows. First, in the state of not applying triaxial stress, use the computer control system to emit ultrasonic waves to the rock specimen, and collect the time from the ultrasonic wave emitting probe emitting ultrasonic waves to the ultrasonic wave receiving probe receiving ultrasonic waves, and then calculate the propagation wave speed of the ultrasonic waves in the rock specimen. Then, turn on the triaxial stress loading component to apply triaxial stress to the rock specimen. After the triaxial stress is stable, use the computer control system to emit ultrasonic waves to the rock specimen, and collect the time from the ultrasonic wave emitting probe emitting ultrasonic waves to the ultrasonic wave receiving probe receiving ultrasonic waves, and then calculate the propagation wave speed of the ultrasonic waves in the rock specimen. Finally, take the ratio of the propagation wave speed of the ultrasonic waves in the rock specimen under the state of applying triaxial stress to the propagation wave speed of the ultrasonic waves in the rock specimen under the state of not applying triaxial stress as the correction coefficient. After the operation of obtaining the correction coefficient is completed, take out the rock specimen from the monitoring device. Step 3: Assemble each component of the monitoring device and another rock specimen together according to the designed connection relationship, and check the monitoring device to ensure that the monitoring device has good sealing performance. Step 4: Before applying the coupling action of triaxial stress, temperature, and seepage to the rock specimen, use the computer control system to emit ultrasonic waves to the rock specimen, and collect the time from the ultrasonic wave emitting probe emitting ultrasonic waves to the ultrasonic wave receiving probe receiving ultrasonic waves, and then calculate the original propagation wave speed of the ultrasonic waves in the rock specimen. Calculate the original porosity and original density of the rock specimen through the time-averaging formula and the volume-weighted formula respectively. Step 5: Apply the coupling action of triaxial stress, temperature, and seepage to the rock specimen. The specific operation is as follows. First, turn on the seepage control component to apply seepage pressure to the rock specimen. After the seepage pressure is stable, turn on the triaxial stress loading component and the temperature control component at the same time to apply triaxial stress and heat to the rock specimen respectively. After the triaxial stress, temperature, and seepage pressure all reach the set values and remain stable, the coupling action is completed. Step 6: Under the condition of keeping the triaxial stress, temperature, and seepage pressure unchanged, the propagation wave velocity of ultrasonic waves in the rock specimen is measured at regular intervals. At the same time, the porosity and density of the rock specimen at this time are calculated respectively by the modified time-averaging formula and volume-weighted formula. The ratio of the porosity at this time to the original porosity is used as the parameter of the degradation degree of the rock specimen at this time. Furthermore, the variation of porosity, density, and degradation degree of the rock specimen with time at a series of different times is obtained, and finally, the variation relationship of porosity, density, and degradation degree of the rock specimen with time under triaxial stress-temperature-seepage coupling is obtained.

10. The method for monitoring the aging degradation of rock under triaxial stress-temperature-seepage coupling according to claim 9, wherein: In Step 1 and Step 3, the rock specimen is obtained by drilling from an underground core, with its surface intact, undamaged, and internal structure complete; the diameter of the rock specimen is 50 mm and the height is 100 mm; In Step 2, according to the triaxial stress conditions at the site where the rock specimen is drilled, triaxial stress is applied to the rock specimen; The correction coefficient formula is , where —— Correction coefficient, dimensionless; ——The wave velocity of ultrasonic waves propagating in a rock specimen under the condition of no triaxial stress state, m / s; ——Wave velocity of ultrasonic wave propagating in rock specimen under triaxial stress state, m / s; The propagation wave velocity of ultrasonic waves in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time; In Step 4, the time-averaging formula is , where —— The original porosity of the rock sample, dimensionless; ——The original propagation wave velocity of ultrasonic waves in the rock specimen, m / s; ——Wave velocity of ultrasonic wave propagating in framework minerals, m / s; —— Wave velocity of ultrasonic wave propagating in pore fluid, m / s; The propagation wave velocity of ultrasonic waves in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time; The volume-weighted formula is , where —— The original density of the rock specimen, g / cm 3 ; —— Density of the framework mineral, g / cm 3 ; —— density of pore fluid, g / cm 3 ; —— The original porosity of the rock sample, dimensionless; In Step 6, the corrected time-average formula is , where —— Porosity of the rock sample at different times, dimensionless; —— Wave velocity of ultrasonic wave in rock specimen at different times, m / s; ——Wave velocity of ultrasonic wave propagating in skeletal minerals, m / s; ——Wave velocity of ultrasonic wave propagation in pore fluid, m / s; —— correction coefficient, dimensionless; The propagation wave velocity of ultrasonic waves in the rock specimen is equal to the ratio of the height of the rock specimen to the propagation time; The corrected volume-weighted formula is , where —— Density of rock specimens at different times, g / cm 3 ; ——Density of the skeletal mineral, g / cm 3 ; —— density of pore fluid, g / cm 3 ; —— Porosity of rock specimens at different times, dimensionless; —— correction coefficient, dimensionless; The deterioration degree of the rock sample is , where ——Deterioration degree of rock specimen, dimensionless; —— Porosity of rock specimens at different times, dimensionless; —— The original porosity of the rock sample, dimensionless; The series of changes over time in the porosity, density, and degradation degree of rock specimens at different times. The porosity is expressed as , the density is expressed as , and the degradation degree is expressed as , .

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