Experimental system and method for a reinforced concrete structure in the ground under the action of seismic waves

Abstract

This invention belongs to the field of seismic testing technology for underground structures, and discloses an experimental system and method for testing underground reinforced concrete structures under seismic wave action. The system includes a model mounting platform, a model box, a reaction steel frame, a loading and vibration system, and a control system. The model mounting platform includes a fixed base plate and bidirectional intersecting sliding tracks mounted on the fixed base plate. The model box is fixedly mounted on the bidirectional intersecting sliding tracks. The reaction steel frame includes a horizontal reaction frame and a vertical reaction frame, used to mount a horizontal high-frequency servo hydraulic cylinder and a vertical ground stress loading hydraulic cylinder, which act on the model box. A reinforced concrete model is fixedly placed inside the model box and filled with soil. Monitoring elements are installed in both the reinforced concrete model and the soil. The advantages of this invention are: it simultaneously simulates the three-dimensional dynamic response of underground structures under real stress conditions combined with seismic waves; and it accurately reflects the coupling effects of soil-structure and ground stress-seismic action.

Description

Technical Field

[0001] This invention belongs to the field of seismic testing technology for underground structures, specifically relating to an experimental system and method for testing underground reinforced concrete structures under seismic wave action. Background Technology

[0002] Underground shaking table testing systems have been widely used in experimental research on the seismic characteristics of underground structures. Many technologies exist for underground shaking table systems and methods. Invention patent (CN202310024449.0) describes a vertical force application device and method for shaking table tests of foundations and underground structures, which solves the problem of difficulty in applying vertical stress by tensioning prestressed steel strands at the bottom. Invention patent (CN202010797952.6) describes a boundary loading device for geomechanical model tests of underground tunnel shaking tables, which designs an airbag loading system to simulate the vertical and lateral ground stresses experienced in underground tunnels. Invention patent (CN201210564730.5) describes a device for simulating surface wave action in shaking table tests of underground structures, which can simulate seismic surface waves by transmitting the seismic wave field to the model box through a panel with a rigid cone.

[0003] Underground structures (such as underground shopping malls, underground frame structures, large basements, and tunnel joint structures) are simultaneously subjected to three-dimensional geostress generated by the buried strata and dynamic disturbances caused by seismic waves in actual service environments. The stress on underground structures under seismic loading is significantly different from that on above-ground structures, and their dynamic response is influenced by multiple factors, including soil constraint effect, lateral pressure of surrounding rock, and vertical self-weight pressure.

[0004] Currently, shaking table tests are used in seismic research on underground structures, but they still have the following key shortcomings: Existing research focuses mainly on the seismic dynamic input itself. For example, the system disclosed in invention patent CN119756750A mainly simulates seismic waveforms of different frequencies and amplitudes through multi-directional actuators. Its technical goal is to improve the control accuracy of the shaking table, especially the error suppression under the coupling effect of liquid sloshing. However, such shaking tables cannot apply the actual three-dimensional static geostress field that exists underground, and cannot simulate the real constraint of soil on the structure under burial depth conditions, making it difficult for the test results to reflect the actual engineering situation. The dynamic response of underground structures strongly depends on soil constraints and soil-structure interaction. Existing shaking table tests usually use steel model boxes or rigid support boxes, lacking the filling of real soil or similar materials, and cannot reflect the burial state of underground structures. The "earthquake experience platform" in invention patent CN113823165A is a public experience device that realizes the vibration that people can perceive through simple longitudinal push rods and transverse sliding rails. It does not involve scientific research elements such as soil, confining pressure, geostress, and monitoring, and does not belong to the same technical field as underground engineering structure experiments.

[0005] When underground structures are subjected to seismic waves, they often exhibit multi-directional coupled displacement. However, most existing shaking tables use rigid base plate loading methods, resulting in a relatively fixed structural model, making it difficult to achieve a realistic horizontal bidirectional motion mode. The lack of a bidirectional sliding rail mechanism means that the lateral cylinders may interact directly with the model box during the experiment, generating unexpected additional forces and affecting the accuracy of the experiment.

[0006] Earthquakes are natural phenomena caused by the fracturing and displacement of deep rock strata, triggering the release of seismic waves in all directions. The fundamental cause of rock strata fracturing and displacement is the large amount of energy accumulated within the strata exceeding their maximum strength. Earthquakes have a significant impact on underground tunnels and building structures, and seismic design concepts have been gradually introduced into engineering projects to reduce the damage to structures and the threat to life and property caused by seismic waves through vibration reduction technologies. Under these circumstances and construction conditions, it is not only necessary to consider the damage to underground foundations and tunnel structures under the action of seismic wave fields, but vibration testing and simulation of underground reinforced concrete structures are also crucial for the stability of underground structures.

[0007] Existing technologies primarily focus on improving and enhancing vibration simulation methods for foundation engineering and tunnel / subway structures. Currently, seismic wave simulation systems are relatively small in size and cannot measure the seismic resistance characteristics of underground structures at the overall level. The selected simulation geometry is generally large, leading to significant differences in accuracy. Research on large-geometry underground structures, especially reinforced concrete structures, is relatively limited. Therefore, improving the seismic performance of underground reinforced concrete models is crucial for perfecting the safety system of the entire underground structure, particularly for the personal and property safety of large-scale projects.

[0008] In summary, current technologies are unable to construct an underground structure vibration test system capable of simultaneously applying three-dimensional geostress and triaxial seismic waves, nor can they accurately reflect the interaction between the underground structure and the soil. Therefore, a completely new experimental system and method are urgently needed. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of the prior art by providing an experimental system and method for testing underground reinforced concrete structures under seismic wave action. This experimental system and method simulates the three-dimensional dynamic response of underground structures under real stress and seismic wave action by installing a model box on a bidirectional cross sliding track and using a loading and vibration system, thereby accurately reflecting the coupling effect of soil-structure and soil stress-seismic action.

[0010] The objective of this invention is achieved through the following technical solutions: An experimental system for testing underground reinforced concrete structures under seismic wave action includes a model mounting platform, a model box, a reaction steel frame, a loading and vibration system, and a control system; wherein: The model mounting platform includes a fixed base plate and a bidirectional cross sliding track mounted on the fixed base plate; the model box is fixedly mounted on the bidirectional cross sliding track. The reaction steel frame includes a vertical reaction frame and a horizontal reaction frame. The bottom end of the vertical reaction frame is fixed to the fixed base plate and distributed on the outer side of the four side walls of the model box. The horizontal reaction frame is supported and fixed above the top surface of the model box. The loading and vibration system includes a Z-axis high-frequency servo cylinder, an X-axis high-frequency servo cylinder, a Y-axis high-frequency servo cylinder, and a vertical ground stress loading cylinder. Several Z-axis high-frequency servo cylinders are positioned below the fixed base plate and provide support. One end of each X-axis high-frequency servo cylinder is fixed to the vertical reaction frame, and the other end supports the side wall of the model box perpendicular to the X-axis. One end of each Y-axis high-frequency servo cylinder is fixed to the vertical reaction frame, and the other end supports the side wall of the model box perpendicular to the Y-axis. The upper end of each vertical ground stress loading cylinder is fixed to the horizontal reaction frame, and the lower end supports the top surface of the model box. The model box contains a reinforced concrete model and is filled with soil. Monitoring elements are installed in the reinforced concrete model and the soil.

[0011] The bidirectional cross sliding track includes several first rails arranged along the X direction, several second rails arranged along the Y direction, and several sliders that slide between the two. The first rails are fixedly installed on the fixed base plate, and the second rails are located above the first rails. A slider is provided at each intersection of the first rails and the second rails to achieve a sliding connection. The bottom surface of the slider has an X-direction groove and the top surface has a Y-direction groove. The X-direction groove is slidably fitted onto the first rail, and the Y-direction groove is slidably fitted onto the second rail.

[0012] The Z-axis high-frequency servo cylinders are in four groups and support the four corners of the fixed base plate respectively. The bottom of each group of Z-axis high-frequency servo cylinders is fixedly supported on a base plate.

[0013] The vertical reaction frame includes two sets of first portal-shaped reaction frames arranged along the X direction and two sets of second portal-shaped reaction frames arranged along the Y direction. The supports of the first portal-shaped reaction frames are located on the outer sides of the two side walls of the model box perpendicular to the X direction, and the supports of the second portal-shaped reaction frames are located on the outer sides of the two side walls of the model box perpendicular to the Y direction.

[0014] There are two sets of horizontal reaction frames. The horizontal reaction frames are of portal frame structure, including a horizontal I-beam and two support columns. The bottom end of the support column is fixed to the top surface of the model box, and the top end of the support column is fixed to the end of the horizontal I-beam. Two vertical stress loading cylinders are installed on the horizontal I-beam.

[0015] The monitoring elements are earth pressure cells, strain gauges, stress bricks, and accelerometers.

[0016] The top of the model box has a loading port, and the side wall of the model box has an openable personnel entrance door.

[0017] An experimental method relating to an experimental system for testing any of the aforementioned underground reinforced concrete structures under seismic wave action includes the following steps: S1: Determine the dimensions of the reinforced concrete model and the magnitude of the ground stress at the simulated burial depth based on the experimental objective; S2: Fix the reinforced concrete model in the bottom slot inside the model box, and install monitoring elements on the reinforced concrete model; S3: Fill the model box with soil material similar to the simulated burial depth and compact it with vibration; S4: The X-axis high-frequency servo cylinder, Y-axis high-frequency servo cylinder, and vertical ground stress loading cylinder are controlled by the control system to extend to fit the surface of the model box. S5: Set lateral and vertical ground stress parameters in the control system. The required lateral ground stress parameters are equivalently converted into the forces applied by the X-axis and Y-axis high-frequency servo cylinders to the side wall of the model box; the required vertical ground stress parameters are equivalently converted into the forces applied by the vertical ground stress loading cylinder to the top surface of the model box; after the forces applied to the model box are completed, wait 1-2 hours to allow the simulated ground stress inside the model box to stabilize; the calculation formula for the equivalent conversion is as follows: ; ; In the formula: F h,j The force exerted by the X-axis high-frequency servo cylinder or the Y-axis high-frequency servo cylinder assigned to the j-th horizontal position on the side wall of the model box, in units of kN ; n The number of high-frequency servo cylinders corresponding to a single side wall of the model box is dimensionless. θ is the internal friction angle of the soil, in degrees. γThe unit weight of soil is 1. kN / m³ ; H The height of the side wall of the model box, in units of m ; B The width of the side wall of the model box is given in units of 1. m ; F v,j To be allocated to the j The vertical force applied to the top surface of the model box by each vertical stress loading cylinder, in units of... kN ; z The depth of the top surface of the model box is given by the unit . m ; A t The area of ​​the top surface of the model box subjected to force is given in units of . m² ; n v The number of vertical stress loading cylinders corresponding to the top surface of the model box, dimensionless; S6: The required vibration frequency of each high-frequency servo cylinder is set through the control system to obtain the original input signal of the seismic wave. r(t) For the original input signal of the seismic wave r(t) The input is shaped to obtain the original shaped acceleration signal. a 0 ( t The calculation formula is as follows:

[0018] In the formula: a 0 ( t The signal is the original acceleration signal after input shaping, in m / s². r(t) This represents the original input signal of the seismic wave, expressed in m / s². ζ The damping ratio has a value range of 0-1 and is dimensionless. t The variable is time, and the unit is seconds (s). t 1 The first time constant represents the first delay time of the seismic wave input signal. t 1 =0, unit is s; t 2The second time constant represents the second delay time of the seismic wave input signal. t 2 = π / ω d The unit is seconds (s). ω d For damped vibration frequency, The unit is rad / s; ω n The pre-identified natural vibration frequency, expressed in rad / s; S7: The control system inputs the original acceleration signal from the shaped seismic wave input signal. a 0 ( t Baseline correction processing is performed, and the corrected acceleration signal is expressed as follows: a ( t The calculation formula is: a ( t )= a 0 ( t )-( c 0 + c 1 t + c 2 t 2 ); In the formula: a 0 ( t () represents the original acceleration signal, in m / s². a ( t () represents the corrected acceleration signal, in m / s². c 0 The constant term coefficient of the baseline correction formula is the constant baseline offset of the acceleration, in m / s². c 1 The coefficient of the first term in the baseline correction formula is the linear baseline drift of the acceleration, expressed in m / s³. c 2 The coefficients of the quadratic term in the baseline correction formula represent the quadratic baseline drift of acceleration, in m / s². 4 ; S8: Vibration is applied to the model box based on the shaped seismic wave input signal, and data is collected in real time through the monitoring element.

[0019] The advantages of this invention are: it simultaneously simulates the three-dimensional dynamic response of in-situ stress and seismic waves in the real stress environment of underground structures; it accurately reflects the coupling effect of soil-structure and in-situ stress-seismic action; it conducts high-fidelity dynamic response tests on large reinforced concrete structure models; the vibration loading path is clear, highly controllable, and the test stability is significantly improved; the soil filling and monitoring system is complete, enabling the study of structural performance under complex working conditions; and it can provide reliable data support for the seismic design of underground structures. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the experimental system for underground reinforced concrete structures under seismic wave action in this invention; Figure 2 This is a schematic diagram of the structure of the model box and the model mounting platform in this invention; Figure 3 This is a schematic diagram of the model mounting platform and the Z-axis high-frequency servo cylinder in this invention; Figure 4 This is a schematic diagram of the X-axis high-frequency servo cylinder in this invention; Figure 5 This is a top view of the interior of the model box in this invention; The markings in the diagram are as follows: Model box 1, Fixed base plate 2, Bidirectional cross sliding track 3, Second rail 3a, Slider 3b, First rail 3c, Z-axis high-frequency servo cylinder 4, Foundation base plate 5, Second portal type reaction frame 6, First portal type reaction frame 7, Horizontal reaction frame 8, X-axis high-frequency servo cylinder 9, Y-axis high-frequency servo cylinder 10, Vertical ground stress loading cylinder 11, Loading port 12, Personnel entrance sealing door 13, Bottom slot 14. Detailed Implementation

[0021] The features and other related features of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so as to facilitate understanding by those skilled in the art: Example: Figure 1 , 2 As shown in Figures 3, 4, and 5, this embodiment specifically relates to an experimental system for an underground reinforced concrete structure under the action of seismic waves. The experimental system includes a model mounting platform, a model box 1, a reaction steel frame, a loading and vibration system, and a control system (not shown in the figure).

[0022] like Figure 1 , 2As shown in Figure 3, the model mounting platform includes a fixed base plate 2 and a bidirectional cross sliding track 3 mounted on the fixed base plate 2. The fixed base plate 2 is a rectangular thick steel plate, supported by four sets of Z-axis high-frequency servo cylinders 4. The bidirectional cross sliding track 3 includes multiple first rails 3c arranged along the X-axis, multiple second rails 3a arranged along the Y-axis, and sliders 3b located at their intersections. The first rails 3c are fixed to the fixed base plate 2 by bolts, and are parallel to each other and equally spaced; the second rails 3a are located above the first rails 3c, are also parallel to each other and equally spaced, and intersect the first rails 3c perpendicularly. A slider 3b is provided at each intersection point. The bottom surface of the slider 3b has an X-axis groove that mates with the first rail 3c, and the top surface has a Y-axis groove that mates with the second rail 3a, thereby realizing a bidirectional sliding connection between the first rails 3c and the second rails 3a. The model box 1 is fixedly installed on the uppermost second steel rail 3a, and can slide freely in the horizontal plane along the X and Y directions with the bidirectional cross sliding track 3.

[0023] like Figure 1 , 2 As shown in Figure 5, the model box 1 is a rigid steel box with space to accommodate soil and reinforced concrete models, measuring 2m x 2m x 2m. The top of the model box 1 has a loading port 12 for filling with soil (soil or simulated rock strata); the side walls have openable personnel entrance doors 13 for personnel to enter the box to install monitoring components and inspect the model. The bottom of the box has a bottom slot 14 for securing the reinforced concrete model. The outer sides of the four side walls of the model box 1 contact the piston rod ends of the X-axis high-frequency servo cylinder 9 and the Y-axis high-frequency servo cylinder 10, respectively, while the top surface of the model box 1 contacts the lower end of the vertical ground stress loading cylinder 11. In non-experimental conditions, except for the bottom Z-axis high-frequency servo cylinder 4 which needs to support the upper model mounting platform, the other cylinders can be retracted, i.e., they do not contact the model box 1.

[0024] like Figure 1 As shown, the reaction frame includes a vertical reaction frame and a horizontal reaction frame 8. The vertical reaction frame consists of two sets of first portal frame 7 and two sets of second portal frame 6. The first portal frame 7 is arranged along the X-direction, with its two supports located on the outer sides of the two side walls of the model box 1 perpendicular to the X-direction, and its bottom end fixed to the fixed base plate 2. The second portal frame 6 is arranged along the Y-direction, with its two supports located on the outer sides of the two side walls of the model box 1 perpendicular to the Y-direction, and its bottom end also fixed to the fixed base plate 2. The horizontal reaction frame 8 consists of two sets of portal frames, each set including a horizontal I-beam and two supports. The bottom end of the supports is fixed to the top surface of the model box 1, and the top end is fixedly connected to both ends of the horizontal I-beam. Two vertical stress loading cylinders 11 are installed on the horizontal I-beam.

[0025] like Figure 1 , 2As shown in Figures 3, 4, and 5, the loading and vibration system is used to achieve ground stress loading and three-phase servo vibration. This system includes a Z-axis high-frequency servo cylinder 4, an X-axis high-frequency servo cylinder 9, a Y-axis high-frequency servo cylinder 10, and a vertical ground stress loading cylinder 11. There are four sets of Z-axis high-frequency servo cylinders 4, each supported below one of the four corners of the fixed base plate 2, with their bottom ends fixed to the foundation base plate 5. They are used to apply high-frequency vibration in the vertical direction (Z-axis) to simulate the vertical component of seismic waves. One end of the X-axis high-frequency servo cylinder 9 is fixed to the support column of the first portal frame 7, and the other end (piston rod end) is supported on the side wall of the model box 1 perpendicular to the X-axis, used to apply horizontal high-frequency vibration in the X-axis direction. One end of the Y-axis high-frequency servo cylinder 10 is fixed to the support column of the second portal frame 6, and the other end is supported on the side wall of the model box 1 perpendicular to the Y-axis, used to apply horizontal high-frequency vibration in the Y-axis direction. The upper end of the vertical stress loading cylinder 11 is fixed to the horizontal I-beam of the horizontal reaction frame 8, and the lower end supports the top surface of the model box 1, used to apply vertical static stress. The effective vibration range of the entire experimental equipment is 0-100mm in three dimensions, and the allowable frequency range is 0-50Hz.

[0026] The control system (not shown) in this embodiment is connected to each high-frequency servo cylinder and the vertical ground stress loading cylinder 11 in the loading and vibration system. It controls the output force, frequency, and waveform of the cylinders to achieve static loading of three-dimensional ground stress and dynamic loading of seismic waves. The control system has a built-in signal processing module that can perform baseline correction and input shaping on the original seismic wave input signal to ensure loading accuracy. The control system uses a PLC desktop computer, and the machine is controlled by a frequency converter. The operating interface can be switched between Chinese and English display and includes vibration waveform encoding program, frequency selection function, vibration energy display function, vibration monitoring record, curve plotting, safety self-check early warning response, allowable adjustment range, ground stress setting options, number of servo cylinders used, help manual, and pre-vibration audible and visual alarms.

[0027] like Figure 1 , 2 As shown in Figures 3, 4, and 5, the experimental method of the experimental system for underground reinforced concrete structures under seismic wave action in this embodiment includes the following steps: S1: Determine the dimensions of the reinforced concrete model and the magnitude of the ground stress at the simulated burial depth based on the experimental objectives.

[0028] S2: Fix the reinforced concrete model to the bottom slot 14 inside model box 1. Install monitoring elements on the reinforced concrete model. After installing the required monitoring elements, lead out the element connection wires through the pre-drilled holes and connect them to the monitoring equipment. The monitoring elements include earth pressure cells, strain gauges, stress blocks, and accelerometers (not shown in the figure) embedded in the soil and reinforced concrete model. They are used to collect real-time data on earth pressure, structural strain, stress, and acceleration response of the model during the test. Earth pressure cells are embedded at different fill locations according to the required monitoring depth to monitor stress changes at different locations inside model box 1 during vibration simulation. Strain gauges are pasted onto the reinforcing bars inside the reinforced concrete model. Their positions are arranged in advance before pouring, and wiring ports are reserved for easy connection to the strain acquisition instrument after installation. Stress blocks are a combination of strain gauges and small concrete blocks that can be embedded in the reinforced concrete model to prevent damage to the strain gauges. Accelerometers are pasted onto insulating blocks and installed in the parts of the reinforced concrete model with high rigidity to prevent local vibration from affecting the test results.

[0029] S3: Fill the model box 1 with soil material similar to the simulated burial depth through the loading port 12 and vibrate to compact it; close the personnel entrance sealing door 13, and vibrate to compact the filled soil material by slightly shaking it through the loading and vibration system. Continue to fill the soil material and vibrate, repeating 3-5 times until the model box 1 is filled with soil material, and close the top loading port 12.

[0030] S4: The X-axis high-frequency servo cylinder 9, Y-axis high-frequency servo cylinder 10, and vertical ground stress loading cylinder 11 are controlled by the control system to extend to fit against the surface of the model box 1. Then, the displacement balance in each vibration direction is reset to zero in the control system operation interface.

[0031] S5: Set the lateral and vertical ground stress parameters in the control system. The required lateral ground stress parameters are equivalently converted into the forces applied to the side wall of the model box 1 by the X-direction high-frequency servo cylinder 9 and the Y-direction high-frequency servo cylinder 10. The required vertical ground stress parameters are equivalently converted into the forces applied to the top surface of the model box 1 by the vertical ground stress loading cylinder 11. After the forces applied to the model box 1 are completed, wait 1-2 hours to allow the simulated ground stress inside the model box 1 to stabilize. The calculation formula for the equivalent conversion is as follows: ; ; In the formula: F h,j The force exerted on the side wall of the model box by the X-axis high-frequency servo cylinder 9 or Y-axis high-frequency servo cylinder 10, which is assigned to the j-th horizontal position, is expressed in units of... kN ; nThe number of high-frequency servo cylinders corresponding to a single side wall of model box 1 is dimensionless. θ is the internal friction angle of the soil, in degrees. γ The unit weight of soil is 1. kN / m³ ; H The height of the side wall of model box 1, in units of m ; B The width of the side wall of model box 1, in units of m ; F v,j To be allocated to the j The vertical force exerted by each vertical stress loading cylinder 11 on the top surface of the model box 1, in units of... kN ; z The depth of the top surface of model box 1, in units of m ; A t The area of ​​the top surface of model box 1 under stress is given by the force-bearing surface, in units of 1. m² ; n v The number of vertical stress loading cylinders 11 corresponding to the top surface of model box 1 is dimensionless.

[0032] S6: Obtain the original input signal of seismic waves by setting the required vibration frequency of each high-frequency servo cylinder through the control system. r(t) For the original input signal of seismic waves r(t) The input is shaped to obtain the original shaped acceleration signal. a 0 ( t The calculation formula is as follows:

[0033] In the formula: a 0 ( t The signal is the original acceleration signal after input shaping, in m / s². r(t) This represents the original input signal of the seismic wave, expressed in m / s². ζ The damping ratio has a value range of 0-1 and is dimensionless. t The variable is time, and the unit is seconds (s). t 1The first time constant represents the first delay time of the seismic wave input signal. t 1 =0, unit is s; t 2 The second time constant represents the second delay time of the seismic wave input signal. t 2 = π / ω d The unit is seconds (s). ω d For damped vibration frequency, The unit is rad / s; ω n The pre-identified natural vibration frequency is expressed in rad / s.

[0034] S7: The control system will reshape the original acceleration signal. a 0 ( t Baseline correction processing is performed, and the corrected acceleration signal is expressed as follows: a ( t The calculation formula is: a ( t )= a 0 ( t )-( c 0 + c 1 t + c 2 t 2 ); In the formula: a 0 ( t () represents the original acceleration signal, in m / s². a ( t () represents the corrected acceleration signal, in m / s². c 0 The constant term coefficient of the baseline correction formula is the constant baseline offset of the acceleration, in m / s². c 1 The coefficient of the first term in the baseline correction formula is the linear baseline drift of the acceleration, expressed in m / s³. c 2The coefficients of the quadratic term in the baseline correction formula represent the quadratic baseline drift of acceleration, in m / s². 4 ; coefficient c 0 , c 1 , c 2 The velocity and displacement after integration can be made to satisfy the boundary conditions by using least squares.

[0035] S8: Vibration is applied to model box 1 based on the shaped seismic wave input signal, and data is acquired in real time through monitoring elements. After vibration is completed, the data is automatically extracted and saved, and the monitoring results are checked to determine whether cyclic vibration is needed. The control system then transmits the obtained corrected acceleration signal... a ( t The data is sent to each high-frequency servo cylinder, and each high-frequency servo cylinder applies vibration loading to the model box 1 according to the corrected acceleration signal. During the vibration process, the model response is collected in real time by monitoring elements arranged inside the model box 1 and at the test site. The monitoring data includes one or more of acceleration, displacement, strain and pressure. After a single vibration is completed, the data acquisition system automatically extracts and saves the monitoring data, and determines whether to perform cyclic vibration based on whether the monitoring results reach the preset response threshold or the preset number of cycles.

[0036] S9: If cyclic vibration is required, the cyclic vibration time interval and number of cycles can be set in the operation interface. Different waveforms can be programmed into the software for each cycle to meet the experimental needs. The experiment ends when the cycle stops.

[0037] S10: Retract the servo cylinder to disengage from the model box 1, shut down the operating system, open the personnel entrance sealing door 13, clean the inside of the model box 1, and tidy it up.

[0038] The beneficial effects of this embodiment are as follows: it simultaneously simulates the three-dimensional dynamic response of geostress and seismic waves in the real stress environment of underground structures; it accurately reflects the coupling effect of soil-structure and geostress-seismic action; it conducts high-fidelity dynamic response tests on large reinforced concrete structure models; the vibration loading path is clear, highly controllable, and the test stability is significantly improved; the soil filling and monitoring system is complete, enabling the study of structural performance under complex working conditions; and it can provide reliable data support for the seismic design of underground structures.

Claims

1. An experimental system for testing underground reinforced concrete structures under seismic wave action, characterized in that... The experimental system includes a model mounting platform, a model box, a reaction steel frame, a loading and vibration system, and a control system; wherein: The model mounting platform includes a fixed base plate and a bidirectional cross sliding track mounted on the fixed base plate; the model box is fixedly mounted on the bidirectional cross sliding track. The reaction steel frame includes a vertical reaction frame and a horizontal reaction frame. The bottom end of the vertical reaction frame is fixed to the fixed base plate and distributed on the outer side of the four side walls of the model box. The horizontal reaction frame is supported and fixed above the top surface of the model box. The loading and vibration system includes a Z-axis high-frequency servo cylinder, an X-axis high-frequency servo cylinder, a Y-axis high-frequency servo cylinder, and a vertical ground stress loading cylinder. Several Z-axis high-frequency servo cylinders are positioned below the fixed base plate and provide support. One end of each X-axis high-frequency servo cylinder is fixed to the vertical reaction frame, and the other end supports the side wall of the model box perpendicular to the X-axis. One end of each Y-axis high-frequency servo cylinder is fixed to the vertical reaction frame, and the other end supports the side wall of the model box perpendicular to the Y-axis. The upper end of each vertical ground stress loading cylinder is fixed to the horizontal reaction frame, and the lower end supports the top surface of the model box. The model box contains a reinforced concrete model and is filled with soil. Monitoring elements are installed in the reinforced concrete model and the soil.

2. The experimental system for an underground reinforced concrete structure under seismic wave action according to claim 1, characterized in that... The bidirectional cross sliding track includes several first rails arranged along the X direction, several second rails arranged along the Y direction, and several sliders that slide between the two. The first rails are fixedly installed on the fixed base plate, and the second rails are located above the first rails. A slider is provided at each intersection of the first rails and the second rails to achieve a sliding connection. The bottom surface of the slider has an X-direction groove and the top surface has a Y-direction groove. The X-direction groove is slidably fitted onto the first rail, and the Y-direction groove is slidably fitted onto the second rail.

3. The experimental system for an underground reinforced concrete structure under seismic wave action according to claim 1, characterized in that... The Z-axis high-frequency servo cylinders are in four groups and support the four corners of the fixed base plate respectively. The bottom of each group of Z-axis high-frequency servo cylinders is fixedly supported on a base plate.

4. The experimental system for underground reinforced concrete structures under seismic wave action according to claim 1, characterized in that... The vertical reaction frame includes two sets of first portal-shaped reaction frames arranged along the X direction and two sets of second portal-shaped reaction frames arranged along the Y direction. The supports of the first portal-shaped reaction frames are located on the outer sides of the two side walls of the model box perpendicular to the X direction, and the supports of the second portal-shaped reaction frames are located on the outer sides of the two side walls of the model box perpendicular to the Y direction.

5. The experimental system for underground reinforced concrete structures under seismic wave action according to claim 1, characterized in that... There are two sets of horizontal reaction frames. The horizontal reaction frames are of portal frame structure, including a horizontal I-beam and two support columns. The bottom end of the support column is fixed to the top surface of the model box, and the top end of the support column is fixed to the end of the horizontal I-beam. Two vertical stress loading cylinders are installed on the horizontal I-beam.

6. The experimental system for an underground reinforced concrete structure under seismic wave action according to claim 1, characterized in that... The monitoring elements are earth pressure cells, strain gauges, stress bricks, and accelerometers.

7. The experimental system for an underground reinforced concrete structure under seismic wave action according to claim 1, characterized in that... The top of the model box has a loading port, and the side wall of the model box has an openable personnel entrance door.

8. An experimental method relating to the experimental system of any one of claims 1-7 for testing underground reinforced concrete structures under seismic wave action, characterized in that... The experimental method includes the following steps: S1: Determine the dimensions of the reinforced concrete model and the magnitude of the ground stress at the simulated burial depth based on the experimental objective; S2: Fix the reinforced concrete model in the bottom slot inside the model box, and install monitoring elements on the reinforced concrete model; S3: Fill the model box with soil material similar to the simulated burial depth and compact it with vibration; S4: The X-axis high-frequency servo cylinder, Y-axis high-frequency servo cylinder, and vertical ground stress loading cylinder are controlled by the control system to extend to fit the surface of the model box. S5: Set lateral and vertical ground stress parameters in the control system. The required lateral ground stress parameters are equivalently converted into the forces applied by the X-axis and Y-axis high-frequency servo cylinders to the side wall of the model box; the required vertical ground stress parameters are equivalently converted into the forces applied by the vertical ground stress loading cylinder to the top surface of the model box; after the forces applied to the model box are completed, wait 1-2 hours to allow the simulated ground stress inside the model box to stabilize; the calculation formula for the equivalent conversion is as follows: ； ； In the formula: F h,j The force exerted by the X-axis high-frequency servo cylinder or the Y-axis high-frequency servo cylinder assigned to the j-th horizontal position on the side wall of the model box, in units of kN ; n The number of high-frequency servo cylinders corresponding to a single side wall of the model box is dimensionless. θ is the internal friction angle of the soil, in degrees. γ The unit weight of soil is 1. kN / m³ ; H The height of the side wall of the model box, in units of m ; B The width of the side wall of the model box is given in units of 1. m ; F v,j To be allocated to the j The vertical force applied to the top surface of the model box by each vertical stress loading cylinder, in units of... kN ; z The depth of the top surface of the model box is given by the unit . m ; A t The area of ​​the top surface of the model box subjected to force is given in units of . m² ; n v The number of vertical stress loading cylinders corresponding to the top surface of the model box, dimensionless; S6: The required vibration frequency of each high-frequency servo cylinder is set through the control system to obtain the original input signal of the seismic wave. r(t) For the original input signal of the seismic wave r(t) The input is shaped to obtain the original shaped acceleration signal. a 0 ( t The calculation formula is as follows: In the formula: a 0 ( t The signal is the original acceleration signal after input shaping, in m / s². r(t) This represents the original input signal of the seismic wave, expressed in m / s². ζ The damping ratio has a value range of 0-1 and is dimensionless. t The variable is time, and the unit is seconds (s). t 1 The first time constant represents the first delay time of the seismic wave input signal. t 1 =0, unit is s; t 2 The second time constant represents the second delay time of the seismic wave input signal. t 2 = π / ω d The unit is seconds (s). ω d For damped vibration frequency, The unit is rad / s; ω n The pre-identified natural vibration frequency, expressed in rad / s; S7: The control system inputs the original acceleration signal from the shaped seismic wave input signal. a 0 ( t Baseline correction processing is performed, and the corrected acceleration signal is expressed as follows: a ( t The calculation formula is: a ( t )= a 0 ( t )-( c 0 + c 1 t + c 2 t 2 )； In the formula: a 0 ( t () represents the original acceleration signal, in m / s². a ( t () represents the corrected acceleration signal, in m / s². c 0 The constant term coefficient of the baseline correction formula is the constant baseline offset of the acceleration, in m / s². c 1 The coefficient of the first term in the baseline correction formula is the linear baseline drift of the acceleration, expressed in m / s³. c 2 The coefficients of the quadratic term in the baseline correction formula represent the quadratic baseline drift of acceleration, in m / s². 4 ; S8: Vibration is applied to the model box based on the shaped seismic wave input signal, and data is collected in real time through the monitoring element.

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