Creep test device for steel ring reinforced shield tunnel lining interface and combination thereof

Abstract

The application provides a creep test device for a steel ring reinforced shield tunnel lining interface, characterized in that the device comprises a support fixing mechanism, a constant ratio loading mechanism, a variable ratio loading mechanism and a test piece; the constant ratio loading mechanism and the variable ratio loading mechanism are arranged on the support fixing mechanism, the constant ratio loading mechanism and the variable ratio loading mechanism form a folded series two-stage lever mechanism, and the purpose of applying a load to the test piece is achieved by adjusting the counterweight and the length of the power arm on the variable ratio loading mechanism. The application also provides a combination device of the above device, and the creep test of the test piece under a pull-shear coupling condition can be realized by the combination of the two devices. The creep test of the steel ring reinforced shield tunnel lining interface by using the device has good load holding performance, can flexibly simulate complex pull-shear coupling conditions, and improves the test efficiency and reduces the test cost.

Description

Technical Field

[0001] This invention relates to the field of long-term service performance evaluation technology for reinforced tunnels, and in particular to a creep testing device for the interface of steel ring reinforced shield tunnel lining and a combination thereof. Background Technology

[0002] Concrete lining structures of shield tunnels in soft soil strata are highly susceptible to structural deformation and cracking under long-term water-soil loads. Applying internal tension steel rings to prevent further tunnel deformation and improve the structure's resistance to deformation is a primary strategy for the reinforcement and maintenance of deformable tunnels. Specifically, steel plates are assembled on the inner surface of the deformable tunnel using high-strength epoxy resin adhesive or bolts. The steel plates and the deformed structure work together to resist external loads, effectively preventing further structural deformation. In this process, the long-term bonding performance between the steel plates and the deformed tunnel is crucial for improving structural stiffness and long-term service performance.

[0003] In recent years, as major projects such as shield tunnels and subway tunnels spanning rivers, lakes, and seas in my country have entered a critical stage of simultaneous construction and maintenance, the scenarios involving the treatment of defects in steel ring-reinforced deformed shield tunnels are increasing, and the deformation characteristics of shield tunnels are becoming increasingly complex. To accurately and efficiently design creep failure tests on the lining interface of steel ring-reinforced shield tunnels, the following three challenges need to be addressed: 1. Long test cycles: creep loading time under any working condition can reach at least several thousand hours; 2. High load stability requirements: taking a tunnel with a 100-year service life as an example, the lateral or longitudinal convergence deformation of any deformed tunnel develops throughout the entire service life, and the change in failure load under small deformation is minimal; 3. Complex failure load effects: the failure of interface materials after deformation of arc-shaped shield tunnel structures exhibits tensile-shear coupling characteristics, with numerous working conditions and diverse characteristics of tensile and shear force effects and their combinations.

[0004] In summary, the loading mode of the interface of tunnel lining reinforced with internally tensioned steel rings is long-term. Under continuous load, the failure of the interface material exhibits tensile-shear coupling characteristics, and the deformation and load at the interface change with the tunnel's service time. This places extremely high demands on the load and equipment stability of conventional hydraulic servo loading systems. Due to the complexity of actual ground stress and lining pressure, the poor flexibility of traditional creep testing equipment makes it difficult to meet the extensive simulation of the long-term complex load characteristics of reinforced tunnels, which greatly limits the verification and testing of tunnel reinforcement schemes. Currently, the industry still lacks efficient and systematic testing equipment for the bond interface failure of internally tensioned steel ring reinforced tunnel linings; under long-term load, determining the shear strength, bond slip, and creep deformation characteristics of the interface material has become a challenge for the stability and durability design of reinforced tunnels. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a creep testing device for the interface of steel ring reinforced shield tunnel lining, and a combined device based on the above device, to solve the problems of poor load-bearing performance, high cost, complex operation, and low data accuracy in creep testing of steel ring reinforced lining interface in tunnels in the prior art.

[0006] To achieve the objective of this invention, this invention provides a creep testing device for the interface of shield tunnel lining reinforced with steel rings. Its innovation lies in the fact that the device includes a support and fixing mechanism, a fixed ratio loading mechanism, a variable ratio loading mechanism, and a specimen.

[0007] The supporting and fixing mechanism includes a support frame and a fixing frame. The support frame includes a bottom beam, a front column, and a rear column. Both the front and rear columns are mounted on the top surface of the bottom beam and are arranged longitudinally along the bottom beam. The longitudinal direction of both the front and rear columns is perpendicular to the top surface of the bottom beam. A front hinge seat is provided on the upper part of the front column, and a rear hinge seat is provided on the upper part of the rear column. The fixing frame is located on the front side of the front column and includes a base plate, a pressure plate, and connecting bolts. The base plate is fixedly mounted on the top surface of the bottom beam and is parallel to the top surface of the bottom beam. The pressure plate is located above the base plate, and the pressure plate and the base plate are connected by connecting bolts.

[0008] The fixed-ratio loading mechanism includes a first lever, a connecting plate, and a connecting mechanism. A lower front hinge, a lower middle hinge, and a lower rear hinge are sequentially arranged from front to back on the lower side of the first lever. The lower front hinge and the lower middle hinge are both located at the front of the first lever, and the lower rear hinge is located at the rear of the first lever. The connecting mechanism includes a connecting rod and a force gauge. The lower end of the connecting rod is hinged to the upper end of the force gauge. The upper end of the connecting rod is hinged to the lower front hinge. The upper end of the connecting plate is hinged to the lower rear hinge.

[0009] The variable ratio loading mechanism includes a second lever, a counterweight basket, and a counterweight block; an upper front hinge and an upper rear hinge are arranged sequentially from front to back on the upper side of the second lever, both of which are located at the rear of the second lever; a hanging ring is provided on the upper part of the counterweight basket, and a basket for placing the counterweight block is provided on the lower part of the counterweight basket; the hanging ring is fitted onto the second lever, thereby suspending the basket below the second lever, and the hanging ring can slide back and forth on the second lever;

[0010] The specimen includes a concrete block and a reinforcing steel plate attached to one side of the concrete block. The upper or outer surface of the reinforcing steel plate is provided with hinges.

[0011] The concrete block of the specimen is fixed to the base plate by a pressure plate and connecting bolts; the upper rear hinge is hinged to the rear hinge, the upper front hinge is hinged to the lower end of the connecting plate, the lower middle hinge is hinged to the front hinge, and the lower end of the tension gauge is hinged to the hinge lug; the first lever can rotate about the hinge point of the lower middle hinge and the front hinge, and the second lever can rotate about the hinge point of the upper rear hinge and the rear hinge; the counterweight is placed inside the basket.

[0012] Furthermore, the first lever, the second lever, and the bottom beam are all horizontally arranged longitudinally.

[0013] Furthermore, the connecting rod is a double-ended turnbuckle, and the upper end of the connecting rod can move left and right within the lower front hinge seat.

[0014] Furthermore, the axial direction of the tension gauge is parallel to that of the reinforcing steel plate.

[0015] Furthermore, the front end of the second lever is provided with a safety baffle to prevent the lifting ring from slipping out.

[0016] The present invention also provides a creep testing device assembly for steel ring reinforced shield tunnel lining interface, the innovation of which is: the device assembly includes a specimen, a cable mechanism, an adjusting pad assembly and two loading devices; the two loading devices include a first loading device and a second loading device;

[0017] A single loading device includes a support and fixing mechanism, a fixed-ratio loading mechanism, and a variable-ratio loading mechanism;

[0018] The supporting and fixing mechanism includes a support frame and a fixing frame. The support frame includes a bottom beam, a front column, and a rear column. Both the front and rear columns are mounted on the top surface of the bottom beam and are arranged longitudinally along the bottom beam. The longitudinal direction of both the front and rear columns is perpendicular to the top surface of the bottom beam. A front hinge seat is provided on the upper part of the front column, and a rear hinge seat is provided on the upper part of the rear column. The fixing frame is located on the front side of the front column and includes a base plate, a pressure plate, and connecting bolts. The base plate is fixedly mounted on the top surface of the bottom beam and is parallel to the top surface of the bottom beam. The pressure plate is located above the base plate, and the pressure plate and the base plate are connected by connecting bolts.

[0019] The fixed-ratio loading mechanism includes a first lever, a connecting plate, and a connecting mechanism. A lower front hinge, a lower middle hinge, and a lower rear hinge are sequentially arranged from front to back on the lower side of the first lever. The lower front hinge and the lower middle hinge are both located at the front of the first lever, and the lower rear hinge is located at the rear of the first lever. The connecting mechanism includes a connecting rod and a first force gauge. The lower end of the connecting rod is hinged to the upper end of the first force gauge. The upper end of the connecting rod is hinged to the lower front hinge. The upper end of the connecting plate is hinged to the lower rear hinge.

[0020] The variable ratio loading mechanism includes a second lever, a counterweight basket, and a counterweight block; an upper front hinge and an upper rear hinge are arranged sequentially from front to back on the upper side of the second lever, both of which are located at the rear of the second lever; a hanging ring is provided on the upper part of the counterweight basket, and a basket for placing the counterweight block is provided on the lower part of the counterweight basket; the hanging ring is fitted onto the second lever, thereby suspending the basket below the second lever, and the hanging ring can slide back and forth on the second lever;

[0021] In a single loading device, the upper rear hinge is hinged to the rear hinge, the upper front hinge is hinged to the lower end of the connecting plate, and the lower middle hinge is hinged to the front hinge; the first lever can rotate about the hinge point between the lower middle hinge and the front hinge, and the second lever can rotate about the hinge point between the upper rear hinge and the rear hinge; the counterweight is placed inside the basket.

[0022] The specimen includes a concrete block and a reinforcing steel plate attached to one side of the concrete block. The upper part of the reinforcing steel plate is provided with a hinge lug, and the outer side of the reinforcing steel plate is provided with an external hinge seat.

[0023] The cable mechanism includes a cable and a second tension gauge. A lifting lug is provided at each end of the cable, and a connecting hinge is provided at each end of the second tension gauge. The first lifting lug of the cable is hinged to the first connecting hinge of the second tension gauge.

[0024] The adjustment pad assembly includes multiple adjustment pads of different thicknesses. By combining and stacking the multiple adjustment pads in different ways, adjustment pad assemblies of different heights can be obtained.

[0025] A redirecting hinge seat is also provided on the upper side of the pressure plate of the second loading device, and a hinge shaft is provided on the upper part of the redirecting hinge seat.

[0026] The concrete block of the specimen is fixed to the base plate of the first loading device by the pressure plate and connecting bolts of the first loading device; the lower end of the first tension gauge of the first loading device is hinged to the hinge lug.

[0027] The adjusting pad assembly is fixed to the base plate of the second loading device by the pressure plate and connecting bolts of the second loading device; the second connecting hinge of the second tension gauge is hinged to the outer hinge, and the second lug of the cable passes under the hinge shaft and is hinged to the lower end of the first tension gauge of the second loading device.

[0028] Furthermore, the axis of the first tension gauge of the first loading device is parallel to the reinforcing steel plate; the axis of the second tension gauge is perpendicular to the reinforcing steel plate.

[0029] Furthermore, the first lever, the second lever, and the bottom beam are all horizontally arranged longitudinally.

[0030] Furthermore, the connecting rod is a double-headed turnbuckle, and the upper end of the connecting rod can move left and right within the lower front hinge seat; the front end of the second lever is provided with a safety baffle to prevent the lifting ring from slipping out.

[0031] The principle of this invention is as follows:

[0032] Creep tests not only require a stable load over a long period, but also a precise load magnitude and loading rate tailored to the specific test requirements. The creep testing device for steel ring-reinforced shield tunnel lining interfaces described in this invention effectively solves these problems through a simple yet ingenious structural design:

[0033] This device directly loads the specimen using a fixed-ratio loading mechanism, while the first lever amplifies the load by a fixed ratio. This amplification aims to provide the required load while reducing the counterweight, thus minimizing equipment space and testing costs. A key feature of this device is the indirect loading of the specimen using a variable-ratio loading mechanism. The second lever of the variable-ratio mechanism and the first lever of the fixed-ratio mechanism form a series lever mechanism, allowing for significant load amplification (up to 100 times in the example below). This further reduces the counterweight size and saves costs. Furthermore, the folding structure of the second and first levers further conserves space, allowing for more equipment to be installed in the same testing space. This enables simultaneous creep testing of multiple batches of specimens with multiple devices, significantly saving time and space costs.

[0034] On the other hand, the counterweight basket of the variable ratio loading mechanism can slide back and forth on the second lever, which actually makes the length of the second lever power arm adjustable, thereby achieving fine adjustment of the load under the same counterweight weight (the adjustment accuracy in the embodiment described later can reach 1N). This not only makes it easy to achieve precise control of the loading load, but also, due to its simple operation, can well meet the control of the loading speed required by the test, so as to better simulate the real working conditions and provide more complete and accurate test data. Moreover, due to the existence of the variable ratio loading mechanism, the required load near the same counterweight block can be achieved without frequent manual changes of the counterweight block specifications, which greatly saves manpower and improves test efficiency.

[0035] Furthermore, the single device described in this invention can perform creep tests on specimens under shear or tensile stress, thus satisfying the data acquisition requirements for single-stress creep tests. By combining two devices, creep tests under both shear and tensile stresses can be performed simultaneously, simulating the actual working conditions where concrete-reinforced steel plates experience both shear and tensile stresses. This yields test data closer to real-world conditions and improves test accuracy.

[0036] Furthermore, the entire loading structure of this invention is a self-balancing system and is equipped with safety displacement baffles, so no special treatment is required for the bottom of the device. This greatly improves the flexibility of installation and use, thereby increasing the applicability and utilization rate of the device, and further reducing the requirements for the test site and lowering the operating costs. Moreover, directly connecting a tension gauge to the specimen to display the load data applied to it ensures that the load on the specimen during the test fully meets the load requirements of the test design, avoiding load value errors caused by factors such as the frictional resistance of mechanical devices and the solid volume of concrete counterweights, further improving the accuracy and precision of the test.

[0037] In summary, the creep testing device described in this invention, based on the lever principle and physical loading mode, greatly optimizes the stability and flexibility of the test load. It can simulate the interface creep failure characteristics of reinforced structures throughout the entire life cycle of deformable tunnels, while saving energy consumption for long-term creep tests lasting thousands of hours. It boasts advantages such as high test control accuracy and low testing cost. Furthermore, the device combination mechanism effectively solves the problem of simulating tension-shear coupled load under complex service environments of deformable tunnels. Biaxial combined loading provides an effective solution for complex interface creep failure problems. The low complexity of the device allows multiple instruments to work collaboratively, improving testing efficiency. The physical and lever loading modes and the device combination design reduce energy requirements, enhancing the economics of large-scale testing. This device is particularly suitable for studying interface creep failure problems of reinforced structures under large sample sizes, providing a scientific basis for the long-term stability performance evaluation of reinforced shield tunnels in engineering, and offering an economical and efficient testing approach for maintenance decisions, repair technology development, and scheme comparison for deformable shield tunnels.

[0038] Therefore, the present invention has the following beneficial effects: the device of the present invention is simple to operate, improves test efficiency, reduces test cost, and improves test accuracy and precision when used for creep testing of steel ring reinforced lining interface in tunnels. Attached Figure Description

[0039] The accompanying drawings of this invention are described below.

[0040] Appendix Figure 1 This is a schematic diagram of the device structure described in this invention;

[0041] Appendix Figure 2 This is a schematic diagram of the structure of the device assembly described in this invention;

[0042] Appendix Figure 3 A schematic diagram of the installation structure for the uniaxial shear test of the specimen;

[0043] Appendix Figure 4 A schematic diagram of the installation structure for the uniaxial tensile test of the specimen;

[0044] Appendix Figure 5 A schematic diagram of the installation structure for the bi-cyclic tensile shear test of the specimen;

[0045] Appendix Figure 6 Creep curves of the bond interface under different shear stress levels;

[0046] Appendix Figure 7 Creep curves of the bond interface under different tensile stress levels.

[0047] In the attached diagram: 1. Support and fixing mechanism; 2. Fixed ratio loading mechanism; 3. Variable ratio loading mechanism; 4. Specimen; 5. Specimen; 6. Cable mechanism; 7. Adjusting pad assembly; 11. Bottom beam; 12. Front column; 13. Rear column; 14. Bottom plate; 15. Pressure plate; 16. Connecting bolt; 21. First lever; 22. Connecting plate; 23. Connecting mechanism; 31. Second lever; 32. Counterweight basket; 33. Counterweight block; 41. Concrete block; 42. Reinforcing steel plate; 43. Hinge; 51. Concrete block. 52. Concrete block; 53. Reinforcing steel plate; 54. Hinge lug; 65. Outer hinge seat; 66. Cable; 67. Second tension gauge; 121. Front hinge seat; 131. Rear hinge seat; 151. Redirecting hinge seat; 152. Hinge shaft; 211. Lower front hinge seat; 212. Lower middle hinge seat; 213. Lower rear hinge seat; 231. Connecting rod; 232. Tension gauge; 232-1. First tension gauge; 311. Upper front hinge seat; 312. Upper rear hinge seat; 313. Safety baffle; 321. Lifting ring; 322. Basketball basket. Detailed Implementation

[0048] The present invention will be further described below with reference to the embodiments.

[0049] As attached Figure 1 The creep test device shown for the steel ring reinforced shield tunnel lining interface includes a support and fixing mechanism 1, a constant ratio loading mechanism 2, a variable ratio loading mechanism 3, and a specimen 4;

[0050] The supporting and fixing mechanism 1 includes a support frame and a fixing frame. The support frame includes a bottom beam 11, a front column 12, and a rear column 13. Both the front column 12 and the rear column 13 are disposed on the top surface of the bottom beam 11 and are arranged longitudinally along the bottom beam 11. The longitudinal direction of both the front column 12 and the rear column 13 is perpendicular to the top surface of the bottom beam 11. A front hinge seat 121 is provided on the upper part of the front column 12, and a rear hinge seat 131 is provided on the upper part of the rear column 13. The fixing frame is disposed on the front side of the front column 12. The fixing frame includes a base plate 14, a pressure plate 15, and connecting bolts 16. The base plate 14 is fixedly disposed on the top surface of the bottom beam 11 and is parallel to the top surface of the bottom beam 11. The pressure plate 15 is disposed above the base plate 14, and the pressure plate 15 and the base plate 14 are connected by connecting bolts 16.

[0051] The fixed-ratio loading mechanism 2 includes a first lever 21, a connecting plate 22, and a connecting mechanism 23. The lower side of the first lever 21 is provided with a lower front hinge 211, a lower middle hinge 212, and a lower rear hinge 213 arranged sequentially from front to back. The lower front hinge 211 and lower middle hinge 212 are both located at the front of the first lever 21, and the lower rear hinge 213 is located at the rear of the first lever 21. The connecting mechanism 23 includes a connecting rod 231 and a force gauge 232. The lower end of the connecting rod 231 is hinged to the upper end of the force gauge 232. The upper end of the connecting rod 231 is hinged to the lower front hinge 211. The upper end of the connecting plate 22 is hinged to the lower rear hinge 213.

[0052] The variable ratio loading mechanism 3 includes a second lever 31, a counterweight basket 32, and a counterweight block 33. An upper front hinge 311 and an upper rear hinge 312 are sequentially arranged from front to back on the upper side of the second lever 31, both located at the rear of the second lever 31. A hanging ring 321 is provided on the upper part of the counterweight basket 32, and a basket 322 for placing the counterweight block 33 is provided on the lower part of the counterweight basket 32. The hanging ring 321 is fitted onto the second lever 31, thereby suspending the basket 322 below the second lever 31, and the hanging ring 321 can slide back and forth on the second lever 31.

[0053] The specimen 4 includes a concrete block 41 and a reinforcing steel plate 42 attached to one side of the concrete block. The upper part or outer side of the reinforcing steel plate 42 is provided with a hinge lug 43.

[0054] The concrete block 41 of the specimen 4 is fixed to the base plate 14 by the pressure plate 15 and the connecting bolts 16; the upper rear hinge 312 is hinged to the rear hinge 131, the upper front hinge 311 is hinged to the lower end of the connecting plate 22, the lower middle hinge 212 is hinged to the front hinge 121, and the lower end of the tension gauge 232 is hinged to the hinge lug 43; the first lever 21 can rotate around the hinge point of the lower middle hinge 212 and the front hinge 121, and the second lever 31 can rotate around the hinge point of the upper rear hinge 312 and the rear hinge 131; the counterweight 33 is placed inside the basket 322.

[0055] To facilitate load adjustment and device stability, the first lever 21, the second lever 31, and the bottom beam 11 are all arranged horizontally in the longitudinal direction.

[0056] To facilitate length adjustment of the connecting rod 231, a double-ended turnbuckle is used. To ensure proper alignment between the connecting rod 231 and the specimen 4, the upper end of the connecting rod 231 can move left and right within the lower front hinge seat 211. Adjusting the length of the connecting rod ensures that both the first and second levers are in a horizontal position, eliminating initial errors.

[0057] To ensure more accurate measurement of shear stress, the axial direction of the tension gauge 232 is parallel to that of the reinforcing steel plate 42.

[0058] To improve the safety of the device, a safety baffle 313 is provided at the front end of the second lever 31 to prevent the lifting ring from slipping out.

[0059] As attached Figure 2 As shown, the present invention also provides a creep testing device assembly for steel ring reinforced shield tunnel lining interface, including specimen 5, cable mechanism 6, and two loading devices 7, including a first loading device and a second loading device;

[0060] A single loading device includes a support and fixing mechanism 1, a fixed ratio loading mechanism 2, and a variable ratio loading mechanism 3;

[0061] The supporting and fixing mechanism 1 includes a support frame and a fixing frame. The support frame includes a bottom beam 11, a front column 12, and a rear column 13. Both the front column 12 and the rear column 13 are disposed on the top surface of the bottom beam 11 and are arranged longitudinally along the bottom beam 11. The longitudinal direction of both the front column 12 and the rear column 13 is perpendicular to the top surface of the bottom beam 11. A front hinge seat 121 is provided on the upper part of the front column 12, and a rear hinge seat 131 is provided on the upper part of the rear column 13. The fixing frame is disposed on the front side of the front column 12. The fixing frame includes a base plate 14, a pressure plate 15, and connecting bolts 16. The base plate 14 is fixedly disposed on the top surface of the bottom beam 11 and is parallel to the top surface of the bottom beam 11. The pressure plate 15 is disposed above the base plate 14, and the pressure plate 15 and the base plate 14 are connected by connecting bolts 16.

[0062] The fixed-ratio loading mechanism 2 includes a first lever 21, a connecting plate 22, and a connecting mechanism 23. The lower side of the first lever 21 is provided with a lower front hinge 211, a lower middle hinge 212, and a lower rear hinge 213 arranged sequentially from front to back. The lower front hinge 211 and the lower middle hinge 212 are both located at the front of the first lever 21, and the lower rear hinge 213 is located at the rear of the first lever 21. The connecting mechanism 23 includes a connecting rod 231 and a first tension gauge 232-1. The lower end of the connecting rod 231 is hinged to the upper end of the first tension gauge 232-1. The upper end of the connecting rod 231 is hinged to the lower front hinge 211. The upper end of the connecting plate 22 is hinged to the lower rear hinge 213.

[0063] The variable ratio loading mechanism 3 includes a second lever 31, a counterweight basket 32, and a counterweight block 33. An upper front hinge 311 and an upper rear hinge 312 are sequentially arranged from front to back on the upper side of the second lever 31, both located at the rear of the second lever 31. A hanging ring 321 is provided on the upper part of the counterweight basket 32, and a basket 322 for placing the counterweight block 33 is provided on the lower part of the counterweight basket 32. The hanging ring 321 is fitted onto the second lever 31, thereby suspending the basket 322 below the second lever 31, and the hanging ring 321 can slide back and forth on the second lever 31.

[0064] In a single loading device, the upper rear hinge 312 is hinged to the rear hinge 131, the upper front hinge 311 is hinged to the lower end of the connecting plate 22, and the lower middle hinge 212 is hinged to the front hinge 121; the first lever 21 can rotate about the hinge point between the lower middle hinge 212 and the front hinge 121, and the second lever 31 can rotate about the hinge point between the upper rear hinge 312 and the rear hinge 131; the counterweight 33 is placed inside the basket 322.

[0065] The specimen 5 includes a concrete block 51 and a reinforcing steel plate 52 attached to one side of the concrete block. The upper part of the reinforcing steel plate 52 is provided with a hinge lug 53, and the outer side surface of the reinforcing steel plate 52 is provided with an outer hinge seat 54.

[0066] The cable mechanism 6 includes a cable 61 and a second force gauge 62. A lifting lug is provided at each end of the cable 6, and a connecting hinge seat is provided at each end of the second force gauge 62. The first lifting lug of the cable 6 is hinged to the first connecting hinge seat of the second force gauge 62.

[0067] The adjusting pad group 7 includes multiple adjusting pads of different thicknesses. By combining and stacking the multiple adjusting pads in different ways, adjusting pad groups of different heights can be obtained.

[0068] A redirecting hinge seat 151 is also provided on the upper side of the pressure plate 15 of the second loading device, and a hinge shaft 152 is provided on the upper part of the redirecting hinge seat.

[0069] The concrete block 51 of the specimen 5 is fixed to the base plate 14 of the first loading device by the pressure plate 15 and connecting bolts 16 of the first loading device; the lower end of the first tension gauge 232-1 of the first loading device is hinged to the hinge lug 53.

[0070] The adjusting pad assembly 7 is fixed to the base plate 14 of the second loading device by the pressure plate 15 and connecting bolts 16 of the second loading device; the second connecting hinge of the second tension gauge 62 is hinged to the outer hinge seat 54, and the second lug of the cable 61 passes under the hinge shaft 152 and is hinged to the lower end of the first tension gauge 232-1 of the second loading device.

[0071] To improve the accuracy of the data measured by the tension gauges, the axis of the first tension gauge 232-1 of the first loading device is parallel to the reinforcing steel plate 52; the axis of the second tension gauge 62 is perpendicular to the reinforcing steel plate 52.

[0072] To facilitate load adjustment and device stability, the first lever 21, the second lever 31, and the bottom beam 11 are all arranged horizontally in the longitudinal direction.

[0073] To facilitate the adjustment of the connecting rod length, the connecting rod 231 is a double-headed turnbuckle. To facilitate the alignment of the connecting rod 231 with the specimen position 5, the upper end of the connecting rod 231 can move left and right within the lower front hinge seat 211. To improve the safety of the device, a safety baffle 313 is provided at the front end of the second lever 31 to prevent the lifting ring from slipping out.

[0074] The following is a detailed description of the implementation process and data acquisition for creep testing using this device:

[0075] (1) Complete the combined connection of the support system, loading system and fixing system according to the above implementation method;

[0076] (2) Figures 3-5 As shown, the specimen in this embodiment includes: a standard size C50 concrete block of 150mm×150mm×150mm, a reinforcing steel plate of 100mm×100mm×20mm, strength grade Q345, and epoxy resin injection type steel bonding adhesive poured between the concrete and the reinforcing steel plate.

[0077] (3) This embodiment mainly verifies the creep mechanical behavior of the bonding interface between the inner steel ring and the tunnel lining under long-term load conditions. Therefore, before the test, resistance strain gauges need to be pasted at appropriate positions on the adhesive layer of the bonding interface between the steel plate and the concrete specimen. The strain gauges selected are foil strain gauges of model BX120-#AA, with a resistance value of 120.0±0.1Ω and a sensitivity of 2.0±1%. For uniaxial shear and biaxial shear specimens, strain gauges with a wire grid size of 5×2mm (BX120-2AA) are selected. Starting from a position 10mm away from the loading end on the side, one strain gauge is evenly arranged at intervals of 20mm, for a total of 5 strain gauges. For uniaxial tensile and biaxial tensile specimens, strain gauges with a wire grid size of 3×2mm (BX120-3AA) are selected. The strain gauges are pasted along the tensile direction of the bonding interface, with 2 strain gauges symmetrically arranged on each side, for a total of 8 strain gauges. In the experiment, the Donghua DH3816N multi-channel static strain gauge was used to record strain data. Temperature compensation was set in the strain gauge channel, the acquisition frequency was 2Hz, and all channels of the acquisition instrument were zeroed before the formal loading.

[0078] (4) In the uniaxial tensile test, the concrete specimen is fixed using a clamping device. A steel handle is welded to the center of the upper surface of the reinforcing steel plate to apply the tensile load. The design of the uniaxial tensile test specimen is shown in the attached figure. Figure 3 As shown.

[0079] In the uniaxial shear test, the concrete specimen is also fixed using a clamp. To avoid force eccentricity during shearing, a steel handle is welded to the middle of the upper side of the reinforcing steel plate to apply the shear load. The design of the uniaxial shear test specimen is shown in the attached figure. Figure 4 As shown.

[0080] In biaxial tensile and biaxial shear tests, since the specimen is subjected to both tensile and shear loads, a steel handle needs to be welded to the center of the upper surface of the reinforcing steel plate and the center of the upper side. The design of the biaxial test specimen is shown in the attached figure. Figure 5 As shown.

[0081] (5) Fix the prepared unit body to the platform with fixing bolts and safety baffle, and connect the steel handle of the reinforcing steel plate to the tension gauge. The tension gauge is an S-type column load cell with model MZLZ / 10T and a maximum range of 10T. This sensor has the advantages of high accuracy, good strength and good stability. When equipped with a digital measuring instrument, it can realize the real-time display and recording of the load value. The digital display instrument is model MZ4896 / 220V and the display accuracy is 1N.

[0082] (6) Before loading, a stress of approximately 0.05 MPa should be applied to the specimen to observe whether it is centered and whether any torsion occurs. If so, the specimen needs to be re-centered until it is in a pure shear or pure tension state. After the stress stabilizes, unload the specimen and reset the digital display reading to zero.

[0083] (7) Level the device by changing the length of the vertical steel tie rod to ensure that the axes of the first lever and the second lever are both horizontal.

[0084] (8) During the formal loading process, the rate of load application needs to be strictly controlled. At the beginning, the load is achieved by gradually increasing the counterweight. When the load value is close to the test design load level, the weight is stopped and the "sliding device" is used to fine-tune the test load value until the digital display reaches the test design maximum stress value. Several representative load values ​​are shown in Table 1.

[0085] Table 1 Creep Test Grouping

[0086]

[0087] (9) Immediately record the instantaneous strain of the specimen when it begins formal loading. Then record test data every 30 seconds until the load reaches the design load level. After the test enters the creep stage, record test data at 1 min, 3 min, 6 min, 9 min, 15 min, 30 min, 45 min, 1 h, 1.5 h, 2 h, 4 h, 8 h, and 12 h. Subsequently, gradually reduce the measurement frequency of test data according to the degree of change in the bond interface strain data until the designed creep test duration of 1000 h is reached. The creep curves under different shear stresses and tensile stresses are shown in the attached figures. Figure 6 and attached Figure 7 As shown.

[0088] If the specimen does not peel off at the interface after 1000 hours of creep as set in the test, static loading is required until the specimen fails. The residual strength of the bond interface after creep is tested, and the effect of creep on the bond strength and failure mode of the bond interface is studied by comparing the results with those of static tests that have not undergone creep.

Claims

1. A creep testing device for steel ring-reinforced shield tunnel lining interface, characterized in that: The creep testing device includes a support and fixing mechanism, a constant ratio loading mechanism, a variable ratio loading mechanism, and a test specimen; The supporting and fixing mechanism includes a support frame and a fixing frame. The support frame includes a bottom beam, a front column, and a rear column. Both the front and rear columns are mounted on the top surface of the bottom beam and are arranged longitudinally along the bottom beam. The longitudinal direction of both the front and rear columns is perpendicular to the top surface of the bottom beam. A front hinge seat is provided on the upper part of the front column, and a rear hinge seat is provided on the upper part of the rear column. The fixing frame is located on the front side of the front column and includes a base plate, a pressure plate, and connecting bolts. The base plate is fixedly mounted on the top surface of the bottom beam and is parallel to the top surface of the bottom beam. The pressure plate is located above the base plate, and the pressure plate and the base plate are connected by connecting bolts. The fixed-ratio loading mechanism includes a first lever, a connecting plate, and a connecting mechanism. A lower front hinge, a lower middle hinge, and a lower rear hinge are sequentially arranged from front to back on the lower side of the first lever. The lower front hinge and the lower middle hinge are both located at the front of the first lever, and the lower rear hinge is located at the rear of the first lever. The connecting mechanism includes a connecting rod and a force gauge. The lower end of the connecting rod is hinged to the upper end of the force gauge. The upper end of the connecting rod is hinged to the lower front hinge. The upper end of the connecting plate is hinged to the lower rear hinge. The variable ratio loading mechanism includes a second lever, a counterweight basket, and a counterweight block; an upper front hinge and an upper rear hinge are arranged sequentially from front to back on the upper side of the second lever, both of which are located at the rear of the second lever; a hanging ring is provided on the upper part of the counterweight basket, and a basket for placing the counterweight block is provided on the lower part of the counterweight basket; the hanging ring is fitted onto the second lever, thereby suspending the basket below the second lever, and the hanging ring can slide back and forth on the second lever; The specimen includes a concrete block and a reinforcing steel plate attached to one side of the concrete block. The upper or outer surface of the reinforcing steel plate is provided with hinges. The concrete block of the specimen is fixed to the base plate by a pressure plate and connecting bolts; the upper rear hinge is hinged to the rear hinge, the upper front hinge is hinged to the lower end of the connecting plate, the lower middle hinge is hinged to the front hinge, and the lower end of the tension gauge is hinged to the hinge lug; the first lever can rotate about the hinge point of the lower middle hinge and the front hinge, and the second lever can rotate about the hinge point of the upper rear hinge and the rear hinge; the counterweight is placed inside the basket.

2. The creep testing device for steel ring-reinforced shield tunnel lining interface as described in claim 1, characterized in that: The first lever, the second lever, and the bottom beam are all set horizontally in the longitudinal direction.

3. The creep testing device for steel ring-reinforced shield tunnel lining interface as described in claim 1 or 2, characterized in that: The connecting rod is a double-ended turnbuckle, and the upper end of the connecting rod can move left and right within the lower front hinge seat.

4. The creep testing device for steel ring-reinforced shield tunnel lining interface as described in claim 1 or 2, characterized in that: The axial direction of the tension gauge is parallel to that of the reinforcing steel plate.

5. The creep testing device for steel ring-reinforced shield tunnel lining interface as described in claim 1 or 2, characterized in that: The front end of the second lever is provided with a safety baffle to prevent the lifting ring from slipping out.

6. A creep testing device assembly for steel ring-reinforced shield tunnel lining interfaces, characterized in that: The creep testing apparatus assembly includes a specimen, a cable mechanism, an adjusting pad assembly, and two loading devices; the two loading devices include a first loading device and a second loading device. A single loading device includes a support and fixing mechanism, a fixed-ratio loading mechanism, and a variable-ratio loading mechanism; The supporting and fixing mechanism includes a support frame and a fixing frame. The support frame includes a bottom beam, a front column, and a rear column. Both the front and rear columns are mounted on the top surface of the bottom beam and are arranged longitudinally along the bottom beam. The longitudinal direction of both the front and rear columns is perpendicular to the top surface of the bottom beam. A front hinge seat is provided on the upper part of the front column, and a rear hinge seat is provided on the upper part of the rear column. The fixing frame is located on the front side of the front column and includes a base plate, a pressure plate, and connecting bolts. The base plate is fixedly mounted on the top surface of the bottom beam and is parallel to the top surface of the bottom beam. The pressure plate is located above the base plate, and the pressure plate and the base plate are connected by connecting bolts. The fixed-ratio loading mechanism includes a first lever, a connecting plate, and a connecting mechanism. A lower front hinge, a lower middle hinge, and a lower rear hinge are sequentially arranged from front to back on the lower side of the first lever. The lower front hinge and the lower middle hinge are both located at the front of the first lever, and the lower rear hinge is located at the rear of the first lever. The connecting mechanism includes a connecting rod and a first force gauge. The lower end of the connecting rod is hinged to the upper end of the first force gauge. The upper end of the connecting rod is hinged to the lower front hinge. The upper end of the connecting plate is hinged to the lower rear hinge. The variable ratio loading mechanism includes a second lever, a counterweight basket, and a counterweight block; an upper front hinge and an upper rear hinge are arranged sequentially from front to back on the upper side of the second lever, both of which are located at the rear of the second lever; a hanging ring is provided on the upper part of the counterweight basket, and a basket for placing the counterweight block is provided on the lower part of the counterweight basket; the hanging ring is fitted onto the second lever, thereby suspending the basket below the second lever, and the hanging ring can slide back and forth on the second lever; In a single loading device, the upper rear hinge is hinged to the rear hinge, the upper front hinge is hinged to the lower end of the connecting plate, and the lower middle hinge is hinged to the front hinge; the first lever can rotate about the hinge point between the lower middle hinge and the front hinge, and the second lever can rotate about the hinge point between the upper rear hinge and the rear hinge; the counterweight is placed inside the basket. The specimen includes a concrete block and a reinforcing steel plate attached to one side of the concrete block. The upper part of the reinforcing steel plate is provided with a hinge lug, and the outer side of the reinforcing steel plate is provided with an external hinge seat. The cable mechanism includes a cable and a second tension gauge. A lifting lug is provided at each end of the cable, and a connecting hinge is provided at each end of the second tension gauge. The first lifting lug of the cable is hinged to the first connecting hinge of the second tension gauge. The adjustment pad assembly includes multiple adjustment pads of different thicknesses. By combining and stacking the multiple adjustment pads in different ways, adjustment pad assemblies of different heights can be obtained. A redirecting hinge seat is also provided on the upper side of the pressure plate of the second loading device, and a hinge shaft is provided on the upper part of the redirecting hinge seat. The concrete block of the specimen is fixed to the base plate of the first loading device by the pressure plate and connecting bolts of the first loading device; the lower end of the first tension gauge of the first loading device is hinged to the hinge lug. The adjusting pad assembly is fixed to the base plate of the second loading device by the pressure plate and connecting bolts of the second loading device; the second connecting hinge of the second tension gauge is hinged to the outer hinge, and the second lug of the cable passes under the hinge shaft and is hinged to the lower end of the first tension gauge of the second loading device.

7. The creep testing device assembly for steel ring-reinforced shield tunnel lining interface as described in claim 6, characterized in that: The axial direction of the first tension gauge of the first loading device is parallel to the reinforcing steel plate; the axial direction of the second tension gauge is perpendicular to the reinforcing steel plate.

8. The creep testing device assembly for steel ring-reinforced shield tunnel lining interface as described in claim 6 or 7, characterized in that: The first lever, the second lever, and the bottom beam are all set horizontally in the longitudinal direction.

9. The creep testing device assembly for steel ring-reinforced shield tunnel lining interface as described in claim 6 or 7, characterized in that: The connecting rod is a double-headed turnbuckle, and the upper end of the connecting rod can move left and right within the lower front hinge seat; the front end of the second lever is provided with a safety baffle to prevent the lifting ring from slipping out.

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