Unsaturated soil column test system capable of measuring lateral force distribution of soil body

Abstract

The invention discloses an unsaturated soil column test system capable of measuring lateral force distribution of a soil body, and belongs to the technical field of geotechnical engineering test equipment.The test system comprises a soil column sample test device, a data monitoring and collecting system and a water conveying and circulating device; the soil column sample test device comprises a soil column sample chamber filled with a test soil column; the data monitoring and acquisition system comprises a soil moisture content monitoring sensor, a soil suction monitoring sensor, a pressure distribution sensor, a camera and a data acquisition device; the water conveying circulating device conveys water to the soil column sample chamber; according to the test system, the dynamic development distribution condition of lateral pressure in the soil seepage humidifying process is measured by arranging the pressure distribution sensor, and the research on the seepage process is deeper and more thorough; the water passing elbows are arranged on the cover plate and the bearing water collecting base, so that the water passing direction can be determined according to test requirements, and the applicability of the test system is improved; the whole test system is simple in composition, high in measurement precision and wide in measurement range.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering test equipment, and in particular relates to an unsaturated soil column test system capable of measuring the lateral force distribution of soil. Background Art

[0002] The permeability characteristics and behavior of unsaturated soil are of great significance in the fields of geotechnical engineering, agriculture, environmental engineering and geology. In the unsaturated state, the soil pores contain both pore water and pore gas, which coexist with solid soil particles, making the properties of the soil complicated. During the humidification process, the soil properties change and the lateral pressure of the soil also changes. Unlike the permeability coefficient of saturated soil, the permeability coefficient of unsaturated soil changes dynamically with its water content or suction, so the measurement method of saturated permeability coefficient is not suitable for measuring the permeability coefficient of unsaturated soil. The traditional soil column test device cannot monitor the distribution changes of the lateral pressure of the soil during the test, and cannot link its permeability characteristics with the development and changes of the lateral pressure of the soil. Summary of the invention

[0003] In view of the above problems in the prior art, the present invention aims to provide an unsaturated soil column test system that can measure the lateral force distribution of the soil, thereby solving the problem that the traditional soil column test device cannot monitor the distribution changes of the lateral pressure of the soil during the test and cannot link its permeability characteristics with the development and changes of the lateral pressure of the soil.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0005] Provided is an unsaturated soil column test system capable of measuring the lateral force distribution of soil, which comprises a soil column sample test device, a data monitoring and acquisition system, and a water circulation device;

[0006] The soil column sample test device comprises a soil column sample chamber with openings at the top and bottom, a cover plate with a water elbow is arranged at the top opening of the soil column sample chamber, and a bearing and water collecting base with a water elbow is arranged at the bottom opening of the soil column sample chamber; a plurality of sensor installation holes are arranged on the side wall of the soil column sample chamber; and a test soil column is filled in the soil column sample chamber;

[0007] The data monitoring and acquisition system includes a soil moisture monitoring sensor, a soil suction monitoring sensor, a pressure distribution sensor, a camera and a data acquisition device that are electrically connected to each other; the soil moisture monitoring sensor and the soil suction monitoring sensor are multiple in number and are respectively installed in multiple sensor installation holes; the pressure distribution sensor is arranged on the inner side of the soil column sample chamber; the camera is arranged outside the soil column sample chamber; specifically, the soil moisture monitoring sensor and the soil suction monitoring sensor are respectively arranged on two opposite side walls of the soil column sample chamber.

[0008] The water circulation device conveys water to the soil column sample chamber through the two water elbows.

[0009] Furthermore, the cross-section of the soil column sample chamber is a rectangular structure, and the manufacturing material of the soil column sample chamber is a transparent material, so that the entire soil column sample chamber is a transparent structure, which is convenient for the camera to collect relevant image data such as displacement, deformation, and wetting peak of the test soil column in the soil column sample chamber.

[0010] Furthermore, as a specific setting method of the soil column sample chamber, connecting flanges are provided on the top and bottom of the soil column sample chamber, so that when soil column sample chambers of different lengths are needed, multiple soil column sample chambers can be selected and spliced ​​and fixed through connecting flanges to meet the test requirements of test soil columns of different heights, thereby improving the scope of use and flexibility of the entire unsaturated soil column test system that can measure the lateral force distribution of the soil.

[0011] Furthermore, the upper end surface of the bearing water collecting base is a sloped inclined surface structure recessed toward its own center, a water-permeable component is arranged on the upper end surface of the bearing water collecting base, and the bottom of the test soil column is arranged on the water-permeable component.

[0012] Furthermore, as a specific arrangement of the water-permeable component, the water-permeable component includes a porous plate, a permeable stone layer and a filter membrane arranged in sequence from bottom to top, and the bottom of the test soil column is arranged on the upper end surface of the porous plate.

[0013] Further, as a specific setting mode of the pressure distribution sensor, the pressure distribution sensor is in the shape of a film, and the pressure distribution sensor is attached to the inner side of the soil column sample chamber. Specifically, the pressure distribution sensor is composed of conductive silver ink printed on a thin polyester substrate. During the manufacturing process, a conductive row is printed on the lower surface of one film, and a conductive column is printed on the lower surface of another film. When the two films are put together, the intersection of the conductive row and the conductive column forms a stress sensing point, which is the position for measuring pressure. It can also be called a "sensing point" or "pressure pixel point". When collecting data, the pressure distribution sensor uses a known voltage to excite the row and column, thereby identifying a specific sensing point, and records the resistance change of each sensing point when scanning the entire sensing point matrix. When pressure is applied or released at a given sensing point, the resistance in the sensing point circuit will change. The data frame mainly records the output value of each sensing point on the sensor at each time node. The measurement height of the pressure distribution sensor is the height of the entire soil column sample chamber, and it has the function of collecting pressure distribution.

[0014] Furthermore, the water circulation device includes a water storage tank and a water level control box which are interconnected, a water supply component is arranged between the water storage tank and the water level control box, the water supply component includes a water pump, the water inlet end of the water pump is connected to the water storage tank, and the water outlet end of the water pump is connected to the water level control box; the bottom of the water level control box is provided with a water outlet pipe which is connected to the water elbow on the bearing water collecting base. The height of the water level in the water level control box is the seepage head height.

[0015] Furthermore, the water supply component also includes a filtering device; the water elbow on the cover plate is connected to the water storage tank. The filtering device is used to filter impurities in the water to prevent the impurities from entering the soil column sample chamber along with the water flow, causing blockage and inaccurate test results.

[0016] The beneficial effects of the present invention are as follows: compared with the existing test devices and methods, the unsaturated soil column test system of the present invention can measure the lateral force distribution of the soil, and measures the dynamic development and distribution of the lateral pressure during the seepage and wetting process of the soil by setting a pressure distribution sensor, so as to make the study of the seepage process more in-depth and thorough; by setting water elbows on the cover plate and the bearing water collecting base, the water flow direction can be determined according to the test requirements, thereby improving the applicability of the test system; the whole test system has a simple composition, low maintenance cost, high measurement accuracy and a wide measurement range. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the front view of the soil column sample test device.

[0018] Figure 2 This is a schematic diagram of the layout structure of the data monitoring and acquisition system.

[0019] Figure 3 It is a cross-sectional schematic diagram of the water collection base.

[0020] Figure 4 It is a structural schematic diagram of the water circulation device.

[0021] Among them, 11. Soil column sample room; 12. Load-bearing water collection base; 13. Test soil column; 14. Connection flange; 15. Cover plate; 16. Water elbow; 17. Porous plate; 18. Permeable stone layer; 19. Filter membrane; 21. Soil moisture content monitoring sensor; 22. Soil suction monitoring sensor; 23. Pressure distribution sensor; 24. Camera; 25. Data acquisition device; 31. Water storage tank; 32. Water level control box; 33. Water supply components. DETAILED DESCRIPTION

[0022] The specific implementation modes of the present invention are described below to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0023] like Figure 1 to Figure 4 As shown, the present invention provides an unsaturated soil column test system capable of measuring the lateral force distribution of soil, which comprises a soil column sample test device, a data monitoring and acquisition system and a water circulation device;

[0024] Specifically, Figure 1 and Figure 3 As shown, the soil column sample test device includes a soil column sample chamber 11 with openings at the top and bottom, a cover plate 15 with a water elbow 16 is provided at the top opening of the soil column sample chamber 11, and a bearing and collecting base 12 with a water elbow 16 is provided at the bottom opening of the soil column sample chamber 11; a plurality of sensor installation holes are provided on the side wall of the soil column sample chamber 11; and a test soil column 13 is filled in the soil column sample chamber 11.

[0025] Specifically, Figure 2 As shown, the data monitoring and acquisition system includes a soil moisture monitoring sensor 21, a soil suction monitoring sensor 22, a pressure distribution sensor 23, a camera 24 and a data acquisition device 25 which are electrically connected to each other; the soil moisture monitoring sensor 21 and the soil suction monitoring sensor 22 are multiple in number and are respectively installed in multiple sensor installation holes; the pressure distribution sensor 23 is arranged on the inner side of the soil column sample chamber 11; the camera 24 is arranged outside the soil column sample chamber 11; specifically, the soil moisture monitoring sensor 21 and the soil suction monitoring sensor 22 are respectively arranged on two opposite side walls of the soil column sample chamber 11. Figure 2 As shown, two soil moisture monitoring sensors 21 are arranged at intervals on the left side wall of the soil column sample chamber 11; two soil suction monitoring sensors 22 are arranged at intervals on the right side wall of the soil column sample chamber 11. The water circulation device delivers water to the soil column sample chamber 11 through the two water elbows 16.

[0026] Preferably, the cross-section of the soil column sample chamber 11 is a rectangular structure, and the manufacturing material of the soil column sample chamber 11 is a transparent material, so that the entire soil column sample chamber 11 is a transparent structure, which is convenient for the camera 24 to collect relevant image data such as displacement, deformation, and wetting peak of the test soil column 13 in the soil column sample chamber 11.

[0027] Preferably, but not limited to, as a specific setting method of the soil column sample chamber 11, the top and bottom of the soil column sample chamber 11 are provided with connecting flanges 14, so that when soil column sample chambers 11 of different lengths are required, multiple soil column sample chambers 11 can be selected and spliced ​​and fixed through connecting flanges 14 to meet the test requirements of test soil columns 13 of different heights, thereby improving the scope of use and flexibility of the entire unsaturated soil column test system that can measure the lateral force distribution of the soil.

[0028] The upper end surface of the water-bearing and water-collecting base 12 is a sloped inclined surface structure that is concave toward its center. A water-permeable component is arranged on the upper end surface of the water-bearing and water-collecting base 12, and the bottom of the test soil column 13 is arranged on the water-permeable component. The water-permeable component includes a porous plate 17, a permeable stone layer 18 and a filter membrane 19 arranged in sequence from bottom to top, and the bottom of the test soil column 13 is arranged on the upper end surface of the porous plate 17.

[0029] like Figure 2 As shown, as a specific setting mode of the pressure distribution sensor 23, the pressure distribution sensor 23 is in the shape of a thin film, and the pressure distribution sensor 23 is attached to the inner side of the four sides of the soil column sample chamber. Specifically, the pressure distribution sensor 23 is composed of conductive silver ink printed on a thin polyester substrate. During the manufacturing process, a conductive row is printed on the lower surface of a film, and a conductive column is printed on the lower surface of another film. When the two films are put together, the intersection of the conductive row and the conductive column forms a stress sensing point, which is the position for measuring pressure, and can also be called a "sensing point" or "pressure pixel point". When collecting data, the pressure distribution sensor uses a known voltage to excite the row and column, so as to identify a specific sensing point, and records the resistance change of each sensing point when scanning the entire sensing point matrix. When pressure is applied or released at a given sensing point, the resistance in the circuit of the sensing point will change. The data frame mainly records the output value of each sensing point on the sensor at each time node. The measurement height of the pressure distribution sensor 23 is the same as the height of the entire soil column sample chamber 11, and has a pressure distribution acquisition function.

[0030] Expansive soils expand or contract in all directions due to the increase or decrease in natural water content. When the volume expansion of expansive soils is restrained, expansion pressure is generated. Unlike ordinary non-expansive soils, during the expansion process, lateral expansion pressure acts as an additional stress, acting on the foundation structure together with the conventional lateral earth pressure. Lateral expansion pressure and conventional lateral earth pressure can be collectively referred to as lateral pressure. Increased lateral expansion pressure may cause various problems in infrastructure, such as retaining walls, basement walls, pile foundations, tunnels and sewers built in or near expansive soils. For piles buried in expansive soils, the increase in lateral pressure will cause pull-out friction along the pile shaft in the expansion zone. The synergistic effect of lateral expansion pressure and ground uplift will not only lead to redistribution of pile axial force, but also cause pile uplift. By setting up a pressure distribution sensor 23 with a thin film structure, the distribution and development of the lateral expansion pressure during the soil moisturizing process are monitored. Together with the data collected by the soil moisture content sensor, the suction monitoring sensor, and the image acquisition system, the relationship between various indicators in the soil moisturizing process is constructed. The various indicators include moisture content, suction, permeability, and lateral expansion pressure, which helps geotechnical engineers to reasonably design retaining structures, pile foundations, tunnels and other infrastructure in engineering practice.

[0031] like Figure 4 As shown, as a specific setting mode of the water conveying circulation device, the water conveying circulation device includes a water storage tank 31 and a water level control box 32 which are interconnected, and a water supply component 33 is arranged between the water storage tank 31 and the water level control box 32, and the water supply component 33 includes a water pump, the water inlet end of the water pump is connected to the water storage tank 31, and the water outlet end of the water pump is connected to the water level control box 32; the bottom of the water level control box 32 is provided with a water outlet pipe connected to the water elbow 16 on the bearing water collecting base 12. The height of the water level in the water level control box 32 is the height of the seepage head. Specifically, the water supply component 33 also includes a filtering device; the water elbow 16 on the cover plate 15 is connected to the water storage tank 31. The filtering device is used to filter impurities in the water to prevent the impurities from entering the soil column sample chamber 11 with the water flow, causing blockage and inaccurate test results.

[0032] In summary, compared with the existing test devices and methods, the unsaturated soil column test system of the present invention can measure the lateral force distribution of the soil. By setting the pressure distribution sensor 23, the dynamic development and distribution of the lateral pressure during the seepage and wetting of the soil is measured, and the research on the seepage process is more in-depth and thorough. By setting the water elbow 16 on the cover plate 15 and the bearing water collecting base 12, the water flow direction can be determined according to the test requirements, thereby improving the applicability of the test system. The entire test system has a simple composition, low maintenance cost, high measurement accuracy and a wide measurement range.

Claims

1. An unsaturated soil column test system capable of measuring the lateral force distribution of soil, characterized in that: It includes soil column sample test device, data monitoring and acquisition system and water circulation device; The soil column sample test device comprises a soil column sample chamber with openings at the top and bottom, a cover plate with a water elbow is arranged at the top opening of the soil column sample chamber, and a bearing and water collecting base with a water elbow is arranged at the bottom opening of the soil column sample chamber; a plurality of sensor installation holes are arranged on the side wall of the soil column sample chamber; and a test soil column is filled in the soil column sample chamber; The data monitoring and acquisition system comprises a soil moisture monitoring sensor, a soil suction monitoring sensor, a pressure distribution sensor, a camera and a data acquisition device which are electrically connected to each other; the soil moisture monitoring sensor and the soil suction monitoring sensor are multiple in number and are respectively installed in multiple sensor installation holes; the pressure distribution sensor is arranged on the inner side of the four sides of the soil column sample chamber; the camera is arranged outside the soil column sample chamber; The water circulation device conveys water to the soil column sample chamber through the two water elbows.

2. The unsaturated soil column test system capable of measuring the lateral force distribution of soil according to claim 1 is characterized in that: The cross section of the soil column sample chamber is a rectangular structure, and the soil column sample chamber is made of transparent material.

3. The unsaturated soil column test system capable of measuring the lateral force distribution of soil according to claim 2, characterized in that: The top and bottom of the soil column sample chamber are both provided with connecting flanges.

4. The unsaturated soil column test system capable of measuring soil lateral force distribution according to claim 3 is characterized in that: The upper end surface of the bearing water collecting base is a sloped inclined surface structure recessed toward its own center, a water-permeable component is arranged on the upper end surface of the bearing water collecting base, and the bottom of the test soil column is arranged on the water-permeable component.

5. The unsaturated soil column test system capable of measuring soil lateral force distribution according to claim 4, characterized in that: The water-permeable component comprises a porous plate, a permeable stone layer and a filter membrane which are arranged in sequence from bottom to top, and the bottom of the test soil column is arranged on the upper end surface of the porous plate.

6. The unsaturated soil column test system capable of measuring soil lateral force distribution according to claim 5, characterized in that: The pressure distribution sensor is in the shape of a thin film and is attached to the inner sides of the soil column sample chamber.

7. The unsaturated soil column test system capable of measuring soil lateral force distribution according to claim 6, characterized in that: The water supply circulation device includes a water storage tank and a water level control box which are interconnected. A water supply component is arranged between the water storage tank and the water level control box. The water supply component includes a water pump. The water inlet end of the water pump is connected to the water storage tank, and the water outlet end of the water pump is connected to the water level control box. A water outlet pipe which is connected to the water elbow on the load-bearing water collecting base is arranged at the bottom of the water level control box.

8. The unsaturated soil column test system capable of measuring soil lateral force distribution according to claim 7, characterized in that: The water supply component also includes a filtering device; the water elbow on the cover plate is connected to the water storage tank.

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