High-temperature cold impact triaxial test device and method

Abstract

The invention provides a high-temperature cold impact triaxial test device and method, and relates to the technical field of rock mechanics tests. The high-temperature cold impact triaxial test device comprises a loading unit, a heating unit, a liquid nitrogen cold impact unit and a sensing device. The high-temperature cold impact triaxial test device and method can accurately simulate the high-temperature cold impact process of a rock sample under the triaxial loading condition, are suitable for researching the influence of different confining pressures and high temperatures and the cold impact coupling effect on the mechanical properties and failure modes of rocks, and have good application prospects. More accurate data support and theoretical basis are provided for quantitative analysis of rock mechanical response in a deep engineering complex environment; the rock sample is simple and convenient to install and operate, the heating, heat preservation and cold impact processes are easy to control, the cold impact rate and amplitude can be accurately adjusted, and test requirements can be effectively met.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mechanics testing, in particular to a high-temperature cold impact triaxial testing device and method. Background Art

[0002] During the exploration and development of deep energy resources, such as deep oil and gas, geothermal energy, and coalbed methane, rocks often face complex environments such as high geostress and cold shock in high-temperature surrounding rocks. These include the cold shock of drilling fluid on the high-temperature surrounding rocks in the wellbore during deep drilling, and the cold shock of water and liquid nitrogen on the high-temperature reservoir rocks during fracturing to stimulate oil and gas reservoir production. Cold shock causes sudden changes in the temperature of the high-pressure, high-temperature surrounding rock, leading to non-uniform deformation within the surrounding rock, the expansion of existing cracks in the surrounding rock, or the initiation of new cracks, which significantly impacts the surrounding rock strength. Exploring the mechanical response and damage mechanisms of rocks under the coupled effects of high temperature, high pressure, and cold shock is crucial for engineering design, stability assessment, and resource extraction efficiency.

[0003] Triaxial compression testing of rock is an important method for studying rock mechanical properties in geotechnical engineering. However, existing triaxial testing equipment primarily focuses on measuring the basic mechanical parameters of rock under normal temperature or stable high-temperature and high-pressure conditions. Although some experimental equipment can achieve rock cooling through water cooling, the water-cooling heat exchange process is time-consuming and slow, making it difficult to achieve the desired effect of high-temperature cold shock. Furthermore, water cooling has a certain delay effect, making it difficult to precisely control the cooling rate and amplitude, making it difficult to accurately simulate the damage and mechanical response of rock under the coupled effects of high pressure, high temperature, and cold shock.

[0004] Therefore, a new type of test device is urgently needed that can simulate high-temperature cold shock of rock samples under triaxial loading conditions, study the influence of confining pressure and high temperature and cold shock coupling on rock mechanical properties and failure modes, and provide more accurate data support and theoretical basis for rock mechanical response analysis in complex environments in deep engineering. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-temperature cold shock triaxial testing device and method to accurately simulate the high-temperature cold shock of rock samples under triaxial loading conditions, and to solve the problems of slow cooling speed and difficult cooling control when performing cold shock tests in existing triaxial testing devices.

[0006] In order to achieve the above objectives, the technical solutions adopted by the present invention are as follows:

[0007] A high-temperature cold shock triaxial testing device comprising:

[0008] A loading unit, on which a rock sample is placed, is used to apply axial pressure and confining pressure to the rock sample;

[0009] a heating unit for transferring heat to the rock sample;

[0010] Liquid nitrogen cold shock unit, used to transfer the cold energy generated by liquid nitrogen vaporization to the rock sample;

[0011] Sensor devices are used to monitor and collect data on the mechanical state of rock samples and changes in the temperature of the environment in which the rock samples are located.

[0012] Preferably, the loading unit comprises a loading frame, an axial pressure cylinder, a loading shaft, a loading pressure head, a loading base, a confining pressure chamber and a confining pressure pump;

[0013] The axial pressure oil cylinder is arranged at the upper end of the loading frame, the telescopic end of the axial pressure oil cylinder is connected to one end of the loading shaft, and the other end of the loading shaft is provided with the loading pressure head;

[0014] The loading base is located directly below the loading pressure head, and a loading pad is provided on the loading base;

[0015] A rock sample is placed between the loading pad and the loading head, and an axial load is applied to the rock sample by the loading pad and the loading head;

[0016] The lower end of the confining pressure chamber is open, and the lower end of the confining pressure chamber can be sealed and connected to the edge of the loading base. The loading shaft passes through the upper end of the confining pressure chamber, and the loading shaft can be dynamically sealed and connected to the confining pressure chamber.

[0017] The confining pressure pump is connected to the confining pressure chamber via a hydraulic pipeline. The confining pressure pump is used to inject confining pressure fluid of a set pressure into the confining pressure chamber, so that the confining pressure fluid applies confining pressure to the rock sample.

[0018] Preferably, the loading frame is provided with a lifting slide rail, and the lifting slide rail is arranged vertically;

[0019] The confining pressure chamber is provided with a lifting slider, and the lifting slider is slidably matched with the lifting rail;

[0020] A lifting cylinder is provided on the loading frame. The lifting cylinder is arranged vertically, and the telescopic end of the lifting cylinder is connected to the confining pressure chamber.

[0021] Preferably, the outer wall of the confining pressure chamber is provided with a thermal insulation layer.

[0022] Preferably, a groove is provided at the upper end of the loading base, and the loading pad is placed in the groove.

[0023] Preferably, the loading unit further comprises a servo controller, and the servo controller is respectively connected to the axial pressure cylinder and the confining pressure pump via signals.

[0024] Preferably, the heating unit includes a resistance wire, a power controller and a power supply. The resistance wire is connected to the power supply via the power controller. The resistance wire is fixed to the top of the confining pressure chamber and is arranged around the rock sample.

[0025] Preferably, the liquid nitrogen cold shock unit comprises a liquid nitrogen storage tank, a multi-way valve, a cooling hollow column and a vacuum pump;

[0026] The liquid nitrogen storage tank is filled with liquid nitrogen, the liquid outlet of the liquid nitrogen storage tank is connected to the liquid inlet of the multi-way valve via a liquid inlet pipeline, and the multiple liquid outlets of the multi-way valve are connected to the cooling hollow column via a liquid infusion pipeline. The cooling hollow column is located in the confining pressure chamber, and the multiple cooling hollow columns are arranged around the rock sample. The cooling hollow columns are connected to the vacuum pump via an air outlet pipeline.

[0027] Preferably, the cooling hollow column is divided into a liquid storage chamber and a vaporization chamber;

[0028] The liquid infusion pipeline is connected to the liquid storage chamber, and the gas outlet pipeline is connected to the gasification chamber;

[0029] The liquid storage chamber and the gasification chamber are connected via a transition pipeline;

[0030] The liquid inlet high-frequency solenoid valve is provided on the liquid infusion pipeline, the gasification high-frequency solenoid valve is provided on the transition pipeline, and the exhaust high-frequency solenoid valve is provided on the gas outlet pipeline;

[0031] By controlling the opening and closing frequency, number of times and duration of the liquid inlet high-frequency solenoid valve, the vaporization high-frequency solenoid valve and the exhaust high-frequency solenoid valve, liquid nitrogen first flows into the liquid storage chamber, and then flows into the vacuum vaporization chamber through the liquid storage chamber. The cooling hollow column realizes cold shock on the rock sample in the confining pressure chamber.

[0032] A high-temperature cold shock triaxial test method, using the above-mentioned high-temperature cold shock triaxial test apparatus, comprises the following steps:

[0033] Step 1: Rock sample installation

[0034] After the rock sample and the loading pad are sealed and wrapped, they are placed on the groove of the loading base. The lifting cylinder drives the confining pressure chamber down so that the lower end of the confining pressure chamber is sealed and connected to the edge of the loading base.

[0035] Step 2: Apply axial pressure and confining pressure

[0036] The axial pressure cylinder drives the loading pressure head to act on the upper end of the rock sample through the loading shaft, applying initial axial pressure to the rock sample. The confining pressure pump injects the set confining pressure fluid into the confining pressure chamber to apply confining pressure to the rock sample.

[0037] Step 3: Heating and insulation

[0038] Turn on the power supply, and use the power controller to control the resistance wire to heat the confining fluid. The heat is transferred to the rock sample through the confining fluid, so that the confining fluid and rock sample are heated to the set temperature and maintained;

[0039] Step 4: Cooling shock

[0040] Liquid nitrogen in the liquid nitrogen storage tank is intermittently injected into the gasification chamber of the cooling hollow column to gasify and absorb heat, thereby reducing the temperature of the confining pressure liquid and the rock sample and performing cold shock on the rock sample;

[0041] Step 5: Rock sample loading

[0042] After the rock sample has undergone the test-set confining pressure, temperature increase, cold shock and cooling, the rock sample is continuously loaded using the loading unit;

[0043] During steps 2 to 5, the sensor device monitors and collects the mechanical state data of the rock sample and the temperature change of the environment in which the rock sample is located in real time;

[0044] Step 6: Rock sample removal

[0045] The confining pressure pump discharges the confining pressure liquid in the confining pressure chamber, the lifting cylinder drives the confining pressure chamber to rise, the rock sample is removed, and the test ends.

[0046] The beneficial technical effects of the present invention are:

[0047] The high-temperature cold shock triaxial test device and method of the present invention arrange a cooling hollow column (gasification chamber) in a confining pressure chamber, utilize the phase change of liquid nitrogen to absorb the heat of the confining pressure liquid, thereby reducing the temperature of the confining pressure liquid and the rock sample in the confining pressure chamber, and realize precise control of the liquid nitrogen gasification frequency and total amount through the control of the liquid inlet high-frequency solenoid valve, the gasification high-frequency solenoid valve, and the exhaust high-frequency solenoid valve, thereby realizing precise control of the cooling rate and cooling amplitude, and the liquid nitrogen gasification rate is fast, and there is no delay in single gasification energy absorption, which effectively solves the problem that the traditional water cooling has a large delay and the cooling rate and cooling amplitude are difficult to accurately control, and is better used for studying the influence of the coupling effect of pressure and high-temperature cold shock on the mechanical properties and failure mode of rock, and provides more accurate data support and theoretical basis for the rock mechanical response analysis under complex environment in engineering; the installation of rock samples and the operation of temperature heating, heat preservation and cooling shock are simple, the cooling rate and amplitude can be accurately controlled, and the test purpose can be easily and accurately achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the structure of a high-temperature cold shock triaxial test device in an embodiment of the present invention;

[0049] Figure 2 This is a schematic structural diagram of a loading unit according to an embodiment of the present invention;

[0050] Figure 3 Schematic diagram of the structure of the heating unit in an embodiment of the present invention;

[0051] Figure 4 Schematic diagram of the structure of the liquid nitrogen cold shock unit in an embodiment of the present invention;

[0052] Figure 5Flowchart of the high-temperature cold shock triaxial test method in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and beneficial effects of the present invention more clearly understood, the present invention is further described below in conjunction with specific embodiments and with reference to the accompanying drawings. Certain embodiments of the present invention will be more fully described below with reference to the accompanying drawings, some, but not all, of which are illustrated. The various embodiments of the present invention may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present invention satisfies applicable legal requirements.

[0054] In the description of the present invention, it should be noted that the terms "inner," "outer," "upper," "lower," "front," and "rear," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0055] In an embodiment of the present invention, a high temperature cold shock triaxial test device and method are provided, please refer to Figures 1 to 5 shown.

[0056] A high-temperature cold shock triaxial testing device comprises a loading unit, a heating unit, a liquid nitrogen cold shock unit and a sensor device.

[0057] A rock sample 4 is placed on the loading unit, and the loading unit is used to apply axial pressure and confining pressure to the rock sample 4 .

[0058] The loading unit includes a loading frame 101 , an axial pressure cylinder 102 , a loading shaft 103 , a loading pressure head 104 , a loading base 111 , a confining pressure chamber 106 and a confining pressure pump 108 .

[0059] The axial pressure cylinder 102 is mounted at the upper end of the loading frame 101. The telescopic end of the axial pressure cylinder 102 is connected to one end of the loading shaft 103. The other end of the loading shaft 103 is provided with a spherical loading head 104. The loading base 111 is located directly below the loading head 104. The upper end of the loading base 111 defines a groove into which the loading pad 105 is placed. A rock sample is placed between the loading pad 105 and the loading head 104, and the loading pad 105 and the loading head 104 apply an axial load to the rock sample 4. The lower end of the confining pressure chamber 106 is open and can be sealed to the edge of the loading base 111. The loading shaft 103 passes through the upper end of the confining pressure chamber 106 and is dynamically and sealably connected to the confining pressure chamber 106. The confining pressure pump 108 is connected to the confining pressure chamber 106 via a hydraulic pipeline. The confining pressure pump 108 is used to inject confining pressure fluid of a set pressure into the confining pressure chamber 106 , so that the confining pressure fluid applies confining pressure to the rock sample 4 .

[0060] Loading frame 101 is equipped with vertically arranged lifting rails 110. The outer wall of confining pressure chamber 106 is provided with lifting blocks that slidably engage with lifting rails 110. A vertically arranged lifting cylinder 109 is installed at the bottom of loading frame 101, with its telescopic end connected to the outer wall of confining pressure chamber 106.

[0061] The outer wall of the confined pressure chamber 106 is provided with a heat-insulating layer 107 for maintaining the temperature inside the confined pressure chamber 106 and preventing the experimenters from getting burned and heat loss.

[0062] The servo controller 112 is connected to the axial pressure cylinder 102 and the confining pressure pump 108 via signal cables, respectively, and is used to control the axial pressure cylinder 102 to apply axial load to the rock sample 4 and the confining pressure pump 108 to apply confining pressure to the rock sample 4, thereby reducing fluctuations in axial load and confining pressure caused by temperature changes of the confining pressure fluid and the rock sample 4.

[0063] The heating unit is used to transfer heat to the rock sample 4.

[0064] The heating unit includes a resistance wire 201, a power controller 202, and a power supply 203. The resistance wire 201 is connected to the power supply 203 via the power controller 202. The resistance wire 201 is fixed to the top of the confining pressure chamber 106 and arranged around the rock sample 4. The power controller 202 controls the power of the resistance wire 201, adjusting the heating rate and amplitude. Several support rods are circumferentially arranged at the top of the confining pressure chamber 106, and the resistance wire 201 is wound around these support rods.

[0065] The resistance wires 201 are arranged around the rock sample 4 and cooperate with the confining pressure liquid in the confining pressure chamber 106. The resistance wires 201 around the rock sample 4 heat the confining pressure liquid in the confining pressure chamber 106, and the confining pressure liquid then conducts heat to the rock sample 4. The confining pressure liquid wraps the rock sample 4, which can quickly and evenly heat the confining pressure liquid and the rock sample 4 to the set temperature value.

[0066] The liquid nitrogen cold shock unit is used to transfer the cold energy generated by the vaporization of liquid nitrogen to the rock sample 4.

[0067] The liquid nitrogen cold shock unit includes a liquid nitrogen storage tank 301 , a multi-way valve 302 , a cooling hollow column and a vacuum pump 304 .

[0068] The liquid nitrogen storage tank 301 is filled with liquid nitrogen. The liquid outlet of the liquid nitrogen storage tank 301 is connected to the liquid inlet of the multi-way valve 302 via a liquid inlet pipeline. Several liquid outlets of the multi-way valve 302 are connected to the cooling hollow columns via liquid infusion pipelines. The cooling hollow columns are located in the confining pressure chamber 106. Several cooling hollow columns are arranged around the rock sample 4. The cooling hollow columns are connected to the vacuum pump 304 via an air outlet pipeline.

[0069] The cooling hollow columns are arranged around the rock sample 4 and cooperate with the confining pressure liquid in the confining pressure chamber 106. The cooling hollow columns around the rock sample 4 cool the confining pressure liquid in the confining pressure chamber 106, and the confining pressure liquid in the confining pressure chamber 106 then transfers the cold energy to the rock sample 4. The confining pressure liquid wraps the rock sample 4, which can quickly and evenly reduce the confining pressure liquid and the rock sample 4 to the set temperature value.

[0070] The cooling hollow column is divided into a liquid storage chamber 3032 and a vaporization chamber 3034. A liquid infusion line connects to the liquid storage chamber 3032, while a gas outlet line connects to the gasification chamber 3034. The liquid storage chamber 3032 and the gasification chamber 3034 are connected via a transition line. The liquid infusion line is equipped with a high-frequency solenoid valve 3031 for liquid inlet, a high-frequency solenoid valve 3033 for gasification, and a high-frequency solenoid valve 3035 for exhaust. The sidewalls of the gasification chamber 3034 are made of a highly thermally conductive material to efficiently absorb external energy.

[0071] Before liquid nitrogen is injected into the vaporization chamber 3034 , the vaporization chamber 3034 is first evacuated by the vacuum pump 304 .

[0072] By controlling the opening and closing frequency, number and duration of the high-frequency solenoid valve 3031 for liquid inlet, the high-frequency solenoid valve 3033 for vaporization and the high-frequency solenoid valve 3035 for exhaust, the liquid inlet frequency, vaporization frequency and exhaust frequency are controlled, and a cycle is operated. By controlling the cycle speed and the number of cycles, the heat absorption speed and heat absorption energy of the vaporization chamber 3034 are controlled.

[0073] The solenoid valve controller 305 is connected to the liquid inlet high-frequency solenoid valve 3031, the vaporization high-frequency solenoid valve 3033 and the exhaust high-frequency solenoid valve 3035 via signal cables to control the opening and closing frequency, number and duration of each high-frequency solenoid valve.

[0074] The liquid nitrogen first flows into the liquid storage chamber 3032, and then flows into the vacuum gasification chamber 3034 through the liquid storage chamber 3032. The liquid nitrogen is converted from liquid to gas in the gasification chamber 3034, and the heat in the confined pressure chamber 106 is absorbed by the phase change of nitrogen gas, thereby reducing the temperature in the confined pressure chamber 106; and then discharged through the exhaust high-frequency electromagnetic valve 3035 and the vacuum pump 304. The gasification chamber 3034 of the cooling hollow column realizes cold shock on the rock sample 4 in the confined pressure chamber 106.

[0075] The sensor device is used to monitor and collect the mechanical state data of the rock sample 4 and the temperature change of the environment in which the rock sample 4 is located.

[0076] The sensor components include temperature sensors, stress sensors, strain sensors and acoustic emission sensors, and the sensor component signals are connected to a data acquisition unit (computer).

[0077] A high-temperature cold shock triaxial test method, using the high-temperature cold shock triaxial test apparatus described above in this embodiment, includes the following steps:

[0078] Step 1: Rock sample installation

[0079] After the rock sample 4 and the loading pad 105 are sealed and wrapped, they are placed on the groove of the loading base 111. The lifting cylinder 109 drives the confining pressure chamber 106 to descend, so that the lower end of the confining pressure chamber 106 is sealed and connected to the edge of the loading base 111.

[0080] Step 2: Apply axial pressure and confining pressure

[0081] The axial pressure cylinder 102 drives the loading pressure head 104 to act on the upper end of the rock sample 4 through the loading shaft 103, applying initial axial pressure to the rock sample 4. The confining pressure pump 108 injects the set confining pressure fluid into the confining pressure chamber 106 to apply confining pressure to the rock sample 4.

[0082] Step 3: Heating and insulation

[0083] Turn on the power supply 203 and control the resistance wire 201 to heat the confining fluid through the power controller 202. The confining fluid transfers heat to the rock sample 4, so that the confining fluid and the rock sample 4 are heated to the set temperature and maintained.

[0084] Step 4: Cooling shock

[0085] The liquid nitrogen in the liquid nitrogen storage tank 301 is intermittently injected into the gasification chamber 3034 of the cooling hollow column to gasify and absorb heat, so as to reduce the temperature of the confining pressure liquid and the rock sample 4 and perform a cold shock on the rock sample 4.

[0086] Specifically, the solenoid valve controller 305 is connected to the liquid inlet high-frequency solenoid valve 3031, the vaporization high-frequency solenoid valve 3033 and the exhaust high-frequency solenoid valve 3035 via signal cables to control the rapid opening and closing of the liquid inlet high-frequency solenoid valve 3031, the vaporization high-frequency solenoid valve 3033 and the exhaust high-frequency solenoid valve 3035.

[0087] The high-frequency liquid inlet solenoid valve 3031 opens, the high-frequency vaporization solenoid valve 3033 closes, and the liquid nitrogen in the liquid nitrogen storage tank 301 enters the liquid storage chamber 3032. The liquid storage chamber 3032 acts as a buffer and pressure stabilizer, completing the liquid inlet operation. The high-frequency liquid inlet solenoid valve 3031 closes, the high-frequency vaporization solenoid valve 3033 opens, and the high-frequency exhaust solenoid valve 3035 closes. The liquid nitrogen enters the vaporization chamber 3034 from the liquid storage chamber 3032. The liquid nitrogen vaporizes and absorbs heat, causing the temperature in the vaporization chamber 3034 to drop sharply. The vaporization chamber 3034 absorbs heat from the confining pressure liquid and rock sample 4 in the confining pressure chamber 106, rapidly reducing the temperature of the confining pressure liquid and rock sample 4, completing the vaporization heat absorption operation and achieving a cold shock to the rock sample 4. The exhaust high-frequency solenoid valve 3035 is opened, the liquid inlet high-frequency solenoid valve 3031 is opened, and the gasification high-frequency solenoid valve 3033 is closed. Under the action of the vacuum pump 304, nitrogen is discharged through the gas outlet pipe, and liquid nitrogen continues to enter the liquid storage chamber 3032 from the liquid nitrogen storage tank 301, completing the exhaust and liquid inlet operations.

[0088] The solenoid valve controller 305 controls the opening and closing frequency, number of times and duration of the liquid inlet high-frequency solenoid valve 3031, the vaporization high-frequency solenoid valve 3033 and the exhaust high-frequency solenoid valve 3035, thereby controlling the frequency, number of times and duration of the vaporization heat absorption of liquid nitrogen in the vaporization chamber 3034, and ultimately accurately controlling the cooling rate and amplitude.

[0089] Step 5: Rock sample loading

[0090] After the rock sample 4 has undergone the test-set confining pressure, temperature increase, cold shock cooling, the rock sample 4 is continuously loaded using the loading unit;

[0091] During steps 2 to 5, the sensor device monitors and collects the mechanical state data of the rock sample 4 and the temperature change of the environment in which the rock sample 4 is located in real time.

[0092] Specifically, the temperature sensor is used to monitor and collect the ambient temperature of the rock sample 4 in real time, the stress sensor and strain sensor are used to collect the stress and strain data of the rock sample 4 during the stress and high-temperature cold shock process, and the tiny stress changes and deformation of the rock sample 4 are recorded in real time. The acoustic emission sensor is used to record the acoustic emission parameters of the rock sample 4 in real time to provide accurate data for subsequent mechanical analysis.

[0093] Step 6: Rock sample removal

[0094] The confining pressure pump 108 discharges the confining pressure liquid in the confining pressure chamber 106, and the lifting cylinder 109 drives the confining pressure chamber 106 to rise. The rock sample 4 is removed and the failure mode of the rock sample 4 is observed. By analyzing the mechanical properties data of the rock sample 4 during the entire high-temperature cold shock and loading process, the influence of the coupling effect of confining pressure and high-temperature cold shock on the mechanical properties and damage of the rock is obtained. The test ends.

[0095] So far, the present embodiment has been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the high-temperature cold shock triaxial test device and method of the present invention. The high-temperature cold shock triaxial test apparatus and method of the present invention disposes a cooling hollow column (gasification chamber 3034) in the confining pressure chamber 106, utilizes the phase change of liquid nitrogen to absorb the heat of the confining pressure liquid, thereby reducing the temperature of the confining pressure liquid and the rock sample 4 in the confining pressure chamber 106, and realizes precise control of the frequency and total amount of liquid nitrogen vaporization through the control of the liquid inlet high-frequency solenoid valve 3031, the gasification high-frequency solenoid valve 3033, and the exhaust high-frequency solenoid valve 3035, thereby realizing precise control of the cooling rate and cooling amplitude. In addition, the liquid nitrogen vaporizes quickly, and there is no delay in single gasification energy absorption, which effectively solves the problem of large time delay and difficulty in precise control of cooling rate and cooling amplitude in traditional water cooling. It is better used for studying the influence of the coupling of pressure and high-temperature cold shock on the mechanical properties and failure mode of rock, and provides more accurate data support and theoretical basis for rock mechanical response analysis under complex environments in engineering. The installation of the rock sample 4 and the operation of temperature heating, heat preservation, and cooling shock are simple, and the cooling rate and amplitude can be accurately controlled, so that the test objectives can be easily and accurately achieved.

[0096] Of course, the specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high temperature cold shock triaxial testing device, characterized in that: include: A loading unit, on which a rock sample is placed, is used to apply axial pressure and confining pressure to the rock sample; a heating unit for transferring heat to the rock sample; Liquid nitrogen cold shock unit, used to transfer the cold energy generated by liquid nitrogen vaporization to the rock sample; Sensor devices are used to monitor and collect data on the mechanical state of rock samples and changes in the temperature of the environment in which the rock samples are located.

2. The high-temperature cold shock triaxial testing device according to claim 1, characterized in that: The loading unit includes a loading frame, an axial pressure cylinder, a loading shaft, a loading pressure head, a loading base, a confining pressure chamber and a confining pressure pump; The axial pressure oil cylinder is arranged at the upper end of the loading frame, the telescopic end of the axial pressure oil cylinder is connected to one end of the loading shaft, and the other end of the loading shaft is provided with the loading pressure head; The loading base is located directly below the loading pressure head, and a loading pad is provided on the loading base; A rock sample is placed between the loading pad and the loading head, and an axial load is applied to the rock sample by the loading pad and the loading head; The lower end of the confining pressure chamber is open, and the lower end of the confining pressure chamber can be sealed and connected to the edge of the loading base. The loading shaft passes through the upper end of the confining pressure chamber, and the loading shaft can be dynamically sealed and connected to the confining pressure chamber. The confining pressure pump is connected to the confining pressure chamber via a hydraulic pipeline. The confining pressure pump is used to inject confining pressure fluid of a set pressure into the confining pressure chamber, so that the confining pressure fluid applies confining pressure to the rock sample.

3. The high temperature cold shock triaxial testing device according to claim 2, characterized in that: The loading frame is provided with a lifting slide rail, and the lifting slide rail is arranged vertically; The confining pressure chamber is provided with a lifting slider, and the lifting slider is slidably matched with the lifting rail; A lifting cylinder is provided on the loading frame. The lifting cylinder is arranged vertically, and the telescopic end of the lifting cylinder is connected to the confining pressure chamber.

4. The high temperature cold shock triaxial testing device according to claim 2, characterized in that: The outer wall of the confining pressure chamber is provided with a thermal insulation layer.

5. The high temperature cold shock triaxial testing device according to claim 2, characterized in that: A groove is formed at the upper end of the loading base, and the loading pad is placed in the groove.

6. The high temperature cold shock triaxial testing device according to claim 2, characterized in that: The loading unit further comprises a servo controller, which is respectively connected to the axial pressure cylinder and the confining pressure pump via signals.

7. The high temperature cold shock triaxial testing device according to claim 2, characterized in that: The heating unit includes a resistance wire, a power controller and a power supply. The resistance wire is connected to the power supply via the power controller, is fixed on the top of the confining pressure chamber, and is arranged around the rock sample.

8. A high temperature cold shock triaxial testing device according to any one of claims 2 to 7, characterized in that: The liquid nitrogen cold shock unit includes a liquid nitrogen storage tank, a multi-way valve, a cooling hollow column and a vacuum pump; The liquid nitrogen storage tank is filled with liquid nitrogen, the liquid outlet of the liquid nitrogen storage tank is connected to the liquid inlet of the multi-way valve via a liquid inlet pipeline, and the multiple liquid outlets of the multi-way valve are connected to the cooling hollow column via a liquid infusion pipeline. The cooling hollow column is located in the confining pressure chamber, and the multiple cooling hollow columns are arranged around the rock sample. The cooling hollow columns are connected to the vacuum pump via an air outlet pipeline.

9. The high temperature cold shock triaxial testing device according to claim 8, characterized in that: The cooling hollow column is divided into a liquid storage chamber and a vaporization chamber; The liquid infusion pipeline is connected to the liquid storage chamber, and the gas outlet pipeline is connected to the gasification chamber; The liquid storage chamber and the gasification chamber are connected via a transition pipeline; The liquid inlet high-frequency solenoid valve is provided on the liquid infusion pipeline, the gasification high-frequency solenoid valve is provided on the transition pipeline, and the exhaust high-frequency solenoid valve is provided on the gas outlet pipeline; By controlling the opening and closing frequency, number of times and duration of the liquid inlet high-frequency solenoid valve, the vaporization high-frequency solenoid valve and the exhaust high-frequency solenoid valve, liquid nitrogen first flows into the liquid storage chamber, and then flows into the vacuum vaporization chamber through the liquid storage chamber. The cooling hollow column realizes cold shock on the rock sample in the confining pressure chamber.

10. A high temperature cold shock triaxial test method, using the high temperature cold shock triaxial test device according to any one of claims 1 to 9, characterized in that: The steps include: Step 1: Rock sample installation After the rock sample and the loading pad are sealed and wrapped, they are placed on the groove of the loading base. The lifting cylinder drives the confining pressure chamber down so that the lower end of the confining pressure chamber is sealed and connected to the edge of the loading base. Step 2: Apply axial pressure and confining pressure The axial pressure cylinder drives the loading pressure head to act on the upper end of the rock sample through the loading shaft, applying initial axial pressure to the rock sample. The confining pressure pump injects the set confining pressure fluid into the confining pressure chamber to apply confining pressure to the rock sample. Step 3: Heating and insulation Turn on the power supply, and use the power controller to control the resistance wire to heat the confining fluid. The heat is transferred to the rock sample through the confining fluid, so that the confining fluid and rock sample are heated to the set temperature and maintained; Step 4: Cooling shock Liquid nitrogen in the liquid nitrogen storage tank is intermittently injected into the gasification chamber of the cooling hollow column to gasify and absorb heat, thereby reducing the temperature of the confining pressure liquid and the rock sample and performing cold shock on the rock sample; Step 5: Rock sample loading After the rock sample has undergone the test-set confining pressure, temperature increase, cold shock and cooling, the rock sample is continuously loaded using the loading unit; During steps 2 to 5, the sensor device monitors and collects the mechanical state data of the rock sample and the temperature change of the environment in which the rock sample is located in real time; Step 6: Rock sample removal The confining pressure pump discharges the confining pressure liquid in the confining pressure chamber, the lifting cylinder drives the confining pressure chamber to rise, the rock sample is removed, and the test ends.

Images