Test device for cumulative damage of tunnel lining structure under cyclic load in sulfate environment

Abstract

The utility model relates to tunnel engineering test technical field discloses a kind of cumulative damage test device of tunnel lining structure under cyclic loading in sulphate environment, including bearing baseplate, lifting mechanism, loading mechanism, surrounding rock simulation mechanism, test piece positioning mechanism and test box body;Test box body and lifting mechanism are set on bearing baseplate, surrounding rock simulation mechanism is set in the inner chamber bottom of test box body, test piece positioning mechanism is laid on test box body, loading mechanism is installed in the power output end of lifting mechanism, and the force end of loading mechanism is towards surrounding rock simulation mechanism arrangement;Loading mechanism, test piece positioning mechanism and surrounding rock simulation mechanism form test piece loading position between them. Realize the full-dimension coupling of sulphate erosion-surrounding rock constraint-dynamic load, provide key experimental means for long-life design of submarine tunnel, saline soil area underground engineering.

Description

Technical Field

[0001] This utility model relates to the field of tunnel engineering testing technology, and in particular, to a test device for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment. Background Technology

[0002] Existing railway tunnel linings in gypsum-salt areas face severe durability problems. High concentrations of sulfates in the groundwater and soil of these areas react chemically with the lining concrete, generating expansion products such as ettringite and gypsum, leading to cracking and spalling of the lining structure. Simultaneously, the cyclic loads generated by passing trains accelerate the lining damage process. Therefore, it is necessary to conduct coupled sulfate erosion-cyclic load tests.

[0003] In response to the above situation, existing studies have mainly focused on the effects of water pressure and seepage field on lining, and developed a test system for water pressure distribution in lining. Other studies have designed corresponding corrosion acceleration test devices to address the problem of sulfate corrosion. However, these devices have failed to effectively solve the problem of the coupling effect between performance degradation and mechanical damage of lining materials under long-term immersion in sulfate solution. Utility Model Content

[0004] This invention provides a test device for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment. It can simultaneously simulate the cumulative damage of tunnel lining structure under sulfate erosion and cyclic loading, so as to facilitate the study of the damage law of lining structure under the coupled effect of the two.

[0005] This utility model provides a test device for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment, including a load-bearing base plate, a lifting mechanism, a loading mechanism, a surrounding rock simulation mechanism, a specimen positioning mechanism, and a test chamber. The test chamber and the lifting mechanism are mounted on the load-bearing base plate, the surrounding rock simulation mechanism is located at the bottom of the inner cavity of the test chamber, the specimen positioning mechanism is arranged on the test chamber, and the loading mechanism is installed at the power output end of the lifting mechanism, with the force application end of the loading mechanism facing the surrounding rock simulation mechanism. The loading mechanism, the specimen positioning mechanism, and the surrounding rock simulation mechanism form a specimen loading position.

[0006] Furthermore, multiple lifting mechanisms are provided, and these multiple lifting mechanisms are evenly arranged along the circumference of the load-bearing base plate; the test chamber is located within the area formed by the multiple lifting mechanisms.

[0007] Furthermore, the lifting mechanism includes a ball screw assembly and a servo motor. The power output end of the servo motor is connected to and drives the ball screw assembly to operate. The loading mechanism is arranged on the lifting movable end of the ball screw assembly. The servo motor drives the ball screw assembly to operate and drives the loading mechanism to descend to apply pressure or rise to release pressure.

[0008] Furthermore, the lifting mechanism can also be a cylinder, a hydraulic cylinder, or a jack.

[0009] Furthermore, the ball screw assembly includes a support base, a screw body, a buffer pad, a fixed base, a screw nut, and a coupling. The support base is mounted on a load-bearing base plate. The first end of the screw body is rotatably mounted on the support base, and the second end of the screw body passes through the loading mechanism and is connected to the power output end of the servo motor via the coupling. The fixed base, screw nut, and buffer pad are sequentially arranged between the coupling and the loading mechanism. The fixed base is located at the end of the coupling and is used to restrict the movement of the screw nut towards the coupling. The screw nut is engaged with the screw body, and the buffer pad is fitted against the loading mechanism. The servo motor drives the screw body to rotate, thereby converting the rotational motion of the screw body into the axial motion of the screw nut, thus applying different degrees of axial loading force to the specimen via the loading mechanism.

[0010] Furthermore, the loading mechanism includes a loading plate and a loading head; the loading mechanism is located at the power output end of the lifting mechanism, and the loading head is located on the side of the loading plate facing the test chamber and is arranged corresponding to the loading position of the specimen.

[0011] Furthermore, the surrounding rock simulation mechanism includes a cushion layer, springs, and a mounting limiting plate; the mounting limiting plate is fixed to the bottom of the inner cavity of the test chamber, multiple springs are arranged in an array on the mounting limiting plate and fixedly connected to the mounting limiting plate, and the cushion layer is placed on the springs to support the specimen.

[0012] Furthermore, multiple springs can be configured to realistically simulate the mechanical scenarios of the surrounding rock based on the conditions of the surrounding rock and the distribution of its elastic mechanical properties.

[0013] Furthermore, the pads, springs, and mounting limit plates are all made of corrosion-resistant components. These corrosion-resistant components are made of 316 stainless steel or 904 stainless steel.

[0014] Furthermore, multiple specimen positioning mechanisms are provided, and these multiple specimen positioning mechanisms are evenly arranged along the circumference of the test chamber.

[0015] Furthermore, the specimen positioning mechanism includes a sealing nut fixedly arranged on the side wall of the test chamber and a positioning screw for passing through the sealing nut and the side wall of the test chamber in sequence. The positioning screw is threadedly engaged with the sealing nut. By rotating the positioning screw to move axially relative to the sealing nut, the positioning screw is pressed against the specimen.

[0016] Furthermore, the sealing nut includes a nut body and a water-stop ring, with the water-stop ring positioned between the side wall of the test chamber and the nut body.

[0017] Furthermore, a hand-held part is provided at the end of the positioning screw facing out of the test chamber; and / or a top abutment plate is provided at the end of the positioning screw facing inward of the test chamber.

[0018] This utility model has the following beneficial effects:

[0019] This invention relates to a test device for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment. Through a controllable sulfate solution environment within the test chamber, it simulates the chemical corrosion conditions caused by underground water seepage or seawater erosion. The lifting and loading mechanisms work together to apply dynamic cyclic loads. Combined with a surrounding rock simulation mechanism to simulate the pressure on the surrounding rock, it simulates the combined effects of chemical corrosion, cyclic loading, and surrounding rock constraint. The specimen positioning mechanism ensures that the lining specimen bears the load in a fixed position, facilitating the realistic simulation of processes such as crack initiation, propagation, and material degradation under load. Adjusting the loading pressure through the lifting mechanism allows for the study of the impact of different stresses on damage accumulation. The surrounding rock simulation mechanism allows for the replacement of springs with different stiffnesses and layouts to simulate surrounding rock conditions ranging from soft to hard rock. Accelerated testing reveals the failure threshold of the lining concrete under the combined effects of sulfate crystallization expansion and fatigue loading, providing a verification platform for protective measures such as anti-corrosion coatings and fiber reinforcement. Damage data provides key parameters for numerical models, optimizing design parameters such as lining reinforcement ratio, concrete grade, and anti-corrosion materials for concrete. The load-bearing base plate and rigid frame design ensure structural stability under high loads. This utility model presents a test device for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment, realizing multi-dimensional coupling of sulfate erosion, surrounding rock constraint, and dynamic load, providing a key experimental method for the durability design of tunnels subjected to long-term sulfate corrosion.

[0020] In addition to the objectives, features, and advantages described above, this utility model has other objectives, features, and advantages. The present utility model will now be described in further detail with reference to the figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0022] Figure 1 This is a schematic diagram of the structure of the test device for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment, according to a preferred embodiment of this utility model.

[0023] Figure 2 This is a schematic diagram of the specimen positioning mechanism of a preferred embodiment of the present invention.

[0024] Legend:

[0025] 100. Load-bearing base plate; 200. Lifting mechanism; 201. Ball screw assembly; 2011. Support seat; 2012. Screw body; 2013. Buffer pad; 2014. Fixed seat; 2015. Screw nut; 2016. Coupling; 202. Servo motor; 300. Loading mechanism; 301. Loading plate; 302. Loading head; 400. Surrounding rock simulation mechanism; 401. Cushion layer; 402. Spring; 403. Mounting limit plate; 500. Specimen positioning mechanism; 501. Sealing nut; 5011. Nut body; 5012. Water-stop ring; 502. Positioning screw; 5021. Hand handle; 5022. Top plate; 600. Test chamber; 700. Specimen; 800. Erosion solution. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0027] Figure 1 This is a schematic diagram of the structure of the test device for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment, according to a preferred embodiment of this utility model. Figure 2 This is a schematic diagram of the specimen positioning mechanism of a preferred embodiment of the present invention.

[0028] like Figure 1As shown, the cumulative damage test device for tunnel lining structure under cyclic loading in a sulfate environment in this embodiment includes a load-bearing base plate 100, a lifting mechanism 200, a loading mechanism 300, a surrounding rock simulation mechanism 400, a specimen positioning mechanism 500, and a test chamber 600. The test chamber 600 and the lifting mechanism 200 are mounted on the load-bearing base plate 100, the surrounding rock simulation mechanism 400 is located at the bottom of the inner cavity of the test chamber 600, the specimen positioning mechanism 500 is arranged on the test chamber 600, and the loading mechanism 300 is installed at the power output end of the lifting mechanism 200, with the force-applying end of the loading mechanism 300 facing the surrounding rock simulation mechanism 400. A specimen loading position is formed between the loading mechanism 300, the specimen positioning mechanism 500, and the surrounding rock simulation mechanism 400. This invention relates to a test device for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment. The device simulates chemical corrosion conditions caused by underground water seepage or seawater erosion within a controlled sulfate solution environment within a test chamber 600. The lifting mechanism 200 and loading mechanism 300 work together to apply dynamic cyclic loads. Combined with the surrounding rock simulation mechanism 400's simulation of surrounding rock pressure, the device simulates the combined effects of chemical corrosion, cyclic loading, and surrounding rock constraint. The specimen positioning mechanism 500 ensures that the lining specimen 700 bears the load in a fixed position, facilitating the realistic simulation of processes such as crack initiation, propagation, and material degradation under load. Adjusting the loading pressure via the lifting mechanism 200 allows for the study of the impact of different stresses on damage accumulation. The surrounding rock simulation mechanism 400 allows for the replacement of springs with different stiffnesses and layouts to simulate surrounding rock conditions ranging from soft to hard rock. Accelerated testing reveals the failure threshold of lining concrete under the combined effects of sulfate crystallization expansion and fatigue loading, providing a verification platform for protective measures such as anti-corrosion coatings and fiber reinforcement. Damage data can provide key parameters for numerical models, optimizing design parameters such as lining reinforcement ratio, concrete grade, and anti-corrosion materials for concrete. The load-bearing base plate 100 and rigid frame design ensure structural stability under high loads. This utility model's cumulative damage testing device for tunnel lining structures under cyclic loading in a sulfate environment achieves multi-dimensional coupling of sulfate erosion, surrounding rock constraint, and dynamic load, providing a key experimental method for the durability design of tunnels subjected to long-term sulfate corrosion.

[0029] like Figure 1As shown, in this embodiment, multiple lifting mechanisms 200 are provided, and these multiple lifting mechanisms 200 are evenly arranged along the circumference of the load-bearing base plate 100; the test chamber 600 is located within the area formed by the multiple lifting mechanisms 200. Through the multiple circumferentially distributed lifting mechanisms 200, radial uniform or non-uniform confining pressure can be applied to the specimen 700 (tunnel lining) to simulate the hydrostatic pressure or bias pressure state of the surrounding rock on the lining at different burial depths; each lifting mechanism 200 can independently adjust the applied force, combined with the dynamic load of the loading mechanism 300, to reproduce the complex stress path of the tunnel under seismic wave propagation or fault displacement; the multiple lifting mechanisms 200 are synchronously controlled by a servo system to achieve cyclic loads with phase coordination such as sine waves and random waves, simulating the propagation effect of vehicle moving loads in the longitudinal direction of the tunnel; by differentiating the load amplitude or frequency of each lifting mechanism 200, local corrosion-fatigue coupling hot spots can be constructed to study the preferential damage propagation law of the lining in the sulfate erosion weak zone; the circumferentially uniformly arranged lifting mechanisms 200 form a symmetrical loading... The loading frame avoids stress concentration at the ends of the specimen 700 caused by traditional single-point / uniaxial loading, ensuring that the effective area in the middle of the specimen 700 is under uniform stress. The spatial frame composed of multiple lifting mechanisms 200 forms a rigid support system with the load-bearing base plate 100, suppressing system stability during mechanism resonance under high-frequency cyclic loading. The loading mode can be quickly switched by turning off / on specific lifting mechanisms 200. The lifting mechanisms 200 and the surrounding rock simulation mechanism 400 (such as a soil spring array) inside the test chamber 600 work together to reproduce the lining-surrounding rock interaction mode. The test chamber 600 is located in the central area surrounded by the lifting mechanisms 200, which facilitates the circumferential arrangement of equipment such as high-definition cameras and laser displacement gauges to achieve 360° monitoring of the spatiotemporal evolution of cracks and corrosion products on the lining surface. This design realizes the simulation of damage evolution of tunnel lining under the coupled action of sulfate erosion-cyclic loading-surrounding rock constraint, and is easy to observe, providing a high-fidelity test platform for the durability design of major projects such as deep-buried tunnels and cross-sea shield tunnels.

[0030] like Figure 1 As shown, in this embodiment, the lifting mechanism 200 includes a ball screw assembly 201 and a servo motor 202. The power output end of the servo motor 202 is connected to and drives the ball screw assembly 201 to operate. The loading mechanism 300 is arranged on the lifting movable end of the ball screw assembly 201. The servo motor 202 drives the ball screw assembly 201 to operate and drives the loading mechanism 300 to descend to apply pressure or rise to release pressure. The ball screw assembly 201, through the backlash-free transmission between the precision-ground threads and the balls, combined with the feedback from the servo motor 202, can ensure the displacement accuracy of the loading mechanism 300, accurately simulating the microcrack propagation and fatigue accumulation process of the tunnel lining under cyclic load.

[0031] In this embodiment, the lifting mechanism 200 can also be a cylinder, hydraulic cylinder, or jack. Optionally, a slide rail mechanism or a slide rod mechanism can be used in conjunction with the lifting mechanism 200. For example, the cylinder, hydraulic cylinder, or jack can be fixed to the slide rod, and the power output end of the cylinder, hydraulic cylinder, or jack can be connected to the loading mechanism 300, with the loading mechanism 300 slidingly engaging with the slide rod; the power output by the cylinder, hydraulic cylinder, or jack is then applied to the specimen 700 via the loading mechanism 300.

[0032] like Figure 1 As shown, in this embodiment, the ball screw assembly 201 includes a support base 2011, a screw body 2012, a buffer pad 2013, a fixed base 2014, a screw nut 2015, and a coupling 2016. The support base 2011 is mounted on the load-bearing base plate 100. The first end of the screw body 2012 is rotatably mounted on the support base 2011, and the second end of the screw body 2012 passes through the loading mechanism 300 and is connected to the power output end of the servo motor 202 through the coupling 2016. Fixed bases 2014 are sequentially arranged between the coupling 2016 and the loading mechanism 300. 014, lead screw nut 2015 and buffer pad 2013, fixed seat 2014 is arranged at the end of coupling 2016 and is used to restrict the movement of lead screw nut 2015 towards coupling 2016. Lead screw nut 2015 is connected to lead screw body 2012. Buffer pad 2013 is arranged in close contact with loading mechanism 300. The lead screw body 2012 is driven to rotate by servo motor 202, thereby converting the rotational motion of lead screw body 2012 into the axial motion of lead screw nut 2015, so that different degrees of axial loading force are applied to the specimen through loading mechanism 300. The threaded engagement between the lead screw body 2012 and the lead screw nut 2015 converts the rotational motion input from the servo motor 202 into the axial linear motion of the lead screw nut 2015, achieving linear and precise load control. The buffer pad 2013 absorbs the reverse impact force when the specimen 700 suddenly fails through elastic deformation, preventing the ball screw transmission system from being subjected to overload impact. The coupling 2016 compensates for the installation coaxiality deviation between the output shaft of the servo motor 202 and the lead screw body 2012, ensuring that the power transmission is lag-free. The mechanical hard contact between the fixed seat 2014 and the lead screw nut 2015 forms an axial movement endpoint limit, preventing the lead screw nut 2015 from directly impacting the coupling 2016. Optionally, the support base 2011 and the fixed base 2014 form an integral frame structure through the frame and the load-bearing base plate 100; the support base 2011 and the fixed base 2014 form a double-end fixed support for the lead screw body 2012, and together with the sliding constraint of the intermediate loading mechanism 300, form a statically indeterminate beam structure, eliminate the deflection deformation of the lead screw under its own weight, and reduce the straightness error of the axial loading force transmission.

[0033] like Figure 1As shown, in this embodiment, the loading mechanism 300 includes a loading plate 301 and a loading head 302. The loading mechanism 300 is arranged at the power output end of the lifting mechanism 200, and the loading head 302 is located on the side of the loading plate 301 facing the test chamber 600 and is arranged corresponding to the specimen loading position. The loading plate 301 acts as a rigid force transmission medium, uniformly distributing the power output by the lifting mechanism 200 to the loading head 302, eliminating local stress concentration in the ball screw assembly 201, and ensuring uniform load distribution on the specimen surface. The corresponding arrangement of the loading head 302 and the specimen loading position forms a spatial matching relationship, so that the loading force acts on the force-bearing surface of the specimen 700. Optionally, the loading head 302 can be independently replaced with modules of different shapes / sizes to quickly match the contact interface of irregularly shaped lining specimens such as circular tunnels and rectangular pipe corridors, maintaining geometric conformity between the loading surface and the specimen. Optionally, the loading plate 301 and the loading head 302 adopt a split structure to suppress the interference of the mechanical resonance of the lifting mechanism 200 on the load carrier shape fidelity.

[0034] like Figure 1 As shown, in this embodiment, the surrounding rock simulation mechanism 400 includes a pad 401, springs 402, and a mounting limiting plate 403. The mounting limiting plate 403 is fixed to the bottom of the inner cavity of the test chamber 600. Multiple springs 402 are arranged in an array on the mounting limiting plate 403 and are fixedly connected to the mounting limiting plate 403. The pad 401 is arranged on the springs 402 and is used to support the specimen. The array of springs 402 forms a multi-directional elastic support system. By adjusting the stiffness of the springs 402 (such as the compression coefficient), the deformation constraint effect of different surrounding rocks (soft rock / hard rock) on the lining specimen 700 can be reproduced. The cushion layer 401 covers the top of the springs 402, which uniformly transfers the load of the specimen 700 to each spring 402 unit, avoiding non-uniform settlement of the specimen 700 caused by local stress concentration. The array arrangement of the springs 402 allows for selective fixing or replacement of springs 402 with different stiffnesses, and quick switching of surrounding rock conditions (such as homogeneous strata → fault fracture zone), adapting to the needs of multi-condition testing. The installation of the limiting plate 403 rigidly fixes the root of the springs 402, suppresses the lateral buckling of the springs 402, and ensures the geometric stability of the support system during long-term cyclic loading.

[0035] In this embodiment, multiple springs 402 can be configured according to the surrounding rock conditions and the distribution of elastic mechanical properties to realistically simulate the surrounding rock mechanics scenario.

[0036] In this embodiment, the pad 401, spring 402 and mounting limit plate 403 are all made of corrosion-resistant components.

[0037] In this embodiment, the corrosion-resistant part is a 316 stainless steel part or a 904 stainless steel part.

[0038] like Figure 1 and 2As shown, in this embodiment, multiple specimen positioning mechanisms 500 are arranged evenly along the circumference of the test chamber 600. These multiple specimen positioning mechanisms 500 form a ring-shaped constraint frame, ensuring that the specimen 700 (such as tunnel lining) is subjected to a uniformly distributed clamping force in the radial direction, suppressing lateral slippage of the specimen 700 due to asymmetrical loads. By adjusting the clamping distance of each specimen positioning mechanism 500, the positioning accuracy of the specimen 700 is ensured, avoiding additional torque errors caused by the eccentric force application of the loading mechanism 300. The circumferentially distributed independent specimen positioning mechanisms 500 can synchronously adjust their clamping radii, accommodating tunnel lining specimens 700 of different sizes, maintaining full circumferential contact between the positioning surface and the outer wall of the specimen 700. The uniformly distributed specimen positioning mechanisms 500 form discrete constraint points on the surface of the specimen 700, dissipating the high-frequency vibration energy of the specimen 700 under cyclic loads through multi-point friction damping.

[0039] like Figure 1 and 2 As shown, in this embodiment, the specimen positioning mechanism 500 includes a sealing nut 501 fixedly arranged on the side wall of the test chamber 600 and a positioning screw 502 for passing through the sealing nut 501 and the side wall of the test chamber 600 in sequence. The positioning screw 502 is threadedly engaged with the sealing nut 501. By rotating the positioning screw 502 to move axially relative to the sealing nut 501, the positioning screw 502 abuts against the specimen. By rotating the positioning screw 502 and engaging the threaded connection with the sealing nut 501, the axial displacement of the positioning screw 502 can be precisely adjusted at the millimeter level (step accuracy ≤ 0.1 mm), ensuring the alignment of the specimen 700 and the loading mechanism 300. The fixed connection between the sealing nut 501 and the side wall of the test chamber 600 forms a rigid sealing interface, preventing sulfate solution from seeping out through the screw movement gap and maintaining the stability of the corrosive environment inside the test chamber. When the positioning screw 502 abuts against the specimen 700, the self-locking characteristic of the threaded pair provides a constant preload force, suppressing the radial movement of the specimen 700 under cyclic load. The positioning screw 502 can be completely unscrewed from the sealing nut 501, forming an unobstructed loading and unloading channel for the specimen 700, accommodating the positioning requirements of irregularly shaped specimens 700. The sealing nut 501 and the positioning screw 502 are made of 316L stainless steel with surface passivation treatment, resulting in better tolerance in sulfate solutions with pH = 2-12.

[0040] like Figure 1 and 2As shown, in this embodiment, the sealing nut 501 includes a nut body 5011 and a water-stop ring 5012. The water-stop ring 5012 is disposed between the side wall of the test chamber 600 and the nut body 5011. The water-stop ring 5012 fills the assembly gap between the side wall of the test chamber 600 and the nut body 5011 through elastic deformation, forming a double sealing line to block the capillary penetration path of sulfate solution along the threaded joint. Optionally, the water-stop ring 5012 is made of fluororubber to absorb the vibration energy generated by the loading mechanism 300 inside the test chamber 600, reducing the fretting wear rate of the sealing interface. The water-stop ring 5012 completely wraps the contact area between the nut body 5011 and the side wall of the test chamber 600 to prevent corrosion and extend the corrosion resistance life of the nut body 5011. The initial compression reaction force of the water-stop ring 5012 provides a continuous clamping force after the nut body 5011 is installed, suppressing the relaxation of preload caused by thread creep.

[0041] like Figure 1 and 2 As shown, in this embodiment, a handheld part 5021 is provided at one end of the positioning screw 502 facing outwards from the test chamber 600; and / or a top plate 5022 is provided at one end of the positioning screw 502 facing inwards from the test chamber 600. The handheld part 5021 (such as a hexagonal head or knurled structure design) allows the operator to directly rotate the positioning screw 502 from the outside of the test chamber 600 without the need for intrusive tools, thus improving adjustment efficiency; the external design of the handheld part 5021 eliminates the need to reserve operating space inside the test chamber 600, maintaining the compactness of the internal structure of the chamber and improving space utilization. The top abutment plate 5022 transforms the end contact of the positioning screw 502 into a surface contact, reducing the surface contact compressive stress of the specimen 700 and preventing local crushing or scratches. The top abutment plate 5022 fits against the surface of the specimen 700, eliminating displacement hysteresis caused by flexible contact and ensuring real-time transmission of constraint force during dynamic loading. The top abutment plate 5022 completely covers the inner end of the housing of the positioning screw 502, preventing corrosive solutions from seeping into the screw thread gap and extending the service life of the threaded pair.

[0042] In practice, a test apparatus is provided for the cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment. This apparatus can simultaneously simulate the cumulative damage of tunnel lining structure under sulfate erosion and cyclic loading to study the damage law of lining structure under the coupled effect of the two.

[0043] (I) Composition of the experimental apparatus:

[0044] (1) Loading System

[0045] 1. The ball screw assembly 201 consists of a coupling 2016, a fixed base 2014, a screw nut 2015, a rubber washer (buffer pad 2013), a support base 2011, a screw body 2012, and balls, etc. The coupling 2016 is connected to the servo motor 202, which enables precise control of the displacement of the screw nut 2015.

[0046] The coupling 2016 is designed to ensure stable and lag-free power transmission between the servo motor 202 and the lead screw 2012, thereby guaranteeing the smoothness and accuracy of the loading process.

[0047] The mounting bracket 2014 prevents the upward displacement of the lead screw nut 2015 from exceeding the limit value.

[0048] Rubber gasket (buffer pad 2013): 5mm thick, installed between the fixed base 2014 and the steel plate (loading plate 301) to buffer the impact of the ball screw nut 2015 on the (loading plate 301) and extend the service life of the ball screw assembly 201.

[0049] The servo motor 202 can precisely control the output force and displacement, providing a stable and adjustable power input for the entire test setup.

[0050] 2. Both the loading steel plate (loading plate 301) and the load-bearing steel plate (load-bearing base plate 100) have holes at the four corners. The ball screw assembly 201 passes through the holes. The entire ball screw assembly 201 is loaded and supported by the support seat 2011 at the lower end of the load-bearing steel plate (load-bearing base plate 100).

[0051] Loading steel plate (loading plate 301) and load-bearing steel plate (load-bearing base plate 100): As a rigid load-bearing platform, the four corners are synchronously controlled by ball screws to ensure that the specimen is subjected to uniform force during the loading process.

[0052] 3. The loading head 302 is a steel round bar, with one end in contact with the loading steel plate (loading plate 301) and the other end in contact with the specimen 700 to transmit axial pressure. Optionally, the loading head 302 and the loading steel plate (loading plate 301) are detachably connected to facilitate the replacement of different loading heads 302 for different specimens 700 and force requirements.

[0053] (2) Test chamber 600

[0054] 1. The test chamber 600 has five sides: front, back, left, right, and bottom. Holes need to be opened in the middle of the walls of the front, back, left, and right sides of the test chamber 600. The positioning screw 502 passes through the hole. The head of the positioning screw 502 is fixed on the outside of the test chamber 600 with a sealing nut 501. The end of the positioning screw 502 is connected to a fixing plate (top abutment plate 5022) to fix the specimen 700.

[0055] The test chamber 600 has a length of 700 mm or more, a width of 300 mm or more, a height of 400 mm or more, and a thickness of 10 mm or more, to accommodate specimens 700 of different sizes, or to place multiple cubic specimens 700 at the same time, and to ensure that the erosion solution 800 can completely overturn the specimen 700 when the specimen 700 is fully immersed in the test.

[0056] 2. A spring array (multiple springs 402 arranged in an array or dynamically) is installed at the bottom of the test chamber 600, which is fixed by a limiting plate 403 to simulate the elastic support effect of the surrounding rock. A pad 401 is placed in the spring array and the specimen 700. Optionally, the pad 401 is a porous permeable plate, such as a polypropylene mesh with a pore size of 2 mm, to ensure that the solution penetrates to the bottom of the specimen 700 and uniformly transmits the reaction force of the springs 402.

[0057] The installation of the limiting plate 403 serves to limit the spring 402, preventing the spring 402 from bending or shifting laterally during compression and ensuring that the spring always deforms axially.

[0058] (II) Experimental Methods

[0059] (1) Equivalent surrounding rock pressure: Based on the stress characteristics of tunnel lining, a uniformly distributed group of springs is used to characterize the uniform constraint effect of the surrounding rock on the lining structure. In specific implementation, the elastic resistance coefficient K of different surrounding rock levels in the current tunnel design code is used as a reference, and the corresponding spring stiffness parameters are determined by theoretical conversion to ensure that the test conditions and actual engineering conditions have a clear correspondence. When the continuous constraint of the surrounding rock is equivalent to a discrete group of springs, the stiffness of the spring group k (N / m) = K (MPa / m)·A (m2), where A is the area of ​​surrounding rock action represented by a single spring.

[0060] To address potential defects in tunnel engineering, this method simulates the real environment in the following ways: 1. Adjusting the spring arrangement density or spring stiffness to characterize the voided area of ​​the surrounding rock; 2. Reducing the stiffness of specific springs to simulate the softening phenomenon of the surrounding rock; 3. Using a combination of variable stiffness springs to reproduce the non-uniform constraint state.

[0061] (2) Depending on the purpose of the experiment, different immersion methods can be adopted for the specimen 700, such as half immersion or full immersion, and different stress modes can be simulated to consider whether a fixing plate (top plate 5022) is needed, that is, fixing or even pressurizing the specimen 700 around its perimeter.

[0062] (3) After the servo motor 202 is powered on and started, it generates rotational power. This power is transmitted to the ball screw assembly 201 through the coupling 2016. Under the action of rotational power, the ball screw assembly 201 rotates, and the screw nut 2015 cooperates with the screw body 2012 to convert the rotational motion of the screw body 2012 into the linear motion of the screw nut 2015. When the screw nut 2015 moves linearly upward or downward, it will generate different degrees of pressure acting on the loading steel plate (loading plate 301), and the loading steel plate (loading plate 301) will transfer the load to the loading head 302. The loading head 302 then directly acts on the specimen 700 to apply a load to the specimen 700.

[0063] Throughout the loading process, the servo motor 202 can be controlled by the accompanying controller. Parameters such as the loading force, displacement, loading speed, and the number and frequency of cyclic loading can be set.

[0064] The experimental apparatus for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment, as described in this invention, has the following advantages:

[0065] 1. By combining a sulfate erosion environment simulation system with a cyclic loading system, a cumulative damage test study on tunnel lining structures under dual loading was achieved.

[0066] 2. A cyclic loading system designed with a stepper motor (servo motor 202), coupling 2016, and ball screw can realistically simulate the stress mode of the lining structure during train operation and automatically adjust the load magnitude and frequency. Furthermore, the cost of this device is low, far lower than that of the MTS universal testing machine.

[0067] 3. This device is suitable for model tests of specimens 700 of various sizes, such as cubes, cuboids, cylinders, etc. Depending on the type and arrangement of the specimens 700, experiments can be carried out under various stress modes, such as compression, bending, and considering confining pressure.

[0068] Any matters not covered in this utility model are common knowledge.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the appended claims.

[0071] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A test apparatus for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment, characterized in that, It includes a load-bearing base plate (100), a lifting mechanism (200), a loading mechanism (300), a surrounding rock simulation mechanism (400), a specimen positioning mechanism (500), and a test chamber (600). The test chamber (600) and the lifting mechanism (200) are mounted on the load-bearing base plate (100), the surrounding rock simulation mechanism (400) is mounted at the bottom of the inner cavity of the test chamber (600), the specimen positioning mechanism (500) is mounted on the test chamber (600), and the loading mechanism (300) is mounted on the power output end of the lifting mechanism (200). The force-applying end of the loading mechanism (300) is positioned towards the surrounding rock simulation mechanism (400). The loading position of the specimen is formed between the loading mechanism (300), the specimen positioning mechanism (500), and the surrounding rock simulation mechanism (400).

2. The test apparatus for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment according to claim 1, characterized in that, Multiple lifting mechanisms (200) are provided, and the multiple lifting mechanisms (200) are evenly arranged along the circumference of the load-bearing base plate (100); The test chamber (600) is located within the area formed by multiple lifting mechanisms (200).

3. The test apparatus for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment according to claim 2, characterized in that, The lifting mechanism (200) includes a ball screw assembly (201) and a servo motor (202). The power output end of the servo motor (202) is connected to and drives the ball screw assembly (201) to operate. The loading mechanism (300) is arranged on the lifting movable end of the ball screw assembly (201). The ball screw assembly (201) is driven by a servo motor (202) to operate and drive the loading mechanism (300) to descend to apply pressure or rise to release pressure.

4. The test apparatus for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment according to claim 3, characterized in that, The ball screw assembly (201) includes a support (2011), a screw body (2012), a buffer pad (2013), a fixed seat (2014), a screw nut (2015), and a coupling (2016). A support base (2011) is mounted on a load-bearing base plate (100). The first end of the lead screw body (2012) is rotatably mounted on the support base (2011). The second end of the lead screw body (2012) passes through the loading mechanism (300) and is connected to the power output end of the servo motor (202) via a coupling (2016). A fixed seat (2014), a lead screw nut (2015), and a buffer pad (2013) are sequentially arranged between the coupling (2016) and the loading mechanism (300). The fixed seat (2014) is located at the end of the coupling (2016) and is used to restrict the lead screw nut (2015) from moving toward the coupling (2016). The lead screw nut (2015) is connected to the lead screw body (2012). The buffer pad (2013) is attached to the loading mechanism (300). The servo motor (202) drives the lead screw body (2012) to rotate, thereby converting the rotational motion of the lead screw body (2012) into the axial motion of the lead screw nut (2015), so that different degrees of axial loading force are applied to the specimen through the loading mechanism (300).

5. The test apparatus for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment according to any one of claims 1 to 4, characterized in that, The loading mechanism (300) includes a loading plate (301) and a loading head (302); The loading mechanism (300) is located at the power output end of the lifting mechanism (200), and the loading head (302) is located on the side of the loading plate (301) facing the test chamber (600) and is arranged corresponding to the loading position of the specimen.

6. The test apparatus for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment according to any one of claims 1 to 4, characterized in that, The surrounding rock simulation mechanism (400) includes a cushion layer (401), a spring (402), and a mounting limit plate (403). The mounting limit plate (403) is fixed to the bottom of the inner cavity of the test chamber (600). Multiple springs (402) are arranged in an array on the mounting limit plate (403) and fixedly connected to the mounting limit plate (403). The pad (401) is placed on the springs (402) and is used to support the test specimen.

7. The test apparatus for cumulative damage of tunnel lining structures under cyclic loading in a sulfate environment according to any one of claims 1 to 4, characterized in that, Multiple specimen positioning mechanisms (500) are arranged, and the multiple specimen positioning mechanisms (500) are evenly arranged along the circumference of the test chamber (600).

8. The test apparatus for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment according to claim 7, characterized in that, The specimen positioning mechanism (500) includes a sealing nut (501) fixedly arranged on the side wall of the test chamber (600) and a positioning screw (502) for passing through the sealing nut (501) and the side wall of the test chamber (600) in sequence. The positioning screw (502) is threadedly engaged with the sealing nut (501). By rotating the positioning screw (502) to move axially relative to the sealing nut (501), the positioning screw (502) is pressed against the specimen.

9. The test apparatus for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment according to claim 8, characterized in that, The sealing nut (501) includes a nut body (5011) and a water-stop ring (5012), with the water-stop ring (5012) positioned between the side wall of the test chamber (600) and the nut body (5011).

10. The test apparatus for cumulative damage of tunnel lining structure under cyclic loading in a sulfate environment according to claim 8 or 9, characterized in that, A handle (5021) is provided at the end of the positioning screw (502) facing outward from the test chamber (600); and / or The end of the positioning screw (502) facing the inside of the test chamber (600) is set as a top abutment plate (5022).

Images