Underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluid

Abstract

The invention provides an underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluid, a first piston plate and a second piston plate which are distributed at an interval are arranged in a shell, and a displacement sensor is arranged between the first piston plate and the second piston plate; one end of the dowel bar is fixed in the middle of the first piston plate, the other end of the dowel bar penetrates through the second piston plate and then is connected with the porous damping plate, and the porous damping plate is slidably assembled in the shell and forms a non-Newtonian fluid cavity with the second piston plate; an air pressure cavity is arranged to simulate the pore pressure rising process, non-Newtonian fluid is adopted to simulate the shear thinning and weakening behavior, and controllable loading, quantitative measurement and repeated testing of the liquefaction behavior are achieved through an air pressure-piston-non-Newtonian fluid-porous damping plate coupling transmission mechanism. And rheological indexes in the liquefaction process can be monitored in real time under disturbance conditions of vibration, impact, cyclic shearing and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underground engineering geological disaster monitoring, and particularly relates to a device for monitoring liquefaction of underground soil based on air pressure and non-Newtonian fluid. BACKGROUND

[0002] Liquefaction monitoring usually relies on pore water pressure gauges, accelerometers, LVDT displacement gauges or optical surface displacement monitoring methods, but these methods have obvious limitations: The pore water pressure monitoring method monitors the pore pressure ratio rise by arranging pore pressure gauges on the bottom or sidewall of the test box. However, the pore pressure gauge is a point monitoring method and cannot form a continuous monitoring surface; it is difficult to capture the spatial diffusion process of the liquefaction propagation zone and the weakening zone; and it cannot monitor the coupling evolution of rheological properties and deep displacement.

[0003] Dynamic response monitoring (accelerometer, LVDT) is mainly used for shaking table liquefaction tests to reflect vibration, strain or surface subsidence changes. Such devices are also discretely arranged and cannot reflect the continuous evolution of internal shear bands and deep weakening zones; and they cannot form a unified coordinate system with pore pressure monitoring, which is not conducive to comprehensive judgment of the entire liquefaction process.

[0004] Optical surface displacement monitoring and surface marker point tracking can observe surface uplift, subsidence or lateral flow after liquefaction, but cannot monitor deep displacement; and there is no corresponding relationship between surface displacement and internal weakening zone, making it difficult to reverse the internal liquefaction structure.

[0005] The traditional monitoring scheme using slurry or sand box tests is mostly a single-function system. Most of them can only monitor pore pressure or can only monitor displacement; they lack real-time capture capability of non-Newtonian fluid rheological properties; and they cannot simultaneously monitor the process of air pressure driving, rheological weakening and liquefaction propagation. There is a lack of coupling control between the loading system and the monitoring system, making it difficult to realize real simulation of air pressure propagation and liquefaction diffusion process.

[0006] In summary, although the existing technology can monitor the liquefaction triggering conditions or local point responses, it still has the following shortcomings: single monitoring index, point sampling, inability to continuously monitor internal weakening zone, difficulty in reflecting rheological changes, inability to realize multi-parameter joint monitoring and mode switching, and difficulty in meeting the system research needs of the entire liquefaction process and weakening propagation mechanism.

[0007] Therefore, it is necessary to provide an improved technical solution to overcome the above-mentioned shortcomings of the prior art. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art, and the present application provides a device for monitoring liquefaction of underground soil based on air pressure and non-Newtonian fluid.

[0009] In order to achieve the above object, the present application provides the following technical scheme: A device for monitoring underground soil liquefaction based on air pressure and non-Newtonian fluid, comprising: A shell, a cylindrical inner cavity is arranged inside the shell, a first piston plate and a second piston plate are arranged inside the shell in a spaced distribution, the first piston plate and the second piston plate are slidingly and sealingly assembled along the inner wall of the shell to form an air pressure cavity, a displacement sensor is arranged between the first piston plate and the second piston plate; A force transmission rod, one end of the force transmission rod is fixed in the middle of the first piston plate, the other end of the force transmission rod passes through the second piston plate and is connected to a porous damping plate, the porous damping plate is slidingly assembled inside the shell and forms a non-Newtonian fluid cavity with the second piston plate; An air tank, the air tank is fixed inside the first end cover and is connected to the air pressure cavity through an air pipe; A reset device, the reset device is arranged inside the second end cover to drive the porous damping plate to reset.

[0010] Preferably, a middle hole for slidingly and sealingly assembling the force transmission rod is arranged in the middle of the second piston plate.

[0011] Preferably, an air pump corresponding to the air tank is further arranged on the first end cover.

[0012] Preferably, O-shaped sealing strips corresponding to the shell are arranged on the outer edges of the first piston plate and the second piston plate.

[0013] Preferably, a plurality of perforations are uniformly distributed on the porous damping plate, so that the non-Newtonian fluid cavity passes through the perforations under the extrusion of the second piston plate.

[0014] Preferably, the reset device is an electric cylinder, and a third piston plate opposite to the porous damping plate is arranged on the driving end of the electric cylinder.

[0015] Preferably, the first end cover and the second end cover are fixed at the two ends of the shell in the form of screwing or threaded assembly, and air permeable holes are arranged on the first end cover and the second end cover.

[0016] Preferably, an air pressure sensor is arranged in the air pressure cavity, and the data line and the power line of the air pressure sensor and the displacement sensor pass through the first piston plate and are connected to a data acquisition module. Preferably, a support column is arranged between the first end cover and the first piston plate. Alternatively, a stepped platform is arranged on the inner wall of the shell and stops on the side of the first piston plate corresponding to the first end cover.

[0017] Beneficial effects: By setting up the air pressure cavity to simulate the pore pressure rising process, using the non-Newtonian fluid to simulate the shear thinning weakening behavior, through the coupling transmission mechanism of "air pressure-piston-non-Newtonian fluid-porous damping plate", the controllable loading, quantitative measurement and repeated test of liquefaction behavior are realized, and the rheological index in the liquefaction process can be monitored in real time under the disturbance conditions of vibration, impact, cyclic shear and the like. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings constituting a part of the specification of the application serve to provide a further understanding of the application, the illustrative embodiments of the application and the description thereof serve to explain the application, and do not constitute an improper limitation on the application. Among them: Figure 1 The result diagram of the monitoring test device in the specific embodiment provided by the application is shown.

[0019] In the figure: 1, first end cover; 2, second end cover; 3, outer shell; 4, electric cylinder; 5, gas tank; 6, air pump; 7, air pipe; 8, first piston plate; 9, second piston plate; 10, porous damping plate; 11, third piston plate; 12, displacement sensor; 13, force transmission rod. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the application.

[0021] In the description of the application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom" and the like are the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the application and do not require the application to be constructed and operated in a specific orientation, therefore, it cannot be understood as a limitation on the application. The terms "connected", "connected" used in the application should be understood in a broad sense, for example, it can be fixed connection, or detachable connection; it can be directly connected, or indirectly connected through an intermediate part, and the specific meanings of the above terms can be understood by those skilled in the art according to the specific circumstances.

[0022] The application will be described in detail below with reference to the drawings and in combination with the embodiments. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0023] As Figure 1As shown, a kind of underground soil liquefaction monitoring test device based on air pressure and non-newtonian fluid, including shell 3, force transmission rod 13, gas tank 5 and reset device, shell 3 can be metal material or transparent polyurethane material, its inside is equipped with columnar inner cavity, first piston plate 8 and second piston plate 9 are arranged at intervals in shell 3, first piston plate 8 and second piston plate 9 are all along the sliding seal assembly of shell 3 inner wall, by this sliding seal structure, it forms a closed air pressure cavity between first piston plate 8, second piston plate 9 and shell 3 inner wall, the air pressure cavity can withstand certain air pressure, displacement sensor 12 is arranged between first piston plate 8 and second piston plate 9, for monitoring the relative displacement change between first piston plate 8 and second piston plate 9, displacement sensor 12 is arranged between first piston plate 8 and second piston plate 9, the displacement sensor 12 can collect the displacement data between two piston plates in real time, and provide basis for analyzing displacement variation characteristics in soil liquefaction process based on the data.

[0024] First piston plate 8, second piston plate 9 are connected by force transmission rod 13, ensure that second piston plate 9 can slide stably along the axial direction of shell 3, one end of force transmission rod 13 is fixed in the middle of first piston plate 8, and the two are threadedly fixed or other detachable fixed, specifically, the threaded end corresponding to first piston plate 8 is arranged on force transmission rod 13, and the screw hole corresponding to force transmission rod 13 is arranged on first piston plate 8.

[0025] The other end of force transmission rod 13 passes through second piston plate 9 and is connected with porous damping plate 10 in a detachable manner, so as to limit the distance between first piston plate 8 and porous damping plate 10, so as to ensure that the internal pressure change acts on the non-newtonian fluid through second piston plate 9, porous damping plate 10 is slidably assembled in shell 3, so that first piston plate 8, second piston plate 9 and porous damping plate 10 after combination can be assembled into shell 3, a closed non-newtonian fluid cavity is formed between porous damping plate 10 and second piston plate 9, non-newtonian fluid is filled in the non-newtonian fluid cavity, non-newtonian fluid is used to simulate the typical rheological characteristics such as viscosity drop and yield stress reduction in sand liquefaction process, and the type and liquefaction characteristics of the simulated soil are determined, so as to ensure that the typical rheological characteristics such as viscosity drop and yield stress reduction of sand and other underground soil in liquefaction process can be accurately simulated. Preferably, shear thinning non-newtonian fluid (such as starch paste, paste fluid or mortar simulation liquid), the fluid can present the viscosity drop phenomenon similar to sand liquefaction when being disturbed.

[0026] In the embodiment, the air tank 5 is fixed to the inner side of the first end cover 1 and communicates with the air pressure cavity through the air pipe 7. The connecting part of the air pipe 7 is sealed to prevent air pressure leakage and ensure that the air tank 5 can stably provide air pressure to the air pressure cavity. By adjusting the air pressure output by the air tank 5, different driving forces can be applied to the first piston plate 8 to simulate the liquefaction of the soil under different external forces.

[0027] In the embodiment, the air pipe 7 has a certain strength, and the support column can be replaced by the air pipe 7. Alternatively, a stepped platform is arranged on the inner wall of the shell 3 and stops on the side of the first piston plate 8 corresponding to the first end cover 1. This time, the first piston plate 8 is limited to ensure that the air pressure inside the air pressure cavity applies pressure to the second piston.

[0028] The reset device is arranged on the inner side of the second end cover 2 to drive the porous damping plate 10 to reset. After the test is completed, the porous damping plate 10 is driven to reset for the next test.

[0029] In an optional embodiment, the second piston plate 9 has a middle hole for slidingly sealing and assembling the middle hole of the transmission rod 13. A sealing rubber ring is arranged between the hollow part and the transmission rod 13 to improve the sealing effect and effectively isolate the non-Newtonian fluid cavity and the air pressure cavity to prevent fluid or gas leakage between the non-Newtonian fluid cavity and the air pressure cavity.

[0030] The first end cover 1 is also provided with a gas pump 6 corresponding to the air tank 5. The gas pump 6 and the air tank 5 are connected through a pipeline, and a valve or other control component can be arranged on the pipeline. The gas pump 6 can inflate the air tank 5 to supplement the gas pressure in the air tank 5. Furthermore, the outer edges of the porous damping plate 10, the first piston plate 8 and the second piston plate 9 are provided with O-shaped sealing strips corresponding to the shell 3 to enhance the sealing performance between the first piston plate 8, the second piston plate 9 and the inner wall of the shell 3, prevent the air pressure cavity and the non-Newtonian fluid cavity from leaking, and affect the accuracy of the test results. The outer edges of the first piston plate 8 and the second piston plate 9 are provided with O-shaped sealing strips corresponding to the shell 3. The O-shaped sealing strips have good elasticity and sealing performance and can always be tightly attached to the inner wall of the shell 3 during the sliding process of the piston plate.

[0031] The porous damping plate 10 is fixed to the end of the transmission rod 13 through threaded connection or other detachable forms. Specifically, a threaded section corresponding to the porous damping plate 10 is arranged on the transmission rod 13, and a screw hole corresponding to the transmission rod 13 is arranged on the porous damping plate 10 to realize stable connection. Furthermore, nuts are arranged on both sides of the porous damping plate 10 in the threaded section.

[0032] The porous damping plate 10 is uniformly provided with a plurality of perforations, which are arranged to enable the non-Newtonian fluid chamber to be extruded by the second piston plate 9, so that the non-Newtonian fluid can flow out smoothly. The number, size and distribution density of the perforations can be designed and adjusted according to the properties of the non-Newtonian fluid, the required flow rate of the test, and the simulated permeability characteristics of the soil, and other factors, to ensure that the non-Newtonian fluid can accurately simulate the flow characteristics of the fluid during soil liquefaction during the flow process, and provide reasonable test conditions for subsequent pressure and displacement monitoring.

[0033] In another optional embodiment, the reset device is an electric cylinder 4, which has the advantages of high control accuracy, stable driving force, rapid response, etc., and can meet the requirements of the reset of the porous damping plate 10. The driving end of the electric cylinder 4 is provided with a third piston plate 11 corresponding to the porous damping plate 10, and the outer wall of the third piston plate 11 is provided with an O-shaped sealing ring, so as to be slidingly sealed in the inner cavity of the shell 3. By applying stress to the third piston plate 11 by the reset device, the internal non-Newtonian fluid can be returned to the non-Newtonian fluid chamber, facilitating the next test. Of course, the gas tank 5 stops supplying gas during the reset process.

[0034] In this embodiment, the first end cover 1 and the second end cover 2 are fixed at the two ends of the shell 3 by screwing or threaded assembly, and both the first end cover 1 and the second end cover 2 are provided with air holes. The air holes balance the air pressure inside and outside the end cover, avoid affecting the normal operation of the test device due to excessive air pressure difference between the inside and outside of the end cover during the test process, and facilitate ventilation and exhaust during device maintenance and repair.

[0035] The air pressure chamber is provided with an air pressure sensor, and the data line and power line of the air pressure sensor and the displacement sensor 12 pass through the first piston plate 8 and are connected to the data acquisition module. The air pressure sensor can accurately collect the air pressure data at different times in the air pressure chamber and transmit the data to the data acquisition module. The data line and power line of the air pressure sensor and the displacement sensor 12 pass through the first piston plate 8 and are connected to the data acquisition module. The data line and power line are sealed at the part where they pass through the first piston plate 8 to prevent gas leakage in the air pressure chamber. The data acquisition module can be a computer, which is used to receive, store and preliminarily process the data collected by the air pressure sensor and the displacement sensor 12 in real time, to provide original data support for subsequent data analysis and liquefaction process characterization.

[0036] The present application can capture the starting point of liquefaction, the change trend of liquefaction intensity and the rheological steady state after complete liquefaction during the whole process of disturbance loading, and realizes the dynamic liquefaction process visualization and continuous quantitative monitoring effect which cannot be achieved by traditional static pore pressure monitoring technology. According to the collected pressure-displacement-flow signals, the following key liquefaction characteristic indexes can be obtained: Viscosity: μ = f(ΔP / flow rate) Liquefaction index LI = f(displacement jump / pressure gradient change) Yield stress τy = f(slippage point characteristic) From this, the liquefaction starting point, liquefaction strength, liquefaction duration, and evolution trend can be judged, and the liquefaction process is specifically characterized based on the following trends.

[0037]

[0038] The above description is merely preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of protection of the claims of the present application.

Claims

1. A test device for monitoring underground soil liquefaction based on air pressure and non-Newtonian fluids, characterized in that, include: The outer shell has a columnar inner cavity inside, and a first piston plate and a second piston plate are spaced apart inside the outer shell. The first piston plate and the second piston plate are slidably and sealed along the inner wall of the outer shell to form a pressure chamber. A displacement sensor is provided between the first piston plate and the second piston plate. A force transmission rod, one end of which is fixed to the middle of the first piston plate, and the other end passes through the second piston plate and is connected to a porous damping plate. The porous damping plate is slidably assembled inside the housing and forms a non-Newtonian fluid cavity with the second piston plate. An air tank, which is fixed to the inside of the first end cap and connected to the air pressure chamber via an air pipe; A reset device is provided inside the second end cover to drive the porous damping plate to reset.

2. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The second piston plate has a central hole in the middle for sliding sealing assembly of the force transmission rod.

3. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The first end cap is also equipped with an air pump corresponding to the air tank.

4. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The outer edges of the first piston plate and the second piston plate are provided with O-ring sealing strips corresponding to the outer shell.

5. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The porous damping plate has multiple perforations evenly distributed so that the Newtonian fluid cavity can pass through the perforations under the compression of the second piston plate.

6. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The reset device is an electric cylinder, and the driving end of the electric cylinder is provided with a third piston plate facing the porous damping plate.

7. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The first end cap and the second end cap are fixed to both ends of the outer casing by screws or threads, and both the first end cap and the second end cap are provided with vent holes.

8. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, The air pressure chamber is equipped with an air pressure sensor. The data lines and power lines of the air pressure sensor and the displacement sensor pass through the first piston plate and are connected to the data acquisition module.

9. The underground soil liquefaction monitoring test device based on air pressure and non-Newtonian fluids according to claim 1, characterized in that, A support column is provided between the first end cap and the first piston plate; Alternatively, a stepped platform may be provided on the inner wall of the outer casing to block the first piston plate on the side corresponding to the first end cap.

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