CN117233837A - Experimental method for earthquake fault simulation based on geotechnical centrifuge platform - Google Patents

Abstract

The invention provides an experimental method for earthquake fault simulation based on a geotechnical centrifuge platform, and relates to the technical field of earthquake disaster simulation. During the experimental process of seismic fault simulation, the method monitors the stress and local deformation of the end of the tunnel, the surface displacement and acceleration and earth pressure of the site covering layer, and the movement amount and action of the horizontal actuating system. dynamics, the surface crack rupture image and the site deformation image. This invention simulates a hypergravity environment through a geotechnical centrifuge platform to truly restore the true stress state of rock and soil, and simultaneously obtains simulated earthquake faults and end stress and local deformation of tunnels in the site covering layer, surface crack rupture images, and site deformation images. As well as the movement amount and force of the horizontal actuator system, it can simulate the entire process of earthquakes caused by the rupture of active faults and the propagation effect of earthquakes in the site, and also realize the simulation experiment of the dynamic response characteristics of engineering structures under the scenario of crossing faults.

Description

Experimental method for earthquake fault simulation based on geotechnical centrifuge platform

Technical field

The invention relates to the technical field of earthquake disaster simulation, and in particular to an experimental method for earthquake fault simulation based on a geotechnical centrifuge platform.

Background technique

In recent years, with the shift in the geographical focus of infrastructure in my country's economic construction, a large number of major projects (such as the Qinghai-Tibet Railway, Sichuan-Tibet Railway, West-East Gas Transmission, etc.) have been deployed and constructed in strong earthquake areas in southwestern my country. However, the active fault structures in southwestern my country are extremely complex and widely distributed, making it impossible for major projects to avoid active fault zones, seriously threatening the construction safety of such projects. There is an urgent need to carry out cutting-edge research on the direction of engineering structures across faults, which is of great scientific value. and engineering application prospects.

Rock and soil materials have typical nonlinear mechanical behavior and are significantly affected by stress states. As the most commonly used and effective research method, physical model testing is widely used in earthquake disaster research. However, conventional physical model tests mostly use scaled models and are carried out in a normal gravity environment, which cannot accurately restore the original stress state of the rock and soil mass, significantly restricting the scientific nature and engineering applicability of the research results. Secondly, in current earthquake disaster research, bottom shaking tables are often used to apply uniform vibrations, and seismic effects are evaluated by observing the dynamic response of the site or engineering structure. This method is suitable for studying working conditions far away from faults, but cannot be used to study the seismic performance of engineering structures across faults. Finally, the key to the seismic safety evaluation of engineering sites or the seismic performance evaluation of engineering structures is to obtain reasonable site ground motions. Although a variety of site earthquake synthesis methods have been proposed internationally based on measured earthquake records, such models cannot fully reflect the possible future earthquake conditions. The root cause is the lack of understanding of earthquake seismogenesis mechanisms and propagation path effects. Physical simulation research will seriously restrict future site earthquake predictions. To sum up, in response to the strategic needs of the country’s western construction, current physical model tests have the following shortcomings when studying earthquake disasters involving cross-faults:

First, scaled tests under conventional gravity cannot reflect the true stress state of rock and soil. The stress level of scaled model tests is significantly lower than the real state, and the mechanical behavior of rock and soil depends on the stress state, thus severely restricting the engineering applicability and scientificity of such research results.

Second, the bottom shaking table vibration test method cannot simulate the scenario of engineering structures crossing faults. At present, model tests mostly apply uniform ground vibrations to the entire model through a bottom shaking table, which cannot simulate the impact of fault dislocation effects on engineering structures when crossing faults.

Third, the synthetic model of site ground motion cannot consider the source mechanism and propagation path effects. Current seismic motion synthetic models are mostly based on the analysis of measured seismic motion records and cannot consider the source mechanism and propagation path effects, resulting in the inability to accurately and comprehensively reflect the future seismic motion occurrence of the site.

Therefore, there is an urgent need to develop a large-scale model test system to accurately restore the true stress state of rock and soil and accurately simulate different fault rupture processes and site propagation effects, thereby providing a scientific basis for the seismic performance evaluation of engineering structures across faults and site seismic motion synthesis.

Contents of the invention

The purpose of the present invention is to provide an experimental method for earthquake fault simulation based on a geotechnical centrifuge platform, which simulates the gravity environment through the geotechnical centrifuge platform, truly restores the true stress state of rock and soil, and simultaneously obtains the simulated earthquake faults and site covering layers. The stress and local deformation at the end of the tunnel, the surface crack rupture image and the site deformation image, as well as the movement amount and force of the horizontal actuator system, thereby simulating the entire process of earthquakes caused by active fault rupture and the occurrence of earthquakes in the site The propagation effect also realizes the simulation experiment of the dynamic response characteristics of engineering structures under the scenario of crossing faults.

In order to achieve the above object, the present invention provides an experimental method for earthquake fault simulation based on a geocentrifuge platform. A model box is provided on the geocentrifuge platform, and there is an accommodation space in the model box. The accommodation space A bottom support system, a simulated earthquake fault and a site covering layer are provided from bottom to top. A horizontal actuating system is provided on the side of the simulated earthquake fault and the site covering layer. A tunnel is provided in the site covering layer. , the tunnel penetrates the site covering layer in the horizontal direction; the method includes the following steps:

Set the action direction and action rate of the horizontal action system, and during the experimental process of earthquake fault simulation, monitor the stress and local deformation of the end of the tunnel, the surface displacement and acceleration of the site covering layer, and Earth pressure, actuating amount and actuating force of the horizontal actuating system;

During the experiment of seismic fault simulation, surface crack rupture images and site deformation images of the simulated seismic fault and site overlay and site deformation images are acquired through a high-speed camera facing the front of the model box;

Based on the end stress and local deformation of the tunnel, determine the deformation characteristics of the tunnel when the earthquake fault dislocates;

Based on the surface displacement, acceleration and earth pressure of the site covering layer, determine the propagation change curve of the vibration induced by the earthquake fault dislocation in the site covering layer;

Based on the actuation amount and force of the horizontal actuation system and in combination with the surface displacement of the site covering layer, adjust the actuation direction and actuation rate of the horizontal actuation system;

Based on the surface crack rupture image and the site deformation image, the site shear zone position and site shear zone shape of the covering layer as well as the tunnel fracture position and crack shape when the earthquake fault is displaced are obtained.

The present invention also provides a storage medium on which a computer program is stored. When the computer program is called by a processor, it causes the processor to execute the above-mentioned experimental method.

In one embodiment, the base support system is used to support the horizontal actuation system, the simulated seismic fault, and the site cover;

The horizontal actuation system is used to apply horizontal thrust to the simulated earthquake fault and the site cover;

The simulated earthquake fault is used to fill fault test blocks to simulate the bedrock layer of the earthquake fault;

The site cover is used to fill the simulated earthquake fault with sand layer material to simulate the soil layer of the earthquake fault.

In one embodiment, the stepper motor in the horizontal actuation system is connected to the motion control box through wires, and the actuation direction and actuation rate of the horizontal actuation system are set and adjusted through the motion control box.

In one embodiment, the tunnel is provided with an accelerometer, a strain gauge, and an earth pressure cell. By monitoring the accelerometer, the strain gauge, and the earth pressure cell, the force and local stress at the end of the tunnel are monitored. Deformation.

In one embodiment, a laser displacement meter is provided on the model box, and the surface displacement of the site covering layer is monitored through the laser displacement meter.

In one embodiment, a stroke limiter is provided on the side of the stepper motor facing the simulated earthquake fault, and a spoke sensor is provided on the horizontal actuating system, and the spoke sensor is close to the stepper motor. A flange is provided on one side. When the flange comes into contact with the stroke limiter, the power supply to the stepper motor is cut off and the horizontal actuating system stops moving.

In one embodiment, the bottom support system is provided with a rigid support, an elastic support, a lift support and a motor support;

The footwall of the fault in the simulated earthquake fault is supported by the rigid bearing, and the hanging wall of the fault in the simulated earthquake fault is supported by the elastic bearing;

The screw lifting device in the horizontal actuation system is supported by the elevator bracket, and the stepper motor in the horizontal actuation system is supported by the motor support;

The heights of the rigid support and the elevator support are adjusted so that the fault footwall in the simulated earthquake fault is highly coordinated with the horizontal actuation system.

Description of drawings

Figure 1 is a schematic diagram of the overall partitioning of the system applied to the earthquake fault simulation method based on the geotechnical centrifuge platform according to the present invention;

Figure 2 is a front view of the overall partition of the system applied to the earthquake fault simulation method based on the geotechnical centrifuge platform according to the present invention;

Figure 3 is an overall front view of each component in the system applied to the seismic fault simulation method based on the geotechnical centrifuge platform according to the present invention;

Figure 4 is a side view of the overall partition of the system applied to the earthquake fault simulation method based on the geocentrifuge platform according to the present invention;

Figure 5 is an overall side view of each component in the system applied to the seismic fault simulation method based on the geotechnical centrifuge platform according to the present invention;

Figure 6 is a schematic diagram of a horizontal actuating system in a system applied according to the method of the present invention;

Figure 7 is the top surface of the model box in a system to which the method of the present invention is applied;

Figure 8 is a schematic diagram of the bottom support system in a system to which the method according to the invention is applied;

Figure 9 is an overall schematic diagram of a system applied to the earthquake fault simulation method based on a geotechnical centrifuge platform according to the present invention;

Figure 10 is a schematic flow chart of a method according to the present invention;

Figure 11 is a joint schematic diagram of the system and the wood and soil centrifuge platform applied according to the method of the present invention;

Figure 12 is the earth pressure increment curve at both ends of the tunnel under different fault displacement speeds obtained after implementing the method according to the present invention;

Figures 13a and 13b are image data collected by a high-speed camera after implementation of the method according to the present invention.

Detailed ways

Various embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the drawings do not limit the scope of the present invention, but are only used to illustrate the essential spirit of the technical solution of the present invention.

In the following description, for the purpose of explaining the various disclosed embodiments, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, one skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other instances, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

Unless the context requires otherwise, throughout the specification and claims, the word "include" and variations thereof, such as "includes" and "has" are to be understood in an open, inclusive sense, that is, to mean "includes, but not limited to".

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Additionally, specific features, structures, or characteristics may be combined in any manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms "a," "," and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that the term "or" is generally used in its sense including "or/and" unless the context clearly dictates otherwise.

In the following description, in order to clearly demonstrate the structure and working mode of the present invention, many directional words will be used to describe it, but "front", "back", "left", "right", "outside", "inside" should be used for description. "," "outward", "inward", "up", "down" and other words are to be understood as convenient terms and should not be understood as limiting terms.

The first embodiment of the present invention relates to an earthquake fault simulation method based on a geocentrifuge platform. It is applied to an earthquake fault simulation system based on a geocentrifuge platform and can simulate the entire seismic process and propagation path effect of a fault under a real stress state. and the complex interaction between fault dislocation and engineering structures.

As shown in Figures 1 and 4, the seismic fault simulation system of the geocentrifuge platform includes a model box I placed on the geocentrifuge platform 7-10. There is an accommodation space in the model box I. The accommodation space A bottom support system V, a simulated earthquake fault IV and a site covering layer II are provided in the space from bottom to top. A horizontal actuating system III is provided on the side of the simulated earthquake fault IV and the site covering layer II. The bottom support system V is used to support the horizontal actuating system III, the simulated earthquake fault IV and the site covering layer II. The horizontal actuating system III is used to apply horizontal thrust to the simulated earthquake fault IV and the site covering layer II. The simulated earthquake fault IV is used to fill the fault test block to simulate the bedrock layer of the earthquake fault. The site cover layer II is used to fill the simulated earthquake fault with sand layer material to simulate the soil layer of the earthquake fault. Therefore, this embodiment is developed based on a large-scale geotechnical centrifuge test platform. The centrifuge simulates hypergravity and truly restores the true stress state of rock and soil, laying a solid foundation for such model test research. By setting up simulated earthquake faults and site covering layers, and under the precise control of horizontal actuators, the entire process of earthquake seismogenesis caused by active fault rupture and its propagation effects in the site can be simulated, thereby considering the source mechanism and propagation path. This lays the foundation for the study of the synthetic model of site ground motion effects. Furthermore, by setting simulated earthquake faults directly under the engineering structure, the fault rupture mode is controlled to achieve complex seismic conditions, overcoming the shortcoming of the traditional mode that the bottom shaking table can only apply uniform ground vibration, and truly reproducing the engineering structure when crossing the fault. corresponding dynamic characteristics.

The model box I is mainly composed of an external rigid model box I, which not only provides horizontal reaction support for the horizontal actuator system III, but also facilitates crane lifting by installing a lifting ring. As shown in Figures 2, 3 and 5, model box I is rigidly connected by four thick steel plates: two side plates (left plate 1-1 and right plate 2-11), bottom plate 5-7 and back plate 6 Forming a box with an open top, the two side panels, the bottom panels 5-7 and the back panel 6 are all made of steel plates, and the front of the model box I is provided with a transparent organic glass panel. The top surface of the model box I is removably installed with a tie rod system. The tie rod system is used to hoist the model box I. The top surface is the top free surface. Multi-point connections are realized through the tie rod system to overcome the problem of steel plates due to the connection. Defects caused by insufficient tensile moment caused by point concentration. As shown in Figure 7, the model box I tie rod system includes threaded tie rods 1-3, limit bolts 1-2 and reaction bolts 1-6, which are arranged on the top of the model box I and the front surface facing the empty surface. The threaded tie rod 1-3 is installed by opening an internal threaded hole in the left side plate 1-1, and the internal threaded hole is connected to the threaded tie rod 1-3; the right side plate 2-11 opens a hole slightly larger than the thread diameter, and tightens the reaction bolt 1 -6 provides reaction force. The tie rod system is detachable to improve the convenience of sample filling. The pull rod at the middle position of the top contains two lifting plates 1-4, which are used to connect with the lifting ring of the centrifuge chamber crane to hoist the model box I as a whole into the rigid box in the centrifuge.

It should be noted that in order to control the internal force and deformation of steel components with different connection forms in each small deformation stage, the connection form of the box steel plate is determined according to the stress situation. The side plates and bottom plates are connected by a combination of bolts and double-side welding, and the bottom plate and back plate, side plates and back plates are connected by a combination of bolts and single-side welding.

The horizontal actuating system III is located on the right side of the system in this embodiment, and accurately applies horizontal thrust of different amplitudes to the fault, thereby accurately controlling the cyclic reciprocating motion of the fault in the horizontal direction. Horizontal actuation system III includes screw lifting device 2-10, right-angle reducer 3-1, stepper motor 4-1, and actuation control box 4-5. The screw lifting device 2-10 is used to apply horizontal thrust to the simulated earthquake fault IV and the site covering layer II. The stepper motor 4-1 is connected to the actuation control box 4-5 through wires, and is used to control the screw lifting device 2-10 to produce horizontal movement. The stepper motor 4-1 is connected to the right-angle reducer 3-1 through a transmission shaft 4-3. The right-angle reducer 3-1 is used to lower the screw 2- in the screw lifting device 2-10. 6 rpm. When the power of the stepper motor 4-1 remains unchanged, the right-angle reducer 3-1 increases the horizontal thrust by reducing the rotation speed and increasing the torque. The right-angle reducer 3-1 is connected to the screw rods 2-6 of the upper and lower horizontal propellers through gears, driving the screw rods 2-6 to undergo controllable horizontal movement. The screw rod 2-3 is connected to the contact panel 2-1 through the spoke sensor 2-4, and the three are connected through a combination of pins and internal threads. The spoke sensors 2-4 can obtain real-time thrust values and are connected to the motion control box 4-5 through wires to provide control signals for the stress control test.

As shown in Figures 5 and 6, the screw lifting device 2-10 is provided with a contact panel 2-1, a loading panel 2-2, a spoke sensor 2-4, a flange 2-5, and a screw 2 in sequence along the horizontal direction. -6, rotating shaft 2-9, stroke limiter 2-7 and lift 2-10. The contact panel 2-1 is in direct contact with the simulated fault to control fault movement. One side of the contact panel 2-1 is connected to the loading panel 2-2 through bolts 2-8, and the other side is in close contact with the simulated earthquake fault IV and the site covering layer II. The loading panel 2-2 and the spoke sensor 2-4 are connected by pins 2-3, and the spoke sensor 2-4 and the flange 2-5 are connected by bolts 2-8. There is an internal thread in the center of the sensor 2-4. The internal thread has force sensing performance. Holes are drilled on the periphery of the spoke sensor 2-4 without force-measuring performance and at the corresponding position of the loading panel 2-2 to facilitate the installation of the pin 2-3 and the loading panel 2-2. 2 and the spoke sensors 2-4 are connected through a combination of internal threads and pins 2-3 respectively. Among them, the pin combination only provides shear resistance and does not provide tensile and compressive strength to ensure that all the actuating force fed back by the sensor is borne by the internal thread contact. Make a groove on the contact side of flange plate 2-5 and spoke sensor 2-4, and place the sensor in the groove. Drill holes and make internal threads at the corresponding positions of the non-force-measuring periphery of the spoke sensor 2-4 and the flange plate 2-5, and connect them through bolt combinations. The flange 2-5 and the screw rod 2-6 are a fixed whole, the screw rod 2-6 and the base of the lifter 2-10 are integrated mechanical devices, and the screw rod 2-6 only moves up and down during the operation process. , with a sufficient length of connection to the base.

The base of the elevator 2-10, the right-angle reducer 3-1, and the stepper motor 4-1 are integrated into a whole through the rotating shaft 2-9 and the connector, and are fixed to the side plate and back through the connecting plate 3-2 and the pin 2-3. on the board. The whole is located on the right side of the device, greatly optimizing space utilization efficiency. Wherein, the elevator 2-10 drives the rotating shaft 2-9 and the screw 2-6 to move to generate horizontal thrust, and the horizontal thrust pushes the simulated earthquake in contact with the contact panel 2-1 Fault IV or the site cover II. The stroke limiter 2-7 is arranged on the surface of the elevator 2-10 facing the flange 2-5, and plays a limiting role in the horizontal movement of the elevator 2-10. When the stroke limiter 2-7 7. When the flange 2-5 is touched, the horizontal movement of the lift 2-10 is stopped. For example, a flange 2-4 is provided on the side of the spoke sensor 2-4 close to the stepper motor 4-1. When the flange 2-4 comes into contact with the 2-7 stroke limiter, the stepper motor 4- is automatically cut off. 1 power supply, the horizontal movement stops to ensure the safety of the test system.

Specifically, the contact panel 2-1 controls the overall horizontal movement displacement to be consistent, and the loading panel 2-2 is connected to the spoke sensor 2-4 through a combination of pins 2-3 and internal threads. The internal threads provide normal stiffness to achieve More accurate feedback of horizontal thrust. By controlling the number and frequency of 4-1 pulses of the stepper motor, the momentum and speed are controlled to achieve precise positioning and speed regulation. The rotation speed is reduced by the right-angle reducer 3-1, which can meet the high operating capability of the screw 2-6 at a lower speed. Combined with the force feedback of the spoke sensors 2-4, the working status of the horizontal actuation system III can be obtained, and the actuation rate is adjusted through the control box 4-5 in the centrifuge main control room. When the bottom of the flange plate 2-5 touches the stroke limiter 2-6, the control box 4-5 automatically stops the stepper motor 4-1 to achieve precise control of the actuation stroke of the screw rod 2-6 and avoid contact with the centrifugal force Mechanical aluminum alloy model box Ⅰ side panel.

Bottom support system V mainly includes aluminum rigid supports, steel spring supports, and lift rigid brackets. The rigid support places the specimen at a relatively fixed height, and the spring support provides space for the specimen to move. The lift bracket fixes the position of the horizontal action resultant point, so that the reaction force of the screw lift is close to maximizing the action capability. That is, the bottom support system V includes a rigid support, an elastic support, a lift support and a motor support. The rigid support is used to support the fault footwall in the simulated earthquake fault IV, and the elastic support The seat is used to support the hanging wall of the fault in the simulated earthquake fault IV, the elevator bracket is used to support the screw lifting device in the horizontal actuating system III, and the motor support is used to support the horizontal actuating system. Stepper motor in system III. The supports and lift brackets of the bottom support system V are connected through bolts and steel plates. The rear side is close to the back plate, leaving a gap between the front side and the plexiglass panel side to install threaded tie rods. The bottom support system V can reduce the impact effect during the test and can accurately adjust the vertical spatial position of the fault. As shown in Figures 5 and 8, the bottom support system VV consists of an aluminum rigid support 5-1, a steel spring support 5-2, a shock-absorbing rubber pad 5-3, a support pad 5-4, and a lift bracket It consists of 5-5, motor support 5-6 and base plate 5-7. The aluminum rigid bracket 5-1 is used to support the lower wall of the fault; the spring bracket 5-2 is used to support the upper wall of the fault and allows the upper wall to move within a certain range; the rigid bracket 5-5 is used to support the horizontal actuating device; box The body base 5-6 is used to support the weight of the entire horizontal actuator. Specifically, a lift bracket 5-5 is provided at the bottom of the horizontal actuating system III. The height of the screw rod of the lifting bracket 5-5 is adjusted to change its height, thereby changing the horizontal actuating system III. Correspondingly, by adjusting the rigid support 5-1 at the bottom of the footwall of the simulated earthquake fault IV, its height is coordinated with the height of the horizontal actuating system III; the bottom of the hanging wall of the simulated earthquake fault IV is provided with a steel spring support 5 -2. It can adaptively adjust the height of the upper plate and coordinate with the height of the horizontal actuation system III.

In the site cover layer II and simulated earthquake fault area IV, the rupture, friction excitation intensity and rupture mode of various geological materials can be explored by loading samples of different materials and types. Specifically, the site covering layer II can be made of similar geotechnical materials that meet similar design requirements, and different sites can be simulated by controlling the thickness and composition. The simulated earthquake fault IV can be made using blocks of different materials, dip angles, directions, surface roughness, etc., achieving accurate simulation of different active faults. The contact surface between the model box I and the simulated earthquake fault IV is provided with a rubber cushion to achieve shock absorption and filtering, which can effectively reduce the collision vibration of the specimen and the device during the test, thereby reducing the test error. In some cases, adhesive is used on the side of the rubber pad that contacts the box, and Vaseline is applied on the side that contacts the specimen to reduce friction.

The field covering layer II is also provided with tunnels respectively, and the tunnels penetrate the field covering layer II in the horizontal direction. In this embodiment, the simulated earthquake fault IV is poured with cement mortar, and the site covering layer II is constructed using an ISO standard sand layer. There are different types of tunnel structures inside, and the directions are all in the direction of crossing the fault.

The all-round three-dimensional monitoring system includes high-speed cameras, acceleration sensors, earth pressure cells, displacement sensors, spoke sensors, strain gauges, etc., as well as remote connection to computers, which can accurately record fault dislocation processes, site earthquakes, and engineering structure dynamic responses, etc. characteristic. As shown in Figure 9, the all-round three-dimensional monitoring system VI consists of multiple types of sensor monitoring systems, usually including a laser displacement meter 7-1 (and a displacement meter bracket 7-2), an accelerometer 7-3, and an earth pressure box 7- 5. Strain gauges 7-6, high-speed cameras 7-9, etc. The laser displacement meter 7-1 is arranged on the tie rod system of the model box I to monitor the horizontal displacement and vertical displacement of the ground surface of the site covering layer II. The accelerometer 7-3 and the soil Pressure boxes 7-5 are respectively installed in the sand layer material near the tunnel to monitor the sand layer material, and the strain gauges 7-6 are installed at the top and bottom of the tunnel to monitor all the sand layer materials. To measure the strain difference between the vault and the vault of the tunnel, the high-speed cameras 7-9 are installed on the geocentrifuge platform and face the front of the model box. The laser displacement meter 7-1, the accelerometer 7-3, the earth pressure box 7-5, the strain gauge 7-6, and the high-speed camera 7-9 are all remotely connected to the computer 7-11.

As shown in Figure 10, the specific process of the method in this embodiment is as follows:

S101. Set the actuation direction and actuation rate of the horizontal actuation system. During the experimental process of earthquake fault simulation, monitor the stress and local deformation of the end of the tunnel, the surface displacement and the surface displacement of the site covering layer. Acceleration and earth pressure, and the amount and force of the horizontal actuating system.

S102. During the experimental process of seismic fault simulation, obtain surface crack rupture images and site deformation images of the simulated seismic fault and site overlay and site deformation images through a high-speed camera facing the front of the model box.

S103. Based on the end stress and local deformation of the tunnel, determine the deformation characteristics of the tunnel when the earthquake fault dislocates;

In some examples, S103 also includes a sub-step of determining the propagation change curve of the vibration induced by the earthquake fault dislocation in the site covering layer based on the surface displacement, acceleration and earth pressure of the site covering layer. This propagation change curve reflects the propagation effect of vibrations induced by earthquake fault dislocation in the covering layer of the site, for example, the earth pressure increment curve at both ends of the tunnel under the action of fault dislocation, and the different locations of the tunnel under the action of fault dislocation ( For example, 0.325 and 0.55) bending and shear strain curves, surface vertical displacement change curves at different points of the tunnel under different fault dislocation conditions (for example, 0.23, 0.37 and 0.46), etc.

S104. Based on the amount of movement and force of the horizontal movement system and the surface displacement of the site covering layer, adjust the movement direction and speed of the horizontal movement system.

S105. Based on the surface crack rupture image and the site deformation image, obtain the site shear zone position and site shear zone shape of the covering layer when the earthquake fault displaces, as well as the tunnel fracture position and crack shape.

Specifically, the stress and local deformation at the end of the tunnel are obtained through earth pressure boxes buried at both ends of the tunnel and strain gauges pasted on the surface of the tunnel. Based on the force at the end of the tunnel observed by the earth pressure box, the real-time stress state of the tunnel during earthquake fault displacement is obtained. Based on the strain gauges connected to the full bridge on the tunnel surface, local deformations such as tunnel axial strain, circumferential strain and bending shear strain are obtained, and further combined with Hooke's law, the tunnel surface stress is obtained. Based on the stress and local deformation at the end of the tunnel, the deformation characteristics and failure mode of the cross-fault tunnel during earthquake fault dislocation are revealed.

The surface displacement, acceleration and earth pressure of the site covering layer are distributed through a laser displacement sensor arranged on the top, an acceleration sensor and an earth pressure box inside the site covering layer. Based on the surface displacement of the site covering layer, the deformation characteristics of the site during earthquake fault displacement are obtained. Based on the acceleration of the covering layer of the site, the time and space distribution rules of earthquakes induced by seismic fault dislocation and their distribution characteristics in the time domain and frequency domain are obtained, thereby clarifying the propagation effect of seismic waves in the site. Based on the soil pressure of the site cover layer, the dynamic behavior of the soil under earthquake fault dislocation is obtained.

The actuating amount and actuating force of the horizontal actuating system are obtained through a laser displacement sensor and a spoke sensor respectively. Based on the movement amount and force of the horizontal actuator system, not only the real-time working status of the horizontal actuator can be obtained, but also as the input signal of the horizontal actuator system controller in the main control room, combined with the set control mode, the stepper can be adjusted The number and frequency of motor pulses can be adjusted to achieve precise seismic fault motion control.

The surface crack image and the site graphics are obtained through a high-speed camera installed on the front of the model box. By analyzing the surface crack image and the site graphics, the location and shape of the overlay site shear zone and the tunnel fracture location and crack shape during earthquake fault dislocation were obtained, revealing the complex coupling between the simulated earthquake fault-site cover layer-tunnel. The interaction behavior lays the foundation for understanding the tunnel failure mode and its optimal design.

Based on this embodiment, the following takes the seismic performance research test of a tunnel structure in a near-fault site as an example to explore the site's ground motion response and its interaction with the tunnel structure under different fault dislocation conditions. The specific operation process of the present invention is as follows:

S1. Place the model box I on the ground, install the bottom support system V and the horizontal actuation system III into the model box I in sequence, and test its working performance.

S2. Place the prepared fault test block with a certain inclination angle into the simulated earthquake fault zone IV, drill holes on the top of the fault bedrock (recorded as acquisition system elevation surface 7-7 layer 0) and arrange accelerometers 7-3, soil Pressure box 7-5.

S3. Install panel 1-7, use rubber membrane to wrap the gap between panel 1-7 and the fault test block, allowing centimeter-level horizontal movement.

S4. Use different materials and different design methods to make two tunnels 7-4. Full-bridge strain gauges are pasted on the tunnel surface to measure the strain difference between the tunnel vault and the vault bottom.

S5. Layer the standard sand filling site cover layer II to a certain depth (recorded as layer 1 and layer 2 of the collection system elevation surface 7-7, as shown in Figure 9), and arrange and paste the strains at the same depth and relative position in the site cover layer II. The tunnel model is a piece of tunnel model, the direction is to cross the fault, and horizontal action loading is achieved under the same site and fault movement state.

S6. At the same time, accelerometers 7-3 and earth pressure boxes 7-5 are respectively arranged on the 7-7 layer 1 of the collection system elevation surface and the 7-7 layer 2 of the collection system elevation surface. At this time, it is necessary to first install the two ends of the tunnel 7-4 structure. For rigid sealing, use quick-drying glue to stick the sensors to both ends of tunnel 7-4.

S7. Layer the standard sand filling site cover layer II to reach the surface elevation design value (recorded as the collection system elevation surface 7-7 layer 3), and lay out one accelerometer 7-3 and one earth pressure box 7-5.

S8. Tighten each threaded tie rod 1-3 with the reaction bolts 1-6, seal the model box I, connect the lifting holes 1-5 on the lifting plate 1-4 to the lifting ring of the crane, and insert the model box I side into the centrifuge aluminum Alloy model box.

S9. Install laser displacement meter 7-1 on the centrifuge model box to monitor vertical and horizontal displacement. Lift the centrifuge model box onto the centrifuge vibration table plane 7-10. Install customized camera brackets 7-8, fix high-speed cameras 7-9, and install high-power light strips to provide light sources.

S10. According to the principle of Figure 11, connect and debug all sensors (Figure 8), data collector and control device and actuation control box 4-5. Specifically, in the centrifuge room, the fault actuator in the horizontal actuator system is connected to the electro-hydraulic servo valve, and then enters the amplifier for signal amplification, and then enters the collector ring together with the data collected by the data collector, and then the collector ring The flow ring is transmitted to the main control control cabinet.

S11. Start the centrifuge static and dynamic acquisition system, start the control box 4-5, start the geotechnical centrifuge, and observe whether the curve when the centrifuge speed reaches the preset value is normal.

S12. Start the test according to the test plan. Change the action direction and speed through the control box 4-5 in the main control room to obtain real-time acceleration of the site covering layer II at different elevations, end forces of tunnels of different materials, and local Deformation, surface displacement, movement amount and force, as well as monitoring surface crack rupture and site deformation status through the panel.

S13. The test is over. According to the centrifuge usage requirements, turn off the centrifuge driving device, oil pump and power switch in sequence, turn off the device's actuator and acquisition system, and export multi-source monitoring data and continuous images.

S14. Lift out the centrifuge and large model box from the model box I in two steps, disassemble the threaded tie rods 1-3, take photos and record the damage status of the two types of tunnels 7-4 in the site covering layer II in situ, and record the fracture shape. Perform 3D scan analysis.

S15. Remove all materials and sensors. The materials for simulating earthquake fault IV and site cover II can be determined according to the purpose of the test, as well as whether to conduct dynamic response testing of the coupled structure, and repeat S2 to S14 according to the test plan.

Through the above experiments, the earth pressure increment curves at both ends of the tunnel under different fault displacement speeds can be obtained as shown in Figure 12. In the figure, TY-1 and TY-2 respectively represent the earth pressure of one of the non-rigid tunnels in the two tunnels. Curve, TY-3 represents the earth pressure curve of another rigid tunnel. As shown in Figure 13a and Figure 13b, the image data collected by the high-speed camera shows the layered deformation effect of the site under the action of fault dislocation and the inversion image of the site shear zone. Figure 13a shows the inner black sand under the fault dislocation image. Shift, Figure 13b shows the inversion image of the fault dislocation affected area and shear zone.

The preferred embodiments of the present invention have been described in detail above, but it will be understood that aspects of the embodiments can be modified if necessary to employ aspects, features and concepts from various patents, applications and publications to provide additional embodiments.

These and other changes can be made to the embodiments in view of the above detailed description. In general, in the claims, the terms used should not be construed as limiting to the specific embodiments disclosed in the specification and claims, but should be understood to include all possible embodiments together with all equivalents to which such claims are entitled. scope.

Claims (8)

1. An experimental method for seismic fault simulation based on a geotechnical centrifuge platform, characterized in that a model box is provided on the geotechnical centrifuge platform, and there is an accommodation space in the model box, and the accommodation space is from bottom to top. A bottom bearing system, a simulated earthquake fault and a site covering layer are provided on the top. A horizontal actuating system is provided on the side of the simulated earthquake fault and the site covering layer. A tunnel is provided in the site covering layer. The tunnel penetrates the site covering layer in the horizontal direction; the method includes the following steps: Set the action direction and action rate of the horizontal action system, and during the experimental process of earthquake fault simulation, monitor the stress and local deformation of the end of the tunnel, the surface displacement and acceleration of the site covering layer, and Earth pressure, actuating amount and actuating force of the horizontal actuating system; During the experiment of seismic fault simulation, surface crack rupture images and site deformation images of the simulated seismic fault and site overlay and site deformation images are acquired through a high-speed camera facing the front of the model box; Based on the end stress and local deformation of the tunnel, determine the deformation characteristics of the tunnel when the earthquake fault dislocates; Based on the surface displacement, acceleration and earth pressure of the site covering layer, determine the propagation change curve of the vibration induced by the earthquake fault dislocation in the site covering layer; Based on the actuation amount and force of the horizontal actuation system and in combination with the surface displacement of the site covering layer, adjust the actuation direction and actuation rate of the horizontal actuation system; Based on the surface crack rupture image and the site deformation image, the site shear zone position and site shear zone shape of the covering layer as well as the tunnel fracture position and crack shape when the earthquake fault is displaced are obtained. 2. The experimental method of seismic fault simulation based on geotechnical centrifuge platform according to claim 1, characterized in that the bottom bearing system is used to support the horizontal actuation system, the simulated earthquake fault and the site covering; The horizontal actuation system is used to apply horizontal thrust to the simulated earthquake fault and the site cover; The simulated earthquake fault is used to fill fault test blocks to simulate the bedrock layer of the earthquake fault; The site cover is used to fill the simulated earthquake fault with sand layer material to simulate the soil layer of the earthquake fault. 3. The experimental method for earthquake fault simulation based on a geotechnical centrifuge platform according to claim 2, characterized in that the stepper motor in the horizontal actuation system is connected to the motion control box through wires, and the motion control box is The box sets and adjusts the action direction and speed of the horizontal action system. 4. The experimental method for seismic fault simulation based on a geotechnical centrifuge platform according to claim 2, characterized in that the tunnel is provided with an accelerometer, a strain gauge and an earth pressure box. By monitoring the accelerometer, the The strain gauge and the earth pressure cell monitor the stress and local deformation at the end of the tunnel. 5. The experimental method for earthquake fault simulation based on a geotechnical centrifuge platform according to claim 2, characterized in that a laser displacement meter is provided on the model box, and the site covering layer is monitored by the laser displacement meter. surface displacement. 6. The experimental method for seismic fault simulation based on a geotechnical centrifuge platform according to claim 3, characterized in that a stroke limiter is provided on the side of the stepper motor facing the simulated seismic fault, and the horizontal The actuating system is provided with a spoke sensor, and a flange is provided on the side of the spoke sensor close to the stepper motor. When the flange comes into contact with the stroke limiter, the stepper motor is cut off. power, the horizontal actuation system stops moving. 7. The experimental method for seismic fault simulation based on a geocentrifuge platform according to claim 2, characterized in that the bottom support system is provided with a rigid support, an elastic support, a lift support and a motor support; The footwall of the fault in the simulated earthquake fault is supported by the rigid bearing, and the hanging wall of the fault in the simulated earthquake fault is supported by the elastic bearing; The screw lifting device in the horizontal actuation system is supported by the elevator bracket, and the stepper motor in the horizontal actuation system is supported by the motor support; The heights of the rigid support and the elevator support are adjusted so that the fault footwall in the simulated earthquake fault is highly coordinated with the horizontal actuation system. 8. A storage medium with a computer program stored thereon, characterized in that when the computer program is called by a processor, it causes the processor to execute the experimental method according to any one of claims 1 to 7.