A cast-in-place concrete-mud skin-soil contact surface characteristic test device and test method

Abstract

The application discloses a cast-in-situ concrete-mud skin-soil contact surface characteristic test device and test method, and the device comprises a main frame, a sample box, a power loading system and a measuring system; the sample box is provided with a detachable sample preparation limiting seat, a soil ring group, a contact surface ring group, a concrete pouring cylinder and a cover plate; during sample preparation, the detachable sample preparation limiting seat limits the ring group and the concrete pouring cylinder in the radial direction and keeps coaxial, so that soil sample filling, mud laying, concrete casting and joint curing are completed; during single shear test, the limiting seat is removed, the sample and the ring group are installed on a trolley, a vertical loading device and a horizontal loading device respectively apply normal pressure and driving displacement, and a measuring system records mud discharge volume, load and displacement. The application solves the problems that the existing device cannot simulate actual working conditions and the contact surface cannot be accurately distinguished, and the test result is stable and reliable, close to the actual situation and applicable to the determination of the cast-in-situ concrete-mud skin-soil contact surface characteristic.

Description

Technical Field

[0001] This invention relates to geotechnical testing equipment, specifically to a testing device and method for testing the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil. Background Technology

[0002] In engineering construction, a variety of materials are often used, and these materials interact with each other, with contact being one of the key relationships. For example, in earth-rock dams built on overburden layers, during the construction of concrete cutoff walls, the interface between the concrete and soil will form a mud cake on the surface of the cutoff wall after the slurry seeps into the overburden layer. The thickness and condition of this mud cake directly affect the stress transfer, deformation coordination, and shear strength of the contact surface, making it a key factor influencing the structural safety and stability.

[0003] Currently, there are existing testing devices both domestically and internationally for determining the mechanical properties of the contact surface between a structure and soil, including direct shear apparatus, single shear apparatus, and related improved devices. These testing devices mostly generate shear displacement by moving the soil sample along the structural surface. However, existing testing devices have the following drawbacks:

[0004] 1. Soil preparation and concrete pouring and curing are usually carried out separately, which makes it impossible to simulate the contact surface conditions at different ages of concrete under its own weight after pouring in actual construction.

[0005] 2. The uniform ring thickness of the stacked ring sample preparation equipment makes it impossible to accurately distinguish the contact surface between concrete and soil during single shear tests, resulting in the inability to truly obtain the mechanical properties of the contact surface between soil and concrete.

[0006] 3. Existing contact surface samples lack standardized mud laying and discharge procedures, making it difficult to accurately control the mud skin thickness.

[0007] Therefore, it is of great significance to develop a test device for the characteristics of the contact surface of cast-in-place concrete-mud cake-soil to solve the problems existing in the prior art. Summary of the Invention

[0008] Purpose of the invention: The purpose of this invention is to provide a test device and method for the characteristics of the contact surface of cast-in-place concrete-mud cake-soil, which solves the problems in the prior art that the device is difficult to continuously complete soil sample filling, concrete casting and joint curing, that the soil stacked ring group, the contact surface stacked ring group and the concrete casting cylinder are prone to relative displacement during the sample preparation process, and that it is difficult to measure the sample preparation slurry discharge volume and single shear test load and displacement separately.

[0009] Technical Solution: The present invention provides a test device for the characteristics of the contact surface of cast-in-place concrete-soil mixture, comprising a main frame, a sample box, a dynamic loading system, and a measurement system; the main frame includes a base, a guide rail mounted on the base, and a trolley capable of moving along the guide rail; the sample box includes a detachable sample preparation limiting seat, a soil stacked ring assembly, a contact surface stacked ring assembly, a concrete casting cylinder, and a cover plate, wherein the contact surface stacked ring assembly is positioned above the soil stacked ring assembly, the concrete casting cylinder is positioned above the contact surface stacked ring assembly, and the cover plate is positioned above the concrete casting cylinder; the sample box has a sample preparation state and a single shear test state, wherein in the sample preparation state, the detachable sample preparation limiting seat is fitted onto the soil stacked ring assembly and the contact surface stacked ring assembly; The ring assembly and the lower half of the concrete casting cylinder are constrained by a limiting seat to restrict the relative horizontal displacement of the soil ring assembly, the contact surface ring assembly, and the concrete casting cylinder, and to keep them coaxial. In the single shear test state, the detachable sample preparation limiting seat is removed, and the soil ring assembly, the contact surface ring assembly, and the concrete casting cylinder are installed on the trolley. The dynamic loading system includes a vertical loading device and a horizontal loading device. The vertical loading device applies vertical pressure to the sample, and the horizontal loading device drives the trolley to move laterally along the guide rail, thereby realizing the single shear test. The measurement system is connected to the sample box and is used to measure the slurry discharge volume during sample preparation and the load and displacement during the single shear test.

[0010] Furthermore, the horizontal loading device is fixed to the base, and the loading end of the horizontal loading device is connected to the trolley; the vertical loading device is fixed below the crossbeam at the top of the main frame, and the loading end of the vertical loading device is positioned opposite to the cover plate.

[0011] Furthermore, the detachable sample preparation limiting seat is a hollow structure with a vertically penetrating limiting cavity inside. The inner contour of the limiting cavity is adapted to the outer contour of the soil stacked ring assembly, the contact surface stacked ring assembly, and the concrete casting cylinder. The soil stacked ring assembly and the contact surface stacked ring assembly are arranged from bottom to top in the lower part of the limiting cavity. The lower end of the concrete casting cylinder is located in the upper part of the limiting cavity and abuts against the upper end of the contact surface stacked ring assembly.

[0012] Furthermore, a slurry discharge port is provided on the side of the cover plate, and the measuring system includes a measuring cylinder, which is connected to the slurry discharge port via a flexible tube.

[0013] Furthermore, the thickness of a single ring in the soil ring group is 10-20 mm, and the thickness of a single ring in the contact surface ring group is less than the thickness of a single ring in the soil ring group.

[0014] Furthermore, the measurement system includes a vertical displacement sensor, a horizontal displacement sensor, a vertical pressure sensor, and a horizontal shear force sensor; wherein the vertical displacement sensor and the vertical pressure sensor are integrated in a vertical loading device; and the horizontal displacement sensor and the horizontal shear force sensor are integrated in a horizontal loading device.

[0015] Furthermore, the height of the detachable sample preparation limiting seat is greater than the sum of the heights of the soil stacked ring group and the contact surface stacked ring group, so that the portion of the detachable sample preparation limiting seat that extends above the contact surface stacked ring group forms a cylindrical limiting section; the lower end of the concrete casting cylinder is inserted into the cylindrical limiting section.

[0016] Furthermore, the inner and outer diameters of the concrete casting cylinder, the soil stacked ring group, and the contact surface stacked ring group are the same, and the three are coaxially arranged; the cover plate has a circular loading part, the outer diameter of which is adapted to the inner diameter of the soil stacked ring group and the contact surface stacked ring group, so that the cover plate can be inserted into the soil stacked ring group along the axial direction of the soil stacked ring group and abut against the soil sample or concrete surface inside the soil stacked ring group.

[0017] Furthermore, a support column is vertically installed at each end of the crossbeam, and the crossbeam is fixedly installed on the base by the two support columns, with the sample box located between the two support columns.

[0018] Based on the same inventive concept, the present invention provides a test method for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil. This method is applied to the aforementioned test apparatus for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil. The method includes:

[0019] S1. Assemble the soil stacked rings into the detachable sample preparation limiting seat, fill the prepared soil sample into the soil stacked rings, place the cover plate into the soil stacked rings along the axial direction of the soil stacked rings, so that the lower surface of the cover plate abuts against the top surface of the soil sample, apply a preset vertical load to the cover plate through the vertical loading device, and transfer the preset vertical load to the soil sample through the cover plate until the top surface of the soil sample is flush with the upper end surface of the soil stacked rings; remove the preset vertical load and take out the cover plate;

[0020] S2. Assemble the contact surface stacked rings into the detachable sample preparation limiting seat and place it above the soil stacked rings. Insert the lower end of the concrete pouring cylinder into the cylindrical limiting section of the detachable sample preparation limiting seat so that the lower end of the concrete pouring cylinder abuts against the upper end of the contact surface stacked rings.

[0021] S3. When preparing mud-smear type concrete contact surface samples, mud slurry is injected into the concrete pouring cylinder, and then the mixed concrete is poured in. After vibration with a vibrator, a cover plate is placed on the concrete surface and a weight is placed on the cover plate to apply the set curing pressure; the measurement system measures the slurry discharge volume during the sample preparation process.

[0022] S4. When preparing direct concrete contact surface samples, do not inject mud. Pour the mixed concrete directly into the concrete pouring cylinder. After vibration with a vibrator, place the cover plate on the concrete surface and place weights on the cover plate to apply the set curing pressure.

[0023] S5. Curing the samples obtained in step S3 or S4 for 14 to 28 days to form mud-skin type concrete contact surface samples or direct type concrete contact surface samples.

[0024] S6. After curing, remove the cover plate, concrete pouring cylinder, detachable sample preparation limiting seat, contact surface stacked ring group and soil stacked ring group in sequence from the sample box, and observe the physical properties of the mud cake type concrete contact surface sample, including the mud cake state and thickness.

[0025] S7. Reload the mud-skin type concrete contact surface specimen or the direct type concrete contact surface specimen into the soil stacked ring group and the contact surface stacked ring group. Without installing the detachable sample preparation limit seat, install the mud-skin type concrete contact surface specimen or the direct type concrete contact surface specimen, the soil stacked ring group, the contact surface stacked ring group and the concrete pouring cylinder on the trolley. Apply a set vertical pressure to the cover plate through the vertical loading device, drive the trolley to move at a set speed through the horizontal loading device, and record the load and displacement data through the measurement system.

[0026] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows:

[0027] (1) The present invention uses a detachable sample preparation limiting seat to radially limit the soil stacked ring group, the contact surface stacked ring group and the concrete pouring cylinder, so that soil sample preparation, concrete pouring and co-curing can be completed continuously in the same sample box. This solves the problem that soil samples and concrete are prepared separately in the prior art and it is difficult to reproduce the actual pouring and co-curing conditions, thereby improving the consistency between the contact surface sample and the actual engineering contact state.

[0028] (2) The present invention sets up a contact surface stacked ring group with a smaller thickness between the soil stacked ring group and the concrete casting cylinder, so that the contact surface area can be individually located and subdivided, which solves the problem that it is difficult to accurately identify the contact area of ​​concrete-mud cake-soil in the stacked ring group of equal thickness, which is conducive to reducing the position deviation of the contact surface and improving the resolution of the contact surface shear characteristics measurement.

[0029] (3) The present invention forms a slurry collection and metering channel by setting a slurry outlet, a hose and a measuring cylinder on the cover plate, so that the slurry discharged during the concrete pouring process can be collected and quantitatively recorded, which solves the problem that the slurry discharge process is difficult to standardize and quantify, and provides a basis for evaluating or controlling the mud cake formation state.

[0030] (4) The present invention uses a vertical loading device to apply a set normal pressure, uses a horizontal loading device to drive the trolley to move along the guide rail, and uses pressure, shear force and displacement sensors to collect force and displacement data simultaneously, so that the sample can complete the single shear test under different normal pressures, thereby obtaining the shear response of the cast-in-place concrete-mud cake-soil contact surface. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of a test device for the characteristics of the contact surface of cast-in-place concrete-mud cake-soil disclosed in an embodiment of the present invention (the detachable sample preparation limiting seat has been removed).

[0032] Figure 2 This is a schematic diagram of the sample box of the present invention in the sample preparation and curing state;

[0033] Figure 3 This is a front view of the sample box in the sample preparation and curing state in this invention. Detailed Implementation

[0034] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0035] Example 1

[0036] like Figures 1 to 3 As shown, the present invention provides a test device for the characteristics of the contact surface of cast-in-place concrete-mud cake-soil, comprising a main frame, a sample box, a dynamic loading system, and a measurement system, specifically involving the following components: measuring cylinder 1, hose 2, slurry outlet 3, cover plate 4, concrete pouring cylinder 5, detachable sample preparation limiting seat 6, contact surface stacked ring assembly 7, soil stacked ring assembly 8, crossbeam 9, support column 10, base 11, guide rail 12, trolley 13, vertical loading device 14, and horizontal loading device 15.

[0037] like Figure 1 As shown, the main frame supports and secures the entire testing apparatus, including a base 11, guide rails 12, a trolley 13, a crossbeam 9, and support columns 10. The guide rails 12 are laid on the base 11, and the trolley 13 is installed within them. A horizontal loading device 15 pushes the trolley 13 along the guide rails 12. A support column 10 is vertically mounted at each end of the crossbeam 9, and the crossbeam 9 is fixedly mounted on the base 11 via the two support columns 10. The sample box is located between the two support columns 10.

[0038] The sample box includes a detachable sample preparation limiting seat 6, a contact surface stacked ring assembly 7, a soil stacked ring assembly 8, a concrete casting cylinder 5, and a cover plate 4. The contact surface stacked ring assembly 7 is positioned above the soil stacked ring assembly 8, the concrete casting cylinder 5 is positioned above the contact surface stacked ring assembly 7, and the cover plate 4 is positioned above the concrete casting cylinder 5. A slurry discharge port 3 is provided on the side of the cover plate 4. The thickness of a single stacked ring in the soil stacked ring assembly 8 is 10–20 mm, and the thickness of a single stacked ring in the contact surface stacked ring assembly 7 is less than the thickness of a single stacked ring in the soil stacked ring assembly 8.

[0039] The inner and outer diameters of the concrete casting cylinder 5, the soil stacked ring group 8, and the contact surface stacked ring group 7 are the same, and they are coaxially arranged. The cover plate 4 has a circular loading part, the outer diameter of which is adapted to the inner diameter of the soil stacked ring group 8 and the contact surface stacked ring group 7, so that the cover plate 4 can be inserted into the soil stacked ring group 8 along the axial direction and abut against the soil sample or concrete surface inside the soil stacked ring group 8.

[0040] The sample box has a sample preparation state and a single shear test state. In the sample preparation state, the detachable sample preparation limiting seat 6 is fitted onto the lower part of the soil stacked ring group 8, the contact surface stacked ring group 7, and the concrete casting cylinder 5. The limiting seat 6 is used to limit the relative horizontal displacement of the soil stacked ring group 8, the contact surface stacked ring group 7, and the concrete casting cylinder 5, and to keep the three coaxial. In the single shear test state, the detachable sample preparation limiting seat 6 is removed, and the soil stacked ring group 8, the contact surface stacked ring group 7, and the concrete casting cylinder 5 are installed on the trolley 13.

[0041] like Figure 3 As shown, the detachable sample-setting limiting seat 6 has a hollow structure with a vertically penetrating limiting cavity inside. The inner contour of the limiting cavity is adapted to the outer contour of the soil stacked ring assembly 8, the contact surface stacked ring assembly 7, and the concrete casting cylinder 5, forming a clearance fit with the above components that allows for axial assembly and disassembly. The soil stacked ring assembly 8 and the contact surface stacked ring assembly 7 are arranged from bottom to top in the lower part of the limiting cavity. The lower end of the concrete casting cylinder 5 is located in the upper part of the limiting cavity and abuts against the upper end of the contact surface stacked ring assembly 7.

[0042] During assembly, the soil ring assembly 8 is first inserted into the lower part of the limiting cavity, followed by the prepared soil. The cover plate 4 is then placed directly into the soil ring assembly 8, with its lower surface abutting against the top surface of the soil sample. The vertical loading head of the vertical loading device 14 abuts against the cover plate 4 and transmits vertical load to the soil sample through the cover plate 4 to preload the soil sample. After the soil sample is preloaded and its top surface is flush with the upper end surface of the soil ring assembly 8, the vertical loading device 14 is unloaded, the cover plate 4 is removed from the soil ring assembly 8, and the contact surface ring assembly 7 is then inserted into the limiting cavity and placed above the soil ring assembly 8. Since the height of the detachable sample preparation limiting seat 6 is greater than the sum of the heights of the soil ring assembly 8 and the contact surface ring assembly 7, the portion of the detachable sample preparation limiting seat 6 that extends above the contact surface ring assembly 7 forms a cylindrical limiting section. Subsequently, the lower end of the concrete pouring cylinder 5 is inserted into the cylinder limiting section until the lower end of the concrete pouring cylinder 5 abuts against the upper end of the contact surface stacked ring assembly 7.

[0043] After assembly, the inner wall of the limiting cavity simultaneously surrounds the soil stacked ring group 8, the contact surface stacked ring group 7, and the outer side of the lower end of the concrete pouring cylinder 5, thereby restricting the horizontal displacement of the above components during soil sample filling, mud injection, concrete pouring, and vibration, and keeping the concrete pouring cylinder 5, the contact surface stacked ring group 7, and the soil stacked ring group 8 coaxial. After the concrete pouring is completed, the cover plate 4 is placed on the concrete surface, and a set curing pressure is applied to the cover plate 4 using weights. The mud discharged during the pouring process flows into the measuring cylinder 1 through the slurry outlet 3 on the cover plate 4 and the hose 2. The discharged mud is collected and quantitatively recorded to provide a basis for evaluating or controlling the mud cake formation state.

[0044] The measurement system is used to measure the slurry discharge volume during the preparation stage and the load and displacement during the single shear test stage. The measurement system includes a measuring cylinder 1, a vertical displacement sensor, a horizontal displacement sensor, a vertical pressure sensor, and a horizontal shear force sensor. During sample preparation, the measuring cylinder 1 is connected to the slurry discharge port 3 on the cover plate 4 via a flexible hose 2 to collect and measure the discharged slurry. During the single shear test, the vertical pressure sensor and vertical displacement sensor in the vertical loading device 14 measure the vertical load and vertical displacement, respectively; the horizontal shear force sensor and horizontal displacement sensor in the horizontal loading device 15 measure the horizontal shear force and horizontal displacement, respectively.

[0045] like Figure 1As shown, the power loading system includes a horizontal loading device 15 and a vertical loading device 14. The horizontal loading device 15 includes a horizontal actuator and a horizontal connector. The horizontal loading device 15 is fixedly installed on the base 11, and its loading end is connected to the trolley 13 through the horizontal connector. It is used to drive the trolley 13 to move laterally along the guide rail 12, thereby realizing the single shear test. A horizontal shear force sensor is set between the horizontal actuator and the trolley 13 to measure the horizontal shear force, and a horizontal displacement sensor is used to measure the horizontal displacement of the trolley 13 relative to the base 11. The vertical loading device 14 is fixed below the crossbeam 9 at the top of the main frame, and the loading end of the vertical loading device 14 is arranged opposite to the cover plate 4. Specifically, the vertical loading device 14 includes a vertical actuator and a vertical loading head. The vertical actuator is fixedly installed below the crossbeam 9 in the main frame, and its output end is connected to the vertical loading head; the vertical loading head is coaxially arranged with the cover plate 4 and can abut against the cover plate 4 to apply vertical pressure to the sample; the vertical pressure sensor and the vertical displacement sensor are used to measure the vertical load and vertical displacement, respectively.

[0046] By simulating the self-weight stress of concrete and achieving both cast-in-place and co-curing, two types of contact surface specimens—mud cake type and direct type—can be prepared. After curing, single shear tests under different vertical pressures are conducted using a loading system. This invention solves the problems of existing devices being unable to simulate actual construction conditions and having inaccurate contact surface differentiation. The test results are stable, reliable, and more closely reflect reality. Furthermore, the device has a simple structure, low cost, and wide applicability, making it suitable for determining the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil.

[0047] Example 2

[0048] The present invention provides a test method for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil, applied to the test apparatus for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil described in Example 1. The test method includes the following steps:

[0049] S1. Insert the soil ring assembly 8 into the detachable sample preparation limiting seat 6, fill the prepared soil sample into the soil ring assembly 8, and place the cover plate 4 into the soil ring assembly 8 along the axial direction of the soil ring assembly 8 so that the lower surface of the cover plate 4 abuts against the top surface of the soil sample. Apply a preset vertical load to the cover plate 4 through the vertical loading device 14, and transfer the preset vertical load to the soil sample through the cover plate 4 until the top surface of the soil sample is flush with the upper end surface of the soil ring assembly 8; remove the preset vertical load and take out the cover plate 4.

[0050] S2. Insert the contact surface stacked ring group 7 into the detachable sample preparation limiting seat 6 and place it above the soil stacked ring group 8. Insert the lower end of the concrete pouring cylinder 5 into the cylindrical limiting section of the detachable sample preparation limiting seat 6 so that the lower end of the concrete pouring cylinder 5 abuts against the upper end of the contact surface stacked ring group 7.

[0051] S3. When preparing mud-smear type concrete contact surface samples, mud is injected into the concrete pouring cylinder 5, and then the mixed concrete is poured in. After vibration with a vibrator, the cover plate 4 is placed on the concrete surface and a weight is placed on the cover plate 4 to apply the set curing pressure; so that the discharged mud flows into the measuring cylinder 1 through the discharge port 3 and the hose 2.

[0052] S4. When preparing a direct concrete contact surface sample, do not inject mud, but pour the mixed concrete directly. After vibration with a vibrator, place the cover plate 4 on the concrete surface and place weights on the cover plate 4 to apply the set curing pressure.

[0053] S5. Curing the samples obtained in step S3 or S4 for 14 to 28 days to form mud-skin type concrete contact surface samples or direct type concrete contact surface samples.

[0054] S6. After curing, remove the cover plate 4, concrete pouring cylinder 5, detachable sample preparation limiting seat 6, contact surface stacked ring group 7 and soil stacked ring group 8 in sequence from the sample box, and observe the physical properties of the mud cake type concrete contact surface sample, including the mud cake state and thickness.

[0055] S7. Reload the mud-smear type concrete contact surface specimen or the direct type concrete contact surface specimen into the soil stacked ring group 8 and the contact surface stacked ring group 7. Without installing the detachable sample preparation limiting seat 6, install the mud-smear type concrete contact surface specimen or the direct type concrete contact surface specimen, the soil stacked ring group 8, the contact surface stacked ring group 7, and the concrete pouring cylinder 5 onto the trolley 13. Apply a set vertical pressure to the cover plate 4 through the vertical loading device 14, and drive the trolley 13 to move at a set speed through the horizontal loading device 15. Record the load and displacement data through the measurement system. This achieves a single shear test on the concrete structure contact surface specimen; the test results are stable and reliable, and more closely approximate the actual contact characteristics.

[0056] In step S7, the force data of the structural sample is recorded by a vertical pressure sensor and a horizontal shear force sensor, and the displacement data is recorded by a vertical displacement sensor and a horizontal displacement sensor.

[0057] The aforementioned test device for measuring the contact surface characteristics of concrete structures solves the problems existing in the prior art, and can meet the requirements for measuring the contact characteristics of concrete structures. During the sample preparation process, it can ensure that the slurry discharged from the cast-in-place concrete forms a mud cake contact surface with the soil or a direct contact surface with the soil. It also approximately simulates the self-weight stress of concrete when pouring a deep underground anti-seepage wall, realizing the joint curing of soil and concrete, which is consistent with actual construction conditions. It can separately measure the contact mechanical characteristics between the mud cake contact surface and the direct contact surface of concrete. It is simple in construction, easy to modify, highly reliable, widely applicable, and low in cost.

Claims

1. A test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil, characterized in that: Includes the main frame, sample box, dynamic loading system, and measurement system; The main frame includes a base (11), a guide rail (12) set on the base (11), and a trolley (13) that can move along the guide rail (12). The sample box includes a detachable sample preparation limiting seat (6), a soil stacked ring group (8), a contact surface stacked ring group (7), a concrete casting cylinder (5), and a cover plate (4). The contact surface stacked ring group (7) is located above the soil stacked ring group (8), the concrete casting cylinder (5) is located above the contact surface stacked ring group (7), and the cover plate (4) is located above the concrete casting cylinder (5). The sample box has a sample preparation state and a single shear test state. In the sample preparation state, the detachable sample preparation limiting seat (6) is sleeved on the lower half of the soil stacked ring group (8), the contact surface stacked ring group (7) and the concrete pouring cylinder (5). The limiting seat (6) is used to limit the relative horizontal displacement of the soil stacked ring group (8), the contact surface stacked ring group (7) and the concrete pouring cylinder (5) and keep the three coaxial. In the single shear test state, the detachable sample preparation limiting seat (6) is removed and the soil stacked ring group (8), the contact surface stacked ring group (7) and the concrete pouring cylinder (5) are installed on the trolley (13). The dynamic loading system includes a vertical loading device (14) and a horizontal loading device (15). The vertical loading device (14) is used to apply vertical pressure to the specimen, and the horizontal loading device (15) is used to drive the trolley (13) to move laterally along the guide rail (12), thereby realizing the single shear test. The measurement system is connected to the sample box and is used to measure the slurry discharge volume during the sample preparation process and the load and displacement during the single shear test.

2. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 1, characterized in that: The horizontal loading device (15) is fixed to the base (11), and the loading end of the horizontal loading device (15) is connected to the trolley (13). The vertical loading device (14) is fixed below the crossbeam (9) at the top of the main frame, and the loading end of the vertical loading device (14) is set opposite to the cover plate (4).

3. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 1, characterized in that: The detachable sample preparation limiting seat (6) is a hollow structure with a vertically penetrating limiting cavity inside. The inner contour of the limiting cavity is adapted to the outer contour of the soil stacked ring group (8), the contact surface stacked ring group (7), and the concrete casting cylinder (5). The soil ring assembly (8) and the contact surface ring assembly (7) are arranged from bottom to top in the lower part of the limiting cavity; The lower end of the concrete casting cylinder (5) is located on the upper part of the limiting cavity and abuts against the upper end of the contact surface stacked ring assembly (7).

4. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 3, characterized in that: The cover plate (4) has a slurry outlet (3) on its side. The measuring system includes a measuring cylinder (1), which is connected to the slurry outlet (3) via a flexible hose (2).

5. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 3, characterized in that: The thickness of a single ring in the soil ring group (8) is 10-20 mm, and the thickness of a single ring in the contact surface ring group (7) is less than the thickness of a single ring in the soil ring group (8).

6. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 1, characterized in that: The measurement system includes a vertical displacement sensor, a horizontal displacement sensor, a vertical pressure sensor, and a horizontal shear force sensor; wherein the vertical displacement sensor and the vertical pressure sensor are integrated in a vertical loading device (14); and the horizontal displacement sensor and the horizontal shear force sensor are integrated in a horizontal loading device (15).

7. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 1, characterized in that: The height of the detachable sample preparation limiting seat (6) is greater than the sum of the heights of the soil stacked ring group (8) and the contact surface stacked ring group (7), so that the part of the detachable sample preparation limiting seat (6) that is higher than the contact surface stacked ring group (7) forms a cylindrical limiting section; The lower end of the concrete casting cylinder (5) is inserted into the cylinder limiting section.

8. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 1, characterized in that: The inner diameter and outer diameter of the concrete casting cylinder (5), the soil stacked ring group (8) and the contact surface stacked ring group (7) are the same, and the concrete casting cylinder (5), the soil stacked ring group (8) and the contact surface stacked ring group (7) are coaxially arranged. The cover plate (4) has a circular loading part. The outer diameter of the circular loading part is adapted to the inner diameter of the soil stacked ring group (8) and the contact surface stacked ring group (7), so that the cover plate (4) can be inserted into the soil stacked ring group (8) along the axial direction of the soil stacked ring group (8) and abut against the soil sample or concrete surface inside the soil stacked ring group (8).

9. The test device for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil according to claim 1, characterized in that: The crossbeam (9) is vertically mounted with a support column (10) at each end. The crossbeam (9) is fixedly mounted on the base (11) by the two support columns (10), and the sample box is located between the two support columns (10).

10. A test method for the characteristics of the contact surface between cast-in-place concrete, mud cake, and soil, characterized in that, This method is applied to the test apparatus for the characteristics of the contact surface of cast-in-place concrete-mud cake-soil as described in claim 1, and the method includes: S1. Insert the soil ring assembly (8) into the detachable sample preparation limiting seat (6), fill the prepared soil sample into the soil ring assembly (8), place the cover plate (4) into the soil ring assembly (8) along the axial direction of the soil ring assembly (8), so that the lower surface of the cover plate (4) abuts against the top surface of the soil sample, apply a preset vertical load to the cover plate (4) through the vertical loading device (14), and transfer the preset vertical load to the soil sample through the cover plate (4) until the top surface of the soil sample is flush with the upper end surface of the soil ring assembly (8); remove the preset vertical load and take out the cover plate (4). S2. Insert the contact surface stacked ring group (7) into the detachable sample preparation limiting seat (6) and place it above the soil stacked ring group (8). Insert the lower end of the concrete pouring cylinder (5) into the cylinder limiting section of the detachable sample preparation limiting seat (6) so that the lower end of the concrete pouring cylinder (5) abuts against the upper end of the contact surface stacked ring group (7). S3. When preparing mud-smear type concrete contact surface samples, mud slurry is injected into the concrete pouring cylinder (5), and then the mixed concrete is poured in. After vibration with a vibrator, the cover plate (4) is placed on the concrete surface and a weight is placed on the cover plate (4) to apply the set curing pressure; the measurement system measures the discharge volume of slurry during the sample preparation process. S4. When preparing a direct concrete contact surface sample, do not inject mud. Pour the mixed concrete directly into the concrete pouring cylinder (5). After vibration with a vibrator, place the cover plate (4) on the concrete surface and place weights on the cover plate (4) to apply the set curing pressure. S5. Curing the samples obtained in step S3 or S4 for 14 to 28 days to form mud-skin type concrete contact surface samples or direct type concrete contact surface samples. S6. After curing, remove the cover plate (4), concrete pouring cylinder (5), detachable sample preparation limiting seat (6), contact surface stacked ring group (7) and soil stacked ring group (8) in sequence from the sample box to observe the physical properties of the mud-skin type concrete contact surface sample, including the mud skin state and thickness. S7. Reload the mud-skin type concrete contact surface specimen or the direct type concrete contact surface specimen into the soil stacked ring group (8) and the contact surface stacked ring group (7). Without installing the detachable sample preparation limit seat (6), install the mud-skin type concrete contact surface specimen or the direct type concrete contact surface specimen, the soil stacked ring group (8), the contact surface stacked ring group (7) and the concrete pouring cylinder (5) on the trolley (13). Apply a set vertical pressure to the cover plate (4) through the vertical loading device (14), drive the trolley (13) to move at a set speed through the horizontal loading device (15), and record the load and displacement data through the measurement system.

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