阅读说明：本技术 列车荷载作用下坎儿井地基塌陷的模型试验装置及方法 (Model test device and method for karez foundation collapse under action of train load ) 是由 刘先峰 张炎飞 李晓辰 袁胜洋 陈伟志 潘高峰 杨文腾 阳剑 高泽飞 陈志明 蒋 于 2020-06-10 设计创作，主要内容包括：一种列车荷载作用下坎儿井地基塌陷的模型试验装置,其组成是：无盖的试验箱体的前面为有机玻璃板；试验箱体内填筑有地基土并埋设有充满水的橡胶水袋、多个土压力盒和多个示踪粒子；地基土表面的中部铺设有混凝土垫板,其表面中部与千斤顶的下端相连；混凝土垫板上固定有位移计,水袋与水管相连,试验箱体外部的水管上还设置有水压力计和电磁阀；试验箱体的前方设置有粒子图像测速装置。该装置能进行列车荷载作用下,坎儿井暗渠塌陷进而引发地基塌陷的模拟试验,以揭示在列车荷载作用下,坎儿井暗渠塌陷进而引发地基塌陷的机理,找出其塌陷原因及各因素对塌陷的影响,进而为坎儿井地区高速铁路的地基加固、抗塌陷设计、修建提供试验依据。(A model test device for karez foundation collapse under the action of train load comprises: the front of the uncovered test box body is an organic glass plate; the test box body is internally filled with foundation soil and is embedded with a rubber water bag filled with water, a plurality of soil pressure cells and a plurality of tracer particles; a concrete cushion plate is laid in the middle of the surface of the foundation soil, and the middle of the surface of the concrete cushion plate is connected with the lower end of the jack; a displacement meter is fixed on the concrete cushion plate, the water bag is connected with a water pipe, and a water pressure meter and an electromagnetic valve are also arranged on the water pipe outside the test box body; the front of the test box body is provided with a particle image speed measuring device. The device can carry out a simulation test of the collapse of the underground canal of the karez to further cause the collapse of the foundation under the action of the train load, so as to reveal the mechanism of the collapse of the underground canal of the karez to further cause the collapse of the foundation under the action of the train load, find out the collapse reasons and the influence of all factors on the collapse, and further provide test basis for the foundation reinforcement, the collapse resistance design and the construction of the high-speed railway in the karez region.)

1. A model test device for karez foundation collapse under the action of train load comprises:

the front surface of the uncovered test box body (1) is an organic glass plate (1a), and the rest surfaces are steel plates; the test box body (1) is filled with foundation soil (2), a water bag (3) filled with water and used for simulating collapse and deformation of a karez underdrain is embedded in the foundation soil (2), the water bag (3) is made of rubber and is cylindrical, and the end face of the water bag is close to the organic glass plate (1 a);

a concrete cushion plate (4) is laid in the middle of the surface of the foundation soil (2), and the middle of the upper surface of the concrete cushion plate (4) is connected with the lower end of a jack (5); the upper end of the jack (5) is connected with the reaction frame (13);

a displacement meter (10) for testing the integral displacement of the foundation is fixed on the concrete cushion plate (4), a plurality of soil pressure boxes (6) are placed in the foundation soil (2), the opening of a water pipe (7) inserted into the test box body (1) is connected with the water bag (3), and a water pressure meter (9) and an electromagnetic valve (8) are also arranged on the water pipe (7) outside the test box body (1); a plurality of tracer particles are uniformly distributed in the foundation soil (2), and a particle image speed measuring device (11) is arranged in front of the test box body (1); and the displacement meter (10), the soil pressure box (6), the electromagnetic valve (8), the water pressure meter (9) and the particle image speed measuring device (11) are electrically connected with a computer.

2. The model test device for karez foundation collapse under train load of claim 1, which is characterized in that: the inner wall of the steel plate of the test box body (1) is also provided with a foam plate (12).

3. The model test device for karez foundation collapse under train load of claim 1, which is characterized in that: the concrete mode of placing a plurality of soil pressure cells (6) in the foundation soil (2) is that 9 soil pressure cells (6) are uniformly distributed above the water bag (3) in a 3-row and 3-column mode, and the soil pressure cells (6) in the middle column are positioned right above the water bag (3).

4. A method for simulating collapse of a karr well foundation under a train load using the model test apparatus for collapse of a karr well foundation under a train load of claim 1, 2 or 3, comprising the steps of:

a: the computer reads and records the data of the displacement meter (10), the soil pressure box (6) and the water pressure meter (9) to obtain the initial position of the foundation soil (2), the initial soil pressure of the foundation soil (2) and the initial pressure of the water bag (3);

b: a jack (5) applies static load to the foundation soil (2) step by step through a concrete cushion plate (4), the static load of each step is kept for at least 50s, and after 50s, a computer reads and records data of a displacement meter (10), a soil pressure box (6) and a water pressure meter (9) under the static load of the step to obtain the displacement of the foundation soil (2) of each step of static load, the soil pressure of the foundation soil (2) and the pressure of a water bag (3); when the static load reaches a set train equivalent load value, the static load is always kept;

c: the computer controls the electromagnetic valve (8) to discharge 1% of water flowing out of the water bag (3) per minute to the outside until the water discharge reaches 20-30% of the volume of the water bag, and the top surface of the water bag (3) sinks slowly to simulate the slow collapse of an underground underdrain; meanwhile, the particle image speed measuring device (11) takes a picture once per minute and uploads the picture taking data to the computer;

d: the computer controls the electromagnetic valve (8) to discharge the water in the water bag (3) outwards at a flow rate of 5 percent of the water flowing out of the water bag (3) per minute until the water in the water bag (3) is discharged completely so as to simulate the rapid collapse of the underground underdrain; meanwhile, the particle image speed measuring device (11) takes a picture once per minute and uploads the picture taking data to the computer;

e: and (3) retracting the jack (5), unloading the load on the foundation soil (2), and then photographing the particle image speed measuring device (11) for the last time to finish the test.

Technical Field

The invention relates to a model test system and a test method for karez foundation collapse.

Background

The karst well is a skillful irrigation and water delivery structure used in desert areas. The main components of the device are a vertical shaft, an underground closed channel and a ground open channel. The structure principle is as follows: the method comprises the steps of searching a water source at a snowfield undercurrent position of a desert high mountain, drilling vertical shafts with gradually-reduced depth from top to bottom according to a certain distance from the water source at a high position to a ground open channel at a low position, digging the underground channels at the bottoms of the vertical shafts, communicating the water source, the vertical shafts and the ground open channels through the underground channels, and accordingly draining the underground water at the high position to the ground open channel at the low position, and conveying and irrigating the water source through the ground open channel.

The karez is mainly distributed in Xinjiang, Shaanxi, Shanxi and Gansu in northwest desert areas. Foreign countries are more distributed in the regions of Zhongya and Western Asia. With the rapid development of high-speed railways, railway subgrades inevitably pass through karez concentrated areas in northwest China, Asia, the west and the like.

Since the karst well is a local important water channel, a high-speed railway is built on the karst well, and the karst well must be ensured not to be damaged or not to influence the normal work of the karst well. Meanwhile, the underground underdrains are locally collapsed or have obviously deteriorated structural performance due to long-term construction of the karez, long-term weathering and the like, and the underground underdrains which are locally collapsed and have obviously deteriorated performance under the action of train load are further collapsed to be completely collapsed, so that the mechanical performance of the foundations in the upper areas of the underground underdrains is obviously deteriorated, the foundations in the areas are collapsed, and the safe operation of the high-speed railway is seriously influenced. Therefore, the design and construction of the high-speed railway in the karez region must ensure that the foundation of the karez region is stable enough and the existing water storage and drainage functions of the karez cannot be abandoned. The solution scheme is as follows: for a high-speed railway with a large included angle (close to 90 degrees) between the walking direction of the karez channel and the line direction of the high-speed railway, bridge engineering can be used for crossing the karez; but the problems of raising railway line position, long bridge length and large engineering investment exist. For a high-speed railway with a small included angle between the walking direction of a karez channel and the line direction, a bridge project is used for crossing the karez, on one hand, the bridge is over long, and the bridge pier is difficult to avoid the karez channel, so that the method cannot be implemented practically. When a roadbed project crosses a karez, the mechanism that the karez underdrains collapse under the load of trains on the roadbed so as to cause foundation collapse must be clarified. Therefore, a model test device and a method for the collapse of the karez foundation under the action of train load are needed to be developed to find out the mechanism of the collapse of the karez underdrains under the action of the load of the trains on the roadbed so as to further cause the collapse of the foundation; the method provides test basis for foundation reinforcement, collapse resistance design and construction of the high-speed railway in the karez region.

Disclosure of Invention

The invention provides a model test device for karez foundation collapse under the action of train load, which can perform a simulation test of karez underdrain collapse and further foundation collapse under the action of train load, so as to reveal the mechanism of karez underdrain collapse and further foundation collapse under the action of train load, find out the influence relationship of collapse reasons and various related factors on collapse, and further provide test basis for foundation reinforcement, collapse resistance design and construction of a high-speed railway in a karez area.

The technical scheme adopted by the invention for realizing the first development is that the model test device for the karez foundation collapse under the action of train load comprises the following components:

the front of the uncovered test box body is an organic glass plate, and the other surfaces are steel plates; the test box body is filled with foundation soil, a water bag filled with water and used for simulating collapse and deformation of a karez underdrain is embedded in the foundation soil, the water bag is made of rubber and is cylindrical, and the end face of the water bag is close to the organic glass plate;

a concrete cushion plate is laid in the middle of the surface of the foundation soil, and the middle of the upper surface of the concrete cushion plate is connected with the lower end of the jack; the upper end of the jack is connected with the reaction frame;

a displacement meter for testing the integral displacement of the foundation is fixed on the concrete cushion plate, a plurality of soil pressure boxes are placed in foundation soil, the pipe orifice of a water pipe inserted into the test box body is connected with a water bag, and a water pressure meter and an electromagnetic valve are also arranged on the water pipe outside the test box body; a plurality of tracer particles are uniformly distributed in the foundation soil, and a particle image speed measuring device is arranged in front of the test box body; and the displacement meter, the soil pressure cell, the electromagnetic valve, the water pressure meter and the particle image speed measuring device are all electrically connected with the computer.

The second invention aims to provide a model test method for the collapse of the karez foundation under the action of the train load by using the model test device for the collapse of the karez foundation under the action of the train load, which can quickly and conveniently reveal the mechanism of the collapse of the karez underground canal and further the collapse of the foundation under the action of the train load, find out the influence relationship of the collapse reason and various relevant factors on the collapse, and further provide test basis for the foundation reinforcement, the collapse resistance design and the construction of a high-speed railway in the karez region.

The technical scheme adopted by the invention for realizing the second invention purpose is that the method for simulating the collapse of the karez foundation under the action of the train load by using the model test device for the collapse of the karez foundation under the action of the train load comprises the following steps:

a: reading and recording data of the displacement meter, the soil pressure cell and the water pressure meter by the computer to obtain the initial position of the foundation soil, the initial soil pressure of the foundation soil and the initial pressure of the water bag;

b: the jack applies static load to the foundation soil step by step through the concrete cushion plate, each stage of static load is kept for at least 50s, and after 50s, the computer reads and records the data of the displacement meter, the soil pressure cell and the water pressure meter under the static load of the stage to obtain the displacement of the foundation soil of each stage of static load, the soil pressure of the foundation soil and the pressure of the water bag; when the static load reaches a set train equivalent load value, the static load is always kept;

c: the computer controls the electromagnetic valve to discharge water of the water bag by 1% of the water quantity flowing out of the water bag per minute until the water discharge reaches 20-30% of the volume of the water bag, and the top surface of the water bag sinks slowly to simulate the slow collapse of the underground closed channel; meanwhile, the particle image velocimeter takes a picture once per minute and uploads the picture data to a computer;

d: the computer controls the electromagnetic valve to ensure that the water in the water bag is discharged outwards at the flow rate of 5 percent of the water bag per minute until the water in the water bag is discharged completely so as to simulate the rapid collapse of the underground underdrain; meanwhile, the particle image velocimeter takes a picture once per minute and uploads the picture data to a computer;

e: and retracting the jack, unloading the load on the foundation soil, and taking a picture of the particle image speed measuring device for the last time to finish the test.

And replacing the materials and specifications of the foundation soil and the water bag filled in the test box body according to the geological exploration results of the foundation and the underdrain of the karez area to be tested and the calculation results of the similar theory. The model experiment of the foundation collapse mechanism caused by the collapse of the underground canals of the karez in different areas under the action of train load can be carried out.

Compared with the prior art, the invention has the beneficial effects that:

in the invention, the water bag is filled with water at the beginning, the water bag supports the surrounding foundation soil, and the support of the karez underdrain to the foundation before deformation and collapse is simulated; and applying a static load with the train equivalent load value to the foundation soil through the concrete cushion plate by using the jack, simulating the load action of the train on the foundation of the karez region, and obtaining the initial total displacement of the foundation soil and the soil pressure values at a plurality of positions in the foundation soil. The water bag slowly drains water at the beginning of the experiment, the water pressure of the water bag is reduced, the water bag is gradually separated from the foundation soil, and the simulation of the initial slow local collapse of the underground canal of the karez is realized; meanwhile, when the underdrain slowly collapses locally, the total displacement of the foundation soil and the soil pressure change right above and laterally above the underdrain in the foundation soil are obtained; and the particle image velocimetry device carries out particle image velocimetry on the tracer particles in the foundation soil, and continuously measures and records the position of each tracer particle in the foundation and the dynamic deformation condition when the underdrain is locally collapsed. Finally, the water bag discharges water quickly, the water bag is separated from the foundation soil completely and quickly, the simulation of the rapid and complete collapse of the covered channel of the karez is realized, and meanwhile, the total displacement of the foundation soil and the soil pressure change right above and laterally above the covered channel in the foundation soil are obtained when the covered channel collapses completely and quickly; and carrying out particle image velocity measurement on the tracer particles in the foundation soil through a particle image velocity measurement device, and continuously measuring and recording the positions of the tracer particles in the foundation and the dynamic deformation condition when the underdrain is locally collapsed when the foundation is collapsed.

In a word, the water bag is ingeniously used for simulating three conditions of deformation and collapse of the under-drain of the karez, slow local collapse and quick complete collapse; simultaneously measuring the displacement change of the foundation soil and the soil pressure change of a plurality of places of the foundation soil under three conditions; and the particle image speed measuring device obtains the space structure of the foundation soil flow field, the flow characteristic of the foundation soil flow field and the dynamic deformation of the underdrain under the conditions of slow collapse and quick collapse of the underdrain, visually displays the evolution development rule of the mechanical characteristic of the karez foundation in the space and time dimensions, and realizes the simulation test of the karez underdrain collapse further causing the foundation collapse under the action of train load. Through analysis of test data and images, the mechanism that the foundation collapses caused by collapse of the underground canals of the karez under the action of train load can be revealed, the influence relationship of collapse reasons and various relevant factors on collapse is found out, test basis is further provided for foundation reinforcement, collapse resistance design and construction of the high-speed railway in the karez area, and the blank in the prior art is successfully filled.

Furthermore, the inner wall of the steel plate of the test box body is also provided with a foam plate.

Therefore, the foundation soil and the steel plate are not in direct frictional contact, and the impact force of the foundation soil on the steel plate can be effectively relieved during loading; and the boundary effect of the foundation soil can be reduced, and the reliability and the precision of the test are improved.

Still further, the concrete mode of placing a plurality of soil pressure cells in the foundation soil is that 9 soil pressure cells are uniformly distributed above the water bag in a 3-row by 3-column mode, and the soil pressure cells in the middle column are positioned right above the water bag.

Therefore, the soil pressure changes at the positions right above the karez and above the two sides and at three different depths can be obtained, and the soil pressure changes above the karez underdrain can be comprehensively reflected when the foundation collapses; thereby more comprehensively and completely analyzing the mechanism of the karez foundation collapse.

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Drawings

FIG. 1 is a left side view schematically showing the structure of the test apparatus of the present invention;

FIG. 2 is a schematic sectional view A-A of FIG. 1.

Detailed Description