Pipe jacking thixotropic slurry drag reduction capability and supporting performance determination system and method

Abstract

The invention discloses a pipe-jacking thixotropic slurry drag reduction capability and supporting performance determination system and method, and relates to the technical field of pipe-jacking engineering, the system comprises a test box and a concrete pipe, a soil body is laid in the test box, the concrete pipe transversely penetrates through the soil body, one end of the concrete pipe is connected with a rotation driving device, and the other end of the concrete pipe is connected with a hydraulic cylinder; the rotary driving device is provided with a torque sensor; the concrete pipe is provided with a plurality of grouting holes, the grouting holes are connected with a grouting pump through a grouting pipe, and the grouting pump is used for pumping thixotropic slurry; a plurality of displacement sensors are distributed above the soil body and are used for detecting the surface settlement of the soil body. Torque is used for replacing jacking force to illustrate the drag reduction effect of the thixotropic slurry, ground surface settlement is used for illustrating the supporting effect of the thixotropic slurry, and the testing effect is more visual and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of pipe jacking engineering, and in particular to a system and method for measuring the drag reduction capacity and supporting performance of thixotropic mud for pipe jacking. Background Art

[0002] Pipe jacking construction is a trenchless or less-excavated pipeline burial construction technology, commonly used for the trenchless laying of various pipelines such as urban underground water supply and drainage pipelines, natural gas and oil pipelines. Pipe jacking construction solves the problems of disturbance to surrounding buildings and traffic congestion during construction. It has the advantages of low construction noise, low environmental pollution, and little impact on the environment and building foundations. During the pipe jacking construction process, the prediction of the jacking force is the decisive factor in the selection and budget of the pipe jacking. The side friction resistance plays a controlling role in the jacking force, and the side friction resistance will gradually increase with the increase of the jacking distance. Under adverse geological conditions such as water-rich sand layers or pebble layers, the process of pipe jacking excavation can easily lead to the collapse of the soil above the pipe section, resulting in excessive surface settlement, affecting the excavation line and the foundation of buildings in the surrounding area, and easily causing property losses and casualties.

[0003] In order to improve the above problems, thixotropic mud is injected into the over-excavation area between the cutter head and the pipe section, and the dry friction between the pipe and the soil before grouting is changed to wet friction between the pipe and the mud sleeve after grouting to achieve the purpose of reducing the side friction resistance. The thixotropic mud is in a gelled state when it is static. After being disturbed by the outside world, the slurry will change from a gelled state to a fluid state, and then change from a fluid state to a gelled state after being static for a period of time. When the jacking pipe is pushed forward, the mud is disturbed and becomes a fluid state, which has a drag reduction effect; when the jacking pipe stops pushing forward, the mud changes from a fluid state to a gelled state, balancing the soil pressure, which can prevent the soil outside the jacking pipe from sinking to a certain extent and play a supporting role.

[0004] At present, most of the research on thixotropic mud is the evaluation of drag reduction performance, and there is less research on the supporting capacity of thixotropic mud. An indoor scaled jacking model is used to simulate the jacking of jacking in actual engineering. For example, CN114216595A discloses a test device and method for measuring the friction resistance of thixotropic mud, driving the sliding box to slide along the test bench toward the baffle, the baffle stops the horizontal dynamometer, so that the loading device and the sliding box produce relative sliding, and the friction resistance between the soil sample and the concrete is displayed by the horizontal dynamometer; CN117890563A discloses a test system and method for the drag reduction and filtration loss performance of thixotropic mud for rectangular jacking pipes, thixotropic mud is laid on the soil, a concrete block is placed on the upper surface of the thixotropic mud, and the pushing end of the jacking device is in contact with the concrete block to measure the dynamic / static friction resistance of the pipe section and the filtration loss performance trend of the thixotropic mud during the jacking of the rectangular jacking pipe. The above operation is relatively complicated and cannot amplify the lubrication and support effect of thixotropic mud on the jacking process; the use of concrete test blocks to simulate the jacking process is quite different from the actual construction process. Only a part of the test block is in contact with the thixotropic mud, which cannot simulate the circumferential friction resistance of the actual jacking project. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a system and method for measuring the drag reduction capacity and supporting performance of thixotropic mud for jacking pipes, using torque instead of jacking force to illustrate the drag reduction effect of thixotropic mud, and using surface settlement to illustrate the supporting effect of thixotropic mud, so that the test effect is more intuitive and reliable.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a system for measuring the drag reduction capacity and support performance of a thixotropic mud for a jacking pipe, comprising a test box and a concrete pipe, wherein soil is laid in the test box, the concrete pipe penetrates the soil in a transverse direction, and one end of the concrete pipe is connected to a rotation drive device, wherein the rotation drive device is provided with a torque sensor;

[0008] The concrete pipe is provided with a plurality of grouting holes, which are connected to a grouting pump through a grouting pipe, and the grouting pump is used to pump thixotropic mud; a plurality of displacement sensors are distributed above the soil body, and the displacement sensors are used to detect the settlement of the soil surface.

[0009] As a further implementation, the rotation drive device includes a motor, and a torque sensor is installed on the motor shaft;

[0010] The torque sensor and the motor are connected to a display.

[0011] As a further implementation method, a top plate is arranged on the upper side of the soil body, and the displacement sensor is arranged on the upper side of the top plate.

[0012] As a further implementation, the displacement sensors are arranged in a row along the center line of the test box, in a row in the direction of the center line of the concrete pipe, and in a row at a distance of one pipe diameter on both sides of the center line.

[0013] As a further implementation, the displacement sensor is connected to a computer.

[0014] As a further implementation method, the thixotropic mud is arranged in a slurry pool, and the slurry pool is connected to the grouting pipe through a grouting pump.

[0015] In a second aspect, an embodiment of the present invention further provides a method for measuring the drag reduction capability and support performance of thixotropic mud for jacking pipes, using the measuring system, comprising:

[0016] Inject thixotropic mud into the concrete pipe; start the rotary drive device to make the concrete pipe rotate at a constant speed according to the set speed; compare the torque before and after adding the thixotropic mud at the same speed to reflect the drag reduction effect of different thixotropic muds under the same soil conditions;

[0017] The concrete pipe stops rotating and stands still for a set time, and then the displacement sensor measures the settlement of the soil surface.

[0018] As a further implementation method, a displacement sensor is used to detect the displacement change of the center line of the concrete pipe and a point one pipe diameter away from the center line.

[0019] As a further implementation, the set standing time satisfies the requirement that the thixotropic mud changes from a fluid state to a gelled state.

[0020] As a further implementation method, a set thickness of soil is first laid in the test box, a concrete pipe is placed in the transverse direction, and then the remaining soil is laid.

[0021] The beneficial effects of the present invention are as follows:

[0022] The present invention simplifies the test of the drag reduction performance of thixotropic mud in the indoor model test of pipe jacking, disturbs the thixotropic mud by rotation, and uses torque to reflect the lateral friction resistance during the jacking process; the thixotropic mud wraps the entire concrete pipe, which is consistent with the actual construction situation; the torque parameter is used to reflect the magnitude of the lateral friction resistance, which is greater than the friction force, and the torque change is more significant, so the lubrication effect of the thixotropic mud can be amplified. The present invention monitors the settlement changes of the soil layer within a certain range by continuously rotating the concrete pipe, which can better illustrate the supporting effect of the thixotropic mud; compared with the indoor pipe jacking machine model test, it is simpler to operate, safer and more intuitive. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 is a perspective view of the present invention according to one or more embodiments;

[0025] Figure 2 is a front view of the present invention according to one or more embodiments;

[0026] Figure 3 is a top view of the present invention according to one or more embodiments;

[0027] Figure 4 is a side view of the present invention according to one or more embodiments.

[0028] Among them, 1. test box, 2. grouting hole, 3. concrete pipe, 4. grouting pipe, 5. grouting pool, 6. thixotropic mud, 7. displacement sensor, 8. computer, 9. coupling, 10. torque sensor, 11. motor, 12. display, 13. soil, and 14. top plate. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] Embodiment 1:

[0031] This embodiment provides a system for measuring the drag reduction capability and support performance of thixotropic mud for pipe jacking. The system uses torque instead of jacking force to illustrate the drag reduction effect of thixotropic mud, and uses surface settlement to illustrate the support effect of thixotropic mud. Figure 1-Figure 4 As shown, it includes a test box 1, a concrete pipe 3, a grouting pool 5, a displacement sensor 7, a rotation drive device, etc. The shape of the test box 1 can be rotated according to actual conditions. For example, a rectangular test box 1 is used; soil 13 and a concrete pipe 3 are filled in the test box 1.

[0032] Since the present embodiment not only tests the drag reduction capability of the thixotropic mud 6 but also tests the supporting performance of the thixotropic mud 6, a soil body 13 of a certain thickness is first laid in the test box 1, and then the concrete pipe 3 is placed and then the soil body 13 is laid close to the top surface of the test box 1; after the laying of the soil body 13 is completed, a top plate 14 is placed, and a plurality of displacement sensors 7 are arranged on the upper surface of the top plate 14, and the displacement sensors 7 are connected to the computer 8 via a data line to detect the surface settlement of the soil body 13.

[0033] In this embodiment, the displacement sensor 7 is arranged as follows: Figure 1 and Figure 3 As shown, a row is arranged horizontally along the center line of the test box 1, and the spacing is equidistant; a row is arranged in the direction of the center line of the concrete pipe 3, one row is arranged at one pipe diameter to the left of the center line, and one row is arranged at one pipe diameter to the right of the center line, and the spacing is equidistant; because the displacement change at the center line is the largest and most significant, one pipe diameter on the left and right corresponds to the change in the settlement of the stratum disturbed by the jacking pipe, and the settlement near the edge is very small and difficult to observe, so the displacement sensor 7 is arranged at the center line and one pipe diameter on the left and right to ensure the accuracy of the acquired data.

[0034] It can be understood that the number of rows of the displacement sensors 7 can be adjusted according to the actual volume of the test box 1 .

[0035] The size of the top plate 14 is adapted to the test box 1 , as long as it is ensured that the top plate 14 can move downward with the soil 13 when the soil 13 settles.

[0036] like Figure 1-Figure 4As shown, the concrete pipe 3 is arranged in the horizontal direction, and a plurality of grouting holes 2 are distributed on its surface. The grouting holes 2 are connected to the grouting pump through the grouting pipe 4. The grouting pump is installed in the grouting pool 5. The thixotropic mud 6 is arranged in the grouting pool 5. The thixotropic mud 6 can be pressed into the space between the concrete pipe 3 and the soil 13 through the grouting holes 2 by the grouting pump. Among them, the grouting pipe 4 is a hose. In this embodiment, the grouting holes 2 are evenly distributed so that the thixotropic mud 6 is evenly arranged between the concrete pipe 3 and the soil 13.

[0037] In order to detect the torque of the concrete pipe 3 when it rotates, one end of the concrete pipe 3 is connected to a rotation driving device, and the concrete pipe 3 is installed outside the test box 1. The rotation driving device drives the concrete pipe 3 to rotate at a constant speed.

[0038] In this embodiment, the rotation drive device includes a motor 11, which is connected to the concrete pipe 3 through a coupling 9 or a transmission mechanism, and the transmission mechanism can be a belt transmission mechanism, a chain transmission mechanism, etc. A torque sensor 10 is installed on the shaft of the motor 11, and the torque value is detected by the torque sensor 10; and the torque sensor 10 and the motor 11 are respectively connected to a display 12 through a data line, and the torque and speed are displayed by the display 12.

[0039] The drag reduction effect of this embodiment is characterized by the torque of the rotating concrete pipe 3, and the supporting effect is evaluated by the surface settlement of the soil 13 detected by the displacement sensor 7 above the test box 1. Compared with the jacking method, it can realize the detection of drag reduction effect and supporting effect at the same time, and it is more intuitive and effective.

[0040] Embodiment 2:

[0041] This embodiment provides a method for measuring the drag reduction capacity and supporting performance of thixotropic mud for jacking pipes. The measuring system described in the first embodiment is used. A soil body 13 of a certain thickness is first laid in a test box 1, and then a concrete pipe 3 is placed on the soil body 13 in a transverse direction. A grouting hole 2 is provided on the concrete pipe 3. The thixotropic mud 6 in the slurry pool can be pressed into between the concrete pipe 3 and the soil body 13 by a grouting pump. The concrete pipe 3 is connected to a motor 11 and can rotate at a constant speed. The display 12 can display the torque size.

[0042] Continue to lay the soil 13 above the concrete pipe 3, then place the top plate 14 with the displacement sensor 7 on the upper side of the soil 13 to detect the displacement changes of the center line of the concrete pipe 3 and at a radius of one pipe from the center line. In this embodiment, the displacement sensor 7 is arranged at the center line and at one pipe diameter on the left and right sides. The reason is that the displacement change at the center line is the largest and most significant, and the one pipe diameter on the left and right sides corresponds to the settlement change of the stratum disturbed by the top pipe. The settlement near the edge is very small and difficult to observe. The injected thixotropic mud 6 is vibrated and in a flow state. By comparing the torque size at the same speed before and after the addition of the thixotropic mud 6, the drag reduction effect of different thixotropic muds 6 under the same soil 13 conditions is reflected.

[0043] The concrete pipe 3 is stopped from rotating and left to stand for a period of time, and the thixotropic mud 6 changes from a fluid state to a gelled state. At this time, the displacement sensor 7 is used to measure the surface settlement of the soil body 13 , and the settlement value reflects the supporting effect of the thixotropic mud 6 .

[0044] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A system for measuring the drag reduction capacity and support performance of thixotropic mud for pipe jacking, characterized in that: It comprises a test box and a concrete pipe, wherein soil is laid in the test box, the concrete pipe penetrates the soil in the horizontal direction, and one end of the concrete pipe is connected to a rotation drive device, wherein the rotation drive device is provided with a torque sensor; The concrete pipe is provided with a plurality of grouting holes, which are connected to a grouting pump through a grouting pipe, and the grouting pump is used to pump thixotropic mud; a plurality of displacement sensors are distributed above the soil body, and the displacement sensors are used to detect the settlement of the soil surface.

2. A system for measuring the drag reduction capability and support performance of thixotropic mud for pipe jacking according to claim 1, characterized in that: The rotary drive device comprises a motor, and a torque sensor is mounted on the motor shaft; The torque sensor and the motor are connected to a display.

3. A system for measuring the drag reduction capability and support performance of thixotropic mud for pipe jacking according to claim 1, characterized in that: A top plate is arranged on the upper side of the soil body, and a displacement sensor is arranged on the upper side of the top plate.

4. A system for measuring the drag reduction capability and support performance of thixotropic mud for pipe jacking according to claim 1 or 3, characterized in that: The displacement sensors are arranged in a row along the center line of the test box, in a row in the direction of the center line of the concrete pipe, and in a row at a distance of one pipe diameter from both sides of the center line.

5. A system for measuring the drag reduction capability and support performance of thixotropic mud for pipe jacking according to claim 4, characterized in that: The displacement sensor is connected to a computer.

6. A system for measuring the drag reduction capability and support performance of thixotropic mud for pipe jacking according to claim 1, characterized in that: The thixotropic slurry is arranged in a slurry pool, and the slurry pool is connected to a grouting pipe through a grouting pump.

7. A method for measuring the drag reduction capacity and support performance of thixotropic mud for pipe jacking, characterized in that: A measuring system as claimed in any one of claims 1 to 6, comprising: Inject thixotropic mud into the concrete pipe; start the rotary drive device to make the concrete pipe rotate at a constant speed according to the set speed; compare the torque before and after adding the thixotropic mud at the same speed to reflect the drag reduction effect of different thixotropic muds under the same soil conditions; The concrete pipe stops rotating and stands still for a set time, and then the displacement sensor measures the settlement of the soil surface.

8. A method for measuring the drag reduction capability and supporting performance of thixotropic mud for jacking pipe according to claim 7, characterized in that: The displacement sensor is used to detect the displacement changes of the center line of the concrete pipe and the point one times the pipe diameter away from the center line.

9. A method for measuring the drag reduction capability and supporting performance of thixotropic mud for jacking pipe according to claim 7, characterized in that: The set standing time is sufficient for the thixotropic mud to change from a fluid state to a gelled state.

10. A method for measuring the drag reduction capability and supporting performance of thixotropic mud for jacking pipe according to claim 7, characterized in that: First, lay the soil of a set thickness in the test box, place the concrete pipe horizontally, and then lay the rest of the soil.

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