A fatigue loading device for simulating tunnel bottom structure and method of use thereof

Abstract

The application relates to the technical field of tunnel engineering, and discloses a fatigue loading device for simulating a tunnel bottom structure and a use method thereof. The device comprises a supporting component, a hydraulic assembly, a pressure monitoring component, a pressure head, an eccentric rotation loading assembly, a deformation monitoring component and a control system. A cross beam is vertically and slidably connected to the supporting component, and a lifting mechanism is arranged between the cross beam and the supporting component. The hydraulic assembly is arranged on the cross beam, and a force transmission frame is arranged at the piston end of the hydraulic assembly. The pressure monitoring component is arranged below the force transmission frame through a first connecting piece. The pressure head is arranged below the pressure monitoring component through a second connecting piece, and the pressure head is located directly above the test piece. The application can more accurately carry out research on the micro-crushing mechanism and migration mechanism of the virtual residue at the tunnel bottom, and can provide guidance for analyzing the evolution process of diseases such as the tunnel bottom structure falling off and the slurry water disease.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a device for simulating fatigue loading of the tunnel bottom structure and its usage method. Background Technology

[0002] Voiding at the tunnel bottom structure is a significant factor affecting tunnel service safety. This defect primarily arises from a loose bond between the tunnel bottom structure and the surrounding rock, meaning there is broken rock, commonly known as loose rock, between them. During service, the tunnel bottom structure vibrates under train dynamic loads, causing the loose rock to shift and compress against each other. This compression leads to micro-fracture in some areas. In water-rich conditions at the tunnel bottom, train dynamic loads trigger groundwater movement, causing these micro-fracture products to migrate out of the tunnel bottom under the influence of water flow, resulting in voids. This, in turn, increases the vibration amplitude of the tunnel bottom structure, making the loose rock more prone to micro-fracture, creating a vicious cycle. Accurately understanding the micro-fracture mechanism and migration mechanism of loose rock at the tunnel bottom under train dynamic loads helps assess the service condition of the tunnel bottom structure, thereby improving tunnel operation and maintenance levels and reducing operational risks. It should be noted that the dynamic pressure on the tunnel bottom structure under train dynamic loads is typically relatively low, with measured values ​​around 95 kPa. Assuming the tunnel invert arch thickness is 2 m, the bottom structure bears a static load of approximately 50 kPa.

[0003] In existing technologies, research on this type of micromechanical mechanism mainly relies on CT scanning tests to conduct precise loading tests on small-sized specimens. However, existing testing equipment is difficult to adapt to its special testing requirements. Conventional mechanical testing machines generally adopt a large-range loading design with low resolution, making it impossible to accurately apply small-amplitude micro-loads, which is insufficient to meet the requirements of precise fatigue loading for small-sized specimens. Meanwhile, tunnel bottom voiding is a long-term fatigue evolution disease, requiring high-frequency, long-term cyclic loading for testing. However, traditional hydraulic loading equipment is limited by the characteristics of the medium, making high-speed loading and unloading impossible, resulting in low testing efficiency. Conventional eccentric vibration equipment is suitable for roadbed compaction conditions, but its load accuracy is low and controllability is poor, making it difficult to meet the high-precision fatigue testing requirements for the evolution of loose slag at the tunnel bottom. The lack of dedicated testing equipment severely restricts the development of related mechanism research and tunnel service safety assessment.

[0004] To address this, a device for simulating fatigue loading of the tunnel bottom structure and its application method are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a device for simulating fatigue loading of the bottom structure of a tunnel and its method of use, aiming to solve or improve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a device for simulating fatigue loading of a tunnel bottom structure, comprising: A support component is provided to support the test piece; a crossbeam is vertically slidably connected to the support component, and a lifting mechanism is installed between the crossbeam and the support component. A hydraulic assembly is mounted on the crossbeam, and a force transmission frame is mounted on the piston end of the hydraulic assembly. A pressure monitoring component is mounted below the force transmission frame via a first connector. The pressure head is mounted below the pressure monitoring component via a second connector, and the pressure head is located directly above the test piece; An eccentric rotary loading assembly is mounted on the first connector; A deformation monitoring component, which is mounted on the sample; The control system includes the lifting mechanism, the hydraulic component, the eccentric rotary loading component, the pressure monitoring component, and the deformation monitoring component, all of which are electrically connected to the control system.

[0007] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein the eccentric rotary loading component includes a servo motor and an eccentric block. The servo motor is fixedly mounted on the top surface of the first connecting member, the eccentric block is mounted on the output shaft of the servo motor, and the servo motor is electrically connected to the control system.

[0008] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein the supporting component comprises: A base, on which a sample stage is mounted, the sample stage being used to support the test piece; A plurality of limiting rods are provided, and all of the plurality of limiting rods are fixedly installed on the top surface of the base. The crossbeam is vertically slidably connected along the plurality of limiting rods. The lifting mechanism is installed between the base and the crossbeam.

[0009] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided. The lifting mechanism includes a plurality of hydraulic rods. The cylinder end of the hydraulic rod is fixedly connected to the base, and the piston end of the hydraulic rod is fixedly connected to the bottom surface of the crossbeam. All of the hydraulic rods are electrically connected to the control system.

[0010] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein a connecting rod is fixedly installed on the top of the force transmission frame, and a flange is fixedly installed on the top of the connecting rod; The hydraulic assembly includes a main hydraulic rod electrically connected to the control system. The cylinder end of the main hydraulic rod is fixedly mounted on the crossbeam, and the flange is fixedly connected to the piston end of the main hydraulic rod by a plurality of first high-strength bolts. The force transmission frame has an inverted U-shape structure, and the opening of the inverted U-shape structure faces the pressure monitoring component. The servo motor is located inside the inverted U-shape structure, and the force transmission frame is fixedly connected to the first connecting member by a number of second high-strength bolts.

[0011] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein the pressure monitoring component adopts a pressure sensor and the deformation monitoring component adopts a displacement sensor.

[0012] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein the base is provided with a plurality of bolt holes.

[0013] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein the servo motor is a dual-axis servo motor, and two eccentric blocks are provided, the two eccentric blocks being respectively installed on the two output shafts of the dual-axis servo motor.

[0014] According to the present invention, a fatigue loading device for simulating the bottom structure of a tunnel is provided, wherein the eccentric block is made of steel, the eccentric block has a semi-circular structure, and the eccentric block has a hole, the hole being fixedly connected to the output shaft of the dual-axis servo motor.

[0015] The present invention also provides a method for using a device for simulating fatigue loading of a tunnel bottom structure, comprising the following steps: Step 1: Place the test piece on the support component; Step 2: Adjust the height of the crossbeam and pressure head using the lifting mechanism; Step 3: Apply the set fatigue load amplitude to the pressure head using the hydraulic components and the eccentric rotary loading components to complete the corresponding loading mode of the test piece; the loading modes include static load loading mode, low-frequency cyclic loading mode, and high-frequency cyclic loading mode. Step 4: Measure the pressure data of the test specimen under each loading mode using the pressure monitoring component, and measure the deformation data of the specimen using the deformation monitoring component. Input the pressure data and the deformation data into the control system to update the instructions of each target control component and obtain the updated corresponding instructions. Step 5: Control the eccentric rotary loading component, lifting mechanism and hydraulic component to perform corresponding actions according to the updated corresponding instructions.

[0016] The present invention discloses the following technical effects: This invention utilizes hydraulic components for displacement adjustment and applying static and low-frequency cyclic loading to the test specimen, while employing an eccentric rotary loading component to apply high-frequency cyclic loading, thereby achieving fatigue simulation testing. Before the test begins, the required static and cyclic loads are calculated, followed by the calculation of the eccentric block mass required for a specified fatigue loading frequency, and then the eccentric block mass of the eccentric rotary loading component is adjusted accordingly. During high-frequency fatigue loading, the control system adjusts the rotational speed of the eccentric rotary loading component to adjust the fatigue load value. The test stops when the fatigue load loading cycle reaches a specified value. This invention enables more precise research on the micro-fracture mechanism and migration mechanism of loose slag at the bottom of tunnels, and can provide guidance for the analysis of issues such as voids and slurry seepage at the bottom of tunnel structures. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the eccentric rotation loading component in this invention; Figure 3 This is a schematic diagram of the pressure head in this invention.

[0019] The components are: 1. Crossbeam; 2. Force transmission frame; 3. Pressure head; 4. Servo motor; 5. Eccentric block; 6. Base; 7. Sample stage; 8. Limiting rod; 9. Hydraulic rod; 10. Connecting rod; 11. Flange; 12. Main hydraulic rod; 13. Bolt hole. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Reference Figures 1-3 The present invention provides a device for simulating fatigue loading of tunnel bottom structure, comprising: A support component is used to support the test piece; a crossbeam 1 is vertically slidably connected to the support component, and a lifting mechanism is installed between the crossbeam 1 and the support component. The hydraulic assembly is mounted on the crossbeam 1, and the piston end of the hydraulic assembly is equipped with a force transmission frame 2. A pressure monitoring component is installed below the force transmission frame 2 via a first connector. The pressure head 3 is installed below the pressure monitoring component via the second connector, and the pressure head 3 is located directly above the test piece; An eccentric rotary loading assembly is mounted on the first connector. Deformation monitoring component, which is installed on the sample; The control system, lifting mechanism, hydraulic components, eccentric rotary loading components, pressure monitoring components, and deformation monitoring components are all electrically connected to the control system.

[0023] This invention utilizes hydraulic components for displacement adjustment and applying static and low-frequency cyclic loading to the test specimen, and an eccentric rotary loading component to apply high-frequency cyclic loading, thereby achieving fatigue simulation testing. Before the test begins, the required static and cyclic loads are calculated, followed by the calculation of the required mass of the eccentric block 5 for a specified fatigue loading frequency, and then the mass of the eccentric block 5 in the eccentric rotary loading component is adjusted. During high-frequency fatigue loading, the control system adjusts the rotational speed of the eccentric rotary loading component to adjust the fatigue load value. When the fatigue load loading times reach a specified value, the test stops. This invention can more accurately study the micro-fracture mechanism and migration mechanism of loose slag at the bottom of tunnels, and can provide guidance for the analysis of issues such as voids and slurry seepage at the bottom of tunnels.

[0024] Further optimization of the scheme: the eccentric rotation loading component includes a servo motor 4 and an eccentric block 5. The servo motor 4 is fixedly installed on the top surface of the first connector, and the eccentric block 5 is installed on the output shaft of the servo motor 4. The servo motor 4 is electrically connected to the control system.

[0025] During operation, the control system can precisely adjust the start / stop, speed, and rotation frequency of the servo motor 4, driving the eccentric block 5 at the end of the output shaft to rotate at high speed. Utilizing the centrifugal excitation force generated by the eccentric rotation, a stable and controllable high-frequency cyclic excitation load is provided to the pressure head 3. Compared to traditional vibration loading structures, the servo motor 4 offers high speed regulation accuracy and strong operational stability, enabling stepless frequency adjustment and accurately simulating complex dynamic loads such as high-frequency micro-amplitude vibrations of vehicles traveling in tunnels. By matching different speeds, the vibration frequency and amplitude of the fatigue load can be flexibly changed. Combined with hydraulic components, high- and low-frequency composite fatigue loading can be achieved, realistically reproducing the long-term complex fatigue stress conditions of the tunnel bottom structure and effectively improving the simulation accuracy of tunnel structure fatigue tests.

[0026] Further optimization of the solution, supporting components include: Base 6, on which a sample stage 7 is mounted, the sample stage 7 is used to support the test piece; Limiting rods 8 are provided in several ways. All limiting rods 8 are fixedly installed on the top surface of the base 6. The crossbeam 1 is vertically slidably connected along the limiting rods 8. The lifting mechanism is installed between the base 6 and the crossbeam 1.

[0027] The base 6 serves as the load-bearing base at the bottom of the device, supporting all the loading structures and specimen loads above, ensuring the overall stability of the machine. The specimen stage 7 is fixed to the top surface of the base 6, used for precise positioning and stable support of various tunnel bottom test specimens, ensuring that the specimens are placed flat and evenly stressed, and preventing specimen offset or tilting from affecting the test results. Multiple limiting rods 8 are vertically fixed to the top surface of the base 6, and the crossbeam 1 slides vertically along the limiting rods 8, forming a multi-point symmetrical guide structure, which can strictly limit the horizontal offset and torsional sway of the crossbeam 1, ensuring that the vertical lifting of the crossbeam 1 is straight and stable, and eliminating the problem of load eccentricity.

[0028] The scheme is further optimized. The lifting mechanism includes several hydraulic rods 9. The cylinder end of the hydraulic rod 9 is fixedly connected to the base 6, the piston end of the hydraulic rod 9 is fixedly connected to the bottom surface of the crossbeam 1, and all the hydraulic rods 9 are electrically connected to the control system.

[0029] Multiple sets of hydraulic rods 9 extend and retract synchronously, stably driving the crossbeam 1 to achieve precise vertical lifting and lowering along the limiting rod 8. Compared to a single lifting drive structure, the multi-point symmetrical hydraulic drive provides more balanced force and smoother lifting and lowering, effectively preventing the crossbeam 1 from tilting or jamming. In the early stages of the test, the vertical height of the crossbeam 1 and the pressure head 3 can be quickly adjusted by extending and retracting the hydraulic rods 9, adapting to test pieces of different thicknesses and sizes, and quickly completing the alignment of the test pieces, adjustment of the pre-compression stroke, and calibration of the initial gap. The control system can precisely control the extension and retraction stroke and start / stop status of the hydraulic rods 9, ensuring height adjustment accuracy and providing a precise initial assembly reference for subsequent static load pressing and cyclic fatigue loading, significantly improving test assembly efficiency and loading coaxiality.

[0030] Further optimization of the scheme: a connecting rod 10 is fixedly installed on the top of the force transmission frame 2, and a flange 11 is fixedly installed on the top of the connecting rod 10; The hydraulic assembly includes a main hydraulic rod 12 electrically connected to the control system. The cylinder end of the main hydraulic rod 12 is fixedly mounted on the crossbeam 1, and the flange 11 is fixedly connected to the piston end of the main hydraulic rod 12 by a number of first high-strength bolts. The force transmission frame 2 has an inverted U-shaped structure, and the opening of the inverted U-shaped structure faces the pressure monitoring component. The servo motor 4 is located inside the inverted U-shaped structure. The force transmission frame 2 is fixedly connected to the first connecting member by several second high-strength bolts. The force transmission frame 2 is fixedly connected to the pressure sensor by the first connecting member.

[0031] The pressure of the main hydraulic rod 12 is completely transmitted to the force transmission frame 2, pressure sensor, and pressure head 3 through the flange 11 and connecting rod 10. The flange bolt connection method has strong contact rigidity, uniform force transmission, and high load-bearing capacity, which can effectively avoid loosening of the connection and pressure loss during loading, and ensure accurate transmission of static load and low-frequency cyclic load. The U-shaped frame structure has high overall rigidity and strong resistance to deformation, which can effectively resist the alternating pressure during fatigue loading and eliminate loading errors caused by micro-deformation of the structure; at the same time, it can enclose and protect the internal servo motor 4, avoiding damage to the motor from vibration, impact, and external force collisions, and greatly improving the operational stability and structural durability of the equipment in long-term fatigue testing.

[0032] The design was further optimized by employing pressure sensors for pressure monitoring and displacement sensors for deformation monitoring. The pressure sensors are positioned along the loading path of the indenter 3, enabling real-time capture of pressure amplitude changes and fluctuation patterns under static load, low-frequency cyclic load, and high-frequency fatigue excitation load, providing accurate feedback on the stress state of the specimen. The deformation sensors are integrated onto the specimen, accurately collecting data on vertical deformation and cumulative residual deformation. Both types of sensors offer fast response and high acquisition accuracy, enabling synchronous data acquisition under high- and low-frequency composite loading conditions. Real-time data is fed back to the control system to form a closed-loop control, correcting loading parameters in real time. This effectively solves the problems of inaccurate loading, data lag, and large errors in traditional tests, ensuring the authenticity and reliability of fatigue test data.

[0033] The design has been further optimized by incorporating several bolt holes 13 on the base 6. These bolt holes 13 securely lock the entire machine onto the test bench foundation, effectively resisting vibrations and micro-slippage generated during high-frequency fatigue loading, preventing resonance and displacement, and ensuring a constant reference position for the equipment throughout the test. Furthermore, the multiple sets of bolt holes 13 can accommodate different test bench surfaces and installation dimensions, providing flexible and reliable installation. This effectively improves the operational stability of the entire machine under high-frequency alternating loading conditions, eliminates interference from equipment shaking on loading accuracy and monitoring data, extends equipment lifespan, and ensures the stability and repeatability of multiple batches of long-term fatigue tests.

[0034] The scheme is further optimized by making the servo motor 4 a dual-axis servo motor and providing two eccentric blocks 5, which are respectively installed on the two output shafts of the dual-axis servo motor.

[0035] The output shafts at both ends of the dual-axis servo motor rotate synchronously, driving the eccentric blocks 5 on both sides to rotate synchronously. The two sets of eccentric centrifugal forces are symmetrically superimposed and cancel each other out, leaving only the vertical excitation force. This completely eliminates the horizontal lateral disturbance caused by the single eccentric structure, avoiding problems such as lateral displacement of the pressure head 3, eccentric stress on the specimen, and lateral vibration of the frame. The dual-axis synchronous drive can significantly improve the output stability of high-frequency fatigue loads, making the excitation load more uniform, symmetrical, and controllable. It can accurately simulate the vertical fatigue vibration conditions of vehicles at the bottom of tunnels, effectively improving the realism of fatigue loading simulation and solving the defects of traditional single eccentric loading, such as impure load, large disturbance, and large test error.

[0036] Further optimization of the design: the eccentric block 5 is made of steel and has a semi-circular structure. The eccentric block 5 also has holes that are fixedly connected to the output shaft of the dual-axis servo motor.

[0037] The eccentric block 5 adopts a semi-circular steel structure with holes. The steel has high density, high hardness, wear resistance, and fatigue resistance, making it resistant to deformation and wear during long-term high-speed rotation, ensuring stable load output under long-term high-frequency excitation conditions. The centrifugal force output during the rotation of the semi-circular structure is regular and the waveform is stable, forming a standard sinusoidal cyclic fatigue load that closely matches the characteristics of periodic vibration loads from tunnel traffic, resulting in a more realistic simulation. An assembly hole is provided in the center of the eccentric block 5, allowing for precise connection and fixation to the output shaft of the dual-axis servo motor 4. This ensures high coaxiality and prevents eccentric swaying during high-speed rotation. Furthermore, by replacing the semi-circular eccentric blocks 5 with different masses and curvatures, the magnitude of the centrifugal force can be flexibly adjusted to achieve gradient adjustment of different fatigue load amplitudes, adapting to the fatigue damage testing requirements of different levels of tunnel bottoms. This significantly improves the equipment's adaptability and test adjustability.

[0038] The present invention also provides a method for using a device for simulating fatigue loading of a tunnel bottom structure, comprising the following steps: Step 1: Place the test piece on the support component; Step 2: Adjust the height of the crossbeam 1 and the pressure head 3 using the lifting mechanism; Step 3: Apply the set fatigue load amplitude to the pressure head 3 using the hydraulic components and the eccentric rotary loading components to complete the corresponding loading mode of the test piece; the loading modes include static load loading mode, low-frequency cyclic loading mode and high-frequency cyclic loading mode. Step 4: Measure the pressure data of the test specimen under each loading mode using the pressure monitoring component, and measure the deformation data of the specimen using the deformation monitoring component. Input the pressure data and deformation data into the control system to update the instructions of each target control component and obtain the updated corresponding instructions. Step 5: Control the eccentric rotary loading component, lifting mechanism and hydraulic component to perform corresponding actions according to the updated corresponding instructions.

[0039] Based on experimental requirements, the control system coordinates the hydraulic components and the eccentric rotary loading components to independently or in combination achieve three modes: static load loading, low-frequency cyclic loading, and high-frequency cyclic loading. This accurately replicates the stress states under various working conditions, including tunnel self-weight static pressure, low-frequency traffic disturbance, and high-frequency vibration fatigue. During the experiment, pressure and deformation sensors collect specimen pressure and deformation data in real time and feed them back to the control system to update operating commands in real time. The system then corrects the loading frequency, load amplitude, and pressurization stroke in a closed loop, ensuring that loading accuracy is controllable throughout the entire process. Through multi-mode precise loading and real-time data feedback control, the system can effectively simulate the evolution process of defects such as loose slag breakage, cumulative structural deformation, and void seepage at the tunnel bottom, providing precise experimental support for the study of fatigue mechanisms in tunnel bottom structures.

[0040] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "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 invention, and are not intended to 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 of this invention.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A device for simulating fatigue loading of tunnel bottom structure, characterized in that, include: A support component, which is used to support the test piece; A crossbeam (1) is vertically slidably connected to the support component, and a lifting mechanism is installed between the crossbeam (1) and the support component; A hydraulic assembly is mounted on the crossbeam (1), and a force transmission frame (2) is mounted on the piston end of the hydraulic assembly. A pressure monitoring component is installed below the force transmission frame (2) via a first connector; The pressure head (3) is installed below the pressure monitoring component via a second connector, and the pressure head (3) is located directly above the test piece; An eccentric rotary loading assembly is mounted on the first connector; A deformation monitoring component, which is mounted on the sample; The control system includes the lifting mechanism, the hydraulic component, the eccentric rotary loading component, the pressure monitoring component, and the deformation monitoring component, all of which are electrically connected to the control system.

2. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 1, characterized in that: The eccentric rotary loading assembly includes a servo motor (4) and an eccentric block (5). The servo motor (4) is fixedly mounted on the top surface of the first connector, and the eccentric block (5) is mounted on the output shaft of the servo motor (4). The servo motor (4) is electrically connected to the control system.

3. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 1, characterized in that: The supporting component includes: A base (6) is provided, on which a sample stage (7) is mounted, the sample stage (7) being used to support the test piece. Limiting rods (8), a plurality of limiting rods (8) are provided, and the plurality of limiting rods (8) are fixedly installed on the top surface of the base (6), and the crossbeam (1) is vertically slidably connected along the plurality of limiting rods (8); The lifting mechanism is installed between the base (6) and the crossbeam (1).

4. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 3, characterized in that: The lifting mechanism includes several hydraulic rods (9), the cylinder end of the hydraulic rod (9) is fixedly connected to the base (6), the piston end of the hydraulic rod (9) is fixedly connected to the bottom surface of the crossbeam (1), and all of the hydraulic rods (9) are electrically connected to the control system.

5. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 2, characterized in that: A connecting rod (10) is fixedly installed on the top of the force transmission frame (2), and a flange (11) is fixedly installed on the top of the connecting rod (10). The hydraulic assembly includes a main hydraulic rod (12) electrically connected to the control system. The cylinder end of the main hydraulic rod (12) is fixedly mounted on the crossbeam (1). The flange (11) is fixedly connected to the piston end of the main hydraulic rod (12) by a number of first high-strength bolts. The force transmission frame (2) has an inverted shape, and the opening of the inverted shape faces the pressure monitoring component. The servo motor (4) is located inside the inverted shape. The force transmission frame (2) is fixedly connected to the first connecting member by several second high-strength bolts.

6. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 1, characterized in that: The pressure monitoring component uses a pressure sensor, and the deformation monitoring component uses a displacement sensor.

7. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 3, characterized in that: The base (6) has several bolt holes (13).

8. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 2, characterized in that: The servo motor (4) is a dual-axis servo motor, and there are two eccentric blocks (5), which are respectively installed on the two output shafts of the dual-axis servo motor.

9. The fatigue loading device for simulating the bottom structure of a tunnel according to claim 8, characterized in that: The eccentric block (5) is made of steel and has a semi-circular structure. The eccentric block (5) has a hole, which is fixedly connected to the output shaft of the dual-axis servo motor.

10. A method of using a fatigue loading device for simulating the bottom structure of a tunnel, based on the fatigue loading device for simulating the bottom structure of a tunnel as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Place the test piece on the support component; Step 2: Adjust the height of the crossbeam (1) and the pressure head (3) using the lifting mechanism; Step 3: Apply the set fatigue load amplitude to the pressure head (3) using the hydraulic components and the eccentric rotary loading components to complete the corresponding loading mode of the test piece; the loading mode includes static load loading mode, low-frequency cyclic loading mode and high-frequency cyclic loading mode; Step 4: Measure the pressure data of the test specimen under each loading mode using the pressure monitoring component, and measure the deformation data of the specimen using the deformation monitoring component. Input the pressure data and the deformation data into the control system to update the instructions of each target control component and obtain the updated corresponding instructions. Step 5: Control the eccentric rotary loading component, lifting mechanism and hydraulic component to perform corresponding actions according to the updated corresponding instructions.

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