A sleeve-type one-dimensional hydrothermal migration test device and test method for soil

Abstract

The present invention discloses a sleeve-type one-dimensional hydrothermal migration test device for soil and a test method. The device includes a sleeve, a cover plate, a heating plate, screws, needle sensors, permeable stones, a porous bottom plate, test soil, etc.; The present invention can carry out experimental determination of the one-dimensional hydrothermal migration law of soil, can conduct local heating experiments on soil samples with different water contents, cut samples for testing and observe the temperature and water content conditions at different distances from the heating surface, and analyze the one-dimensional hydrothermal migration law; It can be used to simulate the high temperature generated by frictional heat during the formation of mud cakes on the metal cutter head during the tunneling process of a shield machine, which affects the properties of the soil at the excavation face and accelerates the formation of mud cakes. To solve this common engineering problem of cutter head mud cake formation, it provides a test means for obtaining the formation mechanism and development law of shield mud cakes.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering model tests, and particularly relates to a one-dimensional hydrothermal migration test device and test method for geotechnical model soil. Background Technique

[0002] When the shield cutter head penetrates through the clay stratum, the clay debris cut off will adhere to the surface of the cutter head, and form solid or semi-solid lumps under the extrusion of the cutter head, and adhere to and block the cutter head, resulting in a decrease in the penetration of the cutter during stratum cutting, and reducing the shield excavation efficiency. Therefore, the adhesion between the soil and the cutter head surface is one of the important reasons for the formation of mud cakes on the cutter head surface. The existence of mud cakes will not only increase the torque of the shield cutter head, but also block the slurry suction port of the slurry discharge pipe, which will seriously affect the shield construction technology and construction safety. The handling and repair of a series of construction problems such as muck improvement, mud cake removal, shield system transformation, shutdown and opening of the cabin, and risk prevention have greatly increased the construction cost.

[0003] Under normal working conditions, the temperature of the shield cutter head is generally 40 - 50 °C. However, during the tunneling process of the shield, especially under the conditions of composite strata, with the formation and increase of mud cakes, the torque and total thrust of the cutter head increase significantly, and the propulsion speed slows down, resulting in the cutter head temperature reaching 400 - 500 °C, or even higher.

[0004] Research shows that the water content and temperature of the soil have a great influence on the adhesion characteristics between the soil and the interface. Therefore, to obtain the formation mechanism and development law of shield mud cakes and solve the common engineering problem of cutter head caking with mud, it is necessary to understand the properties of the soil on the excavation surface affected by the high temperature of the cutter head. Therefore, it is necessary to study the hydrothermal migration law of the soil under the heating state. The present invention can provide a sleeve-type one-dimensional hydrothermal migration test device and test method for soil, providing a test means for solving the law of the influence of temperature on soil properties. Summary of the Invention

[0005] In order to study the variation laws of water and temperature in the soil under the heating state, the present invention provides a model test sleeve-type one-dimensional hydrothermal migration test device and test method for soil, which can conduct local heating tests on soil samples with different water contents, obtain the temperature and water content conditions at different positions at different distances from the heating surface, and analyze the one-dimensional hydrothermal migration law.

[0006] The technical solution adopted by the present invention is:

[0007] A sleeve-type one-dimensional hydrothermal migration test device for soil, characterized in that: the device is composed of a sleeve, a cover plate, a heating plate, screws, a needle sensor, a permeable stone, a porous bottom plate, test soil, etc.; multiple sections of annular sleeves are spliced together and fixed with screws, the porous bottom plate is fixed at the leftmost end with screws, the permeable stone is closely attached to the right side of the bottom plate, and the cover plate is fixed at the rightmost end with screws to form a soil box; the test soil is filled in the soil box, and the test soil is closely attached to the heating plate.

[0008] A heat-insulating layer is provided on the inner wall of the sleeve. One end of each layer of the sleeve has a recessed alignment groove in the inner ring part, and the other end has a protruding part in the inner ring part. A sealing rubber is provided along the outer edge of the protruding part. The sleeves are overlapped at the head and tail and fixed with screws. Small holes are opened on the body of each layer of the sleeve for the needle sensor to be inserted.

[0009] The porous bottom plate and the overlapping sleeve are fixed to each other with screws. A number of small holes are opened on the surface of the porous bottom plate, and the permeable stone is closely attached to the inside of the porous bottom plate.

[0010] The cover plate and the overlapping sleeve are fixed to each other with screws, and a heating plate is arranged inside the cover plate.

[0011] A sleeve-type one-dimensional hydrothermal migration test method for soil, characterized by including the following steps:

[0012] (1) According to the requirements of the hydrothermal migration distance of the test soil, determine the number of sleeve layers, overlap the sleeves and fix them with screws, install and fix the porous bottom plate, apply a layer of vaseline on the inner wall, and place the permeable stone.

[0013] (2) Cut a piece of filter paper with the same cross-sectional size as the permeable stone, place it in the sleeve and stick it to the permeable stone, and fill the test soil in layers and tamp it to the sleeve mouth.

[0014] (3) Fill the test soil in layers and tamp it to the sleeve mouth.

[0015] (4) Cover the cover plate, make the heating plate fit with the test soil, and fix the cover plate.

[0016] (5) Place the device horizontally, insert the needle sensor into the soil through the small hole on the sleeve body.

[0017] (6) Connect the power supply of the heating plate, connect the needle sensor to the data acquisition device, turn on the data acquisition device, and collect temperature data.

[0018] (7) After the test is completed, turn off the power supply and the sensor, pull out the needle sensor, open the cover plate, and remove the sleeves in turn. Each time a layer of sleeve is removed, cut the soil sample neatly along the top surface of the sleeve with a wire saw for geotechnical tests. After weighing and drying, record the change in the water content of the soil at different distances from the heating surface.

[0019] Beneficial effects

[0020] The present invention can conduct experimental measurements on the one-dimensional hydrothermal migration law of soil, and can be used to simulate the high temperature generated by frictional heat during the tunneling process of a shield machine after the metal cutter head forms mud cakes, which affects the properties of the soil at the excavation face and accelerates the formation of mud cakes. To solve this common engineering problem of cutter head mud cake formation and obtain the formation mechanism and development law of shield mud cakes, a testing method is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a three-dimensional view of the sleeve-type one-dimensional soil hydrothermal migration testing device provided by the present invention;

[0022] Figure 2 is a structural diagram of the sleeve-type one-dimensional soil hydrothermal migration testing device provided by the present invention;

[0023] Figure 3 is Figure 1 a partial cross-sectional view of the bottom plate;

[0024] Figure 4 is Figure 1 a partial cross-sectional view of the cover plate;

[0025] Figure 5 is Figure 1 a partial cross-sectional view of the sleeve;

[0026] Figure 6 is Figure 1 a sectional view of the sleeve connection;

[0027] In the attached Figures 1-6 figure

[0028] sleeve 1, cover plate 2, heating plate 3, screw 4, needle-type sensor 5, permeable stone 6, porous bottom plate 7, test soil 8, heat insulation layer 9, sealing rubber 10. DETAILED DESCRIPTION OF THE INVENTION

[0029] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific implementation manners of the present invention will now be described with reference to the accompanying drawings.

[0030] As Figures 1 to 6 shown, a sleeve-type one-dimensional soil hydrothermal migration testing device and testing method, characterized in that:

[0031] A sleeve-type one-dimensional soil hydrothermal migration testing device, characterized in that: the device is composed of a sleeve 1, a cover plate 2, a heating plate 3, a screw 4, a needle-type sensor 5, a permeable stone 6, a porous bottom plate 7, a test soil 8, etc. Multiple sections of annular sleeves 1 are fixedly spliced together with screws 4. The porous bottom plate 7 is fixed at the leftmost end with screws 4. The right side of the bottom plate is closely attached to the permeable stone 6. The cover plate 2 is fixed at the rightmost end with screws 4 to form a soil box; the test soil 8 is filled in the soil box, and the test soil 8 is closely attached to the heating plate 3.

[0032] A heat-insulating layer 9 is provided on the inner wall of the sleeve 1. A counterpoint groove is formed by partial depression of the inner ring at one end of each layer of the sleeve 1, and the inner ring at the other end protrudes. A sealing rubber 10 is provided along the outer edge of the protruding part. The sleeves 1 are counterpointed by the counterpoint grooves and are overlapped with each other at the head and tail and then fixed by screws 4. The number of layers of the sleeves 1 is determined according to the requirements of the test heating influence range. Small holes are opened on the body of each layer of the sleeve 1 for inserting the needle-type sensors 5. To ensure the sealing between the small hole part and the needle-type sensors 5, the gap between the small hole part and the needle-type sensors 5 is filled with hot paraffin or hot resin after inserting the needle-type sensors 5. The sleeve 1 can be one of a hollow cylinder or a hollow prism and is made of metal or engineering plastic. The needle-type sensor 5 can be a temperature sensor, a soil moisture sensor or a multi-functional sensor.

[0033] The porous bottom plate 7 and the overlapping sleeve 1 are fixed to each other by screws 4. A number of small holes are opened on the plate surface of the porous bottom plate 7. The permeable stone 6 is closely attached to the inside of the porous bottom plate 7. In the hydrothermal migration test, due to the sealing of the sleeve 1 wall, the bottom is the only outlet for water and heat, realizing one-dimensional hydrothermal migration.

[0034] The cover plate 2 and the overlapping sleeve 1 are fixed to each other by screws 4. A heating plate 3 is arranged inside the cover plate 2. The size of the heating plate 3 is determined according to the test simulation ratio, and the heating power and temperature can be controlled according to the heating temperature requirements of the test.

[0035] The parameters such as the soil type, water content and compactness of the test soil 8 are determined according to the test requirements. For every 1-2 rings of the overlapping sleeves 1 fixed, the test soil 8 is filled in layers and tamped.

Claims

1. A one-dimensional hydrothermal migration test method for soil in a casing, characterized in that, The test is carried out by using a sleeve-type one-dimensional hydrothermal migration test device for soil; the test device consists of a sleeve (1), a cover plate (2), a heating plate (3), screws (4), a needle sensor (5), a permeable stone (6), a porous bottom plate (7), test soil (8), etc. Multiple sections of annular sleeves (1) are fixed and spliced with each other by screws (4). The porous bottom plate (7) is fixed at the leftmost end by screws (4). The right side of the bottom plate is closely attached to the permeable stone (6). The cover plate (2) is fixed at the rightmost end by screws (4) to form a soil box; the test soil (8) is filled in the soil box, and the test soil (8) is closely attached to the heating plate (3). A heat-insulating layer (9) is provided on the inner wall of the sleeve (1). One end of each layer of the sleeve (1) has a recessed alignment groove in the inner ring part, and the other end has a protrusion in the inner ring part. A sealing rubber (10) is provided on the outer edge of the protruding part. The sleeves (1) are overlapped end to end and fixed with screws (4). Small holes are opened on the body of each layer of the sleeve (1) for the needle sensor (5) to be inserted. The porous bottom plate (7) and the overlapping sleeves (1) are fixed to each other by screws (4). A number of small holes are opened on the plate surface of the porous bottom plate (7), and the permeable stone (6) is closely attached to the inside of the porous bottom plate (7). The cover plate (2) and the overlapping sleeves (1) are fixed to each other by screws (4), and a heating plate (3) is arranged inside the cover plate (2). The method includes the following steps: Step 1: According to the requirements of the hydrothermal migration distance of the test soil (8), determine the number of layers of the sleeve (1). Overlap the sleeves (1) and fix them with screws (4). Install and fix the porous bottom plate (7), apply a layer of vaseline on the inner wall, and place the permeable stone (6). Step 2: Cut a piece of filter paper with the same cross-sectional size as the permeable stone (6), place it in the sleeve (1) and stick it to the permeable stone (6), and fill the test soil (8) in layers and tamp it to the mouth of the sleeve (1). Step 3: Fill the test soil (8) in layers and tamp it to the mouth of the sleeve (1). Step 4: Cover the cover plate (2) to make the heating plate (3) fit with the test soil (8), and fix the cover plate (2). Step 5: Place the device horizontally, and insert the needle sensor (5) into the soil through the small hole on the body of the sleeve (1). Step 6: Connect the power supply of the heating plate (3), connect the needle sensor (5) to the data acquisition device, turn on the data acquisition device, and collect temperature data. Step 7: After the test is completed, turn off the power supply and the sensor, pull out the needle sensor (5), open the cover plate (2), and remove the sleeves (1) in turn. Each time a layer of the sleeve (1) is removed, use a geotechnical test cutting wire saw to cut the soil sample neatly along the top surface of the sleeve (1). After weighing and drying, record the change of the water content of the soil at different distances from the heating surface.

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