A temperature-stress-deformation coupled heat and humidity cycle test device and method

Abstract

A temperature-stress-deformation coupled heat-humidity cycle test device and method, mainly including a loading system, an immersion drying system and a detection system; the loading system includes a base, on which a lower pad, a sample, and an upper pad are placed in order from bottom to top, and the upper pad is pressurized by an upper pressurization system; the immersion drying system includes a water tank, with a water inlet at the upper end and a water outlet at the bottom; one side of the water tank is open and the end face of the opening is sealed and connected to the side of the sample; a heating pipe is provided in the water tank; the detection system includes a displacement sensor, a fiber Bragg grating temperature strain sensor, and an acoustic emission sensor; the displacement sensor is used to monitor the degree of deformation of the sample; the fiber Bragg grating temperature strain sensor is used to monitor the temperature and strain of the sample; the acoustic emission sensor is used to monitor the location and degree of damage to the sample. The invention provides a temperature-stress-deformation coupled heat-humidity cycle test device and method, which can solve the problems of test simulation and related deformation monitoring of rock mass in the drawdown zone of slopes in dry-hot valley areas under complex environmental conditions.

Description

Technical Field

[0001] The invention relates to the field of geotechnical engineering, in particular to a temperature-stress-deformation coupled thermal-humidity cycle test device and method, which is particularly suitable for rock samples in the drawdown zone of reservoir bank slopes in dry-hot river valley areas. Background Art

[0002] In recent years, my country has built many reservoirs in dry and hot valleys in the southwestern region such as the Jinsha River. The environmental conditions in this area are characterized by high temperature, low humidity, and rich light and heat resources. In addition, there are drawdown zones several tens of meters high on both sides of the reservoir area. The rock mass in this drawdown zone is in a continuous cycle of "reservoir water immersion-high temperature drying". In addition, the rock mass in the drawdown zone will also produce stress and deformation under the gravity of the upper rock layer. This hot and humid cycle state under complex environmental conditions such as temperature-stress-deformation will accelerate the degradation of the rock mass in the drawdown zone, affect the long-term stability of the reservoir area, and thus cause geological disasters.

[0003] Therefore, for the experimental device for simulating the thermal and humid cycle of rock mass in the drawdown zone under the influence of complex environmental conditions in the dry-hot valley area, it is necessary to pay attention to the following influencing factors:

[0004] ①60~70℃ drying temperature and reservoir water soaking circulation;

[0005] ② Stress effect of upper rock strata;

[0006] ③ Real-time testing of temperature, humidity and damage inside rock masses at different depths.

[0007] Existing devices, such as the patent "Experimental device and experimental method for simulating thermal and moisture cycle of rock mass on the slope of dry and hot river valley" with application number "202111116441.4", only focus on simulating the influence of factor ①.

[0008] The patent application number "202011191504.8" "A Loaded Dry-Wet Cycle Tester and Test Method for Expansive Rocks" only focuses on simulating the expansion and contraction deformation characteristics of rocks under upper loads and immersion-air drying cycles, without considering the damage of hot and wet cycles to rocks, and also without considering the differences in the degree of impact on the physical and mechanical properties of rocks at different depths."

[0009] However, there is no test simulation device for the rock mass in the drawdown zone under the combined influence of complex environmental conditions such as factors ①~③. In reality, the rock mass in the drawdown zone is often affected by multiple factors. Although different equipment can simulate the impact of one or two factors on the rock mass, the conclusions drawn from these individual factors cannot be combined to judge the adverse consequences of all complex factors on the rock mass in the drawdown zone. This is one-sided and has no basis. Summary of the invention

[0010] The technical problem to be solved by the invention is to provide a temperature-stress-deformation coupled heat-humidity cycle test device and method, which applies stress and heat-humidity cycle coupled environment to rock samples, and uses acoustic emission, fiber Bragg grating temperature and strain testing technology, digital image measurement technology and other technologies to monitor the temperature, humidity, deformation, damage and crack propagation of rock samples at different depths under the influence of heat-humidity cycle. On the one hand, the present invention simulates the environmental conditions of rock masses in the drawdown zone at different depths under the complex influence factors of reservoir water, stress, temperature and heat-humidity cycle; on the other hand, the present invention simultaneously monitors the damage on the surface and inside of the rock sample, as well as the crack propagation on the surface of the rock sample affected by complex environmental conditions.

[0011] In order to solve the above technical problems, the technical solution adopted by the invention is:

[0012] A temperature-stress-deformation coupled heat and humidity cycle test device, comprising a specimen, a loading system, a soaking and drying system and a detection system;

[0013] The loading system comprises a base, on which a lower pad, a sample and an upper pad are placed in order from bottom to top, and the upper pad is pressurized by an upper pressurization system;

[0014] The immersion drying system comprises a water tank, the upper end of the water tank is provided with a water inlet, and the bottom end is provided with a water outlet; one side of the water tank is open, and the end face of the opening is sealed and connected to the side face of the sample through a locking mechanism; a sandwich is provided in the water tank, and a heating tube is installed in the sandwich;

[0015] The detection system includes a displacement sensor, a fiber grating temperature strain sensor, and an acoustic emission sensor;

[0016] Among them, the displacement sensor is installed between the lower pad and the upper pad; the displacement sensor is used to monitor the deformation degree of the sample;

[0017] The fiber Bragg grating temperature and strain sensors are divided into multiple groups and arranged at intervals along the direction of the sample away from the water tank. The fiber Bragg grating temperature and strain sensors are used to monitor the temperature and strain of the sample.

[0018] The acoustic emission sensors are divided into multiple groups and arranged at intervals along the direction of the sample away from the water tank. The acoustic emission sensors are used to monitor the location and degree of damage to the sample.

[0019] The locking mechanism includes a locking port arranged on the lower pad and a sliding groove arranged on the upper pad, wherein the locking port is spliced ​​with the locking beam at the lower part of the water tank, the sliding groove is slidably matched with the large head at one end of the screw rod, and the other end of the screw rod is threadedly connected to the upper end of the water tank.

[0020] The sample is divided into sections along the length direction, and a fiber Bragg grating temperature strain sensor and an acoustic emission sensor are correspondingly installed at a suitable position in each section.

[0021] The fiber Bragg grating temperature strain sensor is provided with two groups, inner and outer, in each section of the sample, wherein the surface fiber Bragg grating temperature strain sensor is arranged on the surface of the sample, and the internal fiber Bragg grating temperature strain sensor is installed in the installation hole of the corresponding section of the sample.

[0022] The acoustic emission sensors are placed in the empty slots reserved in the lower pad and the upper pad and correspond to each section of the sample one by one.

[0023] The contact points between the immersion end surfaces of the lower pad, the sample and the upper pad and the end surface of the water tank are sealed with sealing strips; and the immersion end surfaces of the lower pad and the upper pad are sealed and waterproofed.

[0024] A high-speed camera and an underwater light source are installed on the water tank, wherein the high-speed camera is directly opposite to the sample.

[0025] A temperature-stress-deformation coupled heat and humidity cycle test method comprises the following steps:

[0026] Step 1) Before the test begins, use a marker pen to evenly divide the sample into multiple depth areas along the length direction; then use a sealing strip to wrap around the end surface of the sample that is affected by the heat and humidity cycle and fix it with glue;

[0027] Step 2), first drill a 3mm mounting hole in each partition of the sample, and then install the fiber Bragg grating temperature strain sensor inside the mounting hole; the fiber Bragg grating temperature strain sensor on the surface of each partition of the sample is fixed with silicone rubber, and vaseline is applied to increase the coupling between it and the sample;

[0028] Step 3) The end surfaces of the upper and lower pads on the side that are soaked are sealed and waterproofed, and a sealing strip is also wrapped around the end surfaces;

[0029] Step 4), fix the acoustic emission sensor in the empty slots reserved in the lower pad and the upper pad; then place the lower pad, the sample and the upper pad in order; then adjust the position of the displacement sensor according to the height of the lower pad, the sample and the upper pad, so that the measuring rod of the displacement sensor just touches the displacement measuring plate of the upper pad, and finally fix the displacement sensor to the displacement sensor fixing plate of the lower pad by fixing bolts;

[0030] Step 5), the lower part of the water tank is connected and fixed through the lock at the bottom of the lower pad, and the screw at the upper part of the water tank can be inserted from the slide groove at the upper part of the upper pad. The lower part of the water tank is connected and fixed through the lock at the bottom of the lower pad, and the screw at the upper part of the water tank can be inserted from the slide groove at the upper part of the upper pad, and the screw can be tightened to make the water tank as tightly connected as possible with the lower pad, the sample, and the upper pad; the joints between the water tank and the lower pad, the sample, and the upper pad are sealed with sealing strips;

[0031] Step 6), using the pressure system to apply load, and applying load to the upper pad on the upper part of the sample through the pressure head of the testing machine to simulate the load effect of the upper rock sample on the rock mass in the drawdown zone of the dry hot valley in the actual environment, and at the same time, the load size can be monitored in real time through the load sensor;

[0032] Step 7) When the upper stress is applied to the predetermined value, the loading is stopped, and then water is poured into the water tank to fill the water tank. The water tank is soaked for a sufficient period of time according to the test plan to simulate the soaking stage of the rock mass in the drawdown zone of the dry hot valley after the water level rises. After the soaking is completed, the water outlet regulating valve is opened to drain the water in the water tank from the outlet;

[0033] Step 8), after the water in the water tank is drained, turn on the heating tube and set the temperature to 60°C or set according to the specific situation, so that the test surface of the sample is heated to simulate the baking effect of high temperature on the surface rock after the water level in the drawdown zone of the dry hot valley drops.

[0034] Step 9), repeat the immersion and drying test, and stop the test when the number of cycles reaches the number of times specified in the test plan;

[0035] Step 10) During the immersion-drying cycle test, the temperature, displacement, stress and damage monitoring of the sample are also carried out simultaneously.

[0036] A temperature-stress-deformation coupled heat and humidity cycle test device and method are invented, which has the following technical effects:

[0037] 1) The loading device can simulate the stress of the rock mass in the drawdown zone in the actual environment caused by the upper rock mass; by injecting water into the water tank, the immersion environment of the rock mass in the drawdown zone in the reservoir water can be simulated; by drying the surface of the sample through the heating pipe, the environment of internal water evaporation of the rock mass in the drawdown zone under high temperature in the dry-hot valley can be simulated; In summary, this device simulates the heat and moisture cycle process of the rock mass in the drawdown zone in the actual dry-hot valley area under complex environmental conditions such as high temperature, stress, and immersion, which provides a basis for conducting laboratory tests on the degradation effects of the rock mass in the drawdown zone under the action of heat and moisture cycles.

[0038] 2) Using fiber optic testing technology and taking advantage of its waterproof and high temperature resistance characteristics, the fiber optic Bragg grating temperature strain sensors arranged inside and on the surface of the sample can monitor the internal temperature, humidity and deformation of rock samples at different depths under the action of heat and humidity cycles; the acoustic emission sensor can monitor the internal damage of rock samples at different depths under the action of heat and humidity cycles; after shooting with a high-speed camera and processing with a computer, the crack propagation condition on the surface of the rock sample affected by heat and humidity cycles can be monitored; in summary, this device can monitor the internal temperature, humidity and damage of rock masses at different depths under the action of heat and humidity cycles in complex environmental conditions, and monitor the surface crack propagation condition of rock masses under the action of heat and humidity cycles in complex environmental conditions; ensure that the comprehensive results of rock masses affected by high temperature, stress, immersion and other factors can be measured, checked and analyzed.

[0039] 3) This device uses a screw rod and a water tank threaded connection to make the screw rod length adjustable; at the same time, the big end of the screw rod slides with the slide groove; the adjustable screw length ensures a tight connection between the pad and the water tank, so that the water tank is pressed tightly against the pad and the sample; the screw rod can move up and down relative to the pad and the big end of the screw rod is limited by the slide groove, which avoids deformation and damage of the water tank under the action of the upper load due to fixation with the upper pad.

[0040] 4) The water tank is made of aluminum alloy, which is resistant to high temperatures and has good thermal conductivity. It can ensure that the heat of the heating tube can be transferred to the surface of the sample during the drying stage, and avoid melting of the material due to high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0042] Figure 1 It is an overall schematic diagram of the invention.

[0043] Figure 2 It is a left side view of the invention.

[0044] Figure 3 This is a schematic diagram of the layout of the sample and optical fiber sensor in the invention.

[0045] Figure 4 Schematic diagram of the end face of the upper pad in the invention

[0046] Figure 5 It is a structural schematic diagram of the water tank in the invention.

[0047] Figure 6 It is a schematic diagram of the connection between the water tank and the pad in the invention.

[0048] Figure 7 It is a schematic diagram of the arrangement of sealing strips between the water tank, the gasket and the specimen in the invention.

[0049] Figure 8 It is a schematic diagram of the water outlet in the invention.

[0050] Fig. 9 It is a schematic diagram of the arrangement of the heating tubes in the invention.

[0051] Fig.10 It is a schematic diagram of the displacement sensor in the invention.

[0052] Fig.11 It is a schematic diagram of the arrangement of the acoustic emission sensors in the invention.

[0053] Fig.12 It is a schematic diagram of the connection between the slideway and the screw in the invention.

[0054] Fig.13 It is a schematic diagram of the partitioning of the sample in the invention.

[0055] Fig.14 The cumulative acoustic emission energy change trend curve diagram of the invention (group a).

[0056] Fig.15 This is a curve diagram of the cumulative acoustic emission energy change trend of the invention (group b).

[0057] In the figure: base 1, lower pad 2, sample 3, upper pad 4, pressurizing system 5, water tank 6, water inlet 7, water outlet 8, heating pipe 9, displacement sensor 10, fiber Bragg grating temperature strain sensor 11, acoustic emission sensor 12, lock 13, slide 14, screw 15, mounting hole 16, sealing strip 17, high-speed camera 18, underwater light source 19, computer 20, fiber Bragg grating demodulator 21, acoustic emission model processing system 22, testing machine pressure head 23, load sensor 24, beam 25, column 26, fixing bolt 27, displacement sensor measuring plate 28, displacement sensor fixing plate 29, measuring rod 30. DETAILED DESCRIPTION

[0058] A temperature-stress-deformation coupled heat and humidity cycle test device comprises a loading system, a soaking and drying system and a detection system.

[0059] like Figure 1-2 As shown, the loading system includes a base 1, a column 26 is fixed on the outside of the base 1, a crossbeam 25 is fixed on the top of the column 26, a pressurizing system 5 is installed on the crossbeam 25, and the lower end of the pressurizing system 5 is connected to the testing machine pressure head 23 through a load sensor 24, and an upper pad 4, a sample 3, and a lower pad 2 are arranged in sequence below the testing machine pressure head 23, wherein the lower pad 2 is placed on the base 1.

[0060] like Figure 1-2As shown, the loading system can apply load using the pressurizing system 5, and apply load to the upper pad 4 on the upper part of the sample 3 through the testing machine pressure head 23, so as to simulate the load effect of the upper rock sample on the rock mass in the drawdown zone in the actual environment, and at the same time, the load size can be monitored in real time through the load sensor 24.

[0061] like Figure 3 As shown, the sample 3 has a size of 800mm×200mm×300mm. Before the test, it is necessary to use a marker to divide it into 5 areas along the length direction, so as to facilitate the test of the influence of the heat and humidity cycle on the rock mass at different depths. Then, a sealing strip 17 is wrapped around the side of the heat and humidity cycle to prevent water from penetrating from the side during the immersion process.

[0062] like Figure 4 As shown, the size of the upper pad 4 is slightly larger than the size of the sample. Before the test, the surface of the immersed end face needs to be sealed and waterproofed, and then a sealing strip 17 is wrapped around the end face. A slide groove 14 is arranged on the upper part of the upper pad 4 for connecting the water tank 6.

[0063] like Figure 7 As shown, the size of the lower pad 2 is slightly larger than the size of the sample. Before the test begins, the surface of the immersed end face is sealed and waterproofed, and then a sealing strip 17 is wrapped around the end face. A lock 13 is provided at the bottom of the lower pad for fixing and connecting the water tank 6.

[0064] The upper pad 4 and the lower pad 2 are both made of titanium alloy with high hardness and light material. Their function is to transfer the upper load to the lower part, and at the same time, they play the role of connecting and sealing the water tank with the entire device body.

[0065] like Figure 1-2 As shown, the immersion and drying system includes a water tank 6, which has a water inlet 7 at the upper end and a water outlet 8 at the bottom end; one side of the water tank 6 is open and the open end face is sealed and connected to the side of the sample 3; an interlayer is provided in the water tank 6, and a heating tube 9 is installed in the interlayer.

[0066] like Figure 5 , Figure 7 As shown, the water tank 6 is made of aluminum alloy, and its size is slightly larger than the sample size. Notches are provided on the left and right sides of the upper part of the water tank 6, and a screw 15 is threadedly connected to the notch, and a lock beam is provided at the lower part of the water tank 6. The large head of the screw 15 is slidably set in the slide groove 14 of the upper pad 4, and the lock beam is spliced ​​with the lock mouth of the lower pad 2. By rotating the screw 15, the water tank 6 can be pressed against the sealing strip 17 on the side of the lower pad 2, the sample 3 and the upper pad 4 and kept sealed. The circulation immersion of the dry hot valley rock mass by reservoir water can be simulated by injecting water into and draining water from the water tank 6.

[0067] like Fig.12As shown, the inner wall of the chute 14 is smooth and the inner size is slightly larger than the size of the large head of the screw 15, so that the screw 15 can move freely up and down relative to the chute 14, and the large head of the screw 15 will not be separated from the chute 14. When the upper pad 4 is displaced by the upper load, the upper pad 4 will not be constrained by the water tank 6. In addition, the length of the screw 15 can be adjusted to ensure that the water tank 6 is tightly connected with the lower pad 2, the sample 3 and the upper pad 4;

[0068] like Figure 8 As shown, the water outlet 8 is a water pipe with a water outlet regulating valve, one end of which is connected to the bottom of the water tank 6, and the other end can be connected to the grounded sewer pipe. The water outlet regulating valve can control the outflow of soaking water and the size of the water flow.

[0069] like Fig. 9 As shown, the heating tube 9 has a heating temperature of 10-70°C and is fixed in the inner and outer layers of the water tank 6, and the inner wall of the water tank needs to be waterproofed to prevent water from penetrating into the interlayer and causing safety accidents. In the drying stage, the temperature of the heating tube is set to 60°C or set according to specific conditions, which can simulate the evaporation process of water in the rock mass of the drawdown zone under high temperature and the baking process of sunlight after the water level drops in the dry hot valley.

[0070] like Figure 1-2 As shown, the detection system includes a displacement sensor 10 , a fiber grating temperature strain sensor 11 , and an acoustic emission sensor 12 .

[0071] like Fig.10 As shown, the displacement sensor 10 (LVDTC20-R-40mm-B displacement sensor can be used, with an accuracy of 40mm) is fixed at one end on the displacement sensor fixing plate 29, which is the protruding part on one side of the lower pad 2. After the sample 3, the lower pad 2 and the upper pad 4 are all placed, the upper and lower positions of the displacement sensor 10 can be adjusted by fixing bolts 27 so that the measuring rod 30 at the other end of the displacement sensor 10 just contacts the displacement sensor measuring plate 28, which is the protruding part on one side of the upper pad 4. After the device is loaded, the deformation of the sample can be measured and counted by the computer 20.

[0072] like Figure 3As shown, the fiber Bragg grating temperature strain sensor 11 (which can be a sensitive fiber Bragg grating temperature sensor developed by JEMETECH, with a range of -30°C to 120°C) is a fiber Bragg grating temperature strain sensor 11 (surface) that is arranged close to the surface of the sample, and the fiber Bragg grating temperature strain sensor 11 (inside) needs to pre-drill 3mm mounting holes 16 in each partition of the sample, and then put the fiber Bragg grating temperature strain sensor 11 into the mounting hole 16, and then use the fiber Bragg grating demodulator 21 and the computer 20 to monitor the temperature and strain of the sample surface and inside under various environments.

[0073] like Fig.11 As shown, the acoustic emission sensor 12 (Nano30 acoustic emission sensor can be selected, with a frequency range of 125Hz~750kHz) needs to be placed in the reserved slots in the lower pad 2 and the upper pad 4, and can be fixed with 704 silicone rubber. In addition, vaseline needs to be applied on the surface of the acoustic emission sensor 12 to better couple the acoustic emission sensor 12 with the sample 3. The internal damage of rock samples at different depths under the influence of heat and humidity cycles is monitored. The acoustic emission sensor 12 transmits the signals collected during the test back to the acoustic emission signal processing system 22 (PCI-2 acoustic emission processing system produced by Physical Acoustic Corporation of the United States can be selected), and then transmits them back to the computer 20 after processing, so as to determine the location and degree of damage to the sample.

[0074] The fiber Bragg grating sensor 11 must be arranged on the inside and outside of the sample, and cannot be arranged on the inside and outside of the top and bottom to avoid damage to the sensor when the upper load is applied. The acoustic emission sensor 12 can be pre-reserved with an acoustic emission sensor channel on the upper pad 4 and the lower pad 2 close to the sample side, and the acoustic emission sensor 12 can be arranged, but the upper load may cause damage to the sensor, so the acoustic emission sensor 12 is fixed at the corresponding position before and after the sample to avoid damage to the sensor.

[0075] like Figure 1 As shown, the digital image measurement group includes an underwater light source 19 and a high-speed camera 18 (i-SPEED 726 high-speed camera can be selected, with a maximum shooting frequency of 1,000,000 times / s). The underwater light source 19 provides light for the high-speed camera 18 during the immersion stage, and takes pictures throughout the test process to record the geometric morphology of the sample surface on the side subjected to the heat and moisture cycle during the test. The displacement field and strain field information of the sample surface can be obtained, and the crack extension on the sample surface can be monitored after being processed on the computer 20.

[0076] Test process:

[0077] like Figure 1and Figure 2 The figures show the front view and the left view of the device respectively.

[0078] Preparation stage before the experiment starts:

[0079] Figure 3 The schematic diagram of the sample and the optical fiber sensor layout is shown in FIG. 1 . The sample size is 800 mm × 200 mm × 300 mm. Before the test, the sample 3 is divided into five depth areas along the length direction with a marker. Then the sealing strip 17 is wrapped around the end face of the sample that is affected by the heat and humidity cycle and fixed with 502 glue.

[0080] Arrange fiber Bragg grating temperature strain sensors 11 inside and on the surface of the sample 3, such as Figure 3 As shown, a 3 mm mounting hole 16 is first drilled in each partition of the sample, and then the fiber Bragg grating temperature strain sensor 11 is installed in the mounting hole 16. The fiber Bragg grating temperature strain sensor 11 on the surface of the sample needs to be close to the surface of the sample. The fiber Bragg grating temperature strain sensor 11 can be fixed with 704 silicone rubber and coated with vaseline to increase the coupling between it and the sample.

[0081] The end surfaces of the upper pad 4 and the lower pad 2 on the side subjected to immersion need to be sealed and waterproofed, and a sealing strip needs to be wrapped around the end surfaces. Figure 4 , which is a schematic diagram of the end face of the upper cushion block 4, a slide groove 14 is provided on the upper part.

[0082] like Figure 5 , which is a detailed view of the water tank 6. The lower part of the water tank 6 is connected and fixed with the lock at the bottom of the lower pad 2, and the screw 15 at the upper part of the water tank 6 can be inserted from the slide groove 14 at the upper part of the upper pad 4, and the screw 15 can be tightened to make the water tank 6 as tightly connected as possible with the lower pad 2, the sample 3, and the upper pad 4.

[0083] The lower pad 2, the sample 3, the upper pad 4 and the water tank 6 are as follows Figure 7 The screw 15 and the slide 14 can ensure that when the upper pad 4 is displaced by the upper load, it will not be constrained by the water tank 6. After installation, the joints between the water tank 6 and the lower pad 2, the sample 3, and the upper pad 4 need to be sealed with a sealing strip 17 (such as Figure 6 As shown), and waterproof treatment is carried out to ensure that no water leakage occurs during the test and affects the test results.

[0084] Loading phase:

[0085] The load is applied by the pressurizing system 5, and the load is applied to the upper pad 4 on the upper part of the sample 3 through the testing machine pressure head 23 to simulate the load effect of the upper rock sample on the rock mass in the drawdown zone of the dry hot valley in the actual environment. At the same time, the load size can be monitored in real time through the load sensor 24.

[0086] Soaking phase:

[0087] When the upper stress is applied to a predetermined value, the loading is stopped, and then water is poured into the water tank 6 to fill the water tank 6 with water. The water tank 6 is soaked for a sufficient time according to the test plan to simulate the soaking stage of the rock mass in the drawdown zone of the dry hot valley after the water level rises. After the soaking is completed, the water outlet regulating valve (such as Figure 8 As shown), the water in the water tank 6 is drained from the water outlet 8.

[0088] Drying stage:

[0089] After the water in the water tank 6 is drained, the heating tube 9 is turned on and the temperature is set to 60°C or set according to the specific situation (the specific distribution of the heating tube 9 is as follows Fig. 9 As shown in the figure, the test surface of sample 3 is heated to simulate the baking effect of high temperature on the surface rock mass after the water level in the drawdown zone of the dry hot valley drops.

[0090] The time of the soaking stage and the drying stage can be set according to actual conditions.

[0091] Then repeat the soaking stage and the drying stage, and stop the test when the number of cycles reaches the number predetermined by the test plan.

[0092] Monitoring of samples under heat and humidity cycles:

[0093] During the immersion-drying cycle test, the temperature, displacement, stress and damage of the specimens are also monitored simultaneously.

[0094] After the test preparation stage is completed, the lower pad 2, the sample 3 and the upper pad 4 are placed in order, and then the position of the displacement sensor 10 is adjusted according to the height of the lower pad 2, the sample 3 and the upper pad 4, so that the measuring rod of the displacement sensor 10 just contacts the displacement measuring plate 28 of the upper pad 4, and finally the displacement sensor 10 is fixed to the displacement sensor fixing plate 29 of the lower pad 2 by the fixing bolts 27. Fig.10 shown.

[0095] During the heat and humidity cycle test, the fiber Bragg grating temperature and strain sensors 11 inside and on the surface of the sample transmit the temperature and strain obtained at each measuring point back to the fiber Bragg grating demodulator 21 and the computer 20 for processing and statistics.

[0096] Acoustic emission sensor 12 Fig.11 As shown, they are arranged on both sides of the sample 3, and then fixed with 704 silicone rubber, and vaseline is applied on the acoustic emission sensor 12 to increase the coupling between the acoustic emission sensor 12 and the sample 3. During the heat and humidity cycle test, the acoustic emission sensor 12 transmits the acoustic emission signal of each measuring point sample back to the acoustic emission model processing system 22, and then processes it on the computer 20 to determine the location and degree of damage to the sample 3.

[0097] During the heat and humidity cycle test, the underwater light source 19 in the water tank 6 provides light for the high-speed camera 18. The high-speed camera 18 shoots the entire process and records the geometric shape of the test surface of the sample during the test. Then, the data information of the displacement field and strain field is obtained through analysis, and then the crack propagation and deformation evolution process on the test surface are analyzed.

[0098] The test design is as follows:

[0099] The specimen and test equipment are as follows Figure 1 After being assembled as shown, the specimen needs to be divided into 5 depth zones along the length direction starting from the end face subjected to the heat and humidity cycle, as shown in Fig.13 shown.

[0100] The pressurization system applies a constant load of 5MPa to the sample. Fill the water tank with water, soak for 1.5 hours, then drain the water in the water tank, turn on the heating tube, set the temperature to 70℃, dry the end face of the sample for 0.5 hours, this is a heat and humidity cycle, and then carry out the next cycle of immersion test. Design 20 heat and humidity cycle tests, and count the cumulative acoustic emission energy of each partition in the initial state and the 1st, 3rd, 5th, 8th, 12th, 16th, and 20th heat and humidity cycles, and draw a cumulative acoustic emission energy over time change law diagram (in order to facilitate the observation of the change law, intercept the curve until the cumulative acoustic emission energy is stable for a period of time).

[0101] Another set of control tests is designed in which no axial load is applied (but the pressure head of the testing machine needs to be in close contact with the upper end face of the specimen). Only the end face of the specimen subjected to heat and humidity cycling is subjected to heat and humidity cycling. The other conditions are the same as those of the above tests. The cumulative acoustic emission energy of each partition during the 1st, 3rd, 5th, 8th, 12th, 16th and 20th heat and humidity cycles is counted.

[0102] like Figure 13-14 As shown, Fig.13 is the cumulative acoustic emission energy change trend curve of test group a, Fig.14 This is the cumulative acoustic emission energy change trend curve of test group b.

[0103] From the above analysis, we can see that:

[0104] (1) When only heat and moisture cycle acts on the end face of the specimen, the accumulated acoustic emission energy of each partition is as follows: Fig.14As shown in the figure, the cumulative acoustic emission energy curves of each partition are all increasing, but the specific forms of the cumulative acoustic emission energy curves of different partitions are different. The increasing trend of the first three partitions is an obvious "S" shape. The shallower the depth, the greater the change amplitude of the curve. The change trend of the curve of partition ④ is obviously slow, while the curve of partition ⑤ is approximately a straight line. The above situation illustrates two points. On the one hand, the effect of heat and moisture circulation weakens with the increase of the depth of the sample; on the other hand, the degradation effect of heat and moisture circulation on the surface rock mass is a gradually increasing process in the early stage. At a certain moment, the degradation effect reaches the maximum value, and then as the heat and moisture circulation proceeds, the degradation effect gradually weakens. Under the action of heat and moisture circulation alone, compared with the initial state, the increase values ​​of the cumulative acoustic emission energy of the five depth partitions after 20 cycles are: 0.361, 0.302, 0.214, 0.122, 0.036 (unit: ×10 7 ).

[0105] (2) When the test device of the present invention is used to carry out a temperature-stress-deformation coupled heat and humidity cycle test on a sample, the accumulated acoustic emission energy of each partition is as follows: Fig.15 As shown, the curve shape is basically the same. With the increase of the heat and moisture cycle, the cumulative acoustic emission energy curves of different partitions of the sample show an "S"-shaped increasing trend. In the initial state (that is, there is no heat and moisture cycle, only axial load), the cumulative acoustic emission energy numbers of the five partitions of the sample are basically the same, indicating that the interior of the sample used in the test is relatively uniform. With the increase of the depth of the sample, the increase in the cumulative acoustic emission energy becomes smaller. Under the coupling effect, compared with the initial state, the increase in the cumulative acoustic emission energy of the five depth partitions after 20 cycles are: 2.414, 2.144, 2.055, 1.865, 1.621 (unit: ×10 7 ).

[0106] (3) From the absolute value of the cumulative acoustic emission energy, the degradation effect of the test group is more obvious, indicating that for the rock mass in the drawdown zone of some dry-hot river valleys, it is not enough to only consider the influence of heat and moisture circulation when conducting heat and moisture cycle simulation tests. The test device of the present invention can better simulate the actual occurrence environment of the rock mass in the drawdown zone of some dry-hot river valleys.

Claims

1. A temperature-stress-deformation coupled heat and humidity cycle test device, characterized in that: Including specimen, loading system, soaking and drying system and detection system; The loading system comprises a base (1), on which a lower pad (2), a sample (3), and an upper pad (4) are placed in order from bottom to top, and the upper pad (4) is pressurized by an upper pressurizing system (5); The soaking and drying system comprises a water tank (6), wherein the upper end of the water tank (6) is provided with a water inlet (7) and the lower end is provided with a water outlet (8); one side of the water tank (6) is open and the end face of the opening is sealedly connected to the side face of the sample (3) via a locking mechanism; a sandwich is provided in the water tank (6), and a heating tube (9) is installed in the sandwich; The detection system comprises a displacement sensor (10), a fiber grating temperature strain sensor (11), and an acoustic emission sensor (12); The displacement sensor (10) is installed between the lower pad (2) and the upper pad (4); the displacement sensor (10) is used to monitor the degree of deformation of the sample (3); The fiber Bragg grating temperature and strain sensors (11) are divided into a plurality of groups and arranged at intervals in a direction away from the water tank (6) along the sample (3). The fiber Bragg grating temperature and strain sensors (11) are used to monitor the temperature and strain of the sample (3); The acoustic emission sensors (12) are divided into a plurality of groups and arranged at intervals along the direction of the sample (3) away from the water tank (6). The acoustic emission sensors (12) are used to monitor the location and degree of damage of the sample (3); The locking mechanism comprises a locking opening (13) arranged on the lower pad (2) and a sliding groove (14) arranged on the upper pad (4), wherein the locking opening (13) is spliced ​​with a locking beam at the lower part of the water tank (6), the sliding groove (14) is slidably matched with a large head at one end of a screw rod (15), and the other end of the screw rod (15) is threadedly connected to the upper end of the water tank (6); The sample (3) is divided into sections along the length direction, and a fiber Bragg grating temperature strain sensor (11) and an acoustic emission sensor (12) are installed at appropriate positions in each section; The fiber Bragg grating temperature strain sensor (11) is provided with two groups, inner and outer, in each section of the sample (3), wherein the surface fiber Bragg grating temperature strain sensor (11) is arranged close to the sample surface, and the internal fiber Bragg grating temperature strain sensor (11) is installed in the installation hole (16) of the corresponding section of the sample (3).

2. A temperature-stress-deformation coupled heat and humidity cycle test device according to claim 1, characterized in that: The acoustic emission sensors (12) are placed in the empty slots reserved in the lower pad (2) and the upper pad (4) and correspond one-to-one to each section of the sample (3).

3. The temperature-stress-deformation coupled heat and humidity cycle test device according to claim 1, characterized in that: The contact points between the immersion end surfaces of the lower pad (2), the sample (3) and the upper pad (4) and the end surface of the water tank (6) are sealed with a sealing strip (17); and the immersion end surfaces of the lower pad (2) and the upper pad (4) are sealed and waterproofed.

4. The temperature-stress-deformation coupled heat and humidity cycle test device according to claim 1, characterized in that: A high-speed camera (18) and an underwater light source (19) are installed on the water tank (6), wherein the high-speed camera (18) is directly opposite to the sample (3).

5. A method for conducting a test according to a temperature-stress-deformation coupled heat and humidity cycle test device according to any one of claims 1 to 4, comprising the following steps: Step 1) Before the test begins, use a marker pen to evenly divide the sample (3) into multiple depth regions along the length direction; then use a sealing tape (17) to wrap around the end surface of the sample (3) that is affected by the heat and humidity cycle and fix it with glue; Step 2), first drill a 3 mm mounting hole (16) in each partition of the sample (3), and then install a fiber Bragg grating temperature strain sensor (11) inside the mounting hole (16); the fiber Bragg grating temperature strain sensor (11) on the surface of each partition of the sample (3) is fixed with silicone rubber, and vaseline is applied to increase the coupling between it and the sample (3); Step 3), the end surfaces of the upper pad (4) and the lower pad (2) on the side subjected to immersion are sealed and waterproofed, and a sealing strip is also wrapped around the end surfaces; Step 4), fix the acoustic emission sensor (12) in the empty grooves reserved in the lower pad (2) and the upper pad (4); then place the lower pad (2), the sample (3) and the upper pad (4) in order; then adjust the position of the displacement sensor (10) according to the height of the lower pad (2), the sample (3) and the upper pad (4), so that the measuring rod of the displacement sensor (10) just contacts the displacement measuring plate (28) of the upper pad (4); finally, fix the displacement sensor (10) to the displacement sensor fixing plate (29) of the lower pad (2) by fixing bolts (27); Step 5), the lower part of the water tank (6) is connected and fixed with the lock at the bottom of the lower pad (2), and the screw (15) at the upper part of the water tank (6) can be inserted from the slide groove at the upper part of the upper pad (4). The lower part of the water tank (6) is connected and fixed with the lock at the bottom of the lower pad (2), and the screw (15) at the upper part of the water tank (6) can be inserted from the slide groove (14) at the upper part of the upper pad (4), and the screw (15) can be tightened to make the water tank (6) and the lower pad (2), the sample (3), and the upper pad (4) as tightly connected as possible; the joints between the water tank (6) and the lower pad (2), the sample (3), and the upper pad (4) are sealed with a sealing strip (17); Step 6), using the pressure system (5) to apply a load, and applying a load to the upper pad (4) on the upper part of the sample (3) through the testing machine pressure head (23), so as to simulate the load effect of the upper rock sample on the rock mass in the drawdown zone of the dry hot valley in the actual environment, and at the same time, the size of the load can be monitored in real time through the load sensor (24); Step 7), when the upper stress is applied to a predetermined value, the loading is stopped, and then water is injected into the water tank (6) to fill the water tank (6) with water, and the water tank (6) is soaked for a sufficient time according to the test plan to simulate the soaking stage of the rock mass in the drawdown zone of the dry hot valley after the water level rises; After the soaking is finished, the water outlet regulating valve is opened to drain the water in the water tank (6) from the water outlet (8); Step 8), after the water in the water tank (6) is drained, the heating tube (9) is turned on and the temperature is set to 60°C or set according to the specific situation, so that the test surface of the sample (3) is heated to simulate the baking effect of high temperature on the surface rock mass after the water level in the drawdown zone of the dry hot valley drops; Step 9), repeat the immersion and drying test, and stop the test when the number of cycles reaches the number of times specified in the test plan; Step 10) During the immersion-drying cycle test, the temperature, displacement, stress and damage monitoring of the sample are also carried out simultaneously.

Images