A triaxial loading test device for a shield segment structure

Abstract

The application discloses a kind of shield segment structure triaxial loading test device, including rigid base and steel counterforce frame;Steel counterforce frame inside one side installs fixed hinge support, the other side installs movable hinge support, and two hinge supports hold shield segment structure;Loading control device drives movable hinge support horizontal movement;Shield segment structure front and rear sides are arranged lateral counterforce wall structure, and second servo actuator is arranged between lateral counterforce wall structure and the side of shield segment structure, and loading control device controls second servo actuator to provide lateral shearing force for shield segment structure;Boundary simulation device is arranged on the back of shield segment structure;Steel counterforce frame top is fixedly installed third servo actuator, and third servo actuator is connected with boundary simulation device, and third servo actuator is vertically loaded to shield segment structure;By independent control to all servo actuators, simulate a variety of different stress conditions.The application can test the stress deformation characteristics of segment structure under a variety of abnormal conditions.

Description

Technical Field

[0001] This invention relates to underground tunnel engineering technology, specifically to a triaxial loading test device for shield tunnel segment structures. Background Technology

[0002] With the development of deep underground space, the comprehensive construction of the national water network, and the development of the Yaxia Hydropower Project, engineering construction faces more complex geological environments, placing higher demands on tunnel construction technology. Shield tunneling technology is the most widely used and efficient construction technology in tunnel engineering worldwide. However, as a three-dimensional segmented assembly structure, while highly efficient, shield tunnels have relatively lower structural stiffness compared to traditional lining structures, making them prone to cracking, misalignment, and other phenomena that compromise structural safety. Therefore, to ensure the safety and stability of segmented structures in complex environments, it is essential to study the stress-deformation characteristics of segmented structures.

[0003] Chinese invention patent application CN 119985145 A discloses a standing segment prototype loading test device, solving the problem of obtaining key parameters for scaled-down test devices. Chinese invention patent application CN 120177174 A discloses an IoT-based full-scale loading test device and method for shield tunnel segment circumferential joints, realizing pure bending and pure shear stress tests at the segment circumferential joints, as well as monitoring the continuous deformation of the upper and lower arc surfaces of the segments. Chinese invention patent application CN118961459A discloses a shield tunnel segment torsion-shear test device and method, realizing the simulation of the torsional shear effect of TBM tunnel segment joints. Chinese invention patent application CN11705407A discloses a shield tunnel segment test device and method, realizing the simulation of the structural strength of shield tunnel segments under groundwater pressure conditions. However, the aforementioned test devices mostly employ positive unidirectional or bidirectional loading, using simple supports or fixed boundaries to independently control axial pressure and shear force. This fails to accurately reflect the true three-dimensional stress state of the tunnel segments, hindering the study of the compression-shear coupling effect of the segment structure (segments, segment joints, and ring joints), and the simulation of asymmetric loads and local failure conditions. For example, it cannot address actual conditions such as local stress concentration and failure caused by abnormalities like voids or cavities behind the segments, or the compression-shear deformation characteristics under eccentric loading. Therefore, there is an urgent need to invent a triaxial loading test device and method for shield tunnel segment structures to test the stress-deformation characteristics of the segment structure under various abnormal conditions. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a triaxial loading test device for shield tunnel segment structures, which can test the stress and deformation characteristics of the segment structure under various abnormal working conditions.

[0005] Technical Solution: The present invention provides a triaxial loading test device for a tunnel boring machine (TBM) segment structure, comprising a rigid reaction frame, with a rigid base installed at the bottom of each of the four legs of the rigid reaction frame; a fixed hinge support is fixedly installed on a rigid base on the left side, and a movable hinge support is movably installed on a rigid base on the right side. The fixed and movable hinge supports are symmetrically arranged and together clamp the TBM segment structure; the movable hinge support is connected to a first servo actuator, and a loading control device controls the first servo actuator to move, thereby driving the movable hinge support to move horizontally, thus providing a horizontal jacking force to the TBM segment structure and achieving horizontal loading; two lateral reaction wall structures are symmetrically arranged on the front and rear sides of the TBM segment structure. Two or more second servo actuators are installed between each lateral reaction wall structure and the side of the shield tunnel segment structure. The loading control device controls the second servo actuators to provide lateral shear force to the shield tunnel segment structure to achieve shear loading. A boundary simulation device is installed on the back of the shield tunnel segment structure to simulate local defects on the back of the shield tunnel segment structure. Two third servo actuators are fixedly installed on the top of the rigid reaction frame. The third servo actuators are connected to the boundary simulation device and perform vertical loading on the shield tunnel segment structure. The loading control device independently controls the first servo actuator, all second servo actuators, and third servo actuators to simulate a variety of different stress conditions.

[0006] Furthermore, the boundary simulation device is an overall rigid arc surface structure.

[0007] Furthermore, the boundary simulation device includes an upper loading structure, a lower defect combination structure, and loading blocks; wherein, the upper loading structure and the lower defect combination structure are both arc-shaped; the lower defect combination structure is fitted and disposed below the upper loading structure; a groove is provided on the back of the upper loading structure, and two loading blocks are placed in the groove, the loading blocks being used to connect with a servo actuator.

[0008] Furthermore, the lower defect combination structure is divided into left and right parts. Different initial defects are set on the left and right parts and combined to form simulations of local defects of different positions and sizes. The left and right parts are connected and fixed by fixed steel bars to form the lower defect combination structure.

[0009] Furthermore, by moving the loading block, the performance testing of shield tunnel segment structures with local defect boundaries can be achieved under different bias load conditions.

[0010] Furthermore, the second servo actuator contacts the side of the shield tunnel segment structure through an arc-shaped loading clamp, thereby providing lateral confining pressure to the shield tunnel segment structure.

[0011] Furthermore, a multi-functional loading head is provided on the first servo actuator, the second servo actuator, and the third servo actuator. The multi-functional loading head collects the load and displacement during the loading process in real time through built-in pressure sensors and displacement sensors.

[0012] Furthermore, the multi-functional loading head on the third servo actuator is designed to be horizontal; the multi-functional loading head on the second servo actuator is designed to be arc-shaped, fitting against the curved side of the shield tunnel segment structure.

[0013] Furthermore, it also includes a multi-point loading control system, which comprises a central controller and multiple independently controllable loading systems. The multiple loading systems are connected to and controlled by the central controller.

[0014] Furthermore, the multiple loading systems independently control the output, displacement, and motion mode of each third servo actuator and each second servo actuator.

[0015] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows:

[0016] (1) By independently controlling multiple actuators and servo actuators of the loading device, the present invention enables them to work together to achieve: a) applying pure axial pressure to the segment structure; b) pure shear force; c) arbitrary proportion of compression-shear composite load; d) arbitrary proportion of compression-bending composite load; e) arbitrary proportion of compression-bending-shear composite load, etc., and solves the problems of uncontrollable shear force, inability to separate and composite compression-shear-bending effect of traditional devices.

[0017] (2) The boundary simulation device of the present invention realizes the load characteristic loading test of the segment structure with local defects (geological defects such as karst cavities) under complex stress conditions by means of loading and defect module of upper and lower combined structure. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the boundary simulation device in this invention;

[0020] Figure 3 This is a schematic diagram of the upper and lower layer structures of the boundary simulation device in this invention;

[0021] Figure 4 This is a schematic diagram of the combined defects in the boundary simulation device of the present invention;

[0022] Figure 5 This is a schematic diagram of the installation of the boundary simulation device in this invention. Detailed Implementation

[0023] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0024] like Figure 1-5 As shown, the present invention discloses a triaxial loading test device for a tunnel segment structure, comprising a basic loading control device and system and a boundary simulation device 2. The basic loading control device and system includes the following components: a rigid reaction frame 11, a rigid base 12, a fixed hinge support 13, a movable hinge support 14, a first servo actuator 15, a loading control device 16, a lateral reaction wall structure 17, a second servo actuator 18, a third servo actuator 19, a multi-functional loading head 111, a tunnel segment structure 110, a multi-point loading control system, and a comprehensive data acquisition and control system. The boundary simulation device 2 includes an upper loading structure 21, a lower defect combination structure 22, a loading block 23, a first fixing bolt 24, a groove 25, a fixing steel bar 26, and a second fixing bolt 27.

[0025] like Figure 1 As shown, a rigid base 12 is installed at the bottom of each of the four legs of the rigid reaction frame 11. The rigid reaction frame 11 is a high-rigidity, high-strength integral reaction frame that provides a rigid frame structure for the entire large-tonnage loader and also provides constraint support for the vertical loading system of the entire device.

[0026] A fixed hinge support 13 is fixedly installed on the rigid base 12 on the left front, and a movable hinge support 14 is movably installed on the rigid base 12 on the right front. The fixed hinge support 13 and the movable hinge support 14 are symmetrically arranged and together clamp the shield tunnel segment structure 110. The rigid base 12 provides movement and fixation limits for the fixed hinge support 13 and the movable hinge support 14 through transverse support steel beams, and also provides horizontal constraint support for the shield tunnel segment structure 110. The movable hinge support 14 is connected to a first servo actuator 15. The loading control device 16 controls the first servo actuator 15 to move, and the first servo actuator 15 drives the movable hinge support 14 to move horizontally, thereby providing a horizontal jacking force to the shield tunnel segment structure 110 and realizing horizontal loading.

[0027] In this embodiment, the fixed hinge support 13 and the movable hinge support 14 are fixed to the transverse support steel beam of the rigid base 12 by a combination of sliding grooves and bolts. The fixed position is adjusted by the sliding grooves and pre-drilled bolt holes to accommodate shield tunnel segment structures 110 of different sizes. Specifically, the fixed hinge support 13 is bolted to the transverse support steel beam of the base 12, while the movable hinge support 14 is connected to the transverse support steel beam of the base 12 but not fixed to the rigid base 12. A first servo actuator 15 provides a horizontal jacking force to the tunnel segment, the magnitude of which is controlled by the servo control system. The fixed hinge support 13 and the movable hinge support 14 are rotated to ensure a perpendicular and tight fit with the ends of the shield tunnel segment structure 110. Figure 1 As shown.

[0028] Two lateral reaction wall structures 17 are symmetrically arranged on the front and rear sides of the shield tunnel segment structure 110, providing lateral constraint support for the shield tunnel segment structure 110. Two or more second servo actuators 18 are installed between each lateral reaction wall structure 17 and the side of the shield tunnel segment structure 110. In this embodiment, two second servo actuators 18 are installed between each lateral reaction wall structure 17 and the side of the shield tunnel segment structure 110. The loading control device 16 controls four second servo actuators 18 to provide lateral shear force to the shield tunnel segment structure 110, achieving shear loading.

[0029] In this embodiment, the second servo actuator 18 contacts the side of the shield tunnel segment structure 110 through an arc-shaped loading clamp, thereby providing lateral confining pressure to the shield tunnel segment structure 110. Pure shearing simulation of the shield tunnel segment structure 110 is achieved by combining the push and pull of the four second servo actuators 18 through the loading control device 16.

[0030] like Figure 5 As shown, a boundary simulation device 2 is installed on the back of the shield tunnel segment structure 110. The boundary simulation device 2 is used to simulate local defects on the back of the shield tunnel segment structure 110. Two third servo actuators 19 are fixedly installed on the top of the rigid reaction frame 11. The third servo actuators 19 are connected to the boundary simulation device 2 and perform vertical loading on the shield tunnel segment structure 110.

[0031] Through the aforementioned horizontal loading, shear loading, and vertical loading, a triaxial loading is formed on the shield tunnel segment structure 110.

[0032] By adjusting the position and controlling the loading ratio of two large-tonnage third servo actuators 19 on the rigid reaction frame 11, and in conjunction with the boundary simulation device 2, loading of the shield tunnel segment structure 110 under compression-bending, compression-shear, and combined compression-bending-shear conditions is carried out. The loading control device 16 independently controls the first servo actuator 15, all second servo actuators 18, and third servo actuators 19, thereby simulating various different stress conditions.

[0033] Multifunctional loading heads 111 are installed on the first servo actuator 15, the second servo actuator 18, and the third servo actuator 19. The multifunctional loading heads 19 collect the load and displacement during the loading process in real time through built-in pressure sensors and displacement sensors. The multifunctional loading head 111 on the third servo actuator 19 is designed to be horizontal; the multifunctional loading head 111 on the second servo actuator 18 is designed to have an arc-shaped surface, which fits against the curved side of the shield tunnel segment structure 110.

[0034] The multi-point loading control system comprises a central controller and multiple independently controllable loading systems. These loading systems are connected to and controlled by the central controller. The central controller controls the loading ratio in each direction. Each loading system independently controls the output, displacement, and motion mode of the first servo actuator 15, each third servo actuator 19, and each second servo actuator 18. The multi-point loading control system is an independently controllable loading system in three directions: horizontal, lateral, and vertical. It independently controls the output, displacement, and motion mode of multiple large-tonnage servo actuators in each direction. Then, the three independent systems are integrated together and coordinated by the central controller to achieve triaxial loading of the shield tunnel segment structure 110 under bias, compression-shear, and other modes, as well as cyclic fatigue loading. The loading control device 16 executes different hydraulic servo force outputs according to commands issued by the multi-point loading control system.

[0035] It is worth noting that the loading system is a platform where various commands can be manually input. Then, through the PLC protocol, the control device 16 can be controlled to perform corresponding actions on the commands given by the loading system. For example, during displacement loading, the displacement and rate of extension and retraction can be input through the loading system, and the extension and retraction rods of the loading control device 16 will perform extension and retraction actions with different displacements and rates.

[0036] The integrated data acquisition and control system not only collects the active load and displacement data of all servo actuators, but also includes various stress, strain and displacement data of the segment structure response; including the strain of fiber optic gratings arranged on the steel bars, the strain of bolts, the opening of joints, and the amount of misalignment; and the full-field strain measured on the inner surface of the segment structure through digital image correlation (DIC).

[0037] like Figures 2 to 4As shown, the boundary simulation device 2 is a rigid arc-shaped structure, mainly targeting local defects on the back of the shield tunnel segment structure 110, simulating conditions such as karst caves, confining pressure fracture, or water abundance on the back of the shield tunnel segment structure 110. The boundary simulation device 2 achieves the embedding of defect modules and the access of loading sliding module loads through an upper and lower combined structure. Specifically, the boundary simulation device 2 includes an upper loading structure 21, a lower defect combination structure 22, and a loading block 23; wherein, the upper loading structure 21 and the lower defect combination structure 22 are both arc-shaped. The lower defect combination structure 22 is fitted below the upper loading structure 21, and the upper loading structure 21 and the lower defect combination structure 22 are fixedly connected by a first fixing bolt 24.

[0038] A groove 25 is provided on the back of the upper loading structure 21, and two loading blocks 23 are placed in the groove 25. The two loading blocks 23 can move along the groove 25. The loading blocks 23 are fixed to the back of the upper loading structure 21 by the second fixing bolt 27, and the loading blocks 23 are used to connect with the third servo actuator 19. By moving the loading blocks 23, the performance testing of the shield tunnel segment structure 110 with local defect boundaries under different bias load conditions can be realized. During loading, the loading module 23 must be fixed by the second fixing bolt 27; loading can only be performed after fixing; different loading conditions are achieved by different positions of the second fixing bolt 27.

[0039] The lower defect combination structure 22 is divided into two parts, left and right. Different initial defects are set on the left and right parts and combined to form simulations of local defects of different positions and sizes. The left and right parts are connected and fixed by fixed steel bars 26, thus forming the lower defect combination structure 22.

[0040] The testing method of the triaxial loading test device for shield tunnel segment structure of the present invention is as follows: installation of shield tunnel segment structure 110 and boundary simulation device 2—sensor installation and preloading—load application—synchronous acquisition of multi-source data—comprehensive analysis of results, as detailed below:

[0041] Before conducting the test of the shield tunnel segment structure 110, the shield tunnel segment structure 110 and the boundary simulation device 2 are installed first. The fixed hinge support 13 on the rigid base 12 of the test device is removed to free up transportation space. Then, based on the test conditions, the number of tunnel segments and the joint arrangement are determined. The shield tunnel segment structure 110 is assembled in an open area and fixed in shape by slings or steel bars. The shield tunnel segment structure 110 is transported to the rigid reaction frame 11 and rigid base 12 by a forklift or gantry crane. One end of the shield tunnel segment structure 110 is vertically and tightly attached to the end of the movable hinge support 14. Then, the shield tunnel segment structure 110 is temporarily supported by combined jacks. After the shield tunnel segment structure 110 is stable, the gantry crane or forklift is removed. The angle of the shield tunnel segment structure 110 is adjusted to be tightly attached to the end of the fixed hinge support 13. Then, the data integration data acquisition and control system is turned on. After detecting the load data caused by the gravity of the tunnel segment structure, the fixed hinge supports 13 and movable hinge supports 14 at both ends of the shield tunnel segment structure 110 are fixed and the supporting combined jacks are removed.

[0042] Next, the second servo actuator 18 is controlled by an independent loading control device 16 to fit tightly against the side of the shield tunnel segment structure 110. When the integrated data acquisition and control system detects the load, the slings or steel bars binding the shield tunnel segment structure 110 are removed. Finally, the boundary simulation device 2 is transported to the back of the shield tunnel segment structure 110 using a forklift. Figure 4 The lower defect combination structure 22 shown is assembled, and then as follows: Figure 3 As shown, the upper loading structure 21 and the lower defect combination structure 22 are connected by the first fixing bolt 24. Figure 5 As shown, the boundary simulation device 2 only covers the area of ​​the shield tunnel segment structure 110 where compression and shear occur. Finally, the loading block 23 in the back groove 25 of the boundary simulation device 2 is adjusted to the designated position for fixation. The vertical heavy-duty third servo actuator 19 is controlled by the multi-point loading control system to fit tightly with the loading block 23, so as to realize the three-axis compression and shear loading of the shield tunnel segment structure 110 after installation.

[0043] After the specimen and boundary simulation device 2 are installed, the installation of sensors and preloading of the tunnel segment structure 110 are carried out. Based on the characteristics of the tunnel segment structure 110, strain gauges are first placed at the bolts of the tunnel segment structure 110, and high-precision displacement gauges are placed at the joints. A speckle field is sprayed onto the inner surface of the tunnel segment structure 110, and the surface is monitored directly by a camera. After all sensors are installed and connected to the integrated data acquisition and control system, the loading mode of each loading system is selected by the central controller, and the preload value is input. Then, the servo actuators are controlled by the independent loading system to perform loading. When the integrated data acquisition and control system detects that the data of each loading system and sensor is normal, it indicates that the test preparation work is complete. If the integrated data acquisition and control system observes abnormal data, the corresponding sensors and equipment are promptly adjusted.

[0044] Once all sensors and devices are functioning normally, the loading options for the three-directional servo actuators are determined based on the force conditions under various unfavorable working conditions, as shown in Table 1.1.

[0045]

[0046] Under normal operating conditions: 1) Pure shear: Simulates the shear load during the segment assembly process, causing segment cracking; the horizontal servo actuator (i.e., the first servo actuator 15) and the vertical servo actuator (i.e., the third servo actuator 19) are set with constant confining pressure and maintain pressure, while the four lateral second servo actuators 18 apply different loads or displacements to achieve pure shear loading; 2) Pure bending: Simulates the stable confining pressure experienced by the segment structure after installation. The horizontal and lateral servo actuators are set with constant, smaller confining pressure and maintain pressure, while the two vertical third servo actuators 19 are symmetrically distributed and synchronously apply the same load or displacement through the loading module of the upper structure of the boundary simulation device; 3) Compression bending: Simulates the asymmetrical load experienced by the segment structure after installation, such as asymmetrical ground load, tunnels near slopes, or heavy buildings on one side. 4) Compression-shear: Simulates the tunnel segment structure crossing abrupt geological changes (hard rock suddenly entering soft soil) or crossing intersecting buildings, fracture zones, and sections with localized leakage and uneven settlement deformation; the first servo actuator 15 and the second servo actuator 18 are set with constant, small confining pressure and maintain pressure; the upper structure of the boundary simulation device only covers the compression-shear area of ​​the tunnel segment structure; the two vertical third servo actuators 19 are symmetrically distributed through the loading modules of the upper structure of the boundary simulation device, and then synchronously apply loads or displacements according to the working conditions. 5) Compression-bending-shear: Simulates the tunnel segment structure under seismic loads, or the turning section of a shield tunnel with special geological conditions, or the tunnel facing asymmetrical loads, while simultaneously facing conditions such as localized leakage and uneven settlement deformation. The first servo actuator 15 and the second servo actuator 18 are set with a small, constant confining pressure and maintain pressure. The upper structure of the boundary simulation device only covers the compression and shear area of ​​the segment structure. The two vertical third servo actuators 19 are asymmetrically distributed through the loading module of the upper structure of the boundary simulation device, and then apply different loads or displacements synchronously according to the working conditions.

[0047] When the back of the shield tunnel segment 110 has local defects such as holes, karst caves, voids, localized water accumulation, and fracture zones (abnormal working conditions): Based on the actual location of the defects, adjust the local defects of different locations and sizes on the boundary simulation device 2; then conduct loading tests under pure bending, compression bending, compression shear, and compression bending shear stress states, with the loading options being the same as under normal working conditions. Through different loading combinations, analyze the stress and deformation characteristics under various abnormal working conditions.

[0048] It is worth noting that when conducting the compression-shear failure test of the shield tunnel segment structure under triaxial stress, after all the sensors and equipment are operating normally, the first servo actuator 15 and the second servo actuator 18 are set with a constant small confining pressure and maintain the pressure. The boundary simulation device only covers the compression-shear area of ​​the segment structure 110. The two vertical third servo actuators 19 are symmetrically distributed through the loading module 23 of the boundary simulation device 2, and then synchronous loads or displacements are applied according to the working conditions.

[0049] Once the equipment is successfully commissioned and the operating conditions are selected, during the equipment loading process, the central controller issues working commands to each actuator, and then the integrated data acquisition and control system is activated through PLC commands to synchronously acquire the force and displacement of each servo actuator, as well as the strain of bolts and internal steel bars, displacement, opening, misalignment at joints, and full-field strain acquisition of the inner surface of the shield tunnel segment structure.

[0050] When the tunnel segment structure fails or reaches the design load value, the data from the integrated acquisition system is exported after the test. Using time as the horizontal axis, the ultimate bearing capacity, stiffness degradation, joint performance, failure mode, and overall strain of the segment, as well as the ultimate strain of the bolts and reinforcing bars, are analyzed. Then, using load as the horizontal axis, the strain of the segment and bolts and reinforcing bars, as well as the displacement, opening, and misalignment of the joints, are analyzed. Finally, referring to the joint displacement, opening, and misalignment thresholds specified in the code, as well as the elastic ultimate strain values ​​of the bolts and reinforcing bars and the cracking strain values ​​of the segment structure, safe load thresholds and safe strain thresholds for various actual environmental conditions of the segment structure are set. This provides a reference for design calculations and health monitoring when actual shield tunnels pass through abrupt geological changes / intersecting structures, fracture zones, and sections with localized leakage and uneven settlement deformation.

[0051] This invention discloses a triaxial loading test method for tunnel segment structures. Based on the stress characteristics of shield tunnel segment structures under actual environmental conditions, it precisely controls the axial pressure and shear force in three directions (horizontal, lateral, and vertical) of the shield tunnel segment structure through "decoupled loading" and "boundary condition simulation." Through a complete testing process, it obtains the ultimate bearing capacity, joint performance, failure mode, and overall strain of the segment structure under various complex stress conditions (including local defects). Based on the results, it sets safe load thresholds and safe strain thresholds for shield tunnel segment structures under various actual environmental conditions, providing a reference for design calculations and health monitoring in practical engineering projects.

Claims

1. A triaxial loading test device for shield tunnel segment structures, characterized in that: It includes a rigid reaction frame (11), and a rigid base (12) is installed at the bottom of each of the four legs of the rigid reaction frame (11). A fixed hinge support (13) is fixedly installed on a rigid base (12) on the left side, and a movable hinge support (14) is movably installed on a rigid base (12) on the right side. The fixed hinge support (13) and the movable hinge support (14) are symmetrically arranged and together clamp the shield tunnel segment structure (110). The movable hinge support (14) is connected to the first servo actuator (15). The loading control device (16) controls the first servo actuator (15) to move. The first servo actuator (15) drives the movable hinge support (14) to move horizontally, thereby providing a horizontal top force to the shield tunnel segment structure (110) and realizing horizontal loading. The shield tunnel segment structure (110) has two lateral reaction wall structures (17) symmetrically arranged on the front and rear sides. Each lateral reaction wall structure (17) is provided with two or more second servo actuators (18) between it and the side of the shield tunnel segment structure (110). The loading control device (16) controls the second servo actuators (18) to provide lateral shear force to the shield tunnel segment structure (110) to achieve shear loading. A boundary simulation device (2) is installed on the back side of the shield tunnel segment structure (110). The boundary simulation device (2) is used to simulate local defects on the back side of the shield tunnel segment structure (110). Two third servo actuators (19) are fixedly installed on the top of the rigid reaction frame (11). The third servo actuators (19) are connected to the boundary simulation device (2). The third servo actuators (19) apply vertical loading to the shield tunnel segment structure (110). The loading control device (16) independently controls the first servo actuator (15), all the second servo actuators (18) and the third servo actuator (19), thereby simulating a variety of different force conditions.

2. The triaxial loading test device for shield tunnel segment structure according to claim 1, characterized in that: The boundary simulation device (2) is a rigid arc surface structure.

3. The triaxial loading test device for shield tunnel segment structure according to claim 1, characterized in that: The boundary simulation device (2) includes an upper loading structure (21), a lower defect combination structure (22), and a loading block (23); wherein the upper loading structure (21) and the lower defect combination structure (22) are both arc-shaped. The lower defect combination structure (22) is attached to the lower part of the upper loading structure (21); The upper loading structure (21) has a groove (25) on its back side, in which two loading blocks (23) are placed. The loading blocks (23) are used to connect with the servo actuator (18).

4. The triaxial loading test device for shield tunnel segment structure according to claim 3, characterized in that: The lower defect combination structure (22) is divided into left and right parts. Different initial defects are set on the left and right parts and combined to form simulations of local defects of different positions and sizes. The left and right parts are connected and fixed by fixed steel strips (26) to form the lower defect combination structure (22).

5. The triaxial loading test device for shield tunnel segment structure according to claim 3, characterized in that: The performance test of the shield tunnel segment structure (110) with local defect boundaries under different bias load conditions is achieved by moving the loading block (23).

6. The triaxial loading test device for shield tunnel segment structure according to claim 1, characterized in that: The second servo actuator (18) contacts the side of the shield segment structure (110) through an arc-shaped loading clamp, thereby providing lateral confining pressure to the shield segment structure (110).

7. The triaxial loading test device for shield tunnel segment structure according to claim 1, characterized in that: A multi-functional loading head (111) is provided on the first servo actuator (15), the second servo actuator (18), and the third servo actuator (19). The multi-functional loading head (111) collects the load and displacement during the loading process in real time through the built-in pressure sensor and displacement sensor.

8. The triaxial loading test device for shield tunnel segment structure according to claim 7, characterized in that: The multi-functional loading head (111) on the third servo actuator (19) is designed to be horizontal; The multi-functional loading head (111) on the second servo actuator (18) is designed with an arc surface that fits the curved side of the shield tunnel segment structure (110).

9. The triaxial loading test device for shield tunnel segment structure according to claim 1, characterized in that: It also includes a multi-point loading control system, which comprises a central controller and multiple independently controllable loading systems. The multiple loading systems are connected to and controlled by the central controller.

10. The triaxial loading test device for shield tunnel segment structure according to claim 9, characterized in that: The multiple loading systems independently control the output, displacement, and motion mode of each third servo actuator (19) and each second servo actuator (18).

Images