A test device and method for establishing the relationship between pushing resistance and soil failure

Abstract

The application discloses a kind of test device and method for establishing the relationship between pushing resistance and back soil damage, including power device, propelling device and back soil tank 2 for containing soil layer fixed on base;Propelling device includes propelling plate, thickness is 6mm-10mm and the friction coefficient of upper and lower two sides is same, and pressure sensor is arranged between power device and propelling plate;Back soil tank 2 is close to the end of power device and is equipped with propelling mouth, and the other end is equipped with soil outlet, and back soil tank 2 upper portion is equipped with displacement probe for detecting the change of its internal soil layer.The friction between propelling plate and back soil in the application is single, and simple to operate, easy to calculate, convenient for researchers to collect experimental data, and further study the related rules of back soil damage.

Description

Technical Field

[0001] This invention relates to the field of trenchless underground engineering, specifically to a test apparatus and method for establishing the relationship between jacking resistance and backfill failure. Background Technology

[0002] As a trenchless technology, pipe jacking, especially rectangular pipe jacking, has advantages such as high cross-sectional utilization, no obstruction of ground traffic, strong adaptability to geological formations, and no pollution. It is widely used in projects such as subway entrances and exits, municipal pedestrian crossings, underground commercial street pedestrian passages, and municipal tunnels.

[0003] During construction, since the top of the rectangular pipe jacking machine is almost horizontal, when the jacking depth is shallow, the unloading arch effect of the upper soil is relatively insignificant. The soil within the height of the unloading arch collapses and covers the upper surface of the pipe jacking machine under its own weight. This makes the friction of this soil more significant during the forward jacking process. Under the reaction of the jacking resistance, the soil will be compressed and deformed or moved along the direction of the pipe jacking, just as if the top of the pipe is carrying this part of the soil. This phenomenon is called the soil-carrying effect.

[0004] The back soil effect of pipe jacking can cause uneven settlement of the surface soil, seriously affecting the normal use of ground buildings and structures. In order to find a way to reduce the back soil effect during pipe jacking construction, researchers used an experiment simulating the back soil effect of rectangular pipe jacking to establish the relationship between the jacking resistance and the degree of back soil damage. However, the existing experimental device for simulating the back soil effect of rectangular pipe jacking has a complex structure and the friction force on the back soil is inconvenient to operate and collect friction force data, which has a significant impact on the experiment of the soil displacement effect of pipe jacking. Summary of the Invention

[0005] This invention provides an experimental device and method for establishing the relationship between jacking resistance and backing soil failure, which solves the problems of complex structure, inconvenient operation, and inconvenient collection of friction data in existing experimental devices for simulating the backing soil effect of rectangular pipe jacking.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a test device for establishing the relationship between jacking resistance and backfill failure, including a power unit, a propulsion device, and a backfill box for holding soil layers, all fixed on a base; the propulsion device includes a propulsion plate with a thickness of 6mm-10mm and the same friction coefficient on both the upper and lower surfaces, and a pressure sensor is provided between the power unit and the propulsion plate.

[0008] The soil-carrying box is provided with an inlet at one end near the power device and a discharge outlet at the other end. The propulsion plate enters the soil-carrying box at a constant speed through the inlet under the action of the power device. The upper part of the soil-carrying box is provided with a displacement probe for detecting changes in the soil layer inside.

[0009] The pressure sensor and displacement probe are respectively connected to the data acquisition instrument for communication.

[0010] Furthermore, the propulsion port can accommodate propulsion plates of different widths.

[0011] Furthermore, the propulsion device also includes a slide rail, which is arranged parallel to the propulsion plate. One end of the slide rail passes through the propulsion port and enters the back soil box. The side of the propulsion plate is in smooth contact with the slide rail track. A support frame is provided at the end of the slide rail near the power device.

[0012] Furthermore, the slide rail consists of two movable slide rails distributed on both sides of the push plate, and the movable slide rails can move away from or close to each other.

[0013] Furthermore, the soil-carrying box is made of transparent glass and has an open top.

[0014] Furthermore, the opening of the soil-carrying box is provided with multiple slidable crossbars, and multiple displacement probes are provided on the crossbars.

[0015] Furthermore, each crossbar is spaced 0.2m apart, and the probes on each crossbar are spaced 80mm apart.

[0016] The experimental method for establishing the relationship between jacking resistance and backfill failure includes the following steps:

[0017] Step 1: Fill the backfill box with soil according to the required pipe jacking depth;

[0018] Step 2: Fix the displacement probe to the observation position;

[0019] Step 3: Align one end of the push plate with the push port of the soil-carrying box and make contact with the push port, and make contact with the output of the power unit at the other end, and the push plate and the output of the power unit are always in the same direction;

[0020] Step 4: Start the power unit and begin pushing the propulsion plate forward. Simultaneously, record the values ​​displayed on the data acquisition instrument throughout the process until one end of the propulsion plate reaches the soil discharge port of the back soil box. The test ends by recording the changes in the pressure sensor readings and the real-time data of soil deformation and settlement.

[0021] Step 5: Change the size of the propulsion plate and the thickness of the backfill, and repeat the above experimental steps.

[0022] Compared with existing technologies, this invention has the following advantages: The use of a thinner propulsion plate results in very low, negligible, pushing resistance at the propulsion end and sides when the plate advances at a constant speed within the soil layer of the backing soil box. This allows for calculation of only the frictional force on the upper part of the propulsion plate when assessing the forces acting on the backing soil. Since the friction coefficients on both the upper and lower surfaces of the propulsion plate are the same, and the propulsion force is provided by the power unit, the frictional force on the side of the propulsion plate in contact with the backing soil is half the output force of the power unit. Furthermore, the frictional force between the propulsion plate and the backing soil in this invention is singular, simple to operate, and easy to calculate, facilitating the collection of experimental data by researchers to study the relevant laws governing backing soil failure. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is one of the structural schematic diagrams of the present invention;

[0025] Figure 2 This is the second structural schematic diagram of the present invention;

[0026] Figure 3 This is a structural diagram of the card slot and the movable plate.

[0027] The following are the annotations in the attached drawings: 1. Base; 2. Backing box; 21. Propulsion port; 22. Discharge port; 23. Connection hole; 24. Slot; 3. Propulsion plate; 4. Support frame; 5. Slide rail; 6. Pressure sensor; 7. Crossbar; 8. Displacement probe; 9. Power unit; 10. Movable plate. Detailed Implementation

[0028] To make the technical means, creative features, achieved objectives, and functions of this invention clearer and easier to understand, the technical solution of this invention will be described in detail below. Those skilled in the art should understand that the embodiments described below are merely some specific implementation structures or methods of this invention, and not all embodiments; therefore, the scope of protection of this invention is not limited thereto.

[0029] See Figure 1-3As shown, this invention provides an experimental device for establishing the relationship between jacking resistance and backfill failure, including a power unit 9 fixed on a base 1, a propulsion device, and a backfill box 2 for holding soil layers; the propulsion device includes a propulsion plate 3, the thickness of which is 6mm-10mm. To ensure the structural stability of the propulsion plate 3 and avoid planar bending, the thickness of the propulsion plate 3 is generally 8mm; and the friction coefficients of the upper and lower surfaces of the propulsion plate 3 are the same. A pressure sensor 6 is provided between the power unit 9 and the propulsion plate 3, which facilitates the statistical analysis of the force output by the power unit 9. The soil-carrying box 2 has an inlet 21 at one end near the power device 9 and a outlet 22 at the other end. Under the action of the power device 9, the propulsion plate 3 enters the soil-carrying box 2 at a constant speed through the inlet 21. After entering the soil-carrying box 2 through the inlet 21, the propulsion plate 3 will squeeze out a small amount of soil from the outlet 22. The inlet 21 and the outlet 22 are located on the same plane and face each other. The direction of the force applied by the power device 9 is consistent with the direction of movement of the propulsion plate 3. The thickness of the propulsion plate 3 is very small, so the pushing resistance at the pushing end of the propulsion plate 3 is very small and negligible, reducing the force between the propulsion plate and the soil. Since the power device moves at a constant speed, the force output by the power device 9 is approximately equal to the sum of the pushing resistance on the upper and lower surfaces of the propulsion plate 3. This makes the friction force on the upper and lower surfaces of the propulsion plate 3 the same, which makes it easy to calculate the friction force on the soil. That is, the friction force between the upper surface of the propulsion plate 3 and the soil is equal to half of the output force of the power device 9. The power unit 9 can be a motor, pneumatic rod, lead screw, etc., and the upper part of the backing soil box 2 is equipped with a displacement probe 8 for detecting changes in the soil layers inside. The displacement probe 8 is used to detect the soil settlement height, thereby determining the degree of backing soil damage. The pressure sensor 6 and the displacement probe 8 are respectively connected to a data acquisition instrument. The data acquisition instrument (not shown in the figure) displays the pressure value of the pressure sensor 6 and the displacement value detected by the displacement probe 8, facilitating the recording of the change process of the pressure sensor 6 reading and the real-time data of soil deformation and settlement. This establishes the relationship between the change of the pushing resistance of the propulsion plate 3 and the displacement deformation of the overlying backing soil, and further studies the relevant laws of backing soil failure.

[0030] By using a relatively thin propulsion plate 3, the pushing resistance experienced by the propulsion end and both sides when the propulsion plate 3 is pushed into the soil layer inside the back soil box 2 is very small and can be ignored. This means that when calculating the force on the back soil, only the friction force experienced by the upper part of the propulsion plate 3 needs to be calculated. Since the friction coefficients of the upper and lower surfaces of the propulsion plate 3 are the same, and the propulsion force is provided by the power unit 9, the friction force experienced by the side of the propulsion plate 3 in contact with the back soil is half of the output force of the power unit 9.

[0031] When using it, first fill the back soil box 2 with soil according to the required burial depth of the jacking pipe. The burial depth of the jacking pipe can be selected as 150mm, 100mm, 50mm and 25mm, so as to observe the back soil failure phenomenon under different burial depths.

[0032] Next, fix the displacement probe 8 to the observation position to meet the requirements for collecting longitudinal and cross-sectional settlement data of the ground surface. Then, align one end of the propulsion plate 3 with the propulsion port 21 of the back soil box 2 and make contact with the propulsion port 21, and make contact with the output of the power device 9 at the other end. The output end of the propulsion plate 3 and the power device 9 are always in the same direction. Then, start the power device 9 to start pushing the propulsion plate 3. At the same time, record the values ​​displayed on the data acquisition instrument throughout the process until one end of the propulsion plate 3 reaches the soil discharge port 22 of the back soil box 2. By recording the change process of the pressure sensor 6 and the real-time data of soil deformation and settlement, the relationship between the change of the pushing resistance of the propulsion plate 3 and the displacement and deformation of the overlying back soil is established. That is, to explore the critical pushing resistance for back soil failure under different pipe jacking depths and pipe section widths. When the pushing force exceeds the critical pushing resistance, the back soil is destroyed as a whole. In the experiment, the back soil moves forward with the propulsion plate.

[0033] Furthermore, the propulsion port 21 can accommodate propulsion plates 3 of different widths. In the experiment, we need to obtain multiple sets of test data under different conditions, and using propulsion plates 3 of different widths is one such test condition. The width of the propulsion plate 3 can be selected as 50mm, 70mm, 90mm, and 120mm to observe the backfill failure phenomenon under different propulsion plate 3 widths. The width of the propulsion port 21 and the discharge port is 120mm, and its height is consistent with the thickness of the propulsion plate. When using a smaller width propulsion plate 3, the gaps around the propulsion port 21 can be plugged with a correspondingly shaped plug to make the size of the propulsion port 21 compatible with the propulsion plate 3. Figure 3 As shown, movable plates 10 can also be set on both sides of the inlet 21. A strip hole is set at the end of the movable plate 10 away from the inlet 21, and a connecting hole 23 is set on the back soil box 2 at both ends of the inlet 21. The size of the opening of the inlet 21 can be adjusted by adjusting the movable plates 10.

[0034] Furthermore, the propulsion device also includes a slide rail 5, which is arranged parallel to the propulsion plate 3. One end of the slide rail 5 passes through the propulsion port 21 and enters the soil-carrying box 2. The slide rail 5 serves as a guide for the propulsion plate 3, so that the propulsion plate 3 will not deviate during the propulsion process, thus affecting the experimental results. The side of the propulsion plate 3 is in smooth contact with the track of the slide rail 5, so that there is no friction between the propulsion plate 3 and the slide rail 5, which makes it easier to calculate the friction between the soil-carrying box and the propulsion plate 3 and reduces the impact on the experiment. In addition, a support frame 4 is provided at the end of the slide rail 5 near the power device 9, so that the slide rail 5 is stably supported.

[0035] Furthermore, the slide rails 5 consist of two movable slide rails 5 distributed on both sides of the push plate 3, and the movable slide rails 5 can move away from or close to each other. This makes the push plate 3 more stable during the pushing process. During installation, the support frame 4 uses angle steel, and a transverse strip hole is provided on the base 1, allowing the slide rails 5 to be installed at any transverse position. The slide rails 5 can be divided into two sections: one inside the soil-carrying box 2 and one outside the soil-carrying box 2; the end inside the soil-carrying box 2 can be fixed to the side wall of the soil-carrying box 2, such as... Figure 3 As shown, slots 24 can also be provided at the upper and lower parts of the inlet 21 and the outlet 22 to install the slide rail 5, and the slide rail 5 can be moved left and right in the slots 24 to adjust its position.

[0036] Furthermore, the soil-carrying box 2 is made of transparent glass and has an open top, making it easy to observe changes in the soil layers.

[0037] Furthermore, multiple slidable crossbars 7 are provided at the opening of the backing soil box 2, and multiple displacement probes 8 are installed on the crossbars 7. This reasonable distribution facilitates the collection of settlement data at different locations of the backing soil, allowing the monitoring data from the displacement probes to analyze the surface deformation patterns during pipe jacking. The crossbars 7 can have downward-facing grooves at both ends, which fit onto the upper edges of the backing soil box 2, allowing them to slide back and forth along these edges; alternatively, grooves can be provided on the inner walls of the upper sides of the backing soil box 2, with the ends of the crossbars 7 sliding within these grooves.

[0038] Furthermore, each crossbar 7 is spaced 0.2m apart, and the probes on each crossbar 7 are spaced 80mm apart. The positions of the displacement probes 8 are adjusted to meet the requirements for collecting longitudinal and cross-sectional settlement data of the ground surface, and their reasonable distribution facilitates the collection of backfill settlement information. In this device, there are four crossbars 7, and each crossbar 7 is equipped with five evenly distributed displacement probes 8.

[0039] It should be reiterated that, in this invention, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Therefore, those skilled in the art should understand that any modifications or equivalent substitutions made by those skilled in the art to this embodiment based on the technical principles disclosed in this invention, without departing from the technical spirit of this invention, should be included within the scope of protection of this invention.

Claims

1. A test apparatus for establishing the relationship between jacking resistance and backfill failure, characterized in that, It includes a power unit (9) fixed on a base (1), a propulsion device and a backing box (2) for holding soil layers; the propulsion device includes a propulsion plate (3), the thickness of the propulsion plate (3) is 6mm-10mm and the friction coefficients on the upper and lower surfaces are the same, and a pressure sensor (6) is provided between the power unit (9) and the propulsion plate (3); The back soil box (2) has a propulsion port (21) at one end near the power device (9) and a soil discharge port (22) at the other end. The propulsion plate (3) enters the back soil box (2) at a constant speed through the propulsion port (21) under the action of the power device (9). The back soil box (2) is equipped with a displacement probe (8) on the upper part for detecting changes in the soil layer inside. The pressure sensor (6) and displacement probe (8) are respectively connected to the data acquisition instrument for communication.

2. The experimental apparatus for establishing the relationship between jacking resistance and backfill failure according to claim 1, characterized in that, The propulsion port (21) allows propulsion plates (3) of different widths to pass through.

3. The experimental apparatus for establishing the relationship between jacking resistance and backfill failure according to claim 2, characterized in that, The propulsion device also includes a slide rail (5), which is arranged parallel to the propulsion plate (3). One end of the slide rail (5) passes through the propulsion port (21) and enters the back soil box (2). The side of the propulsion plate (3) is in smooth contact with the track of the slide rail (5). A support frame (4) is provided at the end of the slide rail (5) near the power device (9).

4. The experimental apparatus for establishing the relationship between jacking resistance and backfill failure according to claim 3, characterized in that, The slide rails (5) are two movable slide rails (5) distributed on both sides of the push plate (3), and the movable slide rails (5) can move away from or close to each other.

5. The experimental apparatus for establishing the relationship between jacking resistance and backfill failure according to claim 1, 2, 3 or 4, characterized in that, The soil-carrying box (2) is made of transparent glass and has an open top.

6. The experimental apparatus for establishing the relationship between jacking resistance and backfill failure according to claim 5, characterized in that, Multiple slidable crossbars (7) are provided at the opening of the back soil box (2), and multiple displacement probes (8) are provided on the crossbars (7).

7. The experimental apparatus for establishing the relationship between jacking resistance and backfill failure according to claim 6, characterized in that, The distance between each crossbar (7) is 0.2m, and the distance between the probes on each crossbar (7) is 80mm.

8. An experimental method for establishing the relationship between jacking resistance and backfill failure, characterized in that, The experiment using the apparatus described in any one of claims 1-6 specifically includes the following steps: Step 1: Fill the backfill box (2) with soil according to the required burial depth of the pipe jacking; Step 2: Fix the displacement probe (8) to the observation position; Step 3: Align one end of the push plate (3) with the push port (21) of the back soil box (2) and make contact with the push port (21), and make contact with the output of the power device (9) at the other end, and the push plate (3) and the output end of the power device (9) are always in the same direction; Step 4: Start the power unit (9) and begin to push the propulsion plate (3). At the same time, record the values ​​displayed on the data acquisition instrument throughout the process until one end of the propulsion plate (3) reaches the soil discharge port (22) of the back soil box (2). The test ends by recording the change process of the pressure sensor (6) reading and the real-time data of soil deformation and settlement. Step 5: Change the size of the propulsion plate (3) and the thickness of the backfill, and repeat the above experimental steps.

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