An equivalent simulation device for non-uniform soil reaction forces of buried tubular structures

Abstract

The present invention relates to a device for equivalently simulating non-uniform soil reaction forces of a buried tubular structure, which comprises a cross-section module group (5) composed of a plurality of cross-section modules (1), a test piece (2), a fixing frame, and a base track (4); the cross-section module (1) includes a zero-stiffness composite spring (6) and a cross-section frame (7); the cross-section frame (7) is fixedly connected to the base track (4); the zero-stiffness composite spring (6) is distributed inside the cross-section frame (7) and fixedly connected to the cross-section frame (7); the cross-section module group (5) composed of a plurality of cross-section modules (1) is used to simulate areas with the same soil properties; when non-uniform soil is distributed in the structural length direction, different cross-section module groups (5) are set to simulate non-uniform soil reaction forces; the test piece (2) includes at least one structural model (19), and after the structural models (19) are axially connected, the test piece (2) is formed.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground structure-soil interaction tests, and specifically relates to a device for equivalently simulating non-uniform soil reaction forces on a buried tubular structure. Background Art

[0002] Buried tubular structures are one of the most commonly used engineering structures in production and life, such as oil and gas pipelines, underground tunnels, and buried cables. During the design, construction, and operation stages of buried tubular structures, it is necessary to focus on their interaction with the soil. In particular, buried tubular structures are often extended and large-span structures, and the soil is non-uniform in the length direction, so the underground structure-soil interaction no longer remains consistent. Currently, underground structure-soil interaction tests are mainly carried out in in-situ soil sites and artificial soil sites, such as Chinese Patent Applications 2021103045131, 202123083348.6, and 2020113208802, etc. In-situ soil site tests can obtain real data on the underground structure-soil interaction and are often considered an experimental method that can provide relatively reliable results in engineering. However, in-situ soil site tests often require relevant sensors to be arranged during the construction stage, and subsequent measurement operations are likely to damage the on-site state of the buried tubular structure, making on-site measurement difficult and the costs of test manpower and material resources relatively high. Artificial soil site tests effectively overcome the difficulties and disadvantages of in-situ soil site tests and can simulate various load conditions in a laboratory environment, which are widely used in engineering testing and scientific research. Artificial soil site tests require equipment such as centrifuges and go through steps such as consolidation tests to prepare the test soil, with a large amount of test work, a complex test process, and a long cycle. Chinese Patent Application 202011382075.8 discloses a test device and determination method for simulating a pipeline crossing a strike-slip fault. Pressure-bearing members are arranged on both sides of the pipeline and connected to the outer peripheral wall of the pipeline in the form of a flexible belt winding, for studying the force conditions of the pipeline and the pipe-soil interaction when crossing different fault displacements. This patent can avoid complex processes such as test soil preparation, but there are differences in the loading methods between its test model and theoretical model, and it can only simulate the unidirectional pipe-soil interaction under fault displacement. Therefore, in view of the problems existing in the prior art, there is an urgent need to provide a device and simulation method for equivalently simulating non-uniform soil reaction forces on a buried tubular structure with rigorous theory, simple structure, and convenient operation. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: to provide a device for equivalently simulating non-uniform soil reaction forces on a buried tubular structure, which can simulate the acting forces of the soil around the buried tubular structure on its cross-section and can simultaneously carry out experimental research on buried tubular structure models considering the action of non-uniform soil reaction forces. The technical solution is as follows:

[0004] An equivalent simulation device for non-uniform soil reaction force of a buried tubular structure, comprising a cross-section module group 5 composed of a plurality of cross-section modules 1, a test piece 2, a fixing frame, and a base track 4, wherein:

[0005] The zero-stiffness composite spring 6 includes a metal helical spring 10, rubber 11, a spring top cover 12, a spring fixing screw rod 13, a spring bottom cover 14, a bottom screw rod 15, a contact plate 16, and a displacement-axial force sensor 18; the metal helical spring 10 is embedded in the rubber 11; the top of the rubber 11 is connected to the spring top cover 12, and the bottom is connected to the spring bottom cover 14. A displacement-axial force sensor 18 is arranged along the axis of the zero-stiffness composite spring 6; the spring top cover 12 of the zero-stiffness composite spring 6 is connected to the inner side of the cross-section frame 7 through the spring fixing screw rod 13; the contact plate 16 is connected to the spring bottom cover 14 through the bottom screw rod 15;

[0006] The cross-section module 1 described above includes a zero-stiffness composite spring 6 and a cross-section frame 7; the cross-section frame 7 is fixedly connected to the base track 4; the zero-stiffness composite springs 6 are distributed inside the cross-section frame 7 and fixedly connected to the cross-section frame 7;

[0007] The cross-section module group 5 composed of a plurality of cross-section modules 1 is used to simulate areas with the same soil properties; when non-uniform soil is distributed in the structural length direction, different cross-section module groups 5 are set to simulate non-uniform soil reaction forces;

[0008] The test piece 2 described above includes at least one structural model 19. After the structural models 19 are axially connected, the test piece 2 is formed. The test piece 2 is fixed on the base track 4 through a fixing frame.

[0009] Furthermore, according to the size of the test piece, by adjusting the feed amounts of the spring fixing screw rod 13 and the bottom screw rod 15, the size of the area surrounded by the zero-stiffness composite spring 6 of the cross-section module 1 is changed.

[0010] Furthermore, the cross-section frame 7 is a rounded square cross-section, and four zero-stiffness composite springs 6 are evenly distributed inside one cross-section frame 7.

[0011] Furthermore, the base track 4 described above includes a square-base 23 and a base fixing groove 24; the base fixing groove 24 is located on both sides of the square-base 23 and can pass through a double-headed screw rod for connecting the fixing frame and the cross-section module 1.

[0012] Due to the above technical solutions adopted by the present invention, the following advantages are obtained:

[0013] 1. The zero-stiffness composite spring is adopted to equivalently simulate the soil reaction force, eliminating the need for on-site soil and artificial soil sites. By adjusting the parameters of the zero-stiffness composite spring, soils with different strengths can be simulated, enabling the selection of a larger scale ratio test under the condition of a relatively small overall size of the device. This not only effectively saves test manpower and material resources but also improves test accuracy.

[0014] 2. The adopted cross-section module follows the mechanical principle of the "buried tubular structure - spring" finite element model. The four zero-stiffness composite springs correspond to the nonlinear soil springs on the upper, lower, left, and right of the structural unit cross-section in the finite element model. The load-displacement curves of each zero-stiffness composite spring satisfy the similarity theory with the load-displacement curves of the nonlinear soil springs in the authoritative design code.

[0015] 3. The cross-section module group can be used to assemble test models of any length. By adjusting the parameters of the zero-stiffness composite springs in each cross-section module group, the uneven soil distribution along the length direction of the underground structure can be simulated, which is difficult to achieve in traditional artificial soil site tests.

[0016] 4. The adopted cross-section module allows the structural model to have relative displacements in any direction within the cross-section. The maximum value of the relative displacements in the upper, lower, left, and right directions is the smaller value of half of the contact plate length and the maximum compression deformation of the zero-stiffness composite spring in the corresponding direction.

[0017] 5. Modular design is adopted, and the zero-stiffness composite spring, cross-section module, cross-section module group, and end fixing frame can be modified and replaced. The mechanical structure is simple, manufacturing is economical and convenient, and the operation is simple. It is suitable for experimental research and teaching on the interaction between underground structures and soils. Description of the Drawings

[0018] Figure 1 Overall view of the test device of the present invention

[0019] Figure 2 Schematic diagram of the cross-section module

[0020] Figure 3 Schematic diagram of the zero-stiffness composite spring

[0021] Figure 4 Schematic diagram of the test piece

[0022] Figure 5 Schematic diagram of the end fixing frame

[0023] Figure 6 Schematic diagram of the base track

[0024] Figure 7 Schematic diagram of the load-displacement curve of the zero-stiffness composite spring

[0025] Figure 8 Schematic diagram of the load-displacement curve of the zero-stiffness composite spring

[0026] Figure 9 Schematic diagram of a locally spanning buried pipeline

[0027] Figure 10 Schematic diagram of the modal test of a locally spanning buried pipeline

[0028] Figure 11 Schematic diagram of a circular tunnel passing through non-uniform soil

[0029] Figure 12 Schematic diagram of the modal test of a circular tunnel passing through non-uniform soil

[0030] Explanation of the reference numerals in the figure: 1 - cross-section module; 2 - test piece; 3 - end fixing frame; 4 - base track; 5 - cross-section module group; 6 - zero-stiffness composite spring; 7 - cross-section frame; 8 - base fixing hole; 9 - spring fixing threaded hole; 10 - metal helical spring; 11 - rubber; 12 - spring top cover; 13 - spring fixing screw rod; 14 - spring bottom cover; 15 - bottom screw rod; 16 - contact plate; 17 - contact plate connecting screw rod; 18 - displacement-axial force sensor; 19 - structural model; 20 - specimen flange; 21 - flange fixing hole; 22 - end flange frame; 23 - square base; 24 - base fixing groove Detailed implementation manners

[0031] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or equipment.

[0033] The test piece adopted by the non-uniform soil reaction equivalent simulation device of the buried tubular structure of the present invention can be various buried tubular structures. The embodiments of the present invention mainly relate to two structures, one is a steel buried pipeline, and the other is a circular tunnel.

[0034] The non-uniform soil reaction equivalent simulation device of the buried tubular structure includes: a cross-section module 1, a test piece 2, an end fixing frame 3, a base track 4 and a cross-section module group 5. Among them:

[0035] The described cross-section module 1 includes a zero-stiffness composite spring 6, a cross-section frame 7, a bottom fixing hole 8, and a spring fixing threaded hole 9. According to the symmetry of the buried tubular structure, the cross-section frame 7 is preferably a rounded square cross-section. The spring fixing threaded hole 9 is located at the center positions of the four sides of the cross-section frame 7 for installing the zero-stiffness composite spring 6. The bottom fixing hole 8 is located at symmetric positions on both sides of the bottom edge of the cross-section frame 7 and can pass through the double-headed screw rod for the fixed connection of the cross-section frame 7 with the base track 4.

[0036] The zero-stiffness composite spring 6 includes a metal helical spring 10, rubber 11, a spring top cover 12, a spring fixing screw rod 13, a spring bottom cover 14, a bottom screw rod 15, a contact plate 16, a contact plate connecting screw rod 17, and a displacement-axial force sensor 18. Preferably, the zero-stiffness composite spring 6 adopts a straight cylindrical composite spring recommended in the literature (Zero-stiffness composite spring [J]. Technology Market of Chinese Universities, 1996(12): 5-6.). In addition to the characteristics of ordinary composite springs, a more significant feature is that the offset corresponding to the zero-stiffness characteristic is very large. Let the maximum linear elastic pressure load of the zero-stiffness composite spring 6 be P0, and the corresponding maximum linear elastic compression deformation at this time be Δ0, and Δ1 be the maximum compression deformation allowed by the zero-stiffness of the zero-stiffness composite spring 6. When a pressure load P acts axially on the zero-stiffness composite spring 6, that is, P < P0 or the compression deformation Δ of the zero-stiffness composite spring < Δ0, the metal helical spring 10 and the rubber 11 are compressed simultaneously, and its P-Δ curve is linear elastic; when the P value increases further (P0 < P or Δ0 < Δ < Δ1), the metal helical spring 10 produces compression deformation and shows positive stiffness, and the rubber 11 between the pitches of the metal helical spring 10 changes from compression deformation to shear deformation, and expansion occurs between the pitches, and its elastic modulus decreases to 1 / 3 of the original and shows negative stiffness. After the two are combined, the positive and negative stiffnesses cancel each other out, presenting zero stiffness. According to actual needs, the maximum compression deformation Δ1 allowed by the zero-stiffness should be greater than or equal to the maximum relative displacement that may occur between the underground structure and the soil body. The shape of the above-mentioned P-Δ curve can be adjusted to meet the requirements of different types of soil bodies. The P-Δ curve of the zero-stiffness composite spring 6 satisfies the similarity theory with the non-linear soil spring load-displacement curves specified in the same specification SY / T 0450-2004 "Seismic Design Code for Oil (Gas) Steel Pipelines" and ALA-2001 "Guidelines for the design of buried steel pipe", where P0 corresponds to the maximum soil reaction force received on the discrete length of the structure, and Δ0 corresponds to the structure-soil relative displacement yield value.

[0037] The metal helical spring 10 is embedded in the rubber 11. The cross-section of the rubber 11 is in a circular ring shape, with its top connected to the spring top cover 12 and its bottom connected to the spring bottom cover 14. A displacement-axial force sensor 18 is installed inside. Preferably, according to the needs of the test pipe fitting, by adjusting the feed amounts of the spring fixing screw rod 13 and the bottom screw rod 15, the size of the area enclosed by the four zero-stiffness composite springs 6 in the cross-section module 1 is changed. The spring fixing screw rod 13 cooperates with the spring fixing threaded hole 9 and is used to connect the zero-stiffness composite spring 6 and the cross-section frame 7.

[0038] The bottom plane of the contact plate 16 contacts the test pipe fitting 2, and a contact plate connecting screw rod 17 is welded at the center of the top plane. The contact plate connecting screw rod 17 is connected to the bottom screw rod 15 through the threaded hole on the end face of the bottom screw rod 15. Preferably, the contact plate 16 is a flat plate, allowing the test piece 2 to move within its contact plane, ensuring that only pressure acts between the contact plate 16 and the test piece 2, and they are tangent when in contact. The length of the contact plate 16 should be less than that of the test piece 2, avoiding interference between the four contact plates 16 in the cross-section module 1 after installation and under the relative displacement of the structure-soil in any direction. In the four directions of up, down, left, and right in the cross-section, the maximum value of the allowable relative displacement of the underground structure-soil is the smaller value of half of the length of the contact plate 16 and the maximum compression deformation Δ1 of the corresponding zero-stiffness composite spring 6.

[0039] The working principle of the cross-section module 1 follows the mechanical principle of the "buried tubular structure-spring" finite element model. The finite element model often uses a non-linear soil spring model to describe the action of the surrounding soil on the pipeline. The four zero-stiffness composite springs 6 of the cross-section module 1 correspond to the non-linear soil springs at the nodes or the midpoints of the structural elements of the finite element structure, with directions of horizontally right, horizontally left, vertically up, and vertically down respectively, and are used to equivalently simulate the soil reaction force per unit pipe length. According to the test measurement results published in the literature (Rofooei F R, Jalali H H, Attari N, et al. Parametric study of buried steel and high density polyethylene gas pipelines due to oblique-reverse faulting[J]. Canadian Journal of Civil Engineering, 2015, 42(3):178-189.), when the structure and the soil have relative displacement, the action of the soil on the tensile side of the structure can be ignored, and the soil reaction force only appears on the compressed side of the structure. Therefore, the zero-stiffness composite spring 6 only plays a role under axial compressive load.

[0040] The test piece 2 described above includes a structural model 19, a test piece flange 20, and flange fixing holes 21. The structural model 19 is a full-scale or scaled-down model of a buried tubular structure. When the end boundary condition of the structural model 19 is fully fixed, the test piece flange 20 is welded to the end of the structural model 19, and the double-headed screw rod passes through the flange fixing holes 21 to connect with the end fixing frame 3. Preferably, there are at least 8 flange fixing holes 21 arranged in a circumferential array on the test piece flange to ensure the reliability of the connection. When the end boundary condition of the structural model 19 is simply supported, a circular flat plate of the same material, equal thickness, and equal outer diameter should be welded to its end. A connecting rod is welded to the center of the flat plate, and then it is clamped with foam vibration isolation. Preferably, the implementation method of the simply supported boundary condition can refer to Chinese patent applications 2021103757600 and 2021103757757. When the end boundary condition of the structural model 19 is completely free, no additional connection treatment is required at the end of the structural model 19.

[0041] The end fixing frame 3 described above includes a base fixing hole 8, flange fixing holes 21, and an end flange frame 22. The end flange frame 22 is an end flange plate with a bottom bracket. Preferably, there are at least 8 flange fixing holes 21 arranged in a circumferential array on the end flange plate to ensure the reliability of the connection. The base fixing holes 8 are located at symmetric positions on both sides of the bottom bracket and can pass through the double-headed screw rod for the fixed connection of the end fixing frame 3 and the base track 4.

[0042] The base track 4 described above includes a loop-shaped base 23 and base fixing grooves 24. The base fixing grooves 24 are located on both sides of the loop-shaped base 23 and can pass through the double-headed screw rod for the fixed connection of the end fixing frame 3 and the cross-section module 1 to the base track 4. Preferably, the base fixing grooves 24 can not only reduce the weight of the device but also allow the end fixing frame 3 and the cross-section module 1 to be installed at any position of the base fixing grooves 24.

[0043] The cross-section module group 5 described above includes a plurality of identical cross-section modules 1 used to simulate regions with the same soil properties. When the soil is distributed non-uniformly in the structural length direction, different cross-section module groups 5 are set to simulate the non-uniform soil reaction force.

[0044] (1) Modal test of local suspension of buried pipelines

[0045] Due to ground settlement, water flow scouring, soil property changes, and terrain unevenness, buried pipelines are very likely to have local suspensions. This leads to a sharp increase in the operation risk of the pipeline and seriously affects the safety of pipeline oil and gas transportation. The modal test of local suspension of buried pipelines is used to study the influence of soil properties and suspension length on the vibration characteristics of buried pipelines. The implementation steps are as follows:

[0046] Step 1. Design data arrangement. Determine the geometric parameters, material parameters, and soil parameters of the buried pipeline according to the project design data, including outer diameter, wall thickness, buried section length, span section length, elastic modulus, material yield stress, burial depth, soil cohesion, effective unit weight of overburden soil, effective unit weight of natural soil, total unit weight of natural soil, coefficient of earth pressure at rest, and internal friction angle, etc.; determine the test scale ratio and the geometric dimensions and discrete lengths of the structural model 19.

[0047] Step 2. Fabrication of test piece 2. Fabricate the structural model 19 according to the geometric dimensions determined in Step 1. The end boundary condition of the structural model 8 is fully fixed, and a specimen flange 20 is welded to the end of the structural model 19.

[0048] Step 3. Strain gauge positioning and installation. Mark the boundary lines of the structural discretization on the structural model 19 according to the discrete length determined in Step 1. The middle section between the two boundary lines is the contact position of the zero-stiffness composite spring 6; to obtain the first 6 bending modes of the pipeline, install at least 6 strain gauges in the pipe length direction, and pay attention to avoiding the 1 / N (N = 2, 3, 4, 5, 6) equal division positions in the length direction and the contact position of the zero-stiffness composite spring 6 and the structural model 19.

[0049] Step 4. Calculation of soil spring parameters. Obtain the soil spring parameters corresponding to the structural geometric parameters and soil parameters, including the maximum soil reaction force per unit pipe length and the relative displacement yield value, according to the non-linear soil spring calculation methods recommended in the design code SY / T 0450-2004 "Seismic Design Code for Oil (Gas) Steel Pipelines" and ALA-2001 "Guidelines for the design of buried steel pipe"; calculate P0 and Δ0 of the zero-stiffness composite spring 6 according to the test scale ratio and discrete length.

[0050] Step 5. Debugging of the zero-stiffness composite spring 6. Debug the zero-stiffness composite spring 6 in each direction according to the calculation results in Step 4, so that its P-Δ curve satisfies the similarity theory with the non-linear soil spring load-displacement curve specified in the design code.

[0051] Step 6. Assembly of the cross-section module 1. The zero-stiffness composite spring 6 is installed on the spring fixing threaded hole 9 of the cross-section frame 7 through the spring fixing threaded rod 13; the contact plate 16 is installed on the bottom threaded rod 15 through the contact plate connecting screw rod 17.

[0052] Step 7. Installation of the cross-section module group 5. The double-headed screw rod passes through the base fixing hole 8 and the base fixing groove 24, and the cross-section modules 1 are fixed on the base track 4 one by one according to the unit length of the model. For the partially suspended buried pipeline, two cross-section module groups 5 are required, which are located on both sides of the structural model 19 respectively, corresponding to the buried sections at both ends of the pipeline. No cross-section modules need to be arranged in the middle area between the two cross-section module groups 5, corresponding to the partially suspended pipe section in the middle of the pipeline.

[0053] Step 8. Installation of the test piece 2. First, adjust the feed amounts of the spring fixing screw rod 13 and the bottom screw rod 15 so that the side length of the square area surrounded by the four zero-stiffness composite springs 6 in the cross-section module 1 is slightly larger than the outer diameter of the test piece 2. Then, pass the test piece 2 through each cross-section module group 5. The double-headed screw rod passes through the base fixing hole 8 and the base fixing groove 24 to install the end fixing frame 3 on the base track 4. Finally, finely adjust the feed amounts of the spring fixing screw rod 13 and the bottom screw rod 15 so that the contact plate 16 of the zero-stiffness composite spring 6 contacts the test piece 2. Except for the zero-stiffness composite spring 6 at the bottom, the contact axial forces of the other zero-stiffness composite springs 6 are zero.

[0054] Step 9. Sensor debugging. Connect the displacement-axial force sensor 18 and the strain gauges to the data acquisition instrument, perform communication debugging, and complete zeroing and calibration.

[0055] Step 10. Loading and testing. Use the shaker to excite the structural model 19. Change the excitation position and excitation frequency, and repeat the excitation of the structural model 19.

[0056] Step 11. Data acquisition and analysis. Record the displacement-axial force data, strain data of the zero-stiffness composite spring 6 and the excitation force data in the shaker through the data acquisition instrument; analyze the recorded test data to obtain the frequencies and modes of the structural model 19. Preferably, the strain data analysis method adopts the method recommended by the literature (Trim A D, Braaten H, Lie H, et al. Experimental investigation of vortex-induced vibration of long marinerisers[J]. Journal of Fluids&Structures, 2005, 21(3): 335-361).

[0057] Step 12. Disassembly and storage of the device. After the test, disassemble the end fixing frame 3, the test piece 2, the cross-section module group 5, the cross-section module 1, the zero-stiffness composite spring 6 and the base track 4 in sequence, and organize and store them.

[0058] (2) Modal test of a circular tunnel crossing non-uniform soil

[0059] The circular tunnel is the main structural form of the urban underground traffic system. The modal test of the circular tunnel passing through non-uniform soil is used to study the influence of the non-uniform soil along the way on the vibration characteristics of the circular tunnel. The test piece 2 used in the second embodiment is the structural model 19 of the circular tunnel, which is different from the first embodiment.

[0060] The implementation steps of the modal test of the circular tunnel passing through non-uniform soil are as follows:

[0061] Step 1: Sort out design data. Determine the geometric parameters, material parameters and soil parameters of the circular tunnel according to the project design data, including outer diameter, wall thickness, lengths of buried sections 1, 2 and 3, elastic modulus, material yield stress, burial depth, soil cohesion, effective overburden unit weight, effective unit weight of natural soil, total unit weight of natural soil, coefficient of earth pressure at rest and internal friction angle, etc.; determine the test scale ratio and the geometric dimensions and discrete lengths of the structural model 19.

[0062] Step 2: Process the test piece 2. Process the structural model 19 according to the geometric dimensions determined in Step 1. The end boundary condition of the structural model 19 is completely free, and no additional connection treatment is required at its ends.

[0063] Step 3: Locate and install strain gauges. Mark the boundary lines of the structural discretization on the structural model 19 according to the discrete lengths determined in Step 1. The middle section between the two boundary lines is the contact position of the zero-stiffness composite spring 6; to obtain the first 6 bending modes of the circular tunnel, install at least 6 strain gauges in the length direction, and pay attention to avoiding the 1 / N (N = 2, 3, 4, 5, 6) equal division positions in the length direction and the contact position of the zero-stiffness composite spring 6 and the structural model 19.

[0064] Step 4: Calculate the parameters of the soil spring. Select a suitable foundation model (such as the currently most commonly used Winkler foundation model) to consider the interaction between the tunnel and the soil (Selvadurai A P S. Elastic Analysis of Soil-Structure Interaction [M]. Translated by Fan Wentian. Beijing: China Railway Publishing House, 1984, 16 - 23.), and obtain the soil spring parameters corresponding to the structural geometric parameters and soil parameters, including the maximum soil reaction force per unit length and the relative displacement yield value; calculate P0 and Δ0 of the zero-stiffness composite spring 6 according to the test scale ratio and the discrete length.

[0065] Step 5: Debug the zero-stiffness composite spring 6. Debug the zero-stiffness composite spring 6 in each direction according to the calculation results in Step 4, so that its P-Δ curve satisfies the similarity theory with the non-linear soil spring load-displacement curve specified in the design code.

[0066] Step 6: Assembly of the cross-section module 1. The zero-stiffness composite spring 6 is installed on the spring fixing threaded hole 9 of the cross-section frame 7 through the spring fixing threaded rod 13; the contact plate 16 is installed on the bottom threaded rod 15 through the contact plate connecting screw rod 17.

[0067] Step 7: Installation of the cross-section module group 5. The double-headed threaded rod passes through the base fixing hole 8 and the base fixing groove 24, and the cross-section module 1 is fixed on the base track 4 one by one according to the unit length of the model. According to the soil distribution situation in the longitudinal direction of the circular tunnel, three cross-section module groups 5 need to be arranged in sequence.

[0068] Step 8: Installation of the test piece 2. First, adjust the feed amounts of the spring fixing screw rod 13 and the bottom screw rod 15 so that the side length of the square area enclosed by the four zero-stiffness composite springs 6 in the cross-section module 1 is slightly larger than the outer diameter of the test piece 2. Then, pass the test piece 2 through each cross-section module group 5. The double-headed threaded rod passes through the base fixing hole 8 and the base fixing groove 24 to install the end fixing frame 3 on the base track 4. Finally, finely adjust the feed amounts of the spring fixing screw rod 13 and the bottom screw rod 15 so that the contact plate 16 of the zero-stiffness composite spring 6 contacts the test piece 2. Except for the zero-stiffness composite spring 6 at the bottom, the contact axial force of the other zero-stiffness composite springs 6 is zero.

[0069] Step 9: Sensor debugging. Connect the displacement-axial force sensor 18 and the strain gauges to the data acquisition instrument, perform communication debugging, and complete zeroing and calibration.

[0070] Step 10: Loading and testing. Use the shaker to excite the structural model 19. Change the excitation position and excitation frequency, and repeat the excitation of the structural model 19.

[0071] Step 11: Data acquisition and analysis. Record the displacement-axial force data, strain data of the zero-stiffness composite spring 6 and the excitation force data in the shaker through the data acquisition instrument; analyze the recorded test data, including the frequency and mode of the structural model 19. Preferably, the strain data analysis method adopts the method recommended by the literature (Trim A D, Braaten H, Lie H, et al. Experimental investigation of vortex-induced vibration of long marinerisers[J]. Journal of Fluids&Structures, 2005, 21(3):335-361).

[0072] Step 12: Disassembly and storage of the device. After the test, disassemble the end fixing frame 3, the test piece 2, the cross-section module group 5, the cross-section module 1, the zero-stiffness composite spring 6 and the base track 4 in sequence, and then organize and store them.

[0073] The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. An equivalent simulation device for non-uniform soil reaction forces of a buried tubular structure, comprising a cross-section module group (5) composed of multiple cross-section modules (1), a test piece (2), a fixing frame, and a base track (4), wherein: The zero-stiffness composite spring (6) includes a metal helical spring (10), rubber (11), a spring top cover (12), a spring fixing screw rod (13), a spring bottom cover (14), a bottom screw rod (15), a contact plate (16), and a displacement-axial force sensor (18); the metal helical spring (10) is embedded in the rubber (11); the top of the rubber (11) is connected to the spring top cover (12), and the bottom is connected to the spring bottom cover (14), and a displacement-axial force sensor (18) is arranged axially along the zero-stiffness composite spring (6); the spring top cover (12) of the zero-stiffness composite spring (6) is connected to the inner side of the cross-section frame (7) through the spring fixing screw rod (13); the contact plate (16) is connected to the spring bottom cover (14) through the bottom screw rod (15); The cross-section module (1) described above includes a zero-stiffness composite spring (6) and a cross-section frame (7); the cross-section frame (7) is fixedly connected to the base track (4); the zero-stiffness composite springs (6) are distributed inside the cross-section frame (7) and fixedly connected to the cross-section frame (7); The cross-section module group (5) composed of multiple cross-section modules (1) is used to simulate areas with the same soil properties; when non-uniform soil is distributed in the structural length direction, different cross-section module groups (5) are set to simulate non-uniform soil reaction forces; The test piece (2) includes at least one structural model (19), and each structural model (19) is axially connected to form the test piece (2), and the test piece (2) is fixed on the base track (4) through a fixing frame.

2. The equivalent simulation device for non-uniform soil reaction forces of the buried tubular structure according to claim 1, characterized in that, According to the size of the test piece, by adjusting the feeding amounts of the spring fixing screw rod (13) and the bottom screw rod (15), the size of the area surrounded by the zero-stiffness composite spring (6) of the cross-section module (1) is changed.

3. The equivalent simulation device for non-uniform soil reaction force of the buried tubular structure according to claim 1, characterized in that The cross-section frame (7) is a rounded square cross-section, and four zero-stiffness composite springs (6) are evenly distributed inside one cross-section frame (7).

4. The equivalent simulation device for non-uniform soil reaction forces of the buried tubular structure according to claim 1, wherein, The base track (4) described above includes a square-base base (23) and a base fixing groove (24); the base fixing groove (24) is located on both sides of the square-base base (23) and can pass through a double-headed screw rod for connecting the fixing frame and the cross-section module (1).

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