An end heat exchange in-situ CT triaxial multi-field coupling test system and method

Abstract

This invention provides an in-situ CT triaxial multi-field coupling test system and method with end-heat exchange, relating to geotechnical engineering testing. The system includes: a PEEK pressure chamber comprising a cylinder, an upper heat exchange head, and a lower heat exchange head. A flexible diaphragm is provided inside the cylinder, with the upper and lower ends of the cylinder and the flexible diaphragm respectively embedded in upper and lower grooves, forming a confining pressure cavity between the flexible diaphragm and the inner wall of the cylinder. Both the upper and lower heat exchange heads have circulation channels inside, and both have seepage channels extending into the cylinder on their top surfaces; an axial loading device for applying axial deviatoric stress to the PEEK pressure chamber; a temperature control system connected to the two circulation channels to form an end-heat exchange loop; a fluid injection system connected to the confining pressure cavity and the seepage channels; and a CT scanning system. The beneficial effects of this invention are: reducing interference from the temperature control device on X-ray propagation; and establishing a relatively uniform temperature field inside the rock sample.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, and in particular to an end-heat-exchange in-situ CT triaxial multi-field coupling test system and method. Background Technology

[0002] The mechanical response and microstructural evolution of soil, rock, and porous media under the coupled effects of stress, temperature, and other multi-physics fields directly affect the long-term stability and safety of engineering structures. To elucidate these mechanisms, in-situ testing techniques combining triaxial loading systems with CT scanning have emerged. Through in-situ CT imaging, this technique enables non-destructive, real-time visualization of the internal structure of samples while loads are applied, and has become a key tool for multi-field coupling research.

[0003] Currently, temperature control methods in existing in-situ CT scanning experiments are mainly divided into: 1. Overall heating temperature control method. Patent (US11119056B2) discloses a method to increase the sample temperature by heating the entire pressure chamber or the external environment. Existing overall heating temperature control methods, because heat needs to be transferred to the sample through multiple layers, are prone to slow temperature response and uneven temperature field distribution. Furthermore, when the heating device is close to the CT scanning path, it affects the temperature of the CT scanning system, which can negatively impact image quality. 2. Local direct heating temperature control method. Patent (CN119936081A) discloses a scheme of setting heating elements near or inside the sample. Although local direct heating temperature control can shorten the heat transfer path, the introduction of heating elements can easily cause temperature differences in components such as the PEEK pressure chamber tube, leading to deformation, cracking, or fatigue damage of the PEEK pressure chamber tube, seriously threatening the equipment safety and long-term reliability of multi-field coupling experiments.

[0004] In summary, existing temperature control methods in CT scanning have shortcomings in terms of temperature control accuracy, temperature field uniformity, imaging compatibility, and integration with multi-field coupled loading systems. These shortcomings are particularly pronounced for in-situ CT triaxial systems with a PEEK pressure chamber as their core feature, where overall heating affects imaging and localized heating damages the equipment. Therefore, it is necessary to propose a new temperature control method and experimental system structure to achieve precise temperature control of the sample and reduce its impact on CT imaging. Summary of the Invention

[0005] In view of this, in order to overcome the shortcomings in temperature control accuracy, temperature field uniformity, imaging compatibility and integration with multi-field coupling loading systems, embodiments of the present invention provide an end-heat-exchange in-situ CT triaxial multi-field coupling test system and method.

[0006] Embodiments of the present invention provide an in-situ CT triaxial multi-field coupling test system for end heat exchange, comprising:

[0007] The PEEK pressure chamber includes a cylinder, an upper heat exchange head, and a lower heat exchange head. The cylinder is open at both ends and has a flexible diaphragm inside. The bottom surface of the upper heat exchange head has an upper groove, and the top surface of the lower heat exchange head has a lower groove. The upper and lower ends of the cylinder and the flexible diaphragm are respectively embedded in the upper and lower grooves. The flexible diaphragm is used to wrap the rock sample and forms a confining pressure cavity with the inner wall of the cylinder. Both the upper and lower heat exchange heads have circulation channels inside, which are located near the upper and lower ends of the cylinder. The bottom surface of the upper heat exchange head and the top surface of the lower heat exchange head have seepage channels extending into the cylinder. An axial loading device is provided, wherein the PEEK pressure chamber is detachably installed in the axial loading device, and the axial loading device is used to apply axial deviatoric stress to the PEEK pressure chamber. A temperature control system is connected to the two circulating channels to form an end heat exchange circuit, so as to input heat-carrying fluid into the two circulating channels, thereby heating or cooling the rock sample. A fluid injection system, which is connected to the confining pressure chamber and the seepage channel respectively, to apply confining pressure to the periphery of the rock sample and pore fluid pressure to the interior of the rock sample; And a CT scanning system, which includes an X-ray radiation source and a detector respectively located on both sides of the PEEK pressure chamber.

[0008] Furthermore, the circulating flow channel is a tortuous flow channel, the middle of which is parallel to the middle of the upper and lower ends of the cylinder, and the two ends of the tortuous flow channel are bent multiple times to partially surround the edges of the upper and lower ends of the cylinder.

[0009] Furthermore, both the upper heat exchange head and the lower heat exchange head are made of thermally conductive metal.

[0010] Furthermore, the PEEK pressure chamber also includes a base and an upper pressure plate. The lower heat exchange head is installed on the base, and the upper heat exchange head is installed on the upper pressure plate. One seepage channel is disposed in the base and passes through the lower heat exchange head, extending to the lower end of the cylinder. The other seepage channel is disposed in the upper pressure plate and passes through the upper heat exchange head, extending to the upper end of the cylinder.

[0011] Furthermore, the axial loading device includes a loading frame, a lifting platform, an axial actuator, and a axial pressure rod. The lifting platform is fixedly installed at the bottom of the loading frame and is used to place the PEEK pressure chamber. The axial actuator is rotatably installed at the top of the loading frame. The upper end of the axial pressure rod is connected to the output end of the axial actuator, and the lower end is detachably connected to the upper part of the PEEK pressure chamber. A rotating platform is provided on the upper surface of the lifting platform, and a motor is provided inside the lifting platform. The motor is connected to the rotating platform to drive the rotating platform to rotate.

[0012] Furthermore, the lower end of the axial pressure rod is connected to the upper pressure plate via a dynamic sealing guide sleeve.

[0013] Furthermore, a telescopic rod is connected to the bottom of the lifting platform, and a support base is connected to the lower end of the telescopic rod. The support base is fixedly installed at the bottom of the loading frame.

[0014] Furthermore, the axial loading device also includes a hanging plate with two lifting rings on its edge. The upper heat exchange pressure head has an upper connector on its top. The lower end of the axial pressure rod is detachably connected to the hanging plate, and the hanging plate is detachably connected to the upper connector. The top of the loading frame is provided with a pulley and a pull rope that passes around the pulley. One end of the pull rope is connected to the two lifting rings, and the other end is pulled and released by adding or removing counterweights.

[0015] Furthermore, it also includes a data processing system, which is connected to the axial loading device, the temperature control system, the fluid injection system and the CT scanning system respectively, to control the axial loading device to apply axial deviatoric stress to the PEEK pressure chamber, the temperature control system to input heat transfer fluid into the two circulating channels, the fluid injection system to apply confining pressure to the periphery of the rock sample and to apply pore fluid pressure to the interior of the rock sample, and the CT scanning system to scan the rock sample.

[0016] Furthermore, embodiments of the present invention also provide a method for in-situ CT triaxial multi-field coupling test with end heat exchange, using the aforementioned in-situ CT triaxial multi-field coupling test system with end heat exchange, and including the following steps: S1. Preheat the CT scanning system; S2. Wrap a flexible diaphragm around the surface of the rock sample, then place the rock sample wrapped with the flexible diaphragm into the cylinder, and then embed the upper and lower ends of the rock sample into the upper and lower grooves respectively, and seal the upper and lower ends of the flexible diaphragm into the upper and lower grooves to complete the filling of the rock sample in the PEEK pressure chamber. S3. Transport and install the PEEK pressure chamber onto the axial loading device; S4. Connect the temperature control system to the two circulating channels respectively to form an end heat exchange circuit; connect the fluid injection system to the confining pressure chamber and the seepage channel; S5. High-pressure fluid medium is injected into the confining pressure chamber through the fluid injection system to apply a predetermined confining pressure to the rock sample; seepage liquid is input into the seepage channel through the fluid injection system to apply a preset pore fluid pressure inside the rock sample; heat-carrying fluid is input into the two circulating channels through the temperature control system to heat or cool the rock sample until the rock sample reaches a preset temperature equilibrium. S6. Apply axial deviatoric stress to the rock sample using an axial loading device; S7. Rotational scanning of rock samples under multi-field coupling environment using a CT scanning system.

[0017] The beneficial effects of the technical solutions provided by the embodiments of the present invention are as follows: 1. The present invention provides an end-heat exchange in-situ CT triaxial multi-field coupling test system and method, which sets up circulating channels inside the upper and lower heat exchange heads at both ends of the cylinder, and uses the heat-carrying fluid in the circulating channels to heat or cool the two ends of the rock sample. In this way, a heat exchange structure is set up at the end of the rock sample for temperature control, so that the temperature control component is far away from the CT scanning path, thereby reducing the interference of the temperature control device on X-ray propagation, improving CT imaging conditions, and helping to improve the stability and clarity of the imaging of the internal structure of the sample.

[0018] 2. The present invention provides an end-heat-exchange in-situ CT triaxial multi-field coupling test system and method, which sets up a heat exchange structure at the end of the rock sample for temperature control. By avoiding direct heating of the PEEK pressure chamber wall and using end heat conduction and fluid circulation to control the temperature of the sample, the temperature gradient in the pipe wall area can be reduced, a more uniform temperature field can be established inside the rock sample, the gradient temperature difference of the rock sample can be avoided, and the simulation of multi-physics coupling conditions closer to reality can be achieved.

[0019] 3. The present invention provides an end-heat-exchange in-situ CT triaxial multi-field coupling test system and method. By utilizing a high thermal conductivity end structure and a fluid circulation temperature control method, a relatively uniform temperature field can be established inside the sample. Combined with a fluid injection system, it can simulate the multi-physical field coupling conditions of soil and rock materials. With the synchronous control mechanism of multi-field loading and CT scanning, continuous and non-destructive in-situ CT data can be obtained during the test, providing a technical means for studying the structural evolution behavior of materials under multi-field coupling.

[0020] 4. The present invention provides an end-heat exchange in-situ CT triaxial multi-field coupling test system and method, which sets up a heat exchange structure at the end of the rock sample for heating, thereby reducing the possibility of thermal stress concentration and creep deformation of PEEK material under high temperature and high pressure conditions, and improving the structural safety and service life of the device. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an in-situ CT triaxial multi-field coupling test system for end heat exchange according to the present invention; Figure 2 This is a schematic diagram of a CT scanning system; Figure 3 This is a schematic diagram of a PEEK pressure chamber; Figure 4 This is a schematic diagram of an axial loading device.

[0022] In the diagram: 1. PEEK pressure chamber; 101. Cylinder; 102. Flexible diaphragm; 103. Upper heat exchange head; 104. Lower heat exchange head; 105. Circulation channel; 106. Seepage channel; 107. Lower groove; 108. Upper groove; 109. Upper pressure plate; 110. Base; 111. Upper connector; 2. Axial loading device; 201. Loading frame; 202. Lifting platform; 203. Axial actuator; 204. Axial compression rod; 205. Dynamic sealing guide sleeve; 206. Hanging plate; 207. Telescopic rod; 208. Support seat; 209. Lifting ring; 210. Pulley; 3. Temperature control system; 4. Fluid injection system; 5. CT scanning system; 501. X-ray radiation source; 502. Detector; 6. Data processing system; 7. Rock sample. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0024] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0025] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0027] In the description of this invention, it should be noted that the circuits, electronic components and modules involved in this invention are all prior art, which can be fully implemented by those skilled in the art, and need not be elaborated upon.

[0028] It should be further noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] Please refer to Figure 1 and 2 The present invention provides an end-heat exchange in-situ CT triaxial multi-field coupling test system, including a PEEK pressure chamber 1, an axial loading device 2, a temperature control system 3, a fluid injection system 4, and a CT scanning system 5.

[0030] Please refer to Figure 3 The PEEK pressure chamber 1 is used to fill the rock sample 7. The PEEK pressure chamber 1 mainly includes a cylinder 101, an upper heat exchange pressure head 103, and a lower heat exchange pressure head 104. The cylinder 101 is open at both ends and has a flexible diaphragm 102 inside. The bottom surface of the upper heat exchange pressure head 103 has an upper groove 108. The cylinder 101 is a multifunctional wave-transparent structure. The main body is made of special engineering plastic polyetheretherketone (PEEK) to achieve extremely low X-ray attenuation and no metal artifacts. The tube wall is designed as a thick cylindrical shape to resist creep deformation and brittle fracture under high confining pressure and axial pressure. The inner wall surface utilizes the chemical inertness of the material itself to achieve resistance to acid and alkali fluid corrosion and prevent cross-contamination of the sample.

[0031] The lower heat exchange head 104 has a lower groove 107 on its top surface. The upper and lower ends of the cylinder 101 and the flexible diaphragm 102 are respectively embedded in the upper groove 108 and the lower groove 107. The shape of the upper groove 108 is adapted to the shape of the upper end of the cylinder 101, and the shape of the lower groove 107 is adapted to the shape of the lower end of the cylinder 101, so that the upper and lower ends of the cylinder 101 are respectively sealed and connected to the upper heat exchange head 103 and the lower heat exchange head 104. The upper heat exchange head 103 and the lower heat exchange head 104 are generally made of thermally conductive metal materials, such as stainless steel or titanium alloy, which have excellent heat exchange performance and mechanical load-bearing capacity.

[0032] The flexible diaphragm 102 is used to wrap the rock sample 7 and forms a confining pressure cavity between it and the inner wall of the cylinder 101. The flexible diaphragm 102 is made of rubber, and a certain gap is maintained between the flexible diaphragm 102 and the inner wall of the cylinder 101 to form the annular confining pressure cavity.

[0033] Both the upper heat exchange head 103 and the lower heat exchange head 104 are equipped with circulation channels 105, which are located near the upper and lower ends of the cylinder 101, respectively. The heat-carrying fluid flows into the circulation channels 105 and can exchange heat with the upper and lower ends of the rock sample 7 in the cylinder 101, rapidly transferring heat or cold to both ends of the rock sample 7, thereby achieving precise control of the sample temperature.

[0034] In some embodiments, to ensure a more uniform heat exchange effect, the circulating channel 105 is a tortuous channel, with the middle of the tortuous channel parallel to the middle of the upper and lower ends of the cylinder 101. The two ends of the tortuous channel are bent multiple times to partially surround the edges of the upper and lower ends of the cylinder 101. The tortuous channel extends the heat exchange time and increases the heat exchange area at the upper and lower ends of the cylinder 101 by bending, thereby achieving a more uniform heat exchange effect and improving the temperature field uniformity of the rock sample 7.

[0035] Both the bottom surface of the upper heat exchange head 103 and the top surface of the lower heat exchange head 104 are provided with seepage channels 106 extending into the cylinder 101. Seepage liquid is introduced into the top and bottom of the rock sample 7 through the seepage channels 106, thereby applying pore fluid pressure to the inside of the rock sample 7.

[0036] More specifically, the PEEK pressure chamber 1 also includes a base 110 and an upper pressure plate 109. The lower heat exchange head 104 is installed on the base 110, and the upper heat exchange head 103 is installed on the upper pressure plate 109. One seepage channel 106 is disposed in the base 110 and passes through the lower heat exchange head 104, extending to the lower end of the cylinder 101. The other seepage channel 106 is disposed in the upper pressure plate 109 and passes through the upper heat exchange head 103, extending to the upper end of the cylinder 101.

[0037] Please refer to Figure 4 The PEEK pressure chamber 1 is detachably installed in the axial loading device 2, which is used to apply axial deviatoric stress to the PEEK pressure chamber 1. The axial loading device 2 includes a loading frame 201, a lifting platform 202, an axial actuator 203, and a axial pressure rod 204. The lower end of the loading frame 201 is generally fixedly installed on a fixed structure. The lifting platform 202 is fixedly installed at the bottom of the loading frame 201 and is used to place the PEEK pressure chamber 1. The upper end of the axial actuator 203 is rotatably installed on the top of the loading frame 201. The upper end of the axial pressure rod 204 is connected to the output end of the axial actuator 203, and the lower end is detachably connected to the upper part of the PEEK pressure chamber 1. The upper surface of the lifting platform 205 is provided with a rotating platform (not shown in the figure). The rotating platform is rotatably disposed in the middle of the lifting platform 205 and embedded in the upper surface of the lifting platform 205. A motor is provided inside the lifting platform 205, and the motor is connected to the rotating platform to drive the rotating platform to rotate. The PEEK pressure chamber 1 is placed on the rotating platform, thereby driving the PEEK pressure chamber 1 to rotate.

[0038] The lower end of the axial pressure rod 204 is connected to the upper pressure plate 109 via a dynamic sealing guide sleeve 205. The dynamic sealing guide sleeve 205 is fixed above the upper pressure plate 109, and the axial pressure rod 204 passes through the dynamic sealing guide sleeve 205 to connect to the upper pressure plate 109, applying axial deflection stress to the upper pressure plate 109. This ensures that accurate axial deflection stress is applied to the rock sample 7 inside the cylinder 101, and maintains the sealing of the pressure chamber during the rotational scanning process, ensuring the stability of the in-situ loading test.

[0039] In some embodiments, a telescopic rod 207 is connected to the bottom of the lifting platform 202, and a support base 208 is connected to the lower end of the telescopic rod 207. The support base 208 is fixedly installed on the bottom of the loading frame 201. The lifting platform 202 is driven to rise and fall by the telescopic rod 207, thereby adjusting the height of the rock sample 7.

[0040] In addition, the axial loading device 2 also includes a lifting plate 206, with two lifting rings 209 on each side of the edge of the lifting plate 206. The upper heat exchange pressure head 103 has an upper connector 111 on its top. The lower end of the axial pressure rod 204 is detachably connected to the lifting plate 206, and the lifting plate 206 is detachably connected to the upper connector 111. The top of the loading frame 201 has a pulley 210 and a pull rope that passes around the pulley 210. One end of the pull rope extends into two connecting ropes that are respectively connected to the two lifting rings 209, and the other end is pulled or released by adding or removing counterweights. In this way, the PEEK pressure chamber 1 can be lifted and adjusted to the required height by pulling or releasing the pull rope.

[0041] The temperature control system 3 is connected to the two circulating channels 105 respectively to form an end heat exchange loop, so as to input heat-carrying fluid into the two circulating channels 105, thereby heating or cooling the rock sample 7. The temperature control system 3 regulates the temperature of the rock sample 7 by circulating the heat-carrying fluid into the end heat exchange loop.

[0042] The fluid injection system 4 is connected to both the confining pressure chamber and the seepage channel 106 to apply confining pressure to the periphery of the rock sample 7 and pore fluid pressure to the interior of the rock sample 7. Specifically, the fluid injection system 4 is connected to the confining pressure chamber via a pipe, and a high-pressure fluid medium such as silicone oil or water is introduced into the confining pressure chamber to apply confining pressure to the periphery of the rock sample 7. The fluid injection system 4 is also connected to the seepage channel 106 via a pipe, and seepage liquid is introduced into the seepage channel 106 to apply a preset pore fluid pressure to the interior of the rock sample 7.

[0043] The CT scanning system 5 includes an X-ray source 501 and a detector 502 respectively disposed on both sides of the PEEK pressure chamber 1. The X-ray path generated by the X-ray source 501 passes through the cylindrical body 101 area of ​​the PEEK pressure chamber 1, and there are no metal temperature control elements blocking the path.

[0044] Furthermore, the end-heat-exchange in-situ CT triaxial multi-field coupling test system of the present invention also includes a data processing system 6. The data processing system 6 is selected as a computer control terminal and is connected to the axial loading device 2, the temperature control system 3, the fluid injection system 4, and the CT scanning system 5 respectively. This system controls the axial loading device 2 to apply axial deviatoric stress to the PEEK pressure chamber 1, the temperature control system 3 to input heat-carrying fluid into the two circulating channels 105, the fluid injection system 4 to apply confining pressure to the periphery of the rock sample 7 and pore fluid pressure to the interior of the rock sample 7, and the CT scanning system 5 to scan the rock sample 7. The data processing system 6 coordinates the control of the axial loading device 2, the temperature control system 3, the fluid injection system 4, and the CT scanning system 5 to apply various physical fields and simultaneously acquire mechanical data and CT image data, thereby achieving real-time quantitative monitoring of the microstructural evolution of deep rocks under multi-field coupling conditions.

[0045] Furthermore, embodiments of the present invention also provide a method for in-situ CT triaxial multi-field coupling test with end heat exchange, using the aforementioned in-situ CT triaxial multi-field coupling test system with end heat exchange, and including the following steps: S1. Preheat the CT scanning system 5 to reach the required operating temperature of the CT scanning system 5.

[0046] S2. Wrap the surface of the rock sample 7 with a flexible diaphragm 102, then place the rock sample 7 wrapped with the flexible diaphragm 102 inside the cylinder 101, and then embed the upper and lower ends of the rock sample 7 into the upper groove 108 and the lower groove 107 respectively, and seal the upper and lower ends of the flexible diaphragm 102 into the upper groove 108 and the lower groove 107 to complete the filling of the rock sample 7 into the PEEK pressure chamber 1.

[0047] S3. Transport and install the PEEK pressure chamber 1 onto the axial loading device 2; S4. Connect the temperature control system 3 to the two circulation channels 105 respectively to form an end heat exchange circuit; connect the fluid injection system 4 to the confining pressure cavity and the seepage channel 106.

[0048] S5. High-pressure fluid medium is injected into the confining pressure chamber through the fluid injection system 4 to apply a predetermined confining pressure to the rock sample 7; seepage liquid is input into the seepage channel 106 through the fluid injection system 4 to apply a preset pore fluid pressure inside the rock sample 7; heat-carrying fluid is input into the two circulation channels 105 through the temperature control system 3 to heat or cool the rock sample 7 until the rock sample 7 reaches a preset temperature equilibrium. S6. Apply axial deviatoric stress to the rock sample 7 using the axial loading device 2; transport the entire PEEK pressure chamber 1 to the rotating platform in the middle of the lifting platform using a combination of rope, pulley and hanging plate. S7. The rock sample 7 under multi-field coupling environment is rotated and scanned by the CT scanning system 5. While the rotary table drives the PEEK pressure chamber 1 to rotate, the CT scanning system 5 scans the rock sample 7, thereby obtaining CT slice images of the rock sample 7 in various directions.

[0049] The data processing system 6 synchronously collects and records axial load, displacement, confining pressure, pore pressure and temperature data during the experiment, and performs coupled analysis based on the acquired CT slice images and mechanical data.

[0050] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0051] Where there is no conflict, the embodiments and features described above can be combined with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-axis multi-field coupling test system for end-heat transfer in situ CT, characterized in that, include: The PEEK pressure chamber includes a cylinder, an upper heat exchange head, and a lower heat exchange head. The cylinder is open at both ends and has a flexible diaphragm inside. The bottom surface of the upper heat exchange head has an upper groove, and the top surface of the lower heat exchange head has a lower groove. The upper and lower ends of the cylinder and the flexible diaphragm are respectively embedded in the upper and lower grooves. The flexible diaphragm is used to wrap the rock sample and forms a confining pressure cavity with the inner wall of the cylinder. Both the upper and lower heat exchange heads have circulation channels inside, which are located near the upper and lower ends of the cylinder. The bottom surface of the upper heat exchange head and the top surface of the lower heat exchange head have seepage channels extending into the cylinder. An axial loading device is provided, wherein the PEEK pressure chamber is detachably installed in the axial loading device, and the axial loading device is used to apply axial deviatoric stress to the PEEK pressure chamber. A temperature control system is connected to the two circulating channels to form an end heat exchange circuit, so as to input heat-carrying fluid into the two circulating channels, thereby heating or cooling the rock sample. A fluid injection system, which is connected to the confining pressure chamber and the seepage channel respectively, to apply confining pressure to the periphery of the rock sample and pore fluid pressure to the interior of the rock sample; And a CT scanning system, which includes an X-ray radiation source and a detector respectively located on both sides of the PEEK pressure chamber.

2. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 1, characterized in that: The circulating flow channel is a tortuous flow channel, with the middle part of the tortuous flow channel parallel to the middle parts of the upper and lower ends of the cylinder. The two ends of the tortuous flow channel are bent multiple times to partially surround the edges of the upper and lower ends of the cylinder.

3. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 1, characterized in that: Both the upper heat exchange head and the lower heat exchange head are made of thermally conductive metal.

4. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 1, characterized in that: The PEEK pressure chamber also includes a base and an upper pressure plate. The lower heat exchange head is installed on the base, and the upper heat exchange head is installed on the upper pressure plate. One seepage channel is disposed in the base and passes through the lower heat exchange head, extending to the lower end of the cylinder. The other seepage channel is disposed in the upper pressure plate and passes through the upper heat exchange head, extending to the upper end of the cylinder.

5. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in any one of claims 1-4, characterized in that: The axial loading device includes a loading frame, a lifting platform, an axial actuator, and a axial pressure rod. The lifting platform is fixedly installed at the bottom of the loading frame and is used to place the PEEK pressure chamber. The axial actuator is rotatably installed at the top of the loading frame. The upper end of the axial pressure rod is connected to the output end of the axial actuator, and the lower end is detachably connected to the upper part of the PEEK pressure chamber. A rotating platform is provided on the upper surface of the lifting platform, and a motor is provided inside the lifting platform. The motor is connected to the rotating platform to drive the rotating platform to rotate.

6. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 5, characterized in that: The lower end of the axial pressure rod is connected to the upper pressure plate through a dynamic sealing guide sleeve.

7. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 5, characterized in that: The bottom of the lifting platform is connected to a telescopic rod, and the lower end of the telescopic rod is connected to a support base, which is fixedly installed at the bottom of the loading frame.

8. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 6, characterized in that: The axial loading device also includes a hanging plate with two lifting rings on its edge. The upper heat exchange head has an upper connector on its top. The lower end of the axial pressure rod is detachably connected to the hanging plate. The hanging plate is detachably connected to the upper connector. The top of the loading frame has a pulley and a pull rope that goes around the pulley. One end of the pull rope is connected to the two lifting rings, and the other end is pulled and released by adding or removing counterweights.

9. The in-situ CT triaxial multi-field coupling test system for end heat exchange as described in claim 1, characterized in that: It also includes a data processing system, which is connected to the axial loading device, the temperature control system, the fluid injection system and the CT scanning system respectively, to control the axial loading device to apply axial deviatoric stress to the PEEK pressure chamber, the temperature control system to input heat transfer fluid into the two circulating channels, the fluid injection system to apply confining pressure to the periphery of the rock sample and pore fluid pressure to the interior of the rock sample, and the CT scanning system to scan the rock sample.

10. A method for in-situ CT triaxial multi-field coupling test of end heat transfer, characterized in that: Using an end-heat-transfer in-situ CT triaxial multi-field coupling test system as described in any one of claims 1-9, and comprising the following steps: S1. Preheat the CT scanning system; S2. Wrap a flexible diaphragm around the surface of the rock sample, then place the rock sample wrapped with the flexible diaphragm into the cylinder, and then embed the upper and lower ends of the rock sample into the upper and lower grooves respectively, and seal the upper and lower ends of the flexible diaphragm into the upper and lower grooves to complete the filling of the rock sample in the PEEK pressure chamber. S3. Transport and install the PEEK pressure chamber onto the axial loading device; S4. Connect the temperature control system to the two circulating channels respectively to form an end heat exchange circuit; connect the fluid injection system to the confining pressure chamber and the seepage channel; S5. High-pressure fluid medium is injected into the confining pressure chamber through the fluid injection system to apply a predetermined confining pressure to the rock sample; seepage liquid is input into the seepage channel through the fluid injection system to apply a preset pore fluid pressure inside the rock sample; heat-carrying fluid is input into the two circulating channels through the temperature control system to heat or cool the rock sample until the rock sample reaches a preset temperature equilibrium. S6. Apply axial deviatoric stress to the rock sample using an axial loading device; S7. Rotational scanning of rock samples under multi-field coupling environment using a CT scanning system.

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