Centrifugal vibration equipment for simulating passive pile end bearing arching effect under seismic load

Abstract

The present application relates to a kind of centrifugal vibration equipment of simulating passive pile end bearing arch effect under earthquake load, the device includes test box and model box inside test box, bearing base plate, jacking component, rotating component, baffle component, measuring component, baffle driving component and host computer;Model box is fixed in the upper of bearing base plate, rotating component and jacking component are set in the lower end of bearing base plate, for driving bearing base plate to move up and down, one side of model box is provided with open end, and located in open end, baffle component is splicing structure, for simulating passive pile and soil between piles, baffle component is perpendicular to bearing base plate, baffle driving component is fixed on bearing base plate, and driving connection baffle component, measuring component is used to obtain the real-time image in model box, the stress condition of baffle component and the displacement of bearing base plate, and transmit to host computer.Compared with prior art, the present application has the advantages of simple operation, stable and reliable, etc.

Description

Technical Field

[0001] This invention relates to the fields of geotechnical engineering and geological engineering, and in particular to a centrifugal vibration device for simulating the passive pile end bearing effect under seismic loads. Background Technology

[0002] Located between the Circum-Pacific Seismic Belt and the Eurasian Seismic Belt, my country experiences frequent, intense, and shallow earthquakes. The continuous disturbance from these earthquakes makes geotechnical structures with exposed surfaces, such as foundation pits, slopes, and embankments, prone to landslides and other geological disasters. Passive piles penetrate the landslide mass and reach stable strata, effectively blocking the horizontal movement of sliding soil and improving soil stability. They have been widely used in landslide prevention projects for highways, railways, and water conservancy. The end-bearing arch effect is the main mechanism by which passive piles contain laterally displaced soil. Under a reasonable pile spacing arrangement (i.e., the maximum pile spacing forming the end-bearing arch), the soil thrust drives shear deformation in the soil around the pile, altering the principal stress trajectory of the soil behind the pile and deflecting it towards the pile, forming an "arch-shaped" load transfer path behind the pile. The end-bearing arch changes the distribution of soil pressure on the pile, thus affecting the internal force response of the pile. This is a key load transfer mechanism that needs to be considered in the design of passive pile seismic-resistant structures.

[0003] Currently, domestic and international scholars mainly conduct model test studies on the load and deformation response of passive piles under static loads to the end-bearing arch effect. However, research on the dynamic response of passive piles under seismic loads is limited, and the dynamic evolution mechanism of the end-bearing arch remains unclear. This affects a series of engineering problems such as the seismic design of passive piles and the determination of reasonable pile spacing. Model tests are a commonly used experimental method to explore the end-bearing arch effect of passive piles. Compared with 1g scaled models, centrifugal model tests can more realistically reproduce the stress level of geotechnical structures by increasing the centrifugal acceleration. However, existing centrifugal vibration model tests suffer from difficulties in monitoring soil deformation, quantifying the relationship between the end-bearing arch effect and seismic intensity, and also suffer from high cost and complex operation.

[0004] In summary, current research on the passive pile end bearing effect based on centrifugal vibration still has many limitations and shortcomings. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art, such as difficulty in monitoring soil deformation in centrifugal vibration model tests, difficulty in quantifying the relationship between end-bearing arch effect and seismic intensity, high cost, and complex operation, and to provide a centrifugal vibration device for simulating the end-bearing arch effect of passive piles under seismic loads.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A centrifugal vibration device for simulating the passive pile end bearing arch effect under seismic load includes a test chamber and a model box, a load-bearing base plate, a lifting component, a rotating component, a baffle component, a measuring component, a baffle driving component, and a host computer located inside the test chamber;

[0008] The model box is fixed above the load-bearing base plate. The rotating component is rotatably fixed to the lower left end of the load-bearing base plate, and the lifting component is fixed to the lower right end of the load-bearing base plate to drive the load-bearing base plate to move up and down. The model box has an open end on one side. The shape of the baffle component matches the shape of the open end and is located at the open end. The baffle component is a spliced ​​structure used to simulate passive piles and soil between piles. The baffle component is perpendicular to the load-bearing base plate. The baffle driving component drives the connected baffle component and is fixed to the load-bearing base plate. The measuring component is used to acquire real-time images inside the model box, the stress on the baffle component, and the displacement of the load-bearing base plate, and transmit them to the host computer.

[0009] Preferably, the baffle component includes multiple fixed baffles and movable baffles. The fixed baffles are vertically fixed to the load-bearing base plate, and the movable baffles are connected to a baffle driving component. The baffle driving component drives the movable baffles to move horizontally, and the movable baffles are always perpendicular to the load-bearing base plate.

[0010] Preferably, the measuring component further includes a miniature earth pressure gauge, which is fixed on the side of the fixed baffle that contacts the soil. The miniature earth pressure gauge is connected to a host computer to measure the lateral earth pressure generated by the movable baffle and transmit it to the host computer.

[0011] Preferably, there are multiple miniature earth pressure gauges, and each miniature earth pressure gauge is evenly fixed from top to bottom on the side of the fixed baffle that contacts the soil.

[0012] Preferably, the baffle driving component includes a force transmission component, a horizontal displacement control component, and a load-bearing component;

[0013] The load-bearing component is fixed to the load-bearing base plate, and the horizontal displacement control component is movably fixed to the load-bearing component. The horizontal displacement control component drives the force transmission component to move, and the movement path of the force transmission component is parallel to the upper surface of the load-bearing base plate. The force transmission component is vertically connected to the baffle component.

[0014] Preferably, the force transmission component includes an S-shaped load cell and a connecting rod. One end of the S-shaped load cell is vertically connected to the baffle component for measuring the horizontal load borne by the baffle component, and the other end is vertically fixed to the connecting rod. The connecting rod is connected to a horizontal displacement control component, which drives the connecting rod to move horizontally.

[0015] Preferably, the horizontal displacement control component includes a stepper motor and a transmission rod;

[0016] The stepper motor drives the connecting rod, the connecting rod is fixed to one end of the transmission rod, the stepper motor is fixed to the load-bearing component, and the stepper motor drives the connecting rod to move horizontally through the transmission rod.

[0017] Preferably, the load-bearing component includes a first load-bearing frame, a second load-bearing frame, and a horizontal load-bearing plate. The first and second load-bearing frames are both vertically fixed on the load-bearing base plate to support the horizontal load-bearing plate. One end of the horizontal load-bearing plate is vertically connected to the first load-bearing frame, and the other end is vertically connected to the second load-bearing frame. The stepper motor is fixed on the horizontal load-bearing plate.

[0018] Preferably, the measuring component includes a digital camera for acquiring the displacement trajectory of the soil inside the model box and a differential displacement sensor for acquiring the vertical displacement of the lifting component. The digital camera is fixed above the model box by a tripod, and the differential displacement sensor is fixed on the lifting component. Both the digital camera and the differential displacement sensor are connected to a host computer.

[0019] This solution also provides a method for simulating the passive pile end bearing effect under seismic loads using a centrifugal vibration device, including the following steps:

[0020] S1: The backfill is filled into the model box using a layered filling method, the backfill is compacted, the relative density of the backfill is in the range of 55%-65%, and the soil surface is leveled.

[0021] S2: Hoist the test chamber onto the centrifuge basket, debug the equipment, and after debugging, zero the channel. Take a picture of the soil surface with a digital camera as the reference data, then start the centrifuge. According to the width of the fixed baffle, set the centrifugal acceleration to make the centrifuge reach the set centrifugal acceleration.

[0022] S3: Start the stepper motor to pull the movable baffle at the specified moving speed. The digital camera records the real-time data of soil deformation during the process and uploads it to the host computer.

[0023] S4: Once the earth pressure data measured by the miniature earth pressure gauge on the fixed baffle and the measurement data measured by the S-type weighing sensor remain stable, turn off the stepper motor.

[0024] S5: Maintain a constant centrifugal acceleration, adjust the downward movement distance of the lifting component according to the preset value, and apply a horizontal seismic force according to the preset horizontal seismic acceleration increment. Return to step S3.

[0025] S6: After the experiment, the speckle images acquired by the digital camera under different displacements and different seismic accelerations were analyzed to obtain the deformation field of the soil, and then the static and dynamic evolution process of the end-bearing arch was analyzed to quantify the geometric characteristics of the arch. The load sharing of the pile and soil under different seismic loads was obtained by using S-type weighing sensors and micro weighing sensors to analyze the changes in the load transfer capacity of the end-bearing arch.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) In this scheme, after the model box is filled with soil, the test box is hoisted onto the centrifuge basket, that is, the entire device is transferred into the centrifuge. The baffle component of the spliced ​​structure is driven by the baffle drive component, and the load-bearing base plate is moved up and down by the lifting component, so that the model box rotates around the rotating component, and the horizontal seismic force of different amplitudes is applied to the soil inside the model box. The deformation image and displacement trajectory of the soil inside the model box are obtained by the measuring component, the lateral soil pressure on the baffle component is measured, and the vertical displacement of the lifting component is measured.

[0028] By changing the height of the lifting components, the load-bearing base plate and model box can rotate around the rotating structure at different angles, decomposing the horizontal component generated by gravity, thereby simulating the application of horizontal seismic forces of different amplitudes to the soil. This quasi-static load application method effectively ensures uniform soil stress and deformation, and is simple, stable, and reliable to operate. Furthermore, the data obtained by the measuring components can reveal the pile-soil load distribution under different seismic loads, enabling a more accurate analysis of the changes in the end-bearing arch load transfer capacity of the passive pile.

[0029] (2) The baffle component in this scheme is a spliced ​​structure, including multiple fixed baffles and movable baffles. The fixed baffles and movable baffles can be arranged in order according to requirements. The structural deformation of the baffle component can simulate the differential deformation of the pile and soil, which is more conducive to establishing the evolution process of the end-bearing arch and the relationship between soil deformation. By arranging and combining the moving order of the movable baffles and fixed baffles, the pile spacing can be flexibly changed, avoiding the process of frequently installing and disassembling the pile in conventional model tests. Attached Figure Description

[0030] Figure 1 This is a front view of the centrifugal vibration device provided by the present invention;

[0031] Figure 2 A top view of the centrifugal vibration device provided by the present invention;

[0032] Figure 3 A side view of the centrifugal vibration device provided by the present invention;

[0033] Figure 4 A schematic diagram of the installation structure of the horizontal displacement control component provided by the present invention;

[0034] Figure 5 A diagram showing the arrangement of the miniature earth pressure gauge on the fixed baffle provided by the present invention;

[0035] Figure 6 A schematic diagram of the working process of the centrifugal vibration device provided by the present invention;

[0036] Figure 7 This is a schematic diagram of the structure of the baffle component when the fixed baffle and the movable baffle are arranged in the first order according to the present invention.

[0037] Figure 8 This is a schematic diagram of the structure of the baffle component when the fixed baffle and the movable baffle are arranged in the second order according to the present invention.

[0038] Figure 9 This is a schematic diagram of the structure of the baffle component when the fixed baffle and the movable baffle are arranged in the third order according to the present invention.

[0039] Figure 10 This is a schematic diagram of the structure of the baffle component when the fixed baffle and the movable baffle are arranged in the fourth order according to the present invention.

[0040] In the diagram: 1. Test chamber, 2. Load-bearing base plate, 3. Model box, 4. First nut, 5. First screw, 6. Soil, 7. Baffle assembly, 71. Fixed baffle, 72. Movable baffle, 8. Force transmission component, 81. S-type load cell, 82. Connecting rod, 83. Second nut, 84. Second screw, 9. Horizontal displacement control component, 91. Stepper motor, 92. Transmission rod, 93. Square connecting sleeve, 94. Third nut, 95. Third screw, 10. Load-bearing component, 101. First load-bearing frame, 102. Second load-bearing frame, 103. Horizontal load-bearing plate, 104. Fourth nut, 105. Fourth screw, 11. Rotating component, 12. Lifting component, 13. Digital camera, 14. Miniature earth pressure gauge, 15. Displacement sensor, 16. Host computer. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0045] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0046] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0047] Example 1

[0048] This embodiment provides a centrifugal vibration device for simulating the passive pile end bearing arch effect under seismic loads, such as... Figure 1-3 As shown, it includes a test chamber 1 and a model box 3, a load-bearing base plate 2, a lifting component 12, a rotating component 11, a baffle component 7, a measuring component, a baffle driving component, and a host computer 16 located inside the test chamber 1;

[0049] The model box 3 is fixed above the load-bearing base plate 2. The rotating component is rotatably fixed at the lower left end of the load-bearing base plate 2, and the lifting component is fixed at the lower right end of the load-bearing base plate 2 to drive the load-bearing base plate 2 to move up and down. The model box 3 has an open end on one side. The shape of the baffle component 7 matches the shape of the open end and is located at the open end. The baffle component 7 is a spliced ​​structure used to simulate passive piles and soil between piles. The baffle component 7 is perpendicular to the load-bearing base plate 2. The baffle driving component drives and connects to the baffle component 7. The baffle driving component is fixed on the load-bearing base plate 2. The measuring component, the lifting component, and the baffle driving component are connected to the host computer 16. The measuring component is used to acquire real-time images inside the model box 3, the stress on the baffle component 7, and the displacement of the load-bearing base plate 2, and transmit them to the host computer 16.

[0050] Working principle: After the model box 3 is filled with soil, the test box 1 is hoisted onto the centrifuge basket, that is, the entire device is transferred into the centrifuge. The baffle component 7 of the spliced ​​structure is driven by the baffle drive component, and the load-bearing base plate 2 is moved up and down by the lifting component, so that the model box 3 rotates around the rotating component. The horizontal seismic force of different amplitudes is simulated to be applied to the soil inside the model box 3. The deformation image and displacement trajectory of the soil inside the model box 3 are obtained by the measuring component. The lateral soil pressure on the baffle component 7 is measured, as well as the vertical displacement of the lifting component is measured.

[0051] This scheme involves filling the model box 3 with soil, then hoisting the test box 1 onto the centrifuge basket, thus transferring the entire device into the centrifuge. The baffle component 7 of the spliced ​​structure is driven by the baffle drive component, and the load-bearing base plate 2 is moved up and down by the lifting component. This allows the model box 3 to rotate around the rotating component, simulating the application of horizontal seismic forces of different amplitudes to the soil inside the model box 3. The deformation image and displacement trajectory of the soil inside the model box 3 are obtained by the measuring component, the lateral soil pressure on the baffle component 7 is measured, and the vertical displacement of the lifting component is measured.

[0052] By changing the height of the lifting components, the load-bearing base plate 2 and the model box 3 can rotate around the rotating structure at different angles, decomposing the horizontal component generated by gravity, thereby simulating the application of horizontal seismic forces of different amplitudes to the soil. This quasi-static load application method effectively ensures uniform soil stress and deformation, and is simple, stable, and reliable to operate. Furthermore, the data obtained by the measuring components can reveal the pile-soil load distribution under different seismic loads, enabling a more accurate analysis of the changes in the end-bearing arch load transfer capacity of the passive pile.

[0053] In a preferred embodiment, the baffle component 7 includes a plurality of fixed baffles 71 and movable baffles 72. The fixed baffles 71 are vertically and detachably fixed to the load-bearing base plate 2. The movable baffles 72 are connected to the baffle driving component, which drives the movable baffles 72 to move horizontally, and the movable baffles 72 are always perpendicular to the load-bearing base plate 2.

[0054] The baffle component is a modular structure, including multiple fixed baffles 71 and movable baffles 72. The fixed baffles 71 and movable baffles 72 can be arranged in sequence according to requirements. The structural deformation of the baffle component 7 simulates the differential deformation of the pile and soil, which is more conducive to establishing the evolution process of the end-bearing arch and the relationship between soil deformation. By arranging and combining the moving order of the movable baffles 72 and fixed baffles 71, the pile spacing can be flexibly changed, avoiding the process of frequent installation and disassembly of the pile body required in conventional model tests.

[0055] Specifically, the measuring components also include a miniature earth pressure gauge 14, which is fixed on the side of the fixed baffle 71 that contacts the soil. The miniature earth pressure gauge 14 is connected to the host computer 16 to measure the lateral earth pressure generated by the movable baffle 72 and transmit it to the host computer 16.

[0056] The lateral earth pressure generated between the piles on the fixed baffle 71 is measured by the miniature earth pressure gauge 14 and uploaded to the host computer 16. The host computer 16 monitors the data in real time and determines the current vibration status of the device based on the changes in the measured data.

[0057] like Figure 5 As shown, there are multiple miniature earth pressure gauges 14, each of which is evenly fixed from top to bottom on the side of the fixed baffle 72 that contacts the soil. By longitudinally installing multiple miniature earth pressure gauges 14 on the fixed baffle 71, the lateral earth pressure on the upper and lower parts of the fixed baffle is detected, ensuring that the fill at each layer of the soil has reached a stable state before switching the vibration level, thus improving the accuracy of the data.

[0058] Specifically, the baffle drive component includes a force transmission component 8, a horizontal displacement control component 9, and a load-bearing component 10;

[0059] The load-bearing component 10 is fixed on the load-bearing base plate 2. The horizontal displacement control component 9 is movably fixed on the load-bearing component 10. The horizontal displacement control component 9 drives the force transmission component 8 to move. The movement path of the force transmission component 8 is parallel to the upper surface of the load-bearing base plate 2. The force transmission component 8 is vertically connected to the baffle component 7.

[0060] The force transmission component 8 includes an S-type load cell 81 and a connecting rod 82. One end of the S-type load cell 81 is vertically connected to the baffle component 7 and is used to measure the horizontal load borne by the baffle component. The other end is vertically fixed to the connecting rod 82. The connecting rod 82 is connected to the horizontal displacement control component 9, which drives the connecting rod 82 to move horizontally.

[0061] The horizontal displacement control component 9 includes a stepper motor 91 and a transmission rod 92;

[0062] Stepper motor 91 drives connecting transmission rod 92, connecting rod 82 is fixed at one end of transmission rod 92, stepper motor 91 is fixed on load-bearing member 10, and stepper motor 91 drives connecting rod 82 to move horizontally through transmission rod 92.

[0063] The load-bearing component 10 includes a first load-bearing frame 101, a second load-bearing frame 102, and a horizontal load-bearing plate 103. The first load-bearing frame 101 and the second load-bearing frame 102 are both vertically fixed on the load-bearing base plate 2 to support the horizontal load-bearing plate 103. One end of the horizontal load-bearing plate 103 is vertically connected to the first load-bearing frame 101, and the other end is vertically connected to the second load-bearing frame 102. The stepper motor 91 is fixed on the horizontal load-bearing plate 103.

[0064] The measuring components include a digital camera 13 for acquiring the displacement trajectory of the soil inside the model box 3 and a differential displacement sensor 15 for acquiring the vertical displacement of the lifting component. The digital camera 13 is fixed above the model box 3 by a tripod, and the differential displacement sensor 15 is fixed on the lifting component. Both the digital camera 13 and the differential displacement sensor 15 are connected to the host computer 16.

[0065] This embodiment also provides a method for simulating the passive pile end bearing effect under seismic loads using a centrifugal vibration device, including the following steps:

[0066] S1: The backfill is filled into the model box using a layered filling method, the backfill is compacted, the relative density of the backfill is in the range of 55%-65%, and the soil surface is leveled.

[0067] S2: Hoist the test chamber onto the centrifuge basket, debug the equipment, and after debugging, zero the channel. Take a picture of the soil surface with a digital camera as the reference data, then start the centrifuge. According to the width of the fixed baffle, set the centrifugal acceleration to make the centrifuge reach the set centrifugal acceleration.

[0068] S3: Start the stepper motor to pull the movable baffle at the specified moving speed. The digital camera records the real-time data of soil deformation during the process and uploads it to the host computer.

[0069] S4: Once the earth pressure data measured by the miniature earth pressure gauge on the fixed baffle and the measurement data measured by the S-type weighing sensor remain stable, turn off the stepper motor.

[0070] S5: Maintain a constant centrifugal acceleration, adjust the downward movement distance of the lifting component according to the preset value, and apply a horizontal seismic force according to the preset horizontal seismic acceleration increment. Return to step S3.

[0071] S6: After the experiment, the speckle images acquired by the digital camera under different displacements and different seismic accelerations were analyzed to obtain the deformation field of the soil, and then the static and dynamic evolution process of the end-bearing arch was analyzed to quantify the geometric characteristics of the arch. The load sharing of the pile and soil under different seismic loads was obtained by using S-type weighing sensors and micro weighing sensors to analyze the changes in the load transfer capacity of the end-bearing arch.

[0072] This embodiment also provides an optional implementation method, specifically:

[0073] A centrifuge shaking table device for simulating the passive pile end bearing effect under seismic load, such as Figure 1-6 As shown, it includes a model box, baffle structure, force transmission structure, horizontal displacement control structure, load-bearing structure, lifting structure, rotation structure and monitoring structure.

[0074] The entire experimental setup is fixed to the bottom of the test chamber 1 and placed in the centrifuge basket. The model box 3 is bolted to the load-bearing base plate 2, and the right side is connected to the baffle component 7. Soil 6 is laid layer by layer inside the box. The baffle component 7 includes a fixed baffle 71 and a movable baffle 72, which respectively simulate passive piles and soil between piles. By moving the movable baffle 72, differential deformation between piles and soil is simulated, inducing the end-bearing arching effect. The force transmission component 8 is connected to the baffle component 7 on the left and to the horizontal displacement control component 9 on the right, driving the synchronous horizontal movement of the movable baffle 72. The S-shaped weighing sensor 81 is bolted to the movable baffle 72 and the connecting rod 84. The horizontal displacement control component 9 consists of a stepper motor 91 and a transmission rod 92, and is anchored to the load-bearing component 10 by bolts through a square connecting sleeve 93, outputting a constant horizontal movement. Rate; The load-bearing component 10 is anchored on the load-bearing base plate 2 and consists of the first load-bearing frame 101, the second load-bearing frame 102, the horizontal bearing plate 103, the fourth nut 104, and the fourth screw 105, constraining the horizontal displacement control component 9; The rotating component 11 and the lifting component 12 are respectively composed of a movable hinge and an electric jack, and their lower parts are fixed to the bottom plate of the outer model box 1 and externally connected to the computer 16. The electric jack can be remotely controlled to move down, realize the clockwise rotation of the model box, and apply horizontal seismic force to the backfill; The monitoring component includes a digital camera 13, a miniature earth pressure gauge 14, and a displacement sensor 15. The digital camera 13 is fixed to the upper part of the model box and rotates synchronously with it to obtain soil deformation images.

[0075] In this embodiment, the test chamber 1 has an inner diameter of 900mm × 700mm × 700mm (length × width × height), is composed of a high-strength aluminum alloy frame, has an open top, and one of its side panels along the length direction is detachable for easy installation of structures such as the model box 2. After the test device is installed, the test chamber 1 is hoisted into the centrifuge basket to apply centrifugal force to the soil 6. The model box 2 has an inner diameter of 500mm × 427mm × 330mm (length × width × height), and its three side walls are made of 30mm thick plexiglass sheets bonded together. The lower part is connected to the supporting steel base plate 2 through the first nut 4 and the first screw 5 to improve its rigidity and ensure its structural stability during centrifugal rotation.

[0076] like Figure 2 As shown, in this embodiment, the baffle structure is made of aluminum alloy and includes seven pieces: a fixed baffle 71 and a movable baffle 72. Each piece measures 60mm × 50mm × 330mm (length × width × height). The fixed baffle 71 is bolted to the lower part of the load-bearing steel base plate 2 and remains stationary during the test, simulating a pile with a width of 'a'. The movable baffle 72 has a built-in screw 83 connected to an S-shaped weighing sensor 81, which moves horizontally to the right under the traction of a stepper motor 91, simulating soil compression deformation between piles with a pile spacing of 's'. By arranging and combining the baffle movement sequence, conditions with pile spacings 's' / a = 2, 3, 4, and 5 can be flexibly achieved, such as... Figure 7-10 As shown.

[0077] like Figure 2 As shown, in this embodiment, the force transmission component 8 includes an S-shaped load cell 81, which is stably connected to the movable baffle 72 and the connecting rod 84 on both sides via screws 83, respectively, to monitor the horizontal load on the movable baffle. The right side of the connecting rod 84 is attached to the transmission rod 92 in the horizontal displacement control component 9, driving the S-shaped load cell 81 and the movable baffle 72 to move together. The S-shaped load cell is made of alloy steel, has a measuring range of 50 kg, an output sensitivity of 2.0 ± 10% mV / V, and a response frequency of 10 kHz. The measured load is transmitted back to the computer 16 via a data cable.

[0078] like Figure 4 As shown, in this embodiment, the horizontal displacement control component 9 includes a square cover plate 93 connected to the horizontal bearing plate 102 via a third nut 94 and a third screw 95 to fix the stepper motor 91. During the test, the stepper motor 91 slowly and evenly pulls the transmission rod 92 to the right at a horizontal displacement rate of 1 mm / min, and is connected to the computer 16 to control the start and stop of the stepper motor 91.

[0079] In this embodiment, the load-bearing members 10 are arranged symmetrically front and rear, as shown in the example. Figure 1-2As shown, the first support frame 101 and the second support frame 102 are bolted to the load-bearing base plate 2 through the third nut 104 and the third screw 105. The left and right support frames are welded together by horizontal bearing plates 103, and horizontal displacement control components 9 are fixed on the horizontal bearing plates 103 by bolts.

[0080] In this embodiment, the rotating structure 11 and the lifting structure 12 are respectively composed of a rotating hinge and an electric jack. The upper part of the rotating hinge is embedded in a preset slot in the bearing base plate 2, and the lower part is fixed to the bottom of the test chamber; the electric jack is connected to the computer 16 via a data cable, and controls the model box 3 to rotate clockwise by an angle α through a self-programmed program, intelligently applying seismic force step by step. At this time, the gravitational acceleration g is decomposed into a component perpendicular to the bearing base plate 2, gcosα, and a component parallel to the bearing base plate 2, such as... Figure 6 As shown. Horizontal seismic acceleration coefficient k h Given sinα, based on the horizontal distance L between the rotating hinge and the electric jack, the downward movement distance of the electric jack can be calculated as Ltanα.

[0081] In this embodiment, soil 6 is construction sand. Particle size distribution, relative density, and specific gravity tests were conducted according to the "Standard for Geotechnical Testing Methods" (GB / T 50123—1999). Through two parallel measurements, the specific gravity of the sand was found to be 2.66, the particle size to be 1–2 mm, and the coefficient of uniformity C. u <5, curvature coefficient C c <1 indicates poor gradation; the maximum and minimum dry densities are 1.835 g / cm³. 3 and 1.246 g / cm 3 According to triaxial tests, when the relative density is 60% and the compaction degree is 0.90, the internal friction angle of the sand is 36°.

[0082] In this embodiment, the monitoring components include a digital camera 13, a miniature earth pressure gauge 14, and a displacement sensor 15. The digital camera 13 is a high-resolution digital SLR camera with an image resolution of 2592×1728 pixels. It is fixed to the upper part of the model box 2 with a tripod to maintain relative stillness, and is used to capture the displacement trajectory of the soil. The image data is transmitted to the computer 16 via a data cable. The miniature earth pressure gauge 14 has a range of 500N and is evenly installed from top to bottom on the side of the fixed baffle 71 near the soil to monitor the lateral earth pressure generated between the piles. Figure 5 As shown; the horizontal displacement of the movable baffle is calculated by the horizontal displacement rate and running time of the stepper motor 91; the differential displacement sensor 15 has a range of ±50mm and an accuracy of 0.15μm, and is arranged on the adjacent side of the electric jack to record its vertical displacement.

[0083] In conjunction with the specific centrifugal vibration device described above, this embodiment also provides a test method for a centrifuge model simulating the passive pile end bearing effect under seismic loads, which includes the following steps:

[0084] (1) Prepare experimental materials and equipment

[0085] According to the required dimensions and materials for the test, the following components need to be prepared: test chamber 1, soil 6, S-type load cell 81, stepper motor 91, transmission rod 92, rotating structure 11, lifting structure 12, digital camera 13, miniature earth pressure gauge 14, displacement sensor 15, data cable, screws and nuts of different specifications, etc.; a load-bearing base plate 2, model box 3, fixed baffle 71, movable baffle 72, connecting rod 84, square connecting sleeve 93, first load-bearing frame 101, second load-bearing frame 102, and horizontal load-bearing plate 103.

[0086] (2) Install test equipment

[0087] ① Fix the rotating structure 11 and the lifting structure 12 to the bottom of the test chamber 1, and then install the bearing base plate 2 on it, and adjust the position of the plate to ensure that it is parallel to the bottom surface;

[0088] ② Weld the model box 3 onto the bearing base plate 2, determine the position of the fixed baffle according to the specified pile spacing, and evenly paste the earth pressure gauge on it in advance;

[0089] ③ Weld the first support frame 101, the second support frame 102 and the horizontal support plate 103 together. The lower parts of the first support frame 101 and the second support frame 102 are connected to the support base plate 2 through the fourth nut 104 and the fourth screw 105.

[0090] ④ The third nut 94 and the third screw 95 fix the square cover plate on the horizontal bearing plate 103 and constrain the stepper motor 91;

[0091] ⑤ After adjusting the position of the transmission rod 92, bolt the connecting rod 84, the S-type weighing sensor 81, and the movable baffle 72 to the left in sequence.

[0092] (3) Construct a passive pile reinforced soil model

[0093] The model box 3 is filled using a layered filling method, the soil 6 is compacted to control the relative density to 60%, and the surface of the fill is leveled; the digital camera 13 is fixed to the upper part of the model box 3 by a tripod and connected to the computer 16 by a data cable, and the focus is manually adjusted.

[0094] (4) Start the experiment

[0095] ① Hoist the test chamber 1 onto the centrifuge basket, connect the S-type weighing sensor 81, the lifting structure 12, and the sensor wires to the centrifuge signal channel. After debugging, zero the channel, take a picture of the surface soil with the digital camera 13 as the reference data, and then start the centrifuge.

[0096] ② Based on the width of the fixed baffle, the centrifugal acceleration is set to 50g. When the specified centrifugal acceleration is reached, the stepper motor 91 is started and the movable baffle 72 is pulled according to the specified moving speed. The digital camera 13 records the real-time data of soil deformation during the movement and transmits it back to the computer. The stepper motor is turned off after the soil pressure data on the fixed baffle 71 remains stable.

[0097] ③ Maintaining a constant centrifugal acceleration, apply a horizontal seismic force according to an increment of (0.05 × 50)g in the horizontal seismic acceleration, when k h When the values ​​are 0.05, 0.1, 0.15, and 0.2, the rotating structure rotates clockwise by α = 2.8°, 5.7°, 8.6°, and 11.5° respectively. The displacement sensor 15 monitors the downward movement of the electric jack by the distance Ltanα. Note that after the previous level of seismic force is applied, the next level of seismic force should be applied only after the load on the movable baffle and the fixed baffle has stabilized.

[0098] (5) Analysis of test results

[0099] After the experiment, the Particle Image Velocimetry (PIV) software was used to analyze the speckle images under different displacements and seismic accelerations to obtain the deformation field of the soil, and then to analyze the static and dynamic evolution process of the end-bearing arch and quantify the geometric characteristics of the arch. The pile-soil load sharing under different seismic loads was obtained by using the S-type weighing sensor 81 and the miniature weighing sensor 14 to analyze the changes in the load transfer capacity of the end-bearing arch.

[0100] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A centrifugal vibration device for simulating the passive pile end bearing arch effect under seismic load, characterized in that, Includes a test chamber (1) and a model box (3), a load-bearing base plate (2), a lifting component (12), a rotating component (11), a baffle component (7), a measuring component, a baffle driving component, and a host computer (16) located inside the test chamber (1). The model box (3) is fixed above the load-bearing base plate (2). The rotating component is rotatably fixed at the lower left end of the load-bearing base plate (2). The lifting component is fixed at the lower right end of the load-bearing base plate (2) and is used to drive the load-bearing base plate (2) to move up and down. The model box (3) has an open end on one side. The shape of the baffle component (7) matches the shape of the open end and is located at the open end. The baffle component (7) is a spliced ​​structure and is used to simulate passive piles and soil between piles. The baffle component (7) is perpendicular to the load-bearing base plate (2). The baffle driving component drives the baffle component (7). The baffle driving component is fixed on the load-bearing base plate (2). The measuring component is used to obtain real-time images inside the model box (3), the stress of the baffle component (7) and the displacement of the load-bearing base plate (2), and transmit them to the host computer (16). The baffle driving component includes a force transmission component (8), a horizontal displacement control component (9), and a load-bearing component (10). The load-bearing component (10) is fixed on the load-bearing base plate (2), the horizontal displacement control component (9) is movably fixed on the load-bearing component (10), the horizontal displacement control component (9) drives the force transmission component (8) to move, the movement path of the force transmission component (8) is parallel to the upper surface of the load-bearing base plate (2), and the force transmission component (8) is vertically connected to the baffle component (7). The force transmission component (8) includes an S-type load cell (81) and a connecting rod (82). One end of the S-type load cell (81) is vertically connected to the baffle component (7) for measuring the horizontal load borne by the baffle component. The other end is vertically fixed on the connecting rod (82). The connecting rod (82) is connected to a horizontal displacement control component (9). The horizontal displacement control component (9) drives the connecting rod (82) to move horizontally. The horizontal displacement control component (9) includes a stepper motor (91) and a transmission rod (92). The stepper motor (91) drives the connecting transmission rod (92), the connecting rod (82) is fixed at one end of the transmission rod (92), the stepper motor (91) is fixed on the load-bearing member (10), and the stepper motor (91) drives the connecting rod (82) to move horizontally through the transmission rod (92).

2. The centrifugal vibration device for simulating the passive pile end bearing effect under seismic load as described in claim 1, characterized in that, The baffle component (7) includes multiple fixed baffles (71) and movable baffles (72). The fixed baffles (71) are vertically and detachably fixed on the load-bearing base plate (2). The movable baffles (72) are connected to the baffle driving component. The baffle driving component drives the movable baffles (72) to move horizontally, and the movable baffles (72) are always perpendicular to the load-bearing base plate (2).

3. The centrifugal vibration device for simulating the passive pile end bearing effect under seismic load as described in claim 2, characterized in that, The measuring component also includes a miniature earth pressure gauge (14), which is fixed on the side of the fixed baffle (71) that contacts the soil. The miniature earth pressure gauge (14) is connected to the host computer (16) to measure the lateral earth pressure generated by the movable baffle (72) and transmit it to the host computer (16).

4. The centrifugal vibration device for simulating the passive pile end bearing effect under seismic load as described in claim 3, characterized in that, The number of miniature earth pressure gauges (14) is multiple, and each miniature earth pressure gauge (14) is evenly fixed from top to bottom on the side of the fixed baffle (72) that contacts the soil.

5. A centrifugal vibration device for simulating the passive pile end bearing effect under seismic load as described in claim 1, characterized in that, The load-bearing component (10) includes a first load-bearing frame (101), a second load-bearing frame (102), and a horizontal load-bearing plate (103). The first load-bearing frame (101) and the second load-bearing frame (102) are both vertically fixed on the load-bearing base plate (2) to support the horizontal load-bearing plate (103). One end of the horizontal load-bearing plate (103) is vertically connected to the first load-bearing frame (101), and the other end is vertically connected to the second load-bearing frame (102). The stepper motor (91) is fixed on the horizontal load-bearing plate (103).

6. The centrifugal vibration device for simulating the passive pile end bearing effect under seismic load according to claim 1, characterized in that, The measuring components include a digital camera (13) for acquiring the displacement trajectory of the soil inside the model box (3) and a differential displacement sensor (15) for acquiring the vertical displacement of the lifting component. The digital camera (13) is fixed above the model box (3) by a tripod, and the differential displacement sensor (15) is fixed on the lifting component. Both the digital camera (13) and the differential displacement sensor (15) are connected to the host computer (16).

7. A method for a centrifugal vibration device based on any one of claims 1-6 to simulate the passive pile end bearing effect under seismic load, characterized in that, Includes the following steps: S1: The backfill is carried out by layering the model box, compacting the backfill, with a relative density of 55%-65%, and leveling the soil surface. S2: Hoist the test chamber onto the centrifuge basket, debug the equipment, and after debugging, zero the channel. Take a picture of the soil surface with a digital camera as the reference data, then start the centrifuge. According to the width of the fixed baffle, set the centrifugal acceleration to make the centrifuge reach the set centrifugal acceleration. S3: Start the stepper motor to pull the movable baffle at the specified moving speed. The digital camera records the real-time data of soil deformation during the process and uploads it to the host computer. S4: Once the earth pressure data measured by the miniature earth pressure gauge on the fixed baffle and the measurement data measured by the S-type weighing sensor remain stable, turn off the stepper motor. S5: Maintain a constant centrifugal acceleration, adjust the downward movement distance of the lifting component according to the preset value, and apply a horizontal seismic force according to the preset horizontal seismic acceleration increment. Return to step S3. S6: After the experiment, the speckle images with different displacements and different seismic accelerations collected by the digital camera were analyzed to obtain the deformation field of the soil, and then the static and dynamic evolution process of the end-bearing arch was analyzed to quantify the geometric shape characteristics of the arch. By using S-type and miniature weighing sensors, the load distribution of piles and soil under different seismic loads is obtained, and the changes in the load transfer capacity of the end-bearing arch are analyzed.

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