A high ground temperature tunnel hydraulic thermal damage test device and test method

Abstract

The present invention discloses a high-temperature tunnel hydrothermal damage test device and test method, belonging to the field of rock mechanics testing technology. The test device includes a boundary temperature loading structure, a stress loading structure, a water pressure loading structure, and a center temperature application structure, which are arranged at corresponding positions of a tunnel specimen containing a hole. It also includes a sealing structure that seals at both ends of the hole and a camera structure that extends into the hole. This device can visualize the hydrothermal multi-field loads and the entire test process, more comprehensively reflecting the working state of the tunnel during operation. The test method using the test device has the advantage of stable test progress.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock mechanics testing, and in particular relates to a high ground temperature tunnel hydraulic thermal damage testing device and a testing method. Background Art

[0002] With the implementation of the "Development Plan" in western China, numerous deep-buried hydraulic tunnels have been constructed. These tunnels are located in areas subject to intense tectonic movement and complex geological conditions. High ground temperatures also pose a new challenge for hydraulic tunnels. During tunnel operation, cold water shock can easily create large temperature gradients, leading to the formation of tensile stress fields circumferentially within the tunnel. This can cause cracking in the lining and rock mass, leading to water seepage and threatening the safe and stable operation of the project. Therefore, understanding the spatiotemporal evolution of hydrothermal damage (THMD) in high-geotemperature hydraulic tunnels will undoubtedly provide important insights for the construction and operation of tunnels under high ground temperatures and complex stresses.

[0003] Experimental research is a direct means of understanding the spatiotemporal evolution of hydrothermal damage in high-temperature tunnels. The study of the variability of parameters such as temperature gradients and internal water pressure ranges has a significant impact on the hydrothermal laws of tunnels. Furthermore, the ability to visually display the damage evolution within tunnels is crucial for understanding the fracture mechanics of tunnels. However, existing research and techniques often focus on analyzing a single influencing factor. The paper "Experimental Study on Critical Water Pressure for Hydraulic Fracture of Fractured Rock Masses" proposes a single internal water pressure test, which uses an external I-beam seal for high-pressure water sealing and does not require drilling into the specimen. The paper "Thermomechanical Coupling Model Test of Shield Tunnel Lining Structures Under High Temperatures" proposes a single temperature gradient test, which places the entire tunnel structure on a temperature loading device, eliminating the need for sealing and drilling the specimen. The paper "Bidirectional Rheological Properties of Surrounding Rock in Deep Tunnels" proposes a single confining pressure test, which uses biaxial loading of open-hole tunnel specimens and does not require sealing or drilling. Different from a single load, for hydrothermal multi-field loads, it is required that there is no mutual influence between the load structures, good sealing, and stable test progress. However, there are still some problems. For example, for the sealing requirements of the specimen, a single internal water pressure load can be applied with an I-beam, but considering the confining pressure of the specimen, it is impossible to apply confining pressure with an I-beam because the confining pressure load will hit the I-beam. For this, the specimen can be punched to seal it, but the punching method will cause stress concentration at the punching point, leading to rupture and even seal failure. In addition, due to the complexity of the test, the interior of the tunnel is basically in a closed state, making it difficult to explore the damage evolution process inside the tunnel. A built-in camera can be used, but the hydrothermal multi-field load also affects the structure of the camera. Summary of the Invention

[0004] In response to the technical problem that the existing technology only analyzes a single factor in tunnel damage tests, the present invention proposes a high-geotemperature tunnel hydrothermal damage test device to achieve full visualization of hydrothermal multi-field loads and the test process, and more comprehensively reflect the working status of the tunnel during operation; another purpose of the present invention is to propose a high-geotemperature tunnel hydrothermal damage test method.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions: a high geothermal tunnel hydraulic thermal damage test device, comprising a tunnel specimen, the tunnel specimen being provided with a through hole, and also comprising a data acquisition system connected to an external computer, and also comprising boundary temperature loading structures arranged on the top, bottom, left and right sides of the tunnel specimen, and stress loading structures arranged on the other side of the boundary temperature loading structures on the top, left and right sides; also comprising a sealing structure that seals with the two end faces of the hole, the sealing structure comprising a sealing cover, the sealing cover comprising a front sealing cover and a rear sealing cover; also comprising a water pressure loading structure that applies internal water pressure to the hole through the front sealing cover, a central temperature applying structure that applies central temperature load to the hole through the front sealing cover and the rear sealing cover, and a camera structure that extends into the hole through the front sealing cover.

[0006] Furthermore, the tunnel specimen is in the shape of a cube and is cut from sandstone or marble; the hole is located at the center line of the tunnel specimen and is cylindrical; and the sealing material is stainless steel.

[0007] Furthermore, the cover structure also includes a fixing bolt for passing through the cover and fixing the inside of the tunnel specimen bolt hole, and the fixing bolt is provided with an injection hole for filling epoxy resin into the gap between the fixing bolt and the tunnel specimen bolt hole.

[0008] Furthermore, the camera structure includes a camera rod, and a plurality of camera bracket groups are provided on the camera rod, and the camera bracket group includes a plurality of camera brackets fixed around the circumference of the camera rod, and a camera group is arranged between two adjacent camera bracket groups, and the camera group is a plurality of miniature cameras fixed around the circumference of the camera rod and connected to an external computer; the camera structure also includes a transparent cover mounted on the outside of the camera bracket group, and the miniature camera group and the transparent cover form a space; the camera rod is provided with scale lines along the axial direction for identifying the damage position, and the front cover is provided with scale lines for identifying the rotation angle of the camera rod.

[0009] Furthermore, the water pressure loading structure includes a water storage cylinder, one side of the water storage cylinder is provided with a water inlet and outlet, the other side of the water storage cylinder is provided with a bayonet with an internal thread, a piston is provided in the water storage cylinder, the piston and the water storage cylinder form a closed water storage chamber, the piston is provided with an opening on a side close to the bayonet, a rotor is provided in the piston, the rotor slides on the inner wall of the piston, the rotor is fixedly connected to the motor shaft, one end of the motor shaft extends into the opening and does not contact the opening, the middle section of the outer side of the motor shaft is provided with an external thread adapted to the internal thread, and the other end of the motor shaft is connected to the output end of the motor; the water inlet and outlet are respectively connected to the water inlet pipe and the water outlet pipe, the water inlet pipe is connected to the water tank, the connection between the water inlet and outlet and the water inlet pipe is provided with a water inlet pipe valve, and the connection between the water inlet and outlet and the water outlet pipe is provided with a water outlet pipe valve; the water pressure loading structure also includes a water pressure loading switch for controlling the direction of the motor.

[0010] Furthermore, the boundary temperature loading structure includes a heating plate, and the two side plates of the heating plate are connected by a mesh plate, so that a plurality of mesh cavities for placing heating resistance wires are formed inside the heating plate.

[0011] Furthermore, the stress loading structure includes a stress loading plate and a force transmission shaft arranged on the stress loading plate.

[0012] Furthermore, the central temperature application structure includes a cooling pipe running through the hole, a condenser connected to one end of the cooling pipe, an evaporator connected to the other end of the cooling pipe, and a compressor connecting the cold sensor and the evaporator.

[0013] A test method, using the above-mentioned high ground temperature tunnel hydraulic thermal damage test device, includes the following steps: S1, applying initial internal water pressure: opening the water inlet pipe valve and closing the water outlet pipe valve, turning on the water pressure loading switch to reverse, the motor drives the piston to push the water storage cylinder to fill the water storage chamber with water; closing the water inlet valve and opening the water outlet valve, turning on the water pressure loading switch to rotate forward, the motor drives the piston to push the water storage cylinder to fill the hole with water and reach the internal water pressure value with a slightly rising trend, and then turning off the water pressure loading switch; S2, applying confining pressure: applying pressure to the stress loading plate, and transferring it to the heating plate and the tunnel sample in turn, so that the confining pressure value of the tunnel sample reaches a preset value and is maintained The confining pressure remains unchanged; S3. Apply boundary temperature load: turn on the heating plate to make the boundary temperature load of the tunnel specimen at a preset value above 60°C and maintain a constant temperature; S4. Apply test internal water pressure: turn on the water pressure loading switch and rotate it forward to make the internal water pressure value in the hole reach the preset value of the internal water pressure; S5. Apply center temperature load: turn on the compressor to make the center temperature load in the hole at a constant temperature below 10°C until the inside of the tunnel specimen ruptures; S6. In the above steps, turn on the micro camera to record different rupture characteristics, and record the changes in the rotation angle of the micro camera and the changes in the length of the camera stick inserted into the hole under different rupture characteristics.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention can achieve the application of different boundary temperature loads and confining pressures to tunnel specimens, and different internal water pressures and center temperature loads to the holes in the tunnel specimens. The boundary temperature load is a high ground temperature of more than 60°C, and the center temperature load is a low temperature of less than 10°C. This provides the control of various influencing factors in the multi-physical field coupling, can perform experimental sensitivity analysis, and is suitable for physical test simulations under different tunnel operation conditions in my country.

[0016] (2) The cover structure is designed to achieve the joint loading of internal water pressure and central temperature, and also serves as the entrance of the camera structure, providing conditions for the visualization and positioning of multi-field damage in the tunnel; the cover structure of the present invention adopts fixed bolts with additional injection holes to reduce stress concentration, ensure the stable conduct of the test, and achieve the joint loading of confining pressure and internal water pressure. The present invention can overcome the disadvantages of tunnel damage tests in previous research and technology that can only analyze a single influencing factor, and can simultaneously realize the multi-physical field coupling test of hydraulic and thermal damage during the operation of the tunnel, and more comprehensively reflect the working state of the tunnel during operation;

[0017] (3) A camera bracket group and a camera group are arranged on the slender camera rod, and a transparent cover is set on the outside of the camera bracket group. The transparent cover is made of 3D printed light-cured photosensitive epoxy resin material, which has the advantages of being soft on the outside and hard on the inside and transparent. It realizes the requirements of the camera structure to be strong, waterproof, transparent, and quantitatively adjustable in position under the action of complex hydrothermal fields. It can overcome the shortcomings of previous technologies that the interior of the tunnel is in a closed state, making it difficult to intuitively explore the evolution process of damage inside the tunnel, and realize the full visualization of the hydrothermal damage process of high-temperature tunnels, providing a solid experimental basis for the study of the hydrothermal damage mechanism of high-temperature tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic axonometric diagram of the structure of the test device of the present invention;

[0019] Figure 2 It is a schematic front view of the structure of the test device of the present invention;

[0020] Figure 3 It is a schematic rear view of the structure of the test device of the present invention;

[0021] Figure 4 A schematic top view of the structure of the test device of the present invention;

[0022] Figure 5 This is a schematic assembly diagram of the cover structure of the present invention;

[0023] Figure 6 This is a schematic left side view of the assembly of the cover structure of the present invention;

[0024] Figure 7 It is a schematic diagram of the partial structure of the camera structure of the present invention;

[0025] Figure 8 This is a schematic assembly diagram of the camera rod and the transparent cover of the present invention.

[0026] Figure 9 It is a schematic axonometric diagram of the hydraulic loading structure of the present invention;

[0027] Figure 10 A schematic top view of the hydraulic loading structure of the present invention;

[0028] Figure 11 A schematic cross-sectional view of a local structure of the hydraulic loading structure of the present invention;

[0029] Figure 12 It is a structural schematic diagram of the heating plate of the present invention;

[0030] Figure 13 This is a schematic structural diagram of the central temperature application structure of the present invention;

[0031] Figure 14 This is a schematic diagram of the internal structure of the central temperature application structure of the present invention;

[0032] Among them, 1 is the tunnel sample, 2 is the transparent cover, 3 is the camera stick, 4 is the fixing bolt, 5 is the cover, 6 is the heating plate, 7 is the stress sensor, 8 is the stress loading plate, 9 is the transmission shaft, 10 is the condenser, 11 is the compressor, 12 is the evaporator, 13 is the cooling pipe, 14 is the water storage cylinder, 15 is the motor, 16 is the motor track, 17 is the motor frame, 18 is the water pressure loading switch, 19 is the motor shaft, 20 is the bottom plate, 21 is the water storage cylinder frame, 22 is the outlet pipe valve, 23 is the water inlet and outlet, 24 is the water tank, 25 is the water inlet pipe valve, 26 1 is the water inlet pipe, 27 is the water outlet pipe, 28 is the water pressure monitor, 29 is the external thread, 30 is the internal thread, 31 is the piston, 32 is the water storage chamber, 33 is the rubber ring, 34 is the cover through hole, 35 is the rubber ring through hole, 36 is the cover bolt hole, 37 is the rubber ring bolt hole, 38 is the sample surface bolt hole, 39 is the cover camera through hole, 40 is the rubber ring camera through hole, 41 is the miniature camera, 42 is the camera bracket, 43 is the rotor, 44 is the sliding cavity, 45 is the grid cavity, 46 is the heating resistance wire, 47 is the heating plate side plate, and 48 is the grid plate. DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to the accompanying drawings. In the description of the present invention, the terms "front," "rear," "left," "right," "up," "down," "vertical," "horizontal," "high," "low," "inside," "outside," and the like, indicating directions or positions, are based on the directions or positions shown in the accompanying drawings and are intended solely to facilitate description and simplify 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 direction. Therefore, they should not be construed as limiting the scope of protection of the present invention.

[0034] The present invention provides a high ground temperature tunnel hydraulic thermal damage test device. Figures 1 to 4 It is the overall structure of the present invention, from Figures 1 to 4 It can be seen that it includes a tunnel specimen 1, which is provided with a through hole, and also includes a data acquisition system connected to an external computer, and also includes a boundary temperature loading structure arranged on the top, bottom, left and right sides of the tunnel specimen 1, and a stress loading structure arranged on the other side of the temperature loading structure on the top, left and right sides; it also includes a sealing structure that seals with the two end faces of the hole, the sealing structure includes a sealing cover, and the sealing cover includes a front sealing cover and a rear sealing cover; it also includes a water pressure loading structure that applies internal water pressure to the hole through the front sealing cover, a central temperature applying structure that applies central temperature load to the hole through the front sealing cover and the rear sealing cover, and a camera structure that extends into the hole through the front sealing cover.

[0035] Preferably, the tunnel specimen is in the shape of a cube and is cut from sandstone or marble; the hole is located at the center line of the tunnel specimen and is in the shape of a cylinder; and the sealing material is stainless steel. Figures 1 to 4 As shown, the stress loading structure includes a stress loading plate 8 and a force transmission shaft 9 arranged on the stress loading plate 8.

[0036] The capping structure of the present invention can seal both end faces of the hole so that water pressure is applied inside the hole without leaking; as a connecting part between the water pressure loading structure, the central temperature application structure and the hole, it can realize the combined loading of water pressure and central temperature in the hole; as the entrance of the camera structure, it provides conditions for the visualization and positioning of multi-field damage in the tunnel. The capping structure of the present invention includes a cap 5, a rubber ring 33 for sealing the cap 5 and the tunnel specimen 1, and a fixing bolt 4 for passing through the cap 5 and fixing the inside of the bolt hole of the tunnel specimen, and an injection hole is provided in the fixing bolt for filling the gap between the fixing bolt and the bolt hole of the tunnel specimen with epoxy resin. The cap includes a front cap for sealing the front end face of the hole and a rear cap for sealing the rear end face of the hole, and the cap is a stainless steel cap. As Figure 5 and Figure 6As shown, the end face of the hole is sealed by a stainless steel cover 5 and a rubber ring 33 to prevent water from overflowing. The cover 5 has four cover bolt holes 36, and the rubber ring 33 has four rubber ring bolt holes 37. At the same time, four sample bolt holes 38 are provided on one side of the hole. The fixing bolts 4 pass through the cover bolt holes 36, the rubber ring bolt holes 37, and the sample surface bolt holes 38 in sequence to fix the stainless steel cover 5 and the rubber ring 33 to one side of the hole in the tunnel sample 1, thereby sealing the hole. In the cover structure for sealing the front face of the hole, the front cover has two cover through-holes 34, and the front rubber ring has two rubber ring through-holes 35. The water outlet pipe 27 and the cooling pipe 13 pass through the front cover and the front rubber ring respectively to enter the hole. In the cover structure for sealing the rear face of the hole, the rear cover has a cover through-hole 34, and the rear rubber ring has a rubber ring through-hole 35, so that the cooling pipe 13 can pass through the rear cover and be connected to the hole. The front cover is also provided with a cover camera through hole 39, and the front rubber ring is provided with a rubber ring camera through hole 40, which allows the transparent cover 2 to enter the hole through the cover 5 and the rubber ring 33. The joints of the cover camera through hole 39, the rubber ring camera through hole 40 and the transparent cover 2 are respectively provided with waterstops, which are formed by coating and curing epoxy resin to achieve sealing and prevent water from overflowing from the hole. Preferably, the injection hole includes an axial hole opened in the axial direction by the fixing bolt and a plurality of radial holes evenly distributed in the radial direction and connected to the axial hole. By adding an injection hole on the fixing bolt for filling the gap between the fixing bolt and the tunnel specimen bolt hole with epoxy resin, on the one hand, perforation sealing is achieved, which solves the problem of the impact of the water pressure load in the hole on the cover and affecting the sealing of the cover, and realizes the joint action of multiple field loads; on the other hand, it solves the problem of stress concentration at the perforation caused by perforation, which leads to rupture and even failure of the seal, making it impossible to carry out the test normally; on the third hand, the uniformity of epoxy resin filling is achieved. The traditional method to solve the stress concentration caused by drilling bolt holes is to apply epoxy resin on the surface of the bolt. However, due to the unevenness of the bolt hole, the inner diameter may not be uniform with the depth of the hole. Therefore, this method easily causes the epoxy resin to be squeezed out during the bolt screwing process, resulting in uneven bonding inside the bolt. The present invention designs a bolt curing method that first screws in and then injects. The fixing bolt has a characteristic of connecting the middle opening with the circumferential opening to form an injection hole. After the fixing bolt is screwed into the bolt hole of the tunnel specimen, each position of the bolt hole is connected to the outside through the injection hole, and epoxy resin is injected from the injection hole. The epoxy resin will pass through the axial hole and then through multiple evenly distributed radial holes connected to the axial hole to reach the inner wall of the bolt hole, thereby achieving the function of uniform epoxy resin bonding between the fixing bolt and the inner wall of the tunnel specimen bolt hole, reducing stress concentration, and overcoming the disadvantage of uneven bonding caused by simply applying epoxy resin in the traditional way.

[0037] In the camera structure of the present invention, the camera structure includes a camera rod 3, on which a plurality of camera bracket groups are provided. The camera bracket groups include a plurality of camera brackets 42 fixed around the circumference of the camera rod, and a camera group is provided between two adjacent camera bracket groups. The camera group is a plurality of miniature cameras 41 fixed around the circumference of the camera rod and connected to an external computer. As a specific embodiment, Figure 7 As shown, the camera rod 3 is provided with three camera bracket groups, each camera bracket group is composed of four camera brackets 42 symmetrically fixed around the circumference of the camera rod, and a micro camera group is set between two adjacent camera bracket groups, for a total of two micro camera groups, each micro camera group is composed of four micro cameras 41 symmetrically fixed around the circumference of the camera rod and connected to an external computer. Figure 8 As shown, the camera structure also includes a transparent cover 2 that is mounted on the outside of the camera bracket group. The micro camera 41 is separated from the transparent cover 2. The connection between the transparent cover and the camera bracket has a certain friction force, which can keep the camera position relatively stable and can stably shoot test videos during the test. The camera rod of the present invention is provided with scale lines for identifying the damage position along the axial surface, and angle scale lines are provided on the front cover. The scales are distributed along the axial direction of the camera rod. When the camera rod enters the hole, the length of the camera rod entering the hole can be obtained in real time by reading the scale of the camera rod. At the same time, the front cover has an angle scale feature. When the camera rod rotates to shoot the internal features of the tunnel, the angular position of the camera can be determined in real time. Combined with the length scale and the angle scale, the camera can be accurately positioned in the hole, realizing the identification and determination of the damage position of the tunnel specimen hole and the precise positioning of the fracture site, which is conducive to the analysis of the multi-field coupling mechanism of the hydrothermal damage of the tunnel.

[0038] The present invention employs a camera support assembly and a camera assembly spaced apart on a slender camera rod, addressing the technical problem of previous technologies' inability to penetrate deeply into the enclosed test volume. Compared to acoustic emission technology, the present invention can directly observe the damage evolution process within the tunnel. Compared to CT scanning, the damage process within the tunnel can be directly monitored by the camera, which CT scanning cannot. Furthermore, while the camera position in the prior art is fixed, the present invention's camera rod is designed to move forward, backward, and rotate, allowing for flexible adjustment according to the progress of the test. The scale feature enables accurate camera positioning, thus enabling precise location and definition of the damage location and range within the tunnel. Furthermore, the present invention employs a transparent cover over the camera support assembly. Due to the complex multi-field interaction of hydraulic and thermal forces, the hydraulic effects can adversely affect the camera, requiring a high water pressure resistance for the transparent cover. High-strength glass can address this requirement, but glass is brittle and can crack when impacted by sharp edges. A transparent soft film can be applied to the transparent glass cover, but gaps inevitably form between the soft film and the transparent glass cover, affecting the optical path and, consequently, the micro-camera's capture. The transparent cover of the present invention uses a 3D-printed, light-cured, photosensitive epoxy resin material. The outer layer of the transparent cover wall uses a relatively soft epoxy resin material for curing, while the inner layer of the transparent cover wall uses a relatively hard epoxy resin material for curing. The use of different soft and hard material printing technologies achieves the transparent cover's advantages of being hard inside and soft outside. The transparent cover is strong and resilient, and can be prevented from being crushed. Because the inner and outer layers are printed simultaneously, the materials seamlessly integrate, without affecting light transmittance, allowing for recording by the internal micro-camera. Therefore, while achieving multi-field loading, the present invention also achieves camera structures that are strong, waterproof, transparent, and quantitatively adjustable in position. Furthermore, it can prevent the transparent cover from being damaged by falling after cracking or damage in the tunnel.

[0039] like Figures 9 to 11As shown, the water pressure loading structure includes a water storage cylinder 14, one side of the water storage cylinder 14 is provided with a water inlet and outlet 23, the other side of the water storage cylinder 14 is provided with a bayonet with an internal thread 30, a piston 31 is provided in the water storage cylinder 14, the piston 31 and the water storage cylinder 14 form a closed water storage chamber 32, the piston 31 is provided with an opening on the side close to the bayonet, a rotor 43 is provided in the piston 31, the rotor 43 slides on the inner wall of the piston 31, the rotor 43 is fixedly connected to the motor shaft 19, and one end of the motor shaft 19 extends into the opening The motor shaft 19 has an external thread 29 adapted to the internal thread 30 in the middle section of its exterior, and the other end of the motor shaft 19 is connected to the output end of the motor 15. The water inlet and outlet 23 are respectively connected to the water inlet pipe 26 and the water outlet pipe 27. The water inlet pipe 26 is connected to the water tank 24. The connection between the water inlet and outlet 23 and the water inlet pipe 26 is provided with a water inlet pipe valve 25, and the connection between the water inlet and outlet 23 and the water outlet pipe 27 is provided with a water outlet pipe valve 22. The hydraulic loading structure also includes a hydraulic loading switch 18 for controlling the direction of the motor 15. In the hydraulic loading structure, the motor 15 is mounted on the motor track 16 via the motor frame 17, and the water storage cylinder 14 is mounted on the bottom plate 20 via the water storage cylinder base frame 21. In order for the rotor to slide on the inner wall of the piston, preferably, a sliding cavity 44 filled with lubricating oil is provided between the rotor and the inner wall of the piston. When the rotor rotates forward or backward, since the sliding cavity between the rotor and the inner wall of the piston is filled with lubricating oil, the rotation of the rotor will not drive the piston to rotate, that is, the piston will not rotate, but will move forward or backward with the rotor, which can ensure the stability of the piston's advance and retreat, while maintaining the sealing inside the water storage chamber 32. The prior art uses high-pressure gas to compress the piston. The present invention can achieve stable loading of water pressure by converting the rotation of the motor into straight movement of the piston. The present invention adopts a design in which lubricating oil is provided in the sliding cavity, which can solve the problem of excessive stroke caused by the threaded sleeve of the traditional technology, affecting the effective volume of the water storage chamber. In addition, the water inlet and outlet design of the present invention, and repeated pumping and drainage operations, can achieve stable pressurization of the equipment, while the water storage chamber of the prior art will be mixed with air when filled with water, or high-pressure gas is used for loading. These pressurization methods easily lead to unstable water pressure, which is not conducive to the conduct of experiments.

[0040] In the boundary temperature loading structure, the boundary temperature loading structure includes a heating plate, such as Figure 12As shown, the two side plates 47 of the heating plate are connected by a mesh plate 48, so that a plurality of mesh cavities 45 are formed inside the heating plate to place the heating resistance wires 46. The two side plates of the heating plate of the present invention are made of metal materials with rigidity and good thermal conductivity. Preferably, the metal material is steel. Generally, the thickness of the protective layer of the heating resistance wire is not less than 6 cm. Two points are mainly considered. One is to protect the heating resistance wire from bending due to external force, which causes a short circuit or open circuit and affects the heating effect. The other is that the thickness of the protective layer is sufficient to maintain the overall rigidity of the heating plate during the loading process. At the same time, the thickness of the heating plate should not be too high, and the outer shell should be as thin as possible, so that the heat conduction efficiency is high, the material is saved, and the overall structure is light, which is conducive to the operation of the equipment. Since the heating plate of the present invention is also subject to stress loading compared with the general heating plate, the present invention arranges a grid plate inside the heating plate and places heating resistance wires in each compartment. On the one hand, the heating resistance wires are protected from being affected, and the evenly distributed heating resistance wires also make the heat transfer more uniform. Moreover, the grid plate structure is more conducive to heat conduction, and the heat of the resistance wires can be conducted more quickly, thereby improving the heating efficiency. On the other hand, on the basis of not increasing the thickness of the heating plate, the bending resistance and compressive stiffness of the entire material are improved by adding the grid plate. The connection between the grid plate and the two heating plate side plates can achieve the advantages of wide flanges and large lateral stiffness compared with other structures under the same cross-sectional area. Therefore, the heating plate of the present invention has strong bending resistance, and the two surfaces of the grid plate are parallel to each other, which makes the connection, processing and installation simple. The arrangement of the grid plate saves more overall material and makes the structure lighter, which can avoid the waste of material and bulky structure caused by thickening the loading plate to improve stiffness in the traditional way.

[0041] like Figure 13 and Figure 14 As shown, the core temperature application structure includes a cooling tube 13 extending through the hole, a condenser 10 connected to one end of the cooling tube, an evaporator 12 connected to the other end of the cooling tube, and a compressor 13 connecting the cold sensor and the evaporator. The core temperature application device contains a refrigerant, which is either F12 or R600a. The core temperature application structure primarily converts energy through the refrigerant's circulation and state changes.

[0042] The data acquisition system of the present invention includes a stress sensor 7 mounted on the side of the heating plate 6 near the stress loading plate, a boundary temperature sensor mounted inside the heating plate 6, a water pressure monitor 28 mounted on the water outlet pipe 27 for monitoring the water pressure within the borehole, and a core temperature sensor mounted on the compressor 11. The present invention also includes a computer connected to the data acquisition system and the camera. The computer is configured to obtain the boundary temperature and confining pressure values ​​of the tunnel specimen, as well as the internal water pressure and core temperature values ​​within the borehole, from the data acquisition system, and to capture borehole damage images captured by the micro-camera. The acquired data and images are then used to analyze the hydrothermal damage process in high-temperature tunnels.

[0043] The present invention also provides a test method, which uses the above-mentioned high-temperature tunnel hydraulic thermal damage test device, including the following steps: S1, applying initial internal water pressure: opening the water inlet pipe valve and closing the water outlet pipe valve, turning on the water pressure loading switch to reverse, and the motor drives the piston to push the water storage cylinder to fill the water storage chamber with water; closing the water inlet valve and opening the water outlet valve, turning on the water pressure loading switch to rotate forward, and the motor drives the piston to push the water storage cylinder to fill the hole with water and reach a slightly rising trend in the internal water pressure value, and then closing the water pressure loading switch; S2, applying confining pressure: applying pressure to the stress loading plate, and transferring it to the heating plate and the tunnel sample in turn, so that the confining pressure value of the tunnel sample reaches the preset value, keeping the confining pressure unchanged; S3, applying boundary temperature load: turning on the heating plate to make the boundary temperature load of the tunnel specimen at a preset value above 60°C and maintain a constant temperature; S4, applying test internal water pressure: turning on the water pressure loading switch to rotate forward to make the water pressure value in the hole reach the preset water pressure value; S5, applying center temperature load: turning on the compressor to make the center temperature load in the hole at a constant temperature below 10°C until the inside of the tunnel specimen ruptures; S6, in the above steps, turning on the micro camera to record different rupture characteristics, and recording the changes in the rotation angle of the micro camera and the changes in the length of the camera stick inserted into the hole under different rupture characteristics.

[0044] The test method for applying the initial water pressure in S1 also includes: S11, replenishing the water storage cylinder 14: opening the water inlet pipe valve 25, closing the water outlet pipe valve 22 at the same time, turning on the reversing function of the water pressure loading switch 18, the motor 15 reverses the motor shaft 19, and the external thread 29 is screwed into the internal thread 30, so that the motor 15 moves outward through the motor rack 17, thereby driving the piston 31 to move outward. At this time, the water inside the water tank 24 enters the water storage chamber 32 through the water inlet pipe 26 under the action of atmospheric pressure; when the motor rack 17 moves to the outer terminal of the motor track 16, the water storage chamber 32 is filled with water. , indicating that the water replenishment process of the water storage cylinder 14 is completed, and the water pressure loading switch 18 is turned off; S12, close the water inlet pipe valve 25, open the water outlet pipe valve 22, turn on the forward rotation function of the water pressure loading switch 18, the motor 15 makes the motor shaft 19 rotate forward, the external thread 29 screws out of the internal thread 30, so that the motor 15 moves inward through the motor frame 17, thereby driving the piston 31 to move inward. At this time, the water inside the water tank 24 is driven by the piston 31 to flow from the water storage chamber 32 through the water outlet pipe 27 into the hole; by controlling the progress of the motor 15, the water pressure value of the hole can be adjusted according to the reading of the water pressure monitor 28.

[0045] In the test method of applying the central temperature load in S5, the central temperature applying structure mainly converts energy through the circulation and state change process of the refrigerant. The method steps also include: S51, the compressor 11 works to convert the refrigerant into steam and output it to the inside of the condenser 10, so that the high-temperature and high-pressure superheated steam compressed by the compressor 11 is converted into a normal temperature and high-pressure liquid; S52, the normal temperature and high-pressure liquid is transported from the condenser 10 to the cooling pipe 13, and the cooling pipe 13 passing through the hole can cool the water in the hole by exchanging heat with the water in the hole; S53, by controlling the speed of the compressor 11, the low temperature inside the hole of the tunnel specimen 1 is controlled according to the reading of the central temperature sensor.

[0046] In S6, the damage inside the tunnel is recorded in real time by the micro camera 41 on the camera stick 3, and the initial angle of the camera stick 3 and the initial length of the camera stick 3 entering the hole are determined. According to the actual damage location and range inside the hole during the test, the angle and length of the camera stick 3 entering the hole can be adjusted in real time. The damage location and range inside the hole are defined by reading the scales of the camera stick 3 and the front cover. Each time the camera stick 3 is adjusted to capture the characteristics of the tunnel rupture, the rotation angle of the camera stick 3 and the length of the camera stick 3 entering the hole are immediately recorded until the end of the test.

[0047] The test method of the present invention also includes preparatory work before the test, including Figures 1 to 4The schematic diagram shown connects the test equipment of each structure, specifically including: the tunnel specimen 1 is placed in the center of the boundary temperature loading structure; the water outlet pipe 27 passes through the front cover to communicate with the hole, and the water inlet pipe 26 is connected to the water tank 24; the cooling pipe 13 passes through the front cover and the rear cover to penetrate the hole; the two end surfaces of the hole are sealed by the front cover and the rear cover; the transparent cover 2 is inserted into the hole through the cover camera hole 39 and the rubber ring camera hole 40, and a water stop is set at the junction of the transparent cover and the cover to achieve sealing; the camera stick 3 is inserted into the transparent cover 2 and the position is adjusted, and the micro camera 41 is connected to the external computer system and debugged.

[0048] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of 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 ground temperature tunnel hydraulic thermal damage test device, comprising a tunnel specimen having a through hole, and a data acquisition system connected to an external computer, characterized in that: The tunnel specimen further comprises boundary temperature loading structures arranged on the top, bottom, left and right sides of the tunnel specimen, and stress loading structures arranged on the other side of the boundary temperature loading structures on the top, left and right sides; a cover structure that seals with both end faces of the hole, the cover structure comprising a cover, the cover comprising a front cover and a rear cover; a water pressure loading structure that applies internal water pressure to the hole through the front cover, a central temperature applying structure that applies central temperature load to the hole through the front cover and the rear cover, and a camera structure that extends into the hole through the front cover; The camera structure includes a camera rod, a plurality of camera bracket groups are provided on the camera rod, the camera bracket group includes a plurality of camera brackets fixed around the circumference of the camera rod, a camera group is provided between two adjacent camera bracket groups, the camera group is a plurality of miniature cameras fixed around the circumference of the camera rod and connected to an external computer; the camera structure also includes a transparent cover mounted on the outside of the camera bracket group, the miniature camera group and the transparent cover form a space; the camera rod is provided with scale lines for identifying the damage position along the axial direction, and the front cover is provided with scale lines for identifying the rotation angle of the camera rod; the water pressure loading structure includes a water storage cylinder, one side of the water storage cylinder is provided with a water inlet and outlet, the other side of the water storage cylinder is provided with a bayonet with an internal thread, A piston is provided in the water storage cylinder, and the piston and the water storage cylinder form a closed water storage chamber. An opening is provided on a side of the piston close to the bayonet, and a rotor is provided in the piston, and the rotor slides on the inner wall of the piston. The rotor is fixedly connected to the motor shaft, and one end of the motor shaft extends into the opening and does not contact the opening. The middle section of the outer portion of the motor shaft is provided with an external thread that matches the internal thread, and the other end of the motor shaft is connected to the output end of the motor; the stress loading structure includes a stress loading plate and a force transmission shaft arranged on the stress loading plate; the central temperature application structure includes a cooling pipe running through the hole, a condenser connected to one end of the cooling pipe, an evaporator connected to the other end of the cooling pipe, and a compressor connecting the condenser and the evaporator.

2. The high ground temperature tunnel hydraulic thermal damage test device according to claim 1, characterized in that: The tunnel specimen is in the shape of a cube and is cut from sandstone or marble; the hole is located at the center line of the tunnel specimen and is cylindrical; the sealing material is stainless steel.

3. The high ground temperature tunnel hydraulic thermal damage test device according to claim 1, characterized in that: The cover structure further includes a fixing bolt passing through the cover and fixing the inside of the tunnel specimen bolt hole. The fixing bolt is provided with an injection hole for filling epoxy resin into the gap between the fixing bolt and the tunnel specimen bolt hole.

4. The high ground temperature tunnel hydraulic thermal damage test device according to claim 1, characterized in that: The water inlet and outlet are respectively connected to the water inlet pipe and the water outlet pipe, the water inlet pipe is connected to the water tank, an inlet pipe valve is provided at the connection between the water inlet and outlet and the water inlet pipe, and an outlet pipe valve is provided at the connection between the water inlet and outlet and the water outlet pipe; the water pressure loading structure also includes a water pressure loading switch for controlling the direction of the motor.

5. The high ground temperature tunnel hydraulic thermal damage test device according to claim 1, characterized in that: The boundary temperature loading structure includes a heating plate, and two side plates of the heating plate are connected by a grid plate, so that a plurality of grid cavities for placing heating resistance wires are formed inside the heating plate.

6. A high ground temperature tunnel hydraulic thermal damage test method, characterized in that: The high geothermal tunnel hydraulic thermal damage test device according to any one of claims 1 to 5 comprises the following steps: S1, applying initial internal water pressure: opening the water inlet valve and closing the water outlet valve, turning on the water pressure loading switch to reverse, and the motor drives the piston to push the water storage cylinder to fill the water storage chamber with water; closing the water inlet valve and opening the water outlet valve, turning on the water pressure loading switch to rotate forward, and the motor drives the piston to push the water storage cylinder to fill the hole with water and reach a slightly rising trend in the internal water pressure value, and then turning off the water pressure loading switch; S2, applying confining pressure: applying pressure to the stress loading plate, and transferring it to the heating plate and the tunnel sample in turn, so that the confining pressure value of the tunnel sample reaches a preset value, and the confining pressure value of the tunnel sample is maintained at a preset value. Maintain the confining pressure unchanged; S3. Apply boundary temperature load: Turn on the heating plate to make the boundary temperature load of the tunnel specimen at a preset value above 60°C and maintain a constant temperature; S4. Apply test internal water pressure: Turn on the water pressure loading switch and rotate it forward to make the internal water pressure in the hole reach the preset value of the internal water pressure; S5. Apply center temperature load: Turn on the compressor to make the center temperature load in the hole at a constant temperature below 10°C until the inside of the tunnel specimen ruptures; S6. In the above steps, turn on the micro camera to record different rupture characteristics, and record the changes in the rotation angle of the micro camera and the changes in the length of the camera stick inserted into the hole under different rupture characteristics.

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