A device and method for testing the characteristics of a fissure rock mass frost heaving load and damage propagation

Abstract

This application provides an experimental apparatus and method for testing the frost heave load and damage propagation characteristics of fractured rock masses. The apparatus includes a model chamber, an automatic temperature control system, and a data acquisition system. A fractured rock mass specimen is placed inside the model chamber. A first temperature sensor and a second temperature sensor are respectively installed at the top and middle of the fractured rock mass specimen. The automatic temperature control system includes a low-temperature control module and a high-temperature control module. The low-temperature control module is located at the top of the fractured rock mass specimen and cools the specimen by monitoring the temperature of the second temperature sensor. The high-temperature control module is located at the bottom of the fractured rock mass specimen and heats the specimen by monitoring the temperature of either the first or second temperature sensor. The experimental apparatus of this application can simulate the frost heave load and damage propagation characteristics of fractured rock masses under natural environmental temperature changes more closely, and can accurately measure the frost heave load and deformation propagation characteristics.

Description

Technical Field

[0001] This application belongs to the field of frozen rock mass testing technology, and more specifically, relates to a test device and method for testing the frost heave load and damage propagation characteristics of fractured rock mass. Background Technology

[0002] Frost heave damage in fractured rock masses is a common phenomenon in nature, posing a serious threat to the reliability of rock mass engineering in cold regions. The damage propagation in fractured rock masses is closely related to the formation and dissipation mechanisms of frost heave loads. Considering that rock mass engineering in cold regions is constantly affected by the natural environment, and that the natural environment exhibits a certain diurnal cycle, differences in freezing rates and the number of freeze-thaw cycles significantly influence the frost heave deformation propagation characteristics of fractured rock masses. Therefore, conducting research on the frost heave load and deformation propagation characteristics of rock masses under different freezing rates and freeze-thaw cycle conditions can reveal the formation and dissipation mechanisms of frost heave loads, which is of great significance for analyzing the fracture initiation and propagation mechanisms of fractured rock masses.

[0003] Currently, freeze-thaw tests on rock masses are typically conducted by directly exposing them to low-temperature environments, neglecting the influence of temperature on the freeze-thaw process. This differs from the actual freeze-thaw environment of rock masses, leading to generally inflated experimental data and difficulty in accurately describing the frost heave load characteristics of rock masses during the freeze-thaw process. Therefore, determining experimental methods that better reflect the natural environment is crucial for studying the propagation of freeze-thaw damage in rock masses, especially for investigating the formation and dissipation of frost heave forces and crack propagation. Thus, there is an urgent need to develop an experimental device that can conform to the natural environment, precisely control the temperature field, and accurately measure frost heave load and deformation propagation characteristics. Summary of the Invention

[0004] The purpose of this application is to provide a test device and method for frost heave load and damage propagation characteristics of fractured rock mass, so as to solve the technical problem that the freeze-thaw test in the prior art cannot accurately control the freezing rate of rock and accurately measure the frost heave load and frost heave damage of fractured rock mass.

[0005] To achieve the above objectives, a first aspect of this application provides a test apparatus for frost heave load and damage propagation characteristics in fractured rock masses, comprising:

[0006] A model chamber contains a fractured rock mass specimen. The specimen has a through-fracture hole, a plug at the through-fracture hole, and the through-fracture hole is filled with water, which is sealed by the plug. A first temperature sensor and a second temperature sensor are respectively installed at the top and middle of the specimen, with the second temperature sensor positioned close to the through-fracture hole. A pressure sensor is installed inside the through-fracture hole to detect the pressure on its wall. The model chamber is equipped with an insulation layer.

[0007] An automatic temperature control system includes a low-temperature control module and a high-temperature control module; the low-temperature control module is located at the top of the fractured rock mass specimen, and cools the specimen by monitoring the temperature of a second temperature sensor; the high-temperature control module is located at the bottom of the fractured rock mass specimen, and heats the specimen by monitoring the temperature of a first temperature sensor or a second temperature sensor; and...

[0008] A data acquisition system is used to receive pressure data from the pressure sensor.

[0009] Furthermore, the low-temperature control module includes a cooling plate, a liquid silica gel layer, a liquid silica gel storage tank, and a coolant tank. The liquid silica gel layer abuts against the top of the fractured rock mass specimen, and the cooling plate abuts against the liquid silica gel layer. The liquid silica gel storage tank is connected to the liquid silica gel layer via a liquid silica gel guide pipe, and a flow-regulating peristaltic pump is installed on the liquid silica gel guide pipe. The coolant tank is connected to the cooling plate via a coolant inlet pipe and a coolant outlet pipe, and a cooling circulation pump is installed on the coolant inlet pipe or the coolant outlet pipe. U-shaped grooves are provided on opposite sides of the upper part of the model chamber to allow the cooling plate and the liquid silica gel layer to move vertically within the model chamber. The vertical movement of the cooling plate and the liquid silica gel layer is achieved by placing the cooling plate in the air above the model chamber.

[0010] Furthermore, the high-temperature control module includes a temperature control plate, a heating controller, and a temperature controller PLC. The temperature control plate abuts against the bottom of the fractured rock mass specimen, and the temperature controller PLC controls the heating controller to control the temperature of the temperature control plate.

[0011] Furthermore, it also includes a water replenishment system, which comprises a water replenishment unit, a permeable stone ring surrounding the outer wall of the fractured rock mass specimen, and a permeable stone slab located at the bottom of the fractured rock mass specimen, the permeable stone slab abutting against the bottom of the fractured rock mass specimen; the water replenishment unit delivers water to the permeable stone ring and the permeable stone slab through a first water guide pipe and a second water guide pipe, respectively. Opening the first water guide pipe allows water to be replenished to the fractured rock mass specimen near the freezing front through the permeable stone ring; opening the second water guide pipe allows water to be replenished to the fractured rock mass specimen near the freezing front through the permeable stone slab, specifically through the migration of water through its internal micropores.

[0012] Furthermore, the water replenishment unit includes a Marshall bottle, a Marshall bottle support, a pressure balancing pipe, a liquid level sensor, an air pump, a pneumatic pipe, and a liquid level control PLC. The air pump is connected to the Marshall bottle through the pneumatic pipe. The liquid level control PLC controls the liquid level in the Marshall bottle through the liquid level sensor. The pressure balancing pipe is used to balance the air pressure in the Marshall bottle. The Marshall bottle delivers water to the permeable stone ring and the permeable stone slab through the first water guide pipe and the second water guide pipe, respectively.

[0013] Furthermore, it also includes an acoustic emission detection system, which includes two sets of low-temperature acoustic emission sensors. The two sets of low-temperature acoustic emission sensors are located at different heights of the fractured rock mass specimen to detect the frost heave damage process and crack propagation process of the fractured rock mass specimen at different temperatures. The data acquisition system also receives signals from the low-temperature acoustic emission sensors.

[0014] Furthermore, it also includes a CT scanning system for performing CT scanning imaging on the fractured rock mass specimen.

[0015] Furthermore, it also includes an assembly system, which includes a fixed support, a movable bracket, and a fixed bracket. The fixed support is provided with a first transmission track groove, and the movable bracket and the fixed bracket are slidably connected on the fixed support through the first transmission track groove.

[0016] The CT scanning system includes an X-ray tube, a detector, and a rotating stage. The X-ray tube is slidably connected to the fixed support via a second transmission track groove, and the detector is slidably connected to the movable support via a third transmission track groove. The rotating stage is slidably connected to the fixed support via a first transmission track groove. The model chamber is placed on the rotating stage.

[0017] Furthermore, the rotating stage includes a stage and a signal conductive slip ring. The model chamber is placed on the stage, and the stage is driven to rotate by a drive motor. The signal conductive slip ring is disposed in the internal cavity of the stage, and the rotor of the signal conductive slip ring is fixed on the rotor of the stage. The center of the rotor of the signal conductive slip ring and the center of the rotor of the stage are on the same axis, and the signal conductive slip ring and the stage rotate coaxially. The rotor interface of the signal conductive slip ring is connected to the connection lines of the pressure sensor, the first temperature sensor, the second temperature sensor, the low-temperature acoustic emission sensor, and the high-temperature temperature control module. The stator interface of the signal conductive slip ring is connected to the connection lines of the high-temperature temperature control module and the data acquisition system.

[0018] A second aspect of this application provides a method for conducting tests using the testing apparatus for frost heave load and damage propagation characteristics of fractured rock masses as described in any of the above claims, comprising the following steps:

[0019] S1: The rock is processed into fractured rock mass specimens and subjected to vacuum saturation with water;

[0020] S2: Install a pressure sensor in the through-fracture hole of the fractured rock mass specimen, then seal both sides of the through-fracture hole, perform air venting and water injection operations on the through-fracture hole, arrange low-temperature acoustic emission sensors at both ends and adjacent sides of the through-fracture hole, and arrange a first temperature sensor and a second temperature sensor at the top and middle of the fractured rock mass specimen respectively.

[0021] S3: Place a permeable stone slab at the bottom of the fractured rock mass specimen and arrange the permeable stone ring in the middle of the fractured rock mass specimen.

[0022] S4: Place a liquid silica gel layer and a cooling plate on the top of the fractured rock mass specimen, and a permeable stone slab and a temperature control plate at the bottom. Seal the sides of the fractured rock mass specimen completely and place it in the model chamber, leaving the cooling plate in the air.

[0023] S5: Initialize the settings for the automatic temperature control system, water replenishment system, CT scanning system, acoustic emission monitoring system, and data acquisition system;

[0024] S6: The temperature field, cooling rate, and number of freeze-thaw cycles of the fractured rock mass specimen are controlled by the automatic temperature control system.

[0025] S7: Measure the frost heave load-time curve using the pressure sensor;

[0026] S8: Monitor the damage process of the fractured rock mass specimen during frost heave using the acoustic emission sensor monitoring system;

[0027] S9: Scan the fractured rock mass specimen with the CT scanning system to obtain CT images of the macroscopic and microscopic crack propagation morphology during each freeze-thaw cycle;

[0028] S10: Collect experimental data through the data acquisition system and process it accordingly.

[0029] Compared with the prior art, this application has the following technical effects:

[0030] The experimental device for testing the frost heave load and damage propagation characteristics of fractured rock mass disclosed in this application can precisely control the temperature of fractured rock mass specimens in the model chamber through an automatic temperature control system, thereby simulating the frost heave load and damage propagation characteristics of fractured rock mass under natural environmental temperature changes. Furthermore, the frost heave load and deformation propagation characteristics can be accurately measured through pressure sensors inside the fractured rock mass specimens. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of the overall structure of a test device for frost heave load and damage propagation characteristics of fractured rock mass provided in an embodiment of this application;

[0033] Figure 2 for Figure 1 A cross-sectional schematic diagram of the rotating platform and model compartment in the diagram;

[0034] Figure 3 for Figure 2 A schematic diagram of the side view structure;

[0035] Figure 4 for Figure 1 A partial structural schematic diagram of a medium-fractured rock mass specimen;

[0036] Figure 5 for Figure 1 Another partial structural schematic diagram of a medium-fractured rock mass specimen;

[0037] Figure 6 Temperature control flowchart provided for embodiments of this application;

[0038] Figure 7 A flowchart of liquid level control provided for an embodiment of this application.

[0039] The following are the labeling elements in the figure:

[0040] 1. Fixed support; 2. Movable support; 3. Fixed support; 4. Transmission track groove; 5. X-ray tube; 6. Detector; 7. Rotating stage; 8. First hydraulic rotary joint; 9. Second hydraulic rotary joint; 10. Insulation layer; 11. U-shaped groove; 12. Temperature control plate; 13. Heating controller; 14. Temperature control PLC; 15. Cooling plate; 16. Liquid silicone layer; 17. Temperature sensor; 18. Resistance temperature transmitter; 19. Peristaltic pump; 20. Liquid silicone guide pipe; 21. Liquid silicone storage tank; 22. Coolant inlet pipe; 23. Coolant outlet pipe; 24. Coolant reservoir. 25. Box, 26. Marshall bottle, 27. Marshall bottle support, 28. Pressure balance tube, 29. Liquid level sensor, 30. Air pump, 31. Pneumatic tube, 32. Liquid level control PLC, 33. Permeable stone ring, 34. Permeable stone slab, 35. Sealing layer, 36. Water guide pipe, 37. Low temperature acoustic emission sensor, 38. Signal amplifier, 39. Signal acquisition instrument, 40. Data processing terminal, 41. Pressure sensor, 351. Pressure acquisition card, 352. First water guide pipe, 353. Second water guide pipe, 401. Three-way valve, 702. Plug, 703. Stage, 704. Signal conductive slip ring. Detailed Implementation

[0041] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0042] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0043] It should be understood that the terms "length", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application.

[0044] Furthermore, the terms "first," "second," "third," "fourth," and "fifth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "third," "fourth," or "fifth" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0045] Please refer to the following: Figures 1 to 7 The present application will now describe a test apparatus and method for testing the frost heave load and damage propagation characteristics of fractured rock mass.

[0046] In one embodiment of this application, a test device for frost heave load and damage propagation characteristics of fractured rock mass includes a model chamber, an automatic temperature control system, and a data acquisition system. The model chamber contains a fractured rock mass specimen. The specimen has a through-fracture hole, with a plug 401 at each hole. The through-fracture hole is filled with water, which is sealed by the plug 401. A first temperature sensor and a second temperature sensor are respectively located at the top and middle of the specimen, with the second temperature sensor positioned close to the through-fracture hole. A pressure sensor 40 is located inside the through-fracture hole to detect the pressure on its wall. The model chamber has an insulation layer 10. The automatic temperature control system includes a low-temperature control module and a high-temperature control module. The low-temperature control module is located at the top of the specimen and cools it by monitoring the temperature of the second temperature sensor. The high-temperature control module is located at the bottom of the specimen and heats it by monitoring the temperature of either the first or second temperature sensor. A data acquisition system receives pressure data from the pressure sensor 40.

[0047] Please see Figure 4 , Figure 5 In this embodiment, the fractured rock mass specimen is rectangular in shape. Through-holes, rectangular or near-rectangular in shape, are formed on opposite side walls of the specimen. These through-holes are filled with water and are used to simulate the macroscopic frost heave load and damage propagation characteristics of the fractured rock mass specimen under frost heave conditions. A pressure sensor 40 is positioned on the fracture surface of the fractured rock mass specimen, specifically on the inner wall of the through-hole. In this embodiment, the pressure sensor 40 is a thin-film pressure sensor. In this embodiment, pressure data from the pressure sensor 40 is collected by a pressure acquisition card 41. The pressure acquisition card 41 transmits the collected data to a data acquisition system, which includes a data processing terminal 39. The pressure acquisition card 41 is connected to both the data processing terminal 39 and the thin-film pressure sensor 40. Figure 1 As shown.

[0048] In the accompanying drawings of this application, both the first temperature sensor and the second temperature sensor are labeled as temperature sensor 17, such as... Figure 2 , Figure 4 As shown.

[0049] In this embodiment, the plug 401 can be sealed with weather-resistant adhesive to prevent water in the through-crack hole from flowing out after freeze-thaw cycles, thus preventing experimental errors.

[0050] An embodiment of this application provides a test device for frost heave load and damage propagation characteristics of fractured rock mass. Through an automatic temperature control system, the device can precisely control the temperature of the fractured rock mass specimen in the model chamber, thereby simulating the frost heave load and damage propagation characteristics of fractured rock mass under natural environmental temperature changes. Furthermore, the device can accurately measure the frost heave load and deformation propagation characteristics through the pressure sensor 40 inside the fractured rock mass specimen.

[0051] Furthermore, the low-temperature control module of this application embodiment includes a cooling plate 15, a liquid silica gel layer 16, a liquid silica gel storage tank 21, and a coolant storage tank 24. The liquid silica gel layer 16 abuts against the top of the fractured rock mass specimen, and the cooling plate 15 abuts against the liquid silica gel layer 16. The liquid silica gel storage tank 21 is connected to the liquid silica gel layer 16 through a liquid silica gel guide pipe 20, and a flow rate regulating peristaltic pump 19 is provided on the liquid silica gel guide pipe 20. The coolant storage tank 24 is connected to the cooling plate 15 through a coolant inlet pipe 22 and a coolant outlet pipe 23, and a cooling circulation pump is provided on the coolant inlet pipe 22 or the coolant outlet pipe 23. A U-shaped groove 11 is provided on the upper part of the opposite side walls of the model chamber so that the cooling plate 15 and the liquid silica gel layer 16 can move up and down in the model chamber to adapt to the different thicknesses of the liquid silica gel layer 16. Figure 1 , Figure 2 , Figure 3 As shown.

[0052] In this embodiment, a flow-regulating peristaltic pump 19 is used to input or extract liquid silica gel from the liquid silica gel storage tank 21 into or from the liquid silica gel layer 16, thereby changing the volume of the liquid silica gel layer 16 and thus its thickness. By adjusting the thickness of the liquid silica gel layer 16, its thermal resistance can be controlled. The cooling and freezing rates of the fractured rock mass specimen are closely related to the thickness of the liquid silica gel layer 16. With a constant thermal conductivity of the liquid silica gel, a thicker liquid silica gel layer 16 results in a higher thermal resistance and a lower heat transfer capacity. This prevents the cooling plate 15 from rapidly cooling the fractured rock mass specimen, leading to a decrease in both the cooling and freezing rates. By controlling the flow rate into the liquid silica gel layer 16 using the micro-flow-regulating peristaltic pump 19, the thickness of the liquid silica gel layer 16 is adjusted, thereby changing its thermal resistance and controlling the cooling and freezing rates.

[0053] In this embodiment, coolant is supplied to the cooling plate 15 through the coolant tank 24 to maintain the cooling plate 15 at a constant low temperature, such as -30°C. The cooling plate 15 cools the fractured rock mass specimen to cause it to freeze, thereby conducting a frost heave test. Since the cooling plate 15 passively cools the fractured rock mass specimen, if a liquid silica gel layer 16 is not used as a separator, the freezing rate will continuously decrease during the cooling process, which is not conducive to controlling the freezing rate of the fractured rock mass specimen. This embodiment fully considers the characteristic of active cooling of the fractured rock mass specimen. During the experiment, the temperature of the coolant in the cooling plate 15 is maintained at -30°C, and the freezing rate of the fractured rock mass specimen is controlled by adjusting the thickness of the liquid silica gel layer 16.

[0054] Furthermore, the high-temperature control module in this embodiment includes a temperature control plate 12, a heating controller 13, and a temperature controller PLC 14. The temperature control plate 12 abuts against the bottom of the fractured rock mass specimen, and the temperature controller PLC 14 controls the heating controller 13 to control the temperature of the temperature control plate 12. In this embodiment, a resistance temperature transmitter 18 is also connected between the temperature controller PLC 14, the temperature control plate 12, and the heating controller 13. The resistance temperature transmitter 18 converts the change in resistance of the resistance thermometer with temperature into an electrical signal, such as... Figure 1 As shown.

[0055] Furthermore, the test device for frost heave load and damage propagation characteristics of fractured rock mass according to an embodiment of this application also includes a water replenishment system. The water replenishment system includes a water replenishment unit, a permeable stone ring 32 surrounding the outer wall of the fractured rock mass specimen, and a permeable stone slab 33 located at the bottom of the fractured rock mass specimen. The permeable stone slab 33 abuts against the bottom of the fractured rock mass specimen. The water replenishment unit supplies water to the permeable stone ring 32 and the permeable stone slab 33 through a first water pipe 351, a second water pipe 352, and a three-way valve 353, respectively. Both the first water pipe 351 and the second water pipe 352 are connected to the main water pipe 35. Figure 1 As shown, water is supplied to different height positions of the fractured rock mass specimen through the first water pipe 351 and the second water pipe 352. This allows for testing of the differences in frost heave characteristics caused by different water supply positions, and study of the influence of different water supply methods (in-situ water supply and migratory water supply) on the water migration mechanism, thereby investigating the impact on frost heave force. Uniform and slow water supply to the fractured rock mass specimen through the permeable stone ring 32 and permeable stone slab 33 ensures that the natural micropores in the fractured rock mass specimen remain saturated with water throughout the experiment. This increases the frost heave load and deformation propagation characteristics of the natural micropores in the fractured rock mass specimen during the unidirectional freeze-thaw process, which is beneficial for studying the microscopic frost heave load and deformation propagation characteristics of the fractured rock mass specimen.

[0056] In this embodiment, the permeable stone ring 32 is a rectangular ring, the size of which can be just fitted onto the outer surface of the fractured rock mass specimen. The permeable stone slab 33 is a rectangular slab, such as... Figure 5 , Figure 6 As shown, the outer surface of the fractured rock mass specimen, the outer side of the permeable stone ring 32, and the outer side of the permeable stone slab 33 are all covered with a sealant layer 34 to prevent water inside the fractured rock mass specimen from leaking out from its outer surface. The sealant layer 34 can be coated or covered with weather-resistant adhesive.

[0057] Furthermore, the water replenishment unit in this embodiment includes a Marshall bottle 25, a Marshall bottle support 26, a pressure balance pipe 27, a liquid level sensor 28, an air pump 29, a pneumatic pipe 30, and a liquid level control PLC 31. The air pump 29 is connected to the Marshall bottle 25 through the pneumatic pipe 30. The liquid level control PLC 31 controls the liquid level in the Marshall bottle 25 through the liquid level sensor 28. The pressure balance pipe 27 is used to balance the air pressure in the Marshall bottle 25. The Marshall bottle 25 delivers water to the permeable stone ring 32 and the permeable stone slab 33 through the first water guide pipe 351 and the second water guide pipe 352, respectively. The liquid level control PLC 31 is used to control a constant water level difference, thereby replenishing the fractured rock specimen with a constant water level difference. The change in liquid level in the Marshall bottle 25 is achieved by the air pump 29 pumping air out of the Marshall bottle 25.

[0058] The liquid level sensor 28 in this embodiment can be a capacitive liquid level sensor, the air pump 29 is a miniature air pump, and the pneumatic tube 30 is a pressure-resistant pneumatic tube.

[0059] Furthermore, the experimental device for testing the frost heave load and damage propagation characteristics of fractured rock mass according to an embodiment of this application also includes an acoustic emission detection system. The acoustic emission detection system includes two sets of low-temperature acoustic emission sensors 36, which are positioned at different heights on the fractured rock mass specimen to detect the frost heave damage process and crack propagation process of the specimen at different temperatures. The data acquisition system also receives signals from the low-temperature acoustic emission sensors 36. In this embodiment, the acoustic emission detection system further includes a signal amplifier 37. The low-temperature acoustic emission sensors 36 are connected to the signal acquisition instrument 38 and the data processing terminal 39 via the signal amplifier 37. Figure 1 As shown. Two sets of low-temperature acoustic emission sensors 36 are respectively deployed on adjacent sides of the fractured rock specimen, as shown. Figure 6As shown, one set of acoustic emission sensors 36 is located above the through-hole, i.e., above the temperature sensor 17 in the middle. If the temperature at the middle temperature sensor 17 is controlled at 0℃, then the temperature at this set of acoustic emission sensors 36 is below 0℃. At this time, the rock exhibits frost heave, and the frost heave damage process caused by pore frost heave force and the crack propagation process caused by crack frost heave force at the direction of the through-hole can be monitored. The other set of acoustic emission sensors 36 is located below the through-hole, i.e., below the middle temperature sensor 17. The temperature here is above 0℃, and the rock specimen in this location is not frozen. The crack propagation process caused by crack frost heave force at this location of the through-hole can be monitored. Thus, the two sets of acoustic emission sensors 36 serve as control groups for each other.

[0060] Furthermore, the test device for frost heave load and damage propagation characteristics of fractured rock mass according to an embodiment of this application also includes a CT scanning system. The CT scanning system is used to perform CT scanning imaging on fractured rock mass specimens. Through CT scanning imaging, the changes in the macrostructure and microstructure of fractured rock specimens before and after freeze-thaw can be intuitively analyzed to determine the characteristics of frost heave deformation.

[0061] Furthermore, the experimental device for testing the frost heave load and damage propagation characteristics of fractured rock mass according to an embodiment of this application also includes an assembly system. The assembly system includes a fixed support 1, a movable support 2, and a fixed support 3. The fixed support 1 is provided with a first transmission track groove. The movable support 2 and the fixed support 3 are slidably connected to the fixed support 1 through the first transmission track groove. The CT scanning system includes an X-ray tube 5, a detector 6, and a rotating stage 7. The detector 6 is used to detect and receive the light signal from the X-ray tube 5. The X-ray tube 5 is slidably connected to the fixed support 3 through a second transmission track groove. The detector 6 is slidably connected to the movable support 2 through a third transmission track groove. The rotating stage 7 is slidably connected to the fixed support 1 through the first transmission track groove. The model chamber is placed on the rotating stage 7.

[0062] In the accompanying drawings of this application, the first, second, and third transmission track grooves are all labeled as transmission track grooves 4. The various assembly components are connected via this sliding connection through the transmission track grooves 4, facilitating the adjustment of the relative positions of the assembly components. This ensures that the movable support 2, fixed support 3, and rotating platform 7 can be properly fixed on the fixed support 1, and that the X-ray tube 5 and detector 6 can be fixed at appropriate heights on the movable support 2 and fixed support 3. This facilitates CT scanning or water replenishment operations on the fractured rock mass specimen within the model chamber on the rotating platform 7. The transmission track groove 4 can specifically be a T-shaped slide rail, which can cooperate with a corresponding T-shaped groove for sliding operation.

[0063] In this embodiment, the upper end of the fixed bracket 3 is also fixedly connected to a first hydraulic rotary joint 8 and a second hydraulic rotary joint 9. The inlet of the first hydraulic rotary joint 8 is connected to the main water pipe 35, and the outlet is connected to the first water pipe 351 and the second water pipe 352. The second hydraulic rotary joint 9 is a three-inlet, three-outlet joint, which is respectively connected to the liquid silica gel storage tank 21, the coolant storage tank 24, the cooling plate 15, and the liquid silica gel layer 16. Figure 1 As shown.

[0064] Further, the rotating stage 7 in this embodiment includes a stage 701 and a signal conductive slip ring 702. A model chamber is placed on the stage 701, which is driven to rotate by a drive motor. The signal conductive slip ring 702 is disposed in the internal cavity of the stage 701, and its rotor is fixed to the rotor of the stage 701. The center of the rotor of the signal conductive slip ring 702 and the center of the rotor of the stage 701 are on the same axis, and the signal conductive slip ring 702 and the stage 701 rotate coaxially. The rotor interface of the signal conductive slip ring 702 is connected to the connection lines of the pressure sensor 40, temperature sensor 17, low-temperature acoustic emission sensor 36, and the temperature control plate 12 in the high-temperature temperature control module. The stator interface of the signal conductive slip ring 702 is connected to the connection lines of the thermal resistance temperature transmitter 18 and the heating controller 13 of the high-temperature temperature control module, and the pressure acquisition card 41 and signal acquisition instrument 38 of the data acquisition system. Figure 2 , Figure 3 As shown, the signal conductive slip ring 702 can solve the problem of signal connection wires getting tangled and obstructed during the rotation of the stage 701.

[0065] The CT scanning system, acoustic emission monitoring system, and pressure data acquisition system of this application embodiment can share a single data processing terminal 39 for experimental process control and data processing.

[0066] This application discloses an experimental apparatus for analyzing the frost heave load and damage propagation characteristics of fractured rock masses. This apparatus fully considers the influence of factors such as osmotic pressure (which can be altered through a water replenishment system), freezing rate, number of freeze-thaw cycles, and freeze-thaw intervals during the freeze-thaw process. It employs a coupled method of frost heave force and acoustic emission phenomena to analyze the local propagation damage characteristics of frost heave force. Simultaneously, it combines industrial CT scanning technology to identify internal rock features, studying the overall frost heave propagation and microscopic damage distribution characteristics of the rock during freeze-thaw cycles. This apparatus can reveal the macroscopic frost heave force and microscopic frost heave damage characteristics of the rock mass, and establish a matching relationship between temperature and frost heave load characteristics to determine the coupling relationship between frost heave load and deformation propagation characteristics of fractures during the freeze-thaw process.

[0067] An embodiment of this application discloses an experimental device for testing the frost heave load and damage propagation characteristics of fractured rock mass. By controlling the temperature field changes through a temperature control PLC14, the freezing front is kept at the target position of the sample. The device fully utilizes the characteristics of the thin-film pressure sensor 40 and the low-temperature acoustic emission sensor 36. By matching the attenuation law of pressure increase with the acoustic emission phenomenon of rock damage process, the frost heave load and damage characteristics of the fracture surface during the interaction between the fracture and ice are inverted. Combined with CT scanning technology, the device analyzes the frost heave deformation characteristics of fractured rock mass based on the changes in the macroscopic and microscopic structure of the rock before and after freeze-thaw.

[0068] A second aspect of this application provides a method for conducting tests using the aforementioned test apparatus for testing the frost heave load and damage propagation characteristics of fractured rock masses, comprising the following steps:

[0069] S1: The rock is processed into a fractured rock mass specimen and then subjected to vacuum saturation water. Specifically, a complete, high-quality rock is processed into a cubic specimen, a through hole is drilled in the center of the specimen, and then a fracture of a certain size and angle is cut through the through hole by wire saw to form a through fracture hole. After that, the fractured rock specimen is subjected to vacuum saturation water.

[0070] S2: Install a pressure sensor 40 in the through-fracture hole of the fractured rock mass specimen, and then seal both sides of the through-fracture hole with weather-resistant adhesive. The through-fracture hole can be vented and water injected by two syringes. Low-temperature acoustic emission sensors 36 are arranged at both ends and adjacent sides of the through-fracture hole. The first temperature sensor and the second temperature sensor are arranged at the top and middle of the fractured rock mass specimen, respectively. The second temperature sensor is set close to the through-fracture hole.

[0071] S3: Place a permeable stone slab 33 at the bottom of the fractured rock mass specimen, and place a permeable stone ring 32 in the middle of the fractured rock mass specimen near the bottom of the penetrating fracture hole.

[0072] S4: Place a liquid silica gel layer 16 and a cooling plate 15 on the top of the fractured rock mass specimen, and a permeable stone slab 33 and a temperature control plate 12 at the bottom. Seal the sides of the fractured rock mass specimen completely with weather-resistant adhesive, and place it in the model chamber, so that the cooling plate 15 is suspended in the air to ensure that the cooling plate 15 and the liquid silica gel layer 16 have enough space to move up and down.

[0073] S5: Initialize the settings for the automatic temperature control system, water replenishment system, CT scanning system, acoustic emission monitoring system, and data acquisition system;

[0074] S6: The temperature field, cooling rate, and number of freeze-thaw cycles of the fractured rock mass specimen are controlled by an automatic temperature control system;

[0075] S7: Measure the frost heave force time curve using pressure sensor 40;

[0076] S8: Monitor the damage process of fractured rock mass specimens during frost heave using an acoustic emission sensor monitoring system;

[0077] S9: CT images of the macroscopic and microscopic crack propagation morphology of fractured rock mass specimens during each freeze-thaw cycle, obtained by scanning with a CT scanning system;

[0078] S10: Collect experimental data through the data acquisition system and process it accordingly.

[0079] In step S1 above, the selected rock should have good integrity and undeveloped joints.

[0080] In step S2 above, weather-resistant adhesive is used to seal the cracks on the surface of the fractured rock mass specimen to prevent water from flowing out of the through-crack pores during the freeze-thaw process, which could cause experimental errors.

[0081] In step S3 above, when the permeable stone ring 32 is laid out, its inner wall surface is kept in close contact with the side of the fractured rock specimen, and it is sealed with weather-resistant adhesive to realize water replenishment operation under certain water level difference conditions. This can simulate the influence of seepage velocity on the rock frost heave process during the freezing process of water-rich strata.

[0082] In step S5 above, the automatic temperature control system inputs the initial relevant parameters and realizes real-time control of the temperature field through the feedback of the temperature sensor 17. The water replenishment system feeds back to the liquid level control PLC 31 through the liquid level sensor 28 and exhausts air through the micro air pump 29 to keep the water level difference constant during the water replenishment process.

[0083] The temperature control process is as follows: Figure 7As shown, the specific operation is as follows: First, set the freeze-thaw parameters such as the thickness of the liquid silica gel layer 16, the target temperature of the temperature sensor 17 at the middle position, the maximum temperature of the temperature sensor 17 at the top position, the freezing duration, and the number of freeze-thaw cycles; turn on the micro-flow rate adjustable peristaltic pump 19 to adjust the thickness of the liquid silica gel layer 16, and turn off the micro-flow rate adjustable peristaltic pump 19 after the set thickness of the liquid silica gel layer 16 is reached, so that the upper surface of the fractured rock specimen can achieve a relatively constant cooling rate and freezing rate value; then turn on the low temperature cooling circulation pump to keep the cooling plate 15 under constant low temperature conditions; according to the data of the temperature sensor 17 at the middle position of the specimen, the data is transmitted to the temperature control PLC 14. When the temperature reaches the set target temperature, the heating controller 13 is turned on by the temperature control PLC 14 and the timing starts. During this period, the temperature measured by the temperature sensor 17 at the middle position of the specimen decreases, and the temperature control PLC 14 controls the temperature to decrease. The heating controller 13 heats the temperature control plate 12 until the temperature sensor 17 at the middle position reaches the target temperature, at which point the heating stops. When the timer reaches the target duration, a freezing process is considered complete, the low-temperature cooling circulation pump is turned off, and the temperature control PLC 14 controls the heating controller 13 to heat the temperature control plate 12 until the temperature of the temperature control plate 12 reaches the set maximum temperature value, maintaining the stability of the temperature control plate 12. When the temperature measured by the temperature sensor 17 at the top of the sample reaches the maximum temperature value, a freeze-thaw process is considered complete, and the temperature control PLC 14 counts. When the counter is less than the set number of freeze-thaw cycles, the low-temperature cooling circulation pump is restarted, starting a new round of cooling from the top and heating from the bottom. When the counter equals the set number of freeze-thaw cycles, the micro-flow speed-regulating peristaltic pump 19 is started to discharge the liquid silica gel in the liquid silica gel layer 16, ending the experiment.

[0084] Liquid level control process as follows Figure 7 As shown, the specific operation is as follows: First, set the target liquid level value in the liquid level control PLC31; then, the liquid level control PLC31 controls the micro air pump 29 to start, and inputs air into the Marshall bottle 25 through the pressure-resistant pneumatic tube 30 to increase the air pressure inside the Marshall bottle 25, so that the liquid level in the pressure balance tube 27 rises; the liquid level position in the pressure balance tube 27 is measured by the capacitive liquid level sensor 28. When the predetermined value is reached, the liquid level control PLC31 controls the micro air pump 29 to be turned off; at this time, the water level difference between the liquid level in the pressure balance tube 27 and the water level difference between the permeable stone ring 32 and the permeable stone slab 33 is the osmotic pressure of the water in the permeable stone ring 32 and the permeable stone slab 33.

[0085] The method for testing the frost heave load and damage propagation characteristics of fractured rock masses according to an embodiment of this application fully considers factors such as the cooling rate of the freezing process of fractured rock, the time of the freeze-thaw cycle, the maximum temperature and the number of freeze-thaw cycles, and the permeability pressure to analyze the frost heave load characteristics, frost heave deformation propagation characteristics, and the coupling relationship between the two in fractured rock masses.

[0086] The experimental method of this application can simultaneously and effectively control the temperature field of fractured rock mass during freeze-thaw cycles. The acquired frost heave force data helps to explore the formation and dissipation mechanism of frost heave load in fractured rock mass, while the acquired acoustic emission data and CT scan image data help to explore the frost heave damage propagation mechanism in fractured rock mass. This experimental method can simultaneously collect frost heave load within the fracture, acoustic emission data of the rock mass along the fracture direction, and overall CT scan image data. Coupled analysis of frost heave load and frost heave damage characteristics helps to analyze the promoting effect of the loading and unloading process of macroscopic frost heave load on the structural fatigue damage of rock mass along the fracture surface. Combining overall structural image data and constant pressure water replenishment process analysis of the spatial distribution characteristics of micro-pore structure in unidirectional freeze-thaw cycles helps to explore the water migration process during frost heave at the intersection of freezing front and fracture. By changing the fracture orientation, freezing rate, freezing duration, number of freeze-thaw cycles, and permeation pressure in each test, and using the test method for frost heave load and damage propagation characteristics of fractured rock mass under unidirectional freeze-thaw cycle conditions provided in the embodiments of this application, the frost heave load characteristics of fractured rock mass under different freeze-thaw environment parameters can be clarified. In this way, the macroscopic crack propagation evolution characteristics and the fatigue damage characteristics of microscopic pore structure along the fracture surface, as well as the coupled damage propagation characteristics of the two, can be obtained.

[0087] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A test apparatus for frost heave load and damage propagation characteristics in fractured rock masses, characterized in that, include: A model chamber contains a fractured rock mass specimen. The specimen has a through-fracture hole, a plug at the through-fracture hole, and the through-fracture hole is filled with water, which is sealed by the plug. A first temperature sensor and a second temperature sensor are respectively installed at the top and middle of the specimen, with the second temperature sensor positioned close to the through-fracture hole. A pressure sensor is installed inside the through-fracture hole to detect the pressure on the hole wall. The model chamber has an insulation layer. An automatic temperature control system includes a low-temperature control module and a high-temperature control module; the low-temperature control module is located at the top of the fractured rock mass specimen, and cools the specimen by monitoring the temperature of a second temperature sensor; the high-temperature control module is located at the bottom of the fractured rock mass specimen, and heats the specimen by monitoring the temperature of a first temperature sensor or a second temperature sensor; and... A data acquisition system is used to receive pressure data from the pressure sensor; The low-temperature control module includes a cooling plate, a liquid silica gel layer, a liquid silica gel storage tank, and a coolant tank. The liquid silica gel layer abuts against the top of the fractured rock mass specimen, and the cooling plate abuts against the liquid silica gel layer. The liquid silica gel storage tank is connected to the liquid silica gel layer through a liquid silica gel guide pipe, and a flow-regulating peristaltic pump is installed on the liquid silica gel guide pipe. The coolant tank is connected to the cooling plate through a coolant inlet pipe and a coolant outlet pipe, and a cooling circulation pump is installed on the coolant inlet pipe or the coolant outlet pipe. U-shaped grooves are provided on opposite sides of the upper part of the model chamber to allow the cooling plate and the liquid silica gel layer to move up and down within the model chamber.

2. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 1, characterized in that, The high-temperature control module includes a temperature control plate, a heating controller, and a temperature controller PLC. The temperature control plate abuts against the bottom of the fractured rock mass specimen, and the temperature controller PLC controls the heating controller to control the temperature of the temperature control plate.

3. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 1, characterized in that, It also includes a water replenishment system, which includes a water replenishment unit, a permeable stone ring surrounding the outer wall of the fractured rock mass specimen, and a permeable stone slab located at the bottom of the fractured rock mass specimen, the permeable stone slab abutting against the bottom of the fractured rock mass specimen; the water replenishment unit delivers water to the permeable stone ring and the permeable stone slab through a first water pipe and a second water pipe, respectively.

4. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 3, characterized in that, The water replenishment unit includes a Marshall bottle, a Marshall bottle support, a pressure balancing pipe, a liquid level sensor, an air pump, a pneumatic pipe, and a liquid level control PLC. The air pump is connected to the Marshall bottle through the pneumatic pipe. The liquid level control PLC controls the liquid level in the Marshall bottle through the liquid level sensor. The pressure balancing pipe is used to balance the air pressure in the Marshall bottle. The Marshall bottle delivers water to the permeable stone ring and the permeable stone slab through the first water guide pipe and the second water guide pipe, respectively.

5. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 3, characterized in that, It also includes an acoustic emission detection system, which comprises two sets of low-temperature acoustic emission sensors. The two sets of low-temperature acoustic emission sensors are located at different heights of the fractured rock mass specimen. The two sets of low-temperature acoustic emission sensors are respectively located above and below the second temperature sensor, so as to detect the microscopic frost heave damage process and macroscopic crack propagation process of the fractured rock mass specimen below 0°C and the macroscopic crack propagation process above 0°C; the data acquisition system also receives the signals from the low-temperature acoustic emission sensors.

6. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 5, characterized in that, It also includes a CT scanning system, which is used to perform CT scanning imaging on the fractured rock mass specimen.

7. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 6, characterized in that, It also includes an assembly system, which includes a fixed support, a movable support, and a fixed support. The fixed support is provided with a first transmission track groove, and the movable support and the fixed support are slidably connected on the fixed support through the first transmission track groove. The CT scanning system includes an X-ray tube, a detector, and a rotating stage. The X-ray tube is slidably connected to the fixed support via a second transmission track groove, and the detector is slidably connected to the movable support via a third transmission track groove. The rotating stage is slidably connected to the fixed support via the first transmission track groove. The model compartment is placed on the rotating platform.

8. The test device for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 7, characterized in that, The rotating stage includes a stage and a signal conductive slip ring. The model chamber is placed on the stage, and the stage is driven to rotate by a drive motor. The signal conductive slip ring is disposed in the internal cavity of the stage, and the rotor of the signal conductive slip ring is fixed on the rotor of the stage. The center of the rotor of the signal conductive slip ring and the center of the rotor of the stage are on the same axis, and the signal conductive slip ring and the stage rotate coaxially. The rotor interface of the signal conductive slip ring is connected to the connection lines of the pressure sensor, the first temperature sensor, the second temperature sensor, the low-temperature acoustic emission sensor, and the high-temperature temperature control module. The stator interface of the signal conductive slip ring is connected to the connection lines of the high-temperature temperature control module and the data acquisition system.

9. A method for conducting tests using the test apparatus for frost heave load and damage propagation characteristics of fractured rock mass as described in claim 6, characterized in that, Includes the following steps: S1: The rock is processed into fractured rock mass specimens and subjected to vacuum saturation with water; S2: Install a pressure sensor in the through-fracture hole of the fractured rock mass specimen, then seal both sides of the through-fracture hole, perform air venting and water injection operations on the through-fracture hole, arrange low-temperature acoustic emission sensors at both ends and adjacent sides of the through-fracture hole, and arrange a first temperature sensor and a second temperature sensor at the top and middle of the fractured rock mass specimen respectively, with the second temperature sensor located close to the through-fracture hole; S3: Place a permeable stone slab at the bottom of the fractured rock mass specimen, and arrange the permeable stone ring in the middle of the fractured rock mass specimen near the bottom of the through fracture hole. S4: Place a liquid silica gel layer and a cooling plate on the top of the fractured rock mass specimen, and a permeable stone slab and a temperature control plate at the bottom. Seal the sides of the fractured rock mass specimen completely and place it in the model chamber, leaving the cooling plate in the air. S5: Initialize the settings for the automatic temperature control system, water replenishment system, CT scanning system, acoustic emission detection system, and data acquisition system; S6: The temperature field, cooling rate, and number of freeze-thaw cycles of the fractured rock mass specimen are controlled by the automatic temperature control system. S7: Measure the frost heave load-time curve using the pressure sensor; S8: Monitor the damage process of the fractured rock mass specimen during frost heave using the acoustic emission monitoring system; S9: Scan the fractured rock mass specimen with the CT scanning system to obtain CT images of the macroscopic and microscopic crack propagation morphology during each freeze-thaw cycle; S10: Collect experimental data through the data acquisition system and process it accordingly.

Images