Soil pressure cell limiter of expansive soil two-dimensional dilatometer

Abstract

The utility model discloses a soil pressure cell limiter of an expansive soil two-dimensional dilatometer, which comprises a limiter main body and an adjusting screw, the limiter main body is of a cubic structure, and a soil pressure cell accommodating cavity for limiting and placing a soil pressure cell is arranged in the front surface of the limiter main body; the soil pressure box containing cavity is a circular blind hole matched with the outer ring of the soil pressure box, and a through screw hole is formed in the bottom of the soil pressure box containing cavity; the adjusting screw is installed in the screw hole, a limiting stopper opening is formed between the front face of the limiting stopper body and the soil pressure box containing cavity in a penetrating mode, and limiting stopper protruding structures are arranged on the two wings of the back of the limiting stopper body. The soil pressure box limiter of the expansive soil two-dimensional dilatometer is ingenious in structural arrangement, the back face of the limiter body is fixedly adhered to the sensor supporting block, displacement of a miniature soil pressure sensor on a radial plane in the dilatometer can be effectively limited, and data measured by the miniature soil pressure sensor are more stable and accurate.

Description

Technical Field

[0001] This utility model relates to the technical field of geotechnical engineering experimental instruments, specifically to a soil pressure cell limiter for a two-dimensional expansive soil dilatometer. Background Technology

[0002] Expansive soils are found across six continents and 46 countries. This unique type of soil exists in 26 provinces and regions of my country, where over 300 million people live. Rich in montmorillonite and its mixed-layer minerals, expansive soils swell significantly upon absorbing water. When this expansion is restricted, it generates expansive forces, often causing slippage or overturning of retaining structures in expansive soil areas. This poses a significant threat to shallow, lightweight structures such as highways, railways, buildings, and water conservancy facilities, resulting in economic losses of tens of billions of yuan annually in my country. Determining the lateral expansive force of expansive soils and assessing their impact on the stability of retaining structures is a key issue that needs to be addressed in the design of retaining structures in expansive soil areas.

[0003] Existing engineering cases have shown that in expansive soil areas, gravity retaining walls and other retaining structures can experience horizontal sliding of several centimeters after the expansive soil they support becomes moist. Simultaneously with this horizontal sliding, the expansive soil behind the wall undergoes lateral expansion, accompanied by a decrease in lateral expansion force, until the retaining wall reaches a stress equilibrium and ultimately stabilizes. Analyzing the impact of lateral expansion force on retaining wall stability requires first obtaining the relationship between the lateral expansion force and the lateral expansion deformation of the expansive soil. To measure the lateral expansion force generated by the limited expansion deformation due to water absorption in expansive soil and the resulting varying degrees of lateral expansion, strain-type lateral expansion force testing devices and measurement methods have been developed. For example, Chinese Patent: A Strain-Type Lateral Expansion Force Testing Device and Measurement Method, Application No.: 201810410658.8, Application Date: 2018.05.02, Abstract: A strain-type lateral expansion force testing device and measurement method; the device includes a measuring device, a data acquisition device, and a loading device. The measurement method involves conducting immersion expansion tests on specimens under the same initial wet-dense state under no-load and no-lateral-strain conditions to obtain the expansion limit moisture content and corresponding dry density of the specimens at the point of stable expansion. Consolidation tests with progressively increasing loading are then conducted on specimens at the expansion limit moisture content and corresponding dry density to measure the lateral pressure coefficient K0 at different dry densities, thus separating the lateral expansion force from the lateral resultant force. This invention's test method and apparatus are simple, easy to operate, structurally sound, and economical. It solves the long-standing problem in the field of accurately evaluating the stability of expansive soil slopes after humidification and expansion, providing important design parameters for the design of engineering structures and backrest buffer layers in expansive soil areas, and is suitable for widespread engineering application.

[0004] Application research revealed that the aforementioned literature designed a permeable container for soil samples. The top and one side (or free side) of the container cavity allow for soil expansion. A sensor support block is fixed to the free side of the container cavity, and a miniature earth pressure sensor (or earth pressure box) is positioned at the front end of the sensor support block (with the direction closest to the soil sample as the front end). A rigid slider (or baffle) is attached to the front end of the miniature earth pressure sensor, and the lateral earth pressure is transmitted to the miniature earth pressure sensor and measured through the rigid slider. In practical use, the miniature earth pressure sensor lacks a fixing device and slides within the radial plane at the front end of the sensor support block (based on the central axis of the cylindrical earth pressure sensor), requiring repeated adjustments to the sensor position and complicating instrument operation. Furthermore, the miniature earth pressure sensor is difficult to stably position in the center of the front end of the sensor support block, resulting in significant errors in the measured expansion force. Therefore, improvements to the aforementioned strain-type lateral expansion force testing device are needed. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the current strain-type lateral expansion force testing device by providing a soil pressure cell limiter for a two-dimensional expansive soil expansibility. This soil pressure cell limiter can stably position the miniature soil pressure sensor in the center of the front end of the sensor support block, preventing the miniature soil pressure sensor from sliding in the radial plane at the front end of the sensor support block, thus eliminating the need for repeated adjustment of the sensor position.

[0006] This utility model is achieved using the following technical solution:

[0007] A soil pressure cell limiter for a two-dimensional dilatometer for expansive soil includes a limiter body and an adjusting screw. The limiter body is a cuboid structure. The front of the limiter body has a cavity for limiting the placement of the soil pressure cell. The cavity is a circular blind hole matching the outer ring of the soil pressure cell. A through-hole with an inner diameter of 8mm is located at the bottom of the cavity, extending from the cavity to the back of the limiter body. The adjusting screw is installed in the hole. A limiter opening is provided between the front of the limiter body and the cavity. Protruding limiter structures are located on both wings of the back of the limiter body. The soil pressure cell, also known as a miniature soil pressure sensor, has the following specifications: diameter 18mm, thickness 10mm, accuracy ±0.5%FS, and its effective pressure-bearing area is a concentric circle with a center diameter of 12mm on one side. The manufacturer is Liyang Jincheng Instrument Factory, and the product name is strain gauge soil pressure sensor.

[0008] A further preferred embodiment: the main body of the limiter is made of stainless steel.

[0009] Further preferred embodiments: the front length of the limiter body is 20mm, the height is 20mm, and the thickness is 12mm; the single-sided protrusion of the limiter protrusion structure on both wings of the back of the limiter body is 1.5mm in length and 1.5mm in thickness; the depth of the earth pressure box cavity inside the front of the limiter body is 10mm, and the inner diameter is 18.5mm; the distance between the limiter opening and the front of the limiter body is 6mm.

[0010] A further preferred embodiment is a stainless steel slotted headless flat-end screw, with the screw length greater than the screw hole depth, a nominal thread diameter of 8mm, and a screw length of 2.5mm.

[0011] The earth pressure cell limiter of this two-dimensional expansive soil instrument has a cleverly designed structure. The back of the limiter body is bonded and fixed to the sensor support block, which can effectively limit the displacement of the miniature earth pressure sensor in the radial plane inside the instrument, making the data measured by the miniature earth pressure sensor more stable and accurate. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the installation structure of the earth pressure cell limiter of this two-dimensional expansive soil dilatometer.

[0013] Figure 2 This is a top view schematic diagram of the installation structure of the earth pressure cell limiter of this two-dimensional expansive soil dilatometer.

[0014] Figure 3 This is a schematic diagram of the earth pressure cell limiter of the two-dimensional expansibility instrument for expansive soil.

[0015] Figure 4 for Figure 3 A top-view structural diagram;

[0016] Figure 5 for Figure 3 Schematic diagram of the cross section in direction II;

[0017] Figure 6 This is a three-dimensional structural diagram of the earth pressure cell limiter of the two-dimensional expansive soil dilatometer.

[0018] The component names corresponding to the serial numbers in the diagram are:

[0019] 1. Limiter body, 2. Adjusting screw, 3. Earth pressure cell cavity, 4. Limiter opening, 5. Limiter protruding structure, 6. Screw hole, 7. Earth pressure cell, 8. Soil sample, 9. Rigid slider, 10. Sensor support block, 11. Lateral displacement adjustment rod, 12. Loading head, 13. Displacement gauge. Detailed Implementation

[0020] The technical solutions of the invention will be clearly and completely described below with reference to the embodiments. The described embodiments are only a part of the present utility model, and not all of the embodiments. Example

[0021] A soil pressure cell limiter for a two-dimensional expansibility of expansive soil includes a limiter body 1 and an adjusting screw 2. The limiter body 1 is a cuboid structure. An soil pressure cell cavity 3 for limiting the placement of a soil pressure cell 7 is provided on the front of the limiter body 1. The soil pressure cell cavity 3 is a circular blind hole that matches the outer ring of the soil pressure cell 7. A through screw hole 6 is provided at the bottom of the soil pressure cell cavity 3, extending from the soil pressure cell cavity 3 to the back of the limiter body 1. The inner diameter of the screw hole 6 is 8mm. The adjusting screw 2 is installed in the screw hole 6. A limiter opening 4 is provided between the front of the limiter body 1 and the soil pressure cell cavity 3. Limiter protrusions 5 are provided on both wings of the back of the limiter body 1. The Earth Pressure Cell 7, also known as a miniature earth pressure sensor, has the following specifications: diameter 18mm, thickness 10mm, accuracy ±0.5%FS, and its effective pressure-bearing area is a concentric circle area with a center diameter of 12mm on one side. The manufacturer is Liyang Jincheng Instrument Factory, and the product name is strain gauge earth pressure sensor.

[0022] The main body 1 of the limiter is made of stainless steel.

[0023] The front length of the limiter body 1 is 20mm, the height is 20mm, and the thickness is 12mm; the back of the limiter body 1 has two wings with a single-sided protrusion of the limiter protrusion structure 5, which has a length of 1.5mm and a thickness of 1.5mm; the front of the limiter body 1 has a soil pressure box cavity 3 with a depth of 10mm and an inner diameter of 18.5mm; the limiter opening 4 is 6mm deep from the front of the limiter body 1.

[0024] The adjusting screw 2 is a stainless steel slotted headless flat-end screw. The length of the adjusting screw 2 is greater than the depth of the screw hole, the nominal diameter of the thread is 8mm, and the length of the adjusting screw 2 is 2.5mm.

[0025] In use, place the earth pressure box 7 inside the earth pressure box cavity 3 of the limiter body 1, pass the wire of the earth pressure box 7 through the limiter opening 4, adjust the adjusting screw 2 so that the earth pressure box 7 protrudes slightly 0.5mm from the outside of the limiter body 1, then place the limiter body 1 at the front end of the sensor support block 10, and use waterproof glue to bond the limiter body 1 to the sensor support block 10. Then place the rigid slider 9 at the front end of the earth pressure box 7, ensuring that the rigid slider 9 and the earth pressure box 7 fit tightly together. The rigid slider 9 and sensor support block 10 are components of the lateral expansion force testing device. The lateral expansion force testing device refers to the structure of existing strain-type lateral expansion force testing devices, such as the strain-type lateral expansion force testing device in publication number CN108593883A. It includes three parts: a measuring device, a data acquisition device, and a loading device. The measuring device is mounted on the worktable of the loading device, and the data acquisition device is electrically connected to the measuring device. The measuring device includes a housing, a lateral strain detection device, a loading head 12, and a displacement gauge 13. The housing contains a rectangular cavity, and a displacement gauge is provided on one side of the rectangular cavity. The permeable stone has a lateral strain detection device on one side; the chamber formed between the lateral strain detection device and the permeable stone is for placing soil sample 8, and the loading head 12 is inserted into the chamber and contacts the upper surface of the soil sample 8; the loading head 12 contacts the measuring end of the vertical displacement gauge 13; the bottom of the box is provided with a positioning joint that matches the positioning device on the loading device's worktable, and the positioning joint is a slot that matches the positioning boss on the loading device's worktable; the loading device is a triple high-pressure consolidation apparatus, manufactured by Nanjing Taikeao; the product name is TKA-STC-3H; the permeable stone is inserted into the chamber opposite to the load. A water injection groove is formed between the vertical positioning grooves on the two side walls of the container and the other side wall that is perpendicularly connected to the two opposite side walls of the container. The lateral strain detection device is mounted on the vertical positioning steps on the two opposite side walls of the container to ensure that the specimen is not compressed laterally when the lateral strain is zeroed. The loading head 12 is in contact with the measuring end of the vertical displacement gauge 13. A horizontal positioning step is provided on the side wall of the container formed between the lateral strain detection device and the permeable stone. The height of the horizontal positioning step from the bottom surface of the container is the same as the height of the soil sample 8. The loading head 12 is mounted in the container and positioned by the horizontal positioning step to ensure that the loading head is properly positioned. At the moment the loading head 12 applies the overburden load, the entire overburden load transmitted through the loading head is borne by the side wall of the box. The soil sample 8 does not undergo compression deformation due to the overburden load before immersion in water, thus ensuring that the wet and dense state of the specimen does not change before immersion in water. The lateral strain detection device includes an earth pressure box 7, a sensor support block 10, a lateral displacement adjustment rod 11, a lateral displacement reference rod, a lateral displacement gauge 13, and a rigid slider 9. One side of the sensor support block 10 contacts the lateral displacement adjustment rod 11 screwed onto one side wall of the box. One side of the rigid slider 9 is attached to the pressure sensing area of ​​the earth pressure box 7, and the other side contacts the soil sample 8.A lateral displacement reference rod is provided on the sensor support block 10, and a bracket is provided on the housing. The lateral displacement gauge 13 is mounted on the bracket via a horizontal gauge adjustment rod, and its measuring end contacts the lateral displacement reference rod. The rigid slider 9 has a rigid circular protrusion that matches the position of the earth pressure box 7 and contacts the earth pressure box 7. The diameter of the rigid circular protrusion matches the diameter of the pressure sensing area of ​​the sensor. A 0.5-2.0 mm thick silicone gasket is provided between the sensor and the rigid circular protrusion to reduce the test error caused by rigid contact. Since the gasket is very thin and has a certain modulus, the loss of lateral pressure caused by the compression of the gasket is negligible. Compared with the existing strain-type lateral expansion force testing device, a limiter for the miniature earth pressure sensor is added. The earth pressure box 7 is restricted from swaying in the radial plane by the earth pressure box cavity 3. The front and rear positions of the earth pressure box 7 are adjusted by the adjusting screw 2, so that the earth pressure box 7 can be closely connected with the rigid slider, and the measured data is more stable and accurate.

[0026] The above description is not intended to limit the present utility model, nor is the present utility model limited to the above examples. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present utility model should be protected by the present utility model.

Claims

1. A soil pressure cell limiter for a two-dimensional expansibility instrument for expansive soil, characterized in that: The device includes a limiter body (1) and an adjusting screw (2). The limiter body (1) is a cuboid structure. The front of the limiter body (1) is provided with an earth pressure box cavity (3) for limiting the placement of the earth pressure box (7). The bottom of the earth pressure box cavity (3) is provided with a through screw hole (6). The adjusting screw (2) is installed in the screw hole (6). A limiter opening (4) is provided between the front of the limiter body (1) and the earth pressure box cavity (3). The back of the limiter body (1) is provided with two wings of the limiter protrusion structure (5).

2. The earth pressure cell limiter of the two-dimensional expansivity meter for expansive soil according to claim 1, characterized in that: The main body (1) of the limiter is made of stainless steel.

3. The earth pressure cell limiter of the two-dimensional expansibility for expansive soil according to claim 1, characterized in that: The adjusting screw (2) is a stainless steel slotted headless flat-end screw, and the length of the adjusting screw (2) is greater than the depth of the screw hole (6).

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