Axial symmetry stress condition under pipe mud drag reduction device

Abstract

The application belongs to the technical field of underground pipeline construction, and particularly relates to a pipe jacking mud drag reduction device under axial symmetric stress conditions, which comprises a symmetric stress detection device and a mud supplementing device. The symmetric stress detection device comprises a balance cylinder and a plurality of pairs of pressure measuring heads. The balance cylinder is internally slidably connected with a plunger and is closed at both ends and formed with cavities. Each pressure measuring head comprises a pressure measuring pipe and a plunger head. One end of the plunger head is slidably connected in one end of the pressure measuring pipe, and the pressure measuring pipe is communicated to the cavities. The mud supplementing device comprises a mud storage chamber, trigger structures, pairs of valve structures and grouting pipes. Each pair of trigger structures is arranged on the two sides of the plunger. One end of each pair of grouting pipes is communicated with the mud storage chamber, and the other end is respectively connected with the plunger head end of the pressure measuring pipe. The valve structures are arranged on the grouting pipes, and the trigger structures are connected with the valve structures. The application solves the problem of asymmetric friction caused by the damage of the mud sleeve outside the pipeline in the pipe jacking construction process, and avoids the deviation of the pipe jacking in the jacking process.

Description

Technical Field

[0001] This invention belongs to the field of underground pipeline construction technology, specifically relating to a drag reduction device for pipe jacking mud under axisymmetric stress conditions. Background Technology

[0002] Pipe jacking is a construction method that uses the thrust of jacking equipment such as a main jacking pump to push the tool pipe or tunneling machine from the working shaft through the soil layer along the line into the receiving shaft; at the same time, the pipeline following behind is connected in sequence and buried in the pipeline soil layer of the two shafts to lay underground pipelines.

[0003] During pipe jacking, the resistance experienced by the pipeline along the jacking length increases (mainly due to increased friction). With constant normal pressure, the coefficient of friction is the primary influencing factor; therefore, reducing resistance requires decreasing the coefficient of friction. Thus, during construction, thixotropic mud is injected into the outer surface of the pipeline through pre-drilled grouting holes. The basic components of thixotropic mud are bentonite and water, and it is used to reduce the coefficient of friction. When the amount of mud between the pipeline and the surrounding rock is sufficient and the water loss is minimal, a thin, dense mud cake can form on the soil wall, protecting the soil wall and preventing mud loss. This complete mud cake covering the outer surface of the pipeline is called a mud sleeve.

[0004] To ensure the jacking process doesn't deviate, the stress on the outside of the pipe must be axisymmetric (frictional), meaning the mud sleeve needs to remain intact. However, during jacking, the geological environment surrounding the pipe is not uniform. For example, one side of the pipe might be sandy while the other side contains gravel. This uneven geological conditions can cause localized damage to the mud sleeve on one side of the pipe, disrupting the axisymmetric frictional force and making the pipe prone to gradually deviating during jacking. Summary of the Invention

[0005] The present invention aims to provide a mud drag reduction device for pipe jacking under axisymmetric stress conditions, so as to solve the problem of asymmetrical friction caused by damage to the mud sleeve on the outside of the pipe during pipe jacking construction.

[0006] To achieve the above objectives, the present invention provides a drag reduction device for pipe jacking mud under axisymmetric stress conditions, comprising a symmetrical stress detection device and a grouting device.

[0007] The symmetrical stress detection device includes a balance cylinder and several pairs of pressure measuring heads. A plunger is slidably connected inside the balance cylinder. Both ends of the balance cylinder are closed, and a cavity is formed between the two ends of the plunger and the end face of the balance cylinder. Each pressure measuring head includes a pressure measuring tube and a column head. One end of the column head is slidably connected inside one end of the pressure measuring tube. The ends of the two pressure measuring tubes of each pair of pressure measuring heads that are away from the column head are respectively connected to the cavity through conduits.

[0008] The grouting device includes a grout storage chamber, a triggering structure, a pair of valve structures, and grouting pipes. Each pair of triggering structures is located on both sides of the plunger. One end of each pair of grouting pipes is connected to the grout storage chamber, and the other end is connected to the head end of the pressure measuring pipe. The valve structure is located on the grouting pipe, and the triggering structure is connected to the valve structure.

[0009] The working principle and beneficial effects of this scheme are as follows: Pressure testing holes are symmetrically installed on the pipeline, or existing grouting holes are utilized. Pressure testing pipes and grouting pipes are installed on the outer wall of the pipeline through these holes. Each pair of pressure testing heads and grouting pipes is located on opposite sides of the pipeline. One end of the plunger faces the direction of jacking. The pressure testing head moves with the pipeline. When the mud sleeve on the outside of the pipeline is intact, the resistance experienced by both plungers is the same, and the plunger is located in the equilibrium position in the middle of the balance cylinder. When the mud sleeve on one side is damaged, the resistance experienced by the plunger, i.e., the frictional stress, increases significantly. The plunger on that side is compressed into the pressure testing pipe on that side. The air in the pressure testing pipe is compressed and the pressure is transmitted to the plunger. The plunger slides until it touches the triggering structure. The triggering structure controls the corresponding valve structure to open, allowing the thixotropic mud stored in the slurry storage chamber to replenish the grout on that side through the grouting pipe, thereby restoring the frictional stress to axisymmetrical. When the stress on both sides is symmetrical, the resistance of the two column heads is equal, the plunger returns to the equilibrium position, the triggering structure is de-triggered, and the grouting device stops grouting.

[0010] This invention can monitor the frictional stress on the outer wall of the pipeline in real time and automatically adjust the frictional stress on opposite sides of the pipeline to axisymmetric by supplementing grouting, thereby preventing the pipeline from deviating during jacking.

[0011] Optionally, the diameter of the column head is not greater than the thickness of the mud sleeve.

[0012] Optionally, the inner diameter of the end of the grouting pipe away from the grout storage chamber is larger than the outer diameter of the pressure measuring pipe, and the pressure measuring pipe is coaxially fixed inside the end of the grouting pipe away from the grout storage chamber.

[0013] Optionally, the triggering structure includes a proximity switch, the valve structure includes a solenoid valve, and a PLC controller is also included. Both the proximity switch and the solenoid valve are electrically connected to the PLC controller, and the proximity switch is installed inside the cavity. When the proximity switch detects that the distance between the proximity switch and the plunger end face is less than a certain set value, the PLC controller controls the corresponding valve to open, thereby allowing the mud to flow through the grouting pipe for replenishment. When the proximity switch detects that the distance between the proximity switch and the plunger end face has moved away from a certain set value, the PLC controller controls the corresponding valve to close.

[0014] Optionally, the valve structure includes a valve sleeve and a valve core, with the valve core slidably connected within the valve sleeve. The triggering structure includes mating holes at both ends of the valve core and connecting pipe holes on both sides of the valve sleeve corresponding to the mating holes. Each grouting pipe is divided into two sections, each connected to a connecting pipe hole on the same side. A through groove is formed on the balance cylinder, and a connecting rod is connected to the plunger. The connecting rod passes through the through groove and connects to the valve core. Under axisymmetric stress, the mating holes and connecting pipe holes on the valve core are misaligned. Under axisymmetric stress, the two sections of the same grouting pipe are separated by the valve core, preventing grout replenishment. When the valve core moves with the plunger, when the valve core moves to align the mating hole with a connecting pipe hole on one side, the two sections of the grouting pipe on that side are connected by the mating hole, allowing the slurry in the grout storage chamber to flow out through the grouting pipe.

[0015] Optionally, the pressure measuring tube is L-shaped.

[0016] Optionally, the system also includes a receiving groove formed on the outer wall of the pipe to accommodate the vertical end of the pressure measuring tube. A spring structure is installed within the receiving groove, with one end connected to the groove and the other end connected to the outer wall of the vertical end of the pressure measuring tube. During pipe jacking, when the jacking head encounters a rock obstructing the path, the vertical end of the pressure measuring tube is compressed by the rock, overcoming the spring force and automatically retracting into the receiving groove. When there are no rocks obstructing the jacking direction, the spring structure keeps the vertical end of the pressure measuring tube protruding relative to the pipe, ensuring normal pressure measurement function.

[0017] Optionally, a rubber sleeve is fitted onto the column head, with the outer diameter of the end of the rubber sleeve furthest from the column head being smaller than the outer diameter of the end closest to the column head. The rubber sleeve serves two purposes: firstly, it allows the column head to better detect frictional stress; secondly, it allows the column head to deform into a wedge when it contacts a rock in front, thus enabling the pressure measuring tube to retract more smoothly into the receiving groove. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the pipe jacking mud drag reduction device under axisymmetric stress conditions in the first embodiment of the present invention during use;

[0019] Figure 2 This is a schematic diagram of the installation of the pipe jacking mud drag reduction device under axisymmetric stress conditions in the pipe jacking section according to Embodiment 1 of the present invention.

[0020] Figure 3 This is a cross-sectional view of the pressure measuring head in Embodiment 1 of the present invention;

[0021] Figure 4 This is a schematic diagram of the installation of the pipe jacking mud drag reduction device under axisymmetric stress conditions in the pipe jacking section in Embodiment 2 of the present invention. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method:

[0023] The markings in the attached drawings of the instruction manual include: jacking pipe 1, mud sleeve 2, mud and sand 3, pressure measuring pipe 4, grouting hole 5, receiving tank 6, balance cylinder 7, plunger 8, spring plate 9, column head 10, rubber sleeve 11, proximity switch 12, solenoid valve 13, grouting pipe 14, bracket 15, valve sleeve 16, valve core 17, docking hole 18, connecting pipe hole 19, connecting rod 20, slurry storage chamber 21, and guide pipe 22.

[0024] Example 1

[0025] This embodiment is basically as follows: Figure 1 , Figure 2 , Figure 3 As shown: A drag reduction device for pipe jacking mud under axisymmetric stress conditions, including a symmetrical stress detection device and a grouting device.

[0026] The symmetrical stress detection device includes a balance cylinder 7 and two pairs of pressure measuring heads. A plunger 8 is slidably connected inside the balance cylinder 7. The balance cylinder 7 is closed at both ends, and a cavity is formed between the two ends of the plunger 8 and the end face of the balance cylinder 7. Each pressure measuring head includes a pressure measuring tube 4 and a head 10. The pressure measuring tube 4 is L-shaped, with four pressure measuring holes on its side wall (top, bottom, left, and right). The lateral end of the pressure measuring tube 4 is inserted into the pressure measuring hole and slidably connected to it. A receiving groove 6 on the outer wall of the pipe accommodates the vertical end of the pressure measuring tube 4. A spring plate 9 is installed inside the receiving groove 6, with one end fixed inside the receiving groove 6 and the other end fixed to the outer wall of the vertical end of the pressure measuring tube 4. The longitudinal section of the head 10 is T-shaped. The diameter of the head 10 at its maximum point is 5 cm, and it is fitted with a rubber sleeve 11. Only a portion of the head 10 is inserted into the rubber sleeve 11. The outer diameter of the end of the rubber sleeve 11 furthest from the head 10 is smaller than the outer diameter of the end closest to the head 10. The vertical end of the column head 10 is slidably connected to the vertical end of the pressure measuring tube 4. The diameter of the vertical end of the column head 10 is 1cm. A sealing ring is fitted on the vertical end of the column head 10. The vertical end of the column head 10 remains sealed with the pressure measuring tube 4 during the sliding process inside the pressure measuring tube 4. The ends of the two pressure measuring tubes 4 of each pair of pressure measuring heads that are away from the column head 10 are respectively connected to the cavity through the conduit 22.

[0027] The grouting device includes a grout storage chamber 21, a triggering structure, two pairs of valve structures, and two pairs of grouting pipes 14. One end of each pair of grouting pipes 14 is connected to the grout storage chamber 21, and the other end is connected to the head 10 of the pressure measuring pipe 4. The valve structures are installed on the grouting pipes 14. In this embodiment, the triggering structure is a proximity switch 12, the valve structure is a solenoid valve 13, and a PLC controller is also included. Both the proximity switch 12 and the solenoid valve 13 are electrically connected to the PLC controller, and the proximity switch 12 is installed in the cavity. The inner diameter of the end of the grouting pipe 14 away from the grout storage chamber 21 is 3 cm larger than the outer diameter of the pressure measuring pipe 4, and the pressure measuring pipe 4 is coaxially fixed inside the end of the grouting pipe 14 away from the grout storage chamber 21.

[0028] The slurry storage chamber 21 is located directly above the inner wall of the pipe and is fixed to the pipe by the bracket 15. After the thixotropic mud is added to the slurry storage chamber 21, it is pressurized by an air pump. The balance cylinder 7 is also fixed on the bracket 15 and is located directly below the slurry storage chamber 21.

[0029] The specific implementation process is as follows:

[0030] During the jacking construction of pipe 1, the grouting device inside pipe 1 injects thixotropic mud into the outer surface of the pipe through the grouting hole 5, forming a mud sleeve 2 with a thickness of not less than 5cm. When a part of the mud sleeve 2 on one side of the pipe is damaged, the damaged mud sleeve 2 will be refilled with mud and sand 3 under the action of internal pressure. The frictional stress experienced by the column head 10 when passing through the mud and sand 3 will be much greater than the frictional stress when passing through the mud sleeve 2. This leads to an axisymmetric stress imbalance. As reflected in the symmetrical stress detection device, the column head 10 on the side passing through the mud and sand 3 is compressed into the pressure measuring tube 4 on that side. The air in the pressure measuring tube 4 is compressed and the pressure is transmitted to the plunger 8. The plunger 8 slides against the proximity switch 12 set in the balance cylinder 7 on the opposite side. When it approaches the set value, the PLC controls... The controller opens the solenoid valve 13 on the grouting pipe 14 opposite to the proximity switch 12. The thixotropic mud in the grout storage chamber 21 flows into the grouting pipe 14 under the action of gravity and pressure until it is sprayed out from the end of the grouting pipe 14 on the side of the compressed column head 10, repairing the mud sleeve 2 on that side until the frictional stress on the column head 10 on that side is equal to all the frictional stress on the column head 10 on the opposite side. The plunger 8 returns to the equilibrium position. The proximity switch 12 detects that the plunger 8 is away, and the solenoid valve 13, which was opened by the PLC, closes. This keeps the frictional stress axis symmetrical on both sides of the pipe, thereby preventing the jacking pipe 1 from deviating during jacking.

[0031] Due to the spring plate 9, the pressure measuring tube 4 always extends outward relative to the outside of the pipe during the jacking process. The rubber sleeve 11 on the column head 10 allows the column head 10 to better detect frictional stress. However, when the column head 10 encounters a stone blocking its path, the vertical end of the pressure measuring tube 4 can be squeezed by the stone to overcome the spring force. The rubber sleeve 11 allows the column head 10 to deform into a wedge when it contacts the stone, thereby automatically retracting the vertical end of the pressure measuring tube 4 into the receiving groove 6.

[0032] Example 2

[0033] The difference between this embodiment and Embodiment 1 is that: basically as shown in the appendix. Figure 4As shown, the valve structure includes a valve sleeve 16 and a valve core 17. The valve core 17 is slidably connected inside the valve sleeve 16. The triggering structure includes mating holes 18 at both ends of the valve core 17 and connecting pipe holes 19 on both sides of the valve sleeve 16, corresponding to the mating holes 18. Each grouting pipe 14 is divided into two sections and connected to the connecting pipe holes 19 on the same side. A through groove is opened on the balance cylinder 7. A connecting rod 20 is connected to the plunger 8. The connecting rod 20 passes through the through groove and is connected to the valve core 17. Under axisymmetric stress, the mating holes 18 and connecting pipe holes 19 on the valve core 17 are offset.

[0034] Under axisymmetric stress, the docking hole 18 and the connecting hole 19 are misaligned, and the two sections of the same grouting pipe 14 are separated by the valve core 17 to prevent grouting. When the valve core 17 moves with the plunger 8, when the valve core 17 moves to the docking hole 18 and aligns with the connecting hole 19 on one side, the two sections of the grouting pipe 14 on that side are connected by the docking hole 18, so that the mud in the grout storage chamber 21 can flow out through the grouting pipe 14.

[0035] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A pipe jacking mud drag reduction device under axisymmetric stress conditions, characterized in that: The application relates to a symmetric stress detection device and a grouting device. The symmetric stress detection device comprises a balance cylinder and a plurality of pairs of pressure measuring heads, a plunger is slidably connected in the balance cylinder, the balance cylinder is closed at both ends, and cavities are formed between the ends of the plunger and the end faces of the balance cylinder; each pressure measuring head comprises a pressure measuring pipe and a stud, one end of the stud is slidably connected in one end of the pressure measuring pipe, and the two pressure measuring pipes of each pair of pressure measuring heads are respectively connected to the cavities through conduits at ends away from the studs. The grouting device comprises a grout storage chamber, trigger structures, valve structures and grouting pipes arranged in pairs, each pair of trigger structures is arranged on the two sides of the plunger, one end of each grouting pipe of each pair of grouting pipes is communicated with the grout storage chamber, the other end of each grouting pipe is connected with the stud end of the pressure measuring pipe, the valve structures are arranged on the grouting pipes, and the trigger structures are connected with the valve structures.

2. The device for reducing friction of pipe jacking slurry under axisymmetric stress conditions according to claim 1, characterized in that: The diameter of the stud is not greater than the thickness of the mud sleeve.

3. The shaft-symmetrical drag-reducing device for pipe pushing under stress conditions according to claim 2, characterized in that: The inner diameter of the end of the grouting pipe away from the grout storage chamber is greater than the outer diameter of the pressure measuring pipe, and the pressure measuring pipe is coaxially fixed in the end of the grouting pipe away from the grout storage chamber.

4. The shaft-symmetrical drag-reducing device for pipe pushing under stress conditions according to claim 3, characterized in that: The trigger structure comprises a proximity switch, the valve structure comprises a solenoid valve, a PLC controller is further arranged, the proximity switch and the solenoid valve are electrically connected with the PLC controller, and the proximity switch is arranged in the cavity.

5. The shaft-symmetrical drag-reducing device for pipe pushing slurry under stress conditions according to claim 3, characterized in that: The valve structure comprises a valve sleeve and a valve core, the valve core is slidably connected in the valve sleeve, the trigger structure comprises butt joints arranged at the two ends of the valve core and pipe connection holes arranged on the two sides of the valve sleeve and corresponding to the butt joints, each grouting pipe is divided into two sections and connected on the pipe connection hole on the same side, a through groove is arranged on the balance cylinder, a connecting rod is connected on the plunger, the connecting rod passes through the through groove and is connected with the valve core, and the butt joints on the valve core are staggered with the pipe connection holes in the axial symmetric stress state.

6. The shaft-symmetrical drag-reducing device for pipe pushing slurry under stress conditions according to claim 4 or 5, characterized in that: The pressure measuring pipe is L-shaped.

7. The shaft-symmetrical drag-reducing device for pipe pushing slurry under stress conditions according to claim 6, characterized in that: A containing groove for containing the vertical end of the pressure measuring pipe is arranged on the outer wall of the pipeline, a spring structure is arranged in the containing groove, one end of the spring structure is connected with the containing groove, and the other end of the spring structure is connected with the outer wall of the vertical end of the pressure measuring pipe.

8. The shaft-symmetrical drag-reducing device for pipe pushing under stress conditions according to claim 7, characterized in that: A rubber sleeve is sleeved on the stud, and the outer diameter of the end of the rubber sleeve away from the stud is smaller than the outer diameter of the end of the rubber sleeve close to the stud.

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