A system and method for restoring the thixotropic properties of a drag-reducing mud after intermittent shutdown of a pipe

Abstract

The application discloses a system and method for restoring the thixotropic performance of drag-reducing slurry after intermittent shutdown of pipe jacking, which comprises a drag-reducing slurry thixotropic recovery device, a slurry pump and a slurry pipe system, wherein the drag-reducing slurry thixotropic recovery device is located inside a pipe jacking structure, arranged at the middle of two adjacent pipe jacking pipe sections along the length direction of the pipe jacking structure, comprises an inlet and an outlet, and is internally provided with a stirrer and a resistance heating device for slurry activation treatment; the inlet and the outlet are respectively connected with a slurry pump and are communicated with the grouting holes of the pipe jacking pipe sections through the slurry pipe system, so as to replace the drag-reducing slurry with weakened thixotropic performance outside the pipe jacking structure with the activated slurry and maintain the drag-reducing effect of the pipe jacking structure. The application can solve the problem of restoring the thixotropic performance of drag-reducing slurry after intermittent shutdown of pipe jacking, greatly reduce the huge initial jacking force after intermittent shutdown of pipe jacking, and provide important technical support for subsequent long-distance and large-diameter pipe jacking construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of pipe jacking engineering, and in particular to a system and method for restoring the thixotropic performance of resistance-reducing slurry after intermittent stoppage of pipe jacking. BACKGROUND

[0002] Pipe jacking construction is a trenchless pipe laying technology that has been widely used in recent years in urban subway entrances, utility tunnels, underground commercial streets and other projects due to its advantages of not excavating the road surface, small construction disturbance and protection of urban landscapes. In the construction process, pipe jacking needs to overcome the huge frictional resistance of the soil around the pipe, which is particularly evident in long-distance and large-diameter pipe jacking construction. Reducing the frictional resistance in pipe jacking construction is an important basic research topic in pipe jacking engineering.

[0003] In order to reduce the frictional resistance between the pipe and the soil around the pipe, thixotropic slurry is usually injected into the outer wall of the pipe section. Thixotropic slurry is a resistance-reducing material with special mineral structure and thixotropic performance. When it is in a static state, the system is in a suspended gel state. When disturbed by external factors, most of the particle structure is dispersed and destroyed, and the system changes into a gel-like liquid with viscosity and fluidity. After the external disturbance factor stops acting, the gel-like liquid changes back to the gel state. This property is the unique thixotropy of thixotropic slurry.

[0004] After pipe jacking starts, intermittent stoppage is often taken due to equipment failure, changes in geological conditions and construction safety issues. When the intermittent stoppage time is long, the thixotropic slurry will become gel-like after standing. When the jacking construction starts again, a large jacking force and its supporting force are often needed to produce a certain displacement to promote the thixotropic resistance reduction of the slurry. If displacement cannot be produced, the slurry cannot be thixotropic, the frictional resistance cannot be reduced, and the construction cannot continue.

[0005] In actual pipe jacking engineering, whether a relay section needs to be added is determined based on the total jacking force and the bearing capacity of the pipe wall structure in the design stage. When no relay section needs to be added or before the relay section is placed, intermittent stoppage may occur due to equipment failure, changes in geological conditions and construction safety issues. The thixotropic performance of the resistance-reducing slurry is easily weakened, and it is difficult to restart the jacking.

[0006] In view of the problem of excessive initial jacking force caused by the gel-like state of resistance-reducing slurry after intermittent stoppage of pipe jacking, there is currently a lack of effective equipment to restore the thixotropic resistance-reducing performance of the slurry. How to solve the problem of restoring the thixotropic performance of resistance-reducing slurry after intermittent stoppage of pipe jacking and minimize the huge initial jacking force after intermittent stoppage of pipe jacking has become a key issue in pipe jacking construction. Therefore, it is urgent to develop a system and method for restoring the thixotropic performance of resistance-reducing slurry after intermittent stoppage of pipe jacking to provide technical support for the start of intermittent stoppage of pipe jacking. SUMMARY

[0007] The present application aims to provide a pipe jacking intermittent stoppage after the drag reduction mud thixotropy performance recovery system and pipe jacking intermittent stoppage after the restart jacking method to solve the problem of pipe jacking intermittent stoppage after the drag reduction mud static gelation state leading to the starting jacking force too large.

[0008] To this end, the present application provides a pipe jacking intermittent stoppage after the drag reduction mud thixotropy performance recovery system, including the drag reduction mud thixotropy recovery device, the mud pump and the mud pipe system, wherein the drag reduction mud thixotropy recovery device is located inside the pipe jacking structure, and is arranged in the middle of two adjacent pipe jacking pipe sections along the length direction of the pipe jacking structure, including an inlet and an outlet, and the inside is provided with a stirrer and a resistance heating device for mud activation treatment; the inlet and the outlet are respectively connected with a mud pump, and are communicated with the grouting hole of the pipe jacking pipe section through the mud pipe system, so as to replace the mud with weak thixotropy performance outside the pipe jacking structure with the mud after activation treatment.

[0009] The present application also provides a pipe jacking intermittent stoppage after the restart jacking method, which adopts the above-mentioned pipe jacking intermittent stoppage after the drag reduction mud thixotropy performance recovery system, and the method comprises the following steps: S10, when the pipe jacking is intermittently stopped due to reasons, the pipe jacking construction is stopped; S20, the jacking parameters at the time of stoppage are counted, including the maximum jacking force F1 and the jacking distance L1; S30, the stoppage jacking force is evaluated; S40, the jacking system is restarted; S50, after the jacking system is restarted, the jacking effect is evaluated: 1) if the pipe jacking structure can be successfully jacked, the next step S60 is continued; 2) if the pipe jacking structure cannot be successfully jacked, a set of drag reduction mud thixotropy performance recovery device is added, and the steps S40-S50 are repeatedly executed until the pipe jacking structure can be successfully jacked; S60, the thixotropy and drag reduction effect is evaluated: firstly, it is judged whether the drag reduction mud thixotropy performance recovery device is started: 1) if the drag reduction mud thixotropy performance recovery device is not started, the performance weakening coefficient K of the thixotropic mud after static placement is calculated; 2) if the drag reduction mud thixotropy performance recovery device is started, the performance recovery coefficient E of the thixotropic mud using this method is calculated.

[0010] The pipe jacking intermittent stoppage after the drag reduction mud thixotropy performance recovery system and method provided by the present application can solve the problem of thixotropy performance recovery of the drag reduction mud after pipe jacking intermittent stoppage, and can minimize the huge starting jacking force after pipe jacking intermittent stoppage, thereby providing important technical support for subsequent long-distance and large-diameter pipe jacking construction.

[0011] In addition to the objects, features and advantages described above, the present application has other objects, features and advantages. The present application will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0013] Figure 1 2. It is a structural schematic diagram of the system for recovering the thixotropic properties of the drag-reducing mud after the intermittent stoppage of the pipe jacking operation according to the present invention;

[0014] Figure 2 It is a schematic structural diagram of the drag reduction mud thixotropic recovery device of the present invention;

[0015] Figure 3 It is a schematic diagram of the arrangement of grouting holes on the jacking pipe section of the present invention;

[0016] Figure 4 It is a structural schematic diagram of the mud pipe system of the present invention;

[0017] Figure 5 It is a schematic diagram of two adjacent pipe sections of the present invention;

[0018] Figure 6 is a flow chart of the method for restoring the thixotropic properties of the drag reducing slurry of the present invention;

[0019] Figure 7 This is a flow chart of the recovery of the thixotropic performance of the drag-reducing mud after the intermittent stoppage of the pipe jacking work according to the present invention.

[0020] Description of Reference Numerals

[0021] 1. Formation; 2. Jacking pipe structure; 3. Drag-reducing mud thixotropic recovery device; 4. Mud pump; 5. Mud pipe system; 6. Drag-reducing mud; 21. Grouting hole; 22. Two-inch bundled grouting pipe; 31. Cylinder; 32. Top cover; 33. Slurry inlet; 34. Slurry outlet; 35. Agitator; 36. Resistance heating device; 37. Movable pulley; 51. Main mud pipe No. 1; 52. First mud pipe; 53. Main mud pipe No. 2; 54. Second mud pipe. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0023] Combined with reference Figures 1 to 7 The drag-reducing mud thixotropic performance recovery system after intermittent pipe jacking shutdown of the present invention is located inside the pipe jacking structure 2, and includes a drag-reducing mud thixotropic recovery device 3, a mud pump 4 and a mud pipe system 5.

[0024] The jacking pipe structure 2 includes multiple jacking pipe sections, wherein Figure 1Only four jacking pipe sections, namely the first pipe section K1, the second pipe section K2, the third pipe section K3 and the fourth pipe section K4, are shown. Multiple jacking pipe sections are spliced ​​in sequence, and the cross-section of the jacking pipe sections is rectangular, circular or other special-shaped structures.

[0025] The jacking pipe structure 2 is buried in the stratum 1, and drag reducing mud 6 is injected between the jacking pipe structure 2 and the stratum 1. The mud jacket formed by the drag reducing mud 6 is used to reduce the friction resistance between the jacking pipe structure and the stratum 1 during jacking construction.

[0026] The drag-reducing mud thixotropic recovery device 3 is located inside the top pipe structure 2 and is arranged in the middle of the first pipe section K1 and the second pipe section K2 of the two adjacent top pipes along the length direction of the top pipe structure. The drag-reducing mud thixotropic recovery device 3 is placed on the edge of the inner bottom wall of the top pipe section to avoid being arranged in the middle of the inner bottom wall and affecting the transportation of slag by the bucket truck.

[0027] like Figure 2 As shown, the drag reducing mud thixotropic recovery device 3 includes a cylinder 31 , a top cover 32 , a slurry inlet 33 and a slurry outlet 34 , and the drag reducing mud thixotropic recovery device 3 includes an agitator 35 and a resistance heating device 36 inside.

[0028] The slurry inlet 33 and the slurry outlet 34 are provided at the lower side of the barrel 31. The slurry inlet 33 and the slurry outlet 34 are respectively connected to a slurry pump 4 and communicate with the grouting holes 21 of the jacking pipe section through a slurry pipe system 5. The slurry pump 4 is used to extract and inject drag-reducing slurry 6 into the outer wall of the jacking pipe section 2.

[0029] The stirrer 35 is provided on the top cover 32. The stirrer 35 is a fan blade structure, and the blades are placed in the middle of the cylinder 31. The resistance heating device 36 is provided inside the bottom plate of the cylinder 31 and is isolated from the internal space of the cylinder.

[0030] The agitator 35 is used to mechanically activate and maintain the thixotropic property of the drag reducing mud 6. The resistance heating device 36 is used to thermally activate and maintain the thixotropic property of the drag reducing mud 6.

[0031] Movable pulleys 37 are installed around the cylinder 31 to facilitate adjustment of the installation position of the drag-reducing mud thixotropic performance recovery device 3 according to actual conditions.

[0032] like Figure 3 As shown, each jacking pipe segment is arranged with a grouting section S in the middle of the axis along the axial direction, and each grouting section is provided with 6 to 10 grouting holes. The grouting holes are evenly arranged along the jacking pipe segment according to the cross section, 2 to 3 grouting holes are arranged at the upper and lower parts of the jacking pipe segment, and 1 to 2 grouting holes are arranged on the side wall of the jacking pipe segment.

[0033] When pouring the jacking pipe segment, holes penetrating the inner and outer walls of the jacking pipe segment are reserved as grouting holes 21, and a two-inch bundle grouting pipe 22 is installed in the grouting hole. The inner diameter of the two-inch bundle grouting pipe is 50.8 mm.

[0034] The two-inch segment grouting pipe 22 mainly consists of a pipe body, a segment and a grouting nozzle. The pipe body is made of high-quality material and has high strength and corrosion resistance. The segment is used to connect each grouting pipe to ensure the continuity and stability of the grouting process. The grouting nozzle is responsible for uniformly injecting grouting material into the part that needs to be reinforced.

[0035] With reference to Figure 4 The mud pump 4 includes a No. 1 mud pump and a No. 2 mud pump.

[0036] The mud pipe system 5 is two sets, namely a No. 1 mud pipe system and a No. 2 mud pipe system. The No. 1 mud pipe system includes a No. 1 main mud pipe 51 and a first branch mud pipe 52. The No. 2 mud pipe system includes a No. 2 main mud pipe 53 and a second branch mud pipe 54. The No. 1 (2) main mud pipe 51 is connected to the first branch mud pipe 52 (the second branch mud pipe 54) at one end and connected to the No. 1 (2) mud pump at the other end.

[0037] The main mud pipe 51 is fixed along the length direction of the pipe segment to the inner wall of the pipe segment. The first branch mud pipe 52 extends in a door shape along the cross-sectional circumference and closely adheres to the inner wall. The first branch mud pipe 52 is connected to the two-inch segment grouting pipe 22 in each grouting hole.

[0038] The No. 1 mud pump is connected to the grout inlet 33 at one end and connected to the No. 1 main mud pipe 51 at the other end. The No. 2 mud pump is connected to the grout outlet 34 at one end and connected to the No. 2 main mud pipe at the other end. The No. 1 mud pump and the No. 2 mud pump are fixed on the outer wall of the drag-reducing mud thixotropic recovery device 3 by bolts.

[0039] In the pipe jacking structure, a typical grouting system includes a mud conveying pipe extending along the length direction of the pipe jacking structure 2 and a mud pipe system arranged on the set pipe segment. The drag-reducing mud thixotropic recovery system of the present application can share the mud pipe system with the original grouting system. At this time, the No. 1 main mud pipe and the No. 2 main mud pipe are connected to the mud conveying pipe, and the connection and disconnection are controlled by valves.

[0040] With reference to Figure 5 and Figure 6 According to the set control strategy, the drag-reducing mud thixotropic recovery device and the mud pump of the system operate to replace the mud with weakened thixotropic performance outside the pipe jacking structure with the mud after activation treatment.

[0041] The specific control strategy is as follows:

[0042] S1. Before starting the drag-reducing slurry thixotropic property restoration device, lubricant and additives are added to the device. The lubricant is made by mixing expansive soil with water, with a mass ratio of 1:8. Additives such as dispersants, plasticizers, or surfactants are added to compensate for losses caused by prolonged standing or during construction.

[0043] S2. When the drag-reducing mud thixotropic performance recovery device is activated, the agitator and the resistance heating device are turned on until the mud activation conditions are met. Mud temperature has a significant impact on fluidity and slurry absorption speed. The mud temperature is usually controlled at 20-30°C to ensure good working performance.

[0044] S3. Back-pumping the injected drag-reducing mud: start the No. 1 mud pump and the No. 2 mud pump to pump the mud outside the wall of the jacking pipe segment into the cylinder of the drag-reducing mud thixotropic performance recovery device. The mud is transported through the grouting holes and mud pipes on the first pipe segment K1 and the second pipe segment K2. The extraction time t1 is 15 to 30 minutes. The purpose of this step is to extract the drag-reducing mud with weakened thixotropic performance outside the jacking pipe segment for treatment.

[0045] S4. Reinject the drag-reducing mud, i.e., inject the drag-reducing mud that has been mixed with the lubricating material and additives, stirred, and thermally activated. Specifically, adjust the operating directions of the No. 1 and No. 2 mud pumps to re-inject the mud in the drag-reducing mud thixotropic property restoration device through the grouting holes in the first and second pipe sections K1 and K2 to the outside of the jacking pipe section. The re-injection time t2 is set to achieve a constant flow rate of 10 L / min at a fixed grouting pressure.

[0046] S5. Circulating activated mud: After the drag reducing mud is re-injected, the operating direction of the No. 1 mud pump is changed, and the pressure injection from the grouting hole on the second pipe section K2 is changed to back pumping (forming a mud suction area), and the mud outside the second pipe section K2 is pumped into the mixing barrel for further activation, and the drag reducing mud in the mixing barrel is pressure-injected through the grouting hole on the first pipe section K1 through the mud pump and the mud pipe to the outside of the pipe wall of the first pipe section K1 (forming a mud pressure injection area). The pressure difference between the mud suction area and the pressure injection area forms a circulating flow (such as Figure 5 The circulation trajectory shown in the figure ensures that the flow direction of the drag-reducing slurry outside the jacking section is consistent with the jacking direction of the jacking section. If the directions are inconsistent, the grouting from the injection hole on the first jacking section K1 should be changed to backflow to form a circulation flow. The same direction can further reduce the friction of the jacking by utilizing the shear force of the drag-reducing slurry flow.

[0047] like Figure 7 As shown, the method for restarting pipe jacking after an intermittent stop of the present invention includes the following steps S10-S60.

[0048] S10, the pipe jacking is intermittent due to the stoppage, and the pipe jacking construction is stopped;

[0049] S20, the jacking parameters during the stoppage are counted, including the maximum jacking force F1 and the jacking distance L1;

[0050] S30, the jacking force during the stoppage is evaluated;

[0051] S40, the jacking system is restarted;

[0052] S50, the construction effect is evaluated, after the jacking system is restarted, the jacking effect is evaluated: 1) if the pipe structure can be successfully jacked, if the jacking can be continued, the subsequent S60 is continued; 2) if the jacking cannot be successfully performed, a set of thixotropic performance recovery devices for reducing resistance mud is continuously added, the steps S40 and S50 are repeated until the pipe structure can be successfully jacked;

[0053] S60, the thixotropic and resistance reduction effect is evaluated, firstly, it is judged whether the thixotropic performance recovery device for reducing resistance mud is started: 1) if the thixotropic performance recovery device for reducing resistance mud is not started, the performance weakening coefficient K of the thixotropic mud after standing is calculated; 2) if the thixotropic performance recovery device for reducing resistance mud is started, the performance recovery coefficient E of the thixotropic mud using this method is calculated.

[0054] In step S30, the jacking force evaluation is performed according to the following steps:

[0055] S31, when the jacking distance L1 during the stoppage is less than S and the maximum jacking force F1 is less than 0.8×control jacking force P c , step S40 is directly performed;

[0056] S32, when the jacking distance L1 during the stoppage is less than S and the maximum jacking force F1 is greater than or equal to 0.8×control jacking force P c , the thixotropic performance recovery device for reducing resistance mud is started, preheating preparation is performed, a set of thixotropic performance recovery devices for reducing resistance mud is uniformly distributed and added, and the gel structure of the mud is destroyed;

[0057] S33, when the jacking distance L1 is greater than or equal to S, the first relay interval is applied, and step S40 is directly performed.

[0058] When the pipe structure jacking construction is performed, under the condition that the effective resistance reduction of the complete mud sleeve outside the pipe structure is reduced, the position of the first relay interval is calculated according to the following formula:

[0059] (1)

[0060] In the formula, S is the jacking distance (m) when the relay interval needs to be applied; k is the jacking force coefficient, which is preferably 0.5-0.6; P c is the control jacking force (kN); R f is the head resistance of the pipe jacking machine (kN); C is the outer contour circumference of the pipe; qf is the average frictional resistance (kPa) between the outer wall of the jacking pipe structure and the formation (mud jacket).

[0061] The performance weakening coefficient K of thixotropic mud after standing is:

[0062] (2)

[0063] Where, The starting jacking force when the actual pipe jacking project is restarted (kN); The maximum jacking force required to stop the pipe jacking project (kN); is the jacking distance (m); is the average frictional resistance between the outer wall of the jacking pipe structure and the formation (mud jacket) (kPa); is the outer perimeter of the top pipe (m); is the unit weight of the pipe segment (kN / m); is the friction coefficient of the pipe joint due to its own weight.

[0064] The recovery coefficient E of thixotropic mud performance is:

[0065] (3)

[0066] Where, The starting jacking force when the actual pipe jacking project is restarted (kN); The maximum jacking force required to stop the pipe jacking project (kN); is the jacking distance (m); is the average frictional resistance between the outer wall of the jacking pipe structure and the formation (mud jacket) (kPa); is the outer perimeter of the top pipe (m); is the unit weight of the pipe segment (kN / m); is the friction coefficient of the pipe joint due to its own weight.

[0067] In a large-section rectangular pipe jacking project, the outer dimensions of the pipe section are 7m×5m, the length is 3m, and the designed jacking distance is 150m. Control the jacking force P c =4000kN, the head resistance of the pipe jacking machine R f =1200kN, average friction resistance of mud sleeve q f =1.8kPa, top force coefficient k=0.6, unit weight of pipe section W=130kN / m, self-weight friction coefficient =0.2.

[0068] The relay distance S=38.89m was calculated by formula 1, and it was arranged at 40m during the actual construction. The pipe jacking project was stopped for some reason when it was pushed to L1=35m (not reaching 40m between relays). The maximum jacking force F1=2800kN<0.8P c=3200kN and L1=35m <S=38.89m, through analysis and calculation, the drag reduction mud thixotropy recovery device needs to be started, and the jacking system is directly restarted. When jacking to L1=38m, it is stopped due to a fault, and F1=3200kN, reaching 0.8P c , the drag reduction mud thixotropy recovery device needs to be started, and the mud is activated by stirring (200r / min) and heating (25℃). After the activation treatment, the jacking is restarted, the measured starting jacking force F=2700kN, the thixotropic mud performance recovery coefficient E=19% is obtained by calculation by using formula 3, the thixotropic performance of the mud is recovered by 19.0%, the jacking force is reduced by 15.6% (500kN), and the effectiveness of the system under the critical jacking force scene is verified.

[0069] The drag reduction mud thixotropy performance recovery system of the application can be used as a long-term starting device to continuously reduce the jacking friction resistance of the pipe jacking; after intermittent shutdown, the jacking is difficult to restart due to the weakening of the thixotropy performance of the drag reduction mud, and the drag reduction mud thixotropy performance recovery device needs to be started.

[0070] The above only describes the embodiments of the application and is not used to limit the application. For those skilled in the art, the application can have various changes and variations. Any modification, replacement, improvement, etc. within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A system for restoring the thixotropic properties of drag-reducing slurry after an intermittent stoppage of pipe jacking, characterized in that: It includes a drag reduction mud thixotropic recovery device, a mud pump and a mud pipe system, wherein The drag-reducing mud thixotropic recovery device is located inside the jacking pipe structure and is arranged in the middle of two adjacent jacking pipe sections along the length direction of the jacking pipe structure. It includes a slurry inlet and a slurry outlet, and is equipped with an agitator and a resistance heating device inside for mud activation treatment. The slurry inlet and the slurry outlet are respectively connected to a slurry pump and are connected to the grouting holes of the jacking pipe section through the slurry pipe system, so as to replace the thixotropically weakened slurry outside the jacking pipe structure with activated slurry. The drag-reducing mud thixotropic recovery device and the mud pump operate according to the following control strategy to replace the mud with weakened thixotropic properties outside the jacking pipe structure with activated mud: S1. Before the drag reducing mud thixotropic performance recovery device is started, lubricating material and additives are added to the drag reducing mud thixotropic performance recovery device; S2. When the drag-reducing mud thixotropic performance recovery device is started, the agitator and the resistance heating device are turned on until the grouting conditions are met; S3. Back-pumping the injected drag-reducing mud: Start the mud pumps at the slurry inlet and outlet to pump the mud outside the jacking structure into the drag-reducing mud thixotropic performance recovery device. The pumping time is set to t1. S4. Re-injection of drag-reducing mud: Adjust the running direction of the mud pumps at the slurry inlet and outlet, and re-inject the mud in the drag-reducing mud thixotropic performance recovery device to the outside of the jacking structure. The re-injection time is set to t2; S5. Circulating activated mud: After the drag-reducing mud is heavily injected, the operating direction of the mud pump at the slurry inlet is changed separately, and pressure injection is changed to back pumping, so that the drag-reducing mud forms a circulating flow inside and outside the jacking structure; or conversely, the operating direction of the mud pump at the slurry outlet is changed separately, and pressure injection is changed to back pumping, so as to ensure that the flow direction of the drag-reducing mud outside the jacking structure is consistent with the jacking direction of the jacking pipe section.

2. The system for recovering the thixotropic properties of drag-reducing slurry after intermittent pipe jacking shutdown according to claim 1 is characterized in that: During the pouring process, holes penetrating the inner and outer walls of the jacking pipe segment are reserved as grouting holes, and two-inch bundled grouting pipes are installed in the grouting holes. Each of the jacking pipe sections is provided with a grouting section, and each grouting section is provided with 6 to 10 grouting holes. 2 to 3 grouting holes are respectively arranged on the upper and lower parts of the jacking pipe section, and 1 to 2 grouting holes are arranged on the side wall of the jacking pipe section.

3. The system for recovering the thixotropic properties of drag-reducing slurry after intermittent pipe jacking shutdown according to claim 1 is characterized in that: The drag reduction mud thixotropic recovery device includes a cylinder and a top cover, and the slurry inlet and slurry outlet are arranged at the lower part of the side of the cylinder; The stirrer is provided on the top cover and is a fan-blade stirring structure. The resistance heating device is provided inside the bottom plate of the cylinder and is isolated from the internal space of the cylinder. A movable pulley is installed at the bottom of the cylinder.

4. The system for recovering the thixotropic properties of the drag-reducing mud after an intermittent stoppage of pipe jacking according to claim 3 is characterized in that: The mud pipe system includes a main mud pipe and branch mud pipes, the main mud pipe is connected to the mud pump, and the branch mud pipes are connected to the grouting holes on the pipe section; The main mud pipe is fixed on the inner wall of the top pipe segment along the length direction of the pipe segment, and the branch mud pipe extends in a gate shape along the circumference of the cross section of the pipe segment, close to the inner wall.

5. A method for restarting pipe jacking after an intermittent stoppage, characterized in that: The system for recovering the thixotropic properties of the drag-reducing slurry after an intermittent stoppage of pipe jacking according to claim 1 is adopted, and the method comprises the following steps: S10, when the pipe jacking is temporarily stopped for some reason, the pipe jacking construction is stopped; S20, statistics of jacking parameters during shutdown, including the maximum jacking force during shutdown F 1 and jacking distance L 1; S30, shutdown force evaluation; S40, restart the jacking system; S50: After the jacking system is restarted, the jacking effectiveness is evaluated: 1) If the jacking structure is successfully jacked, proceed to the next step S60; 2) If the jacking structure is not successfully jacked, add a set of drag-reducing mud thixotropic performance recovery devices, and repeat steps S40-S50 until the jacking structure is successfully jacked; S60. Evaluation of thixotropy and drag reduction effects: First, determine whether the drag reduction mud thixotropic performance recovery device is activated: 1) If the drag reduction mud thixotropic performance recovery device has not been activated, calculate the performance weakening coefficient K of the thixotropic mud after standing; 2) If the drag reduction mud thixotropic performance recovery device is activated, calculate the thixotropic mud performance recovery coefficient E using this method.

6. The pipe jacking method for restarting after an intermittent stop according to claim 5 is characterized in that: The shutdown force evaluation is carried out in the following steps: 1) When the work is stopped and the jacking distance is L 1< S And the maximum top force F 1<0.8×controlled top force P c , directly execute step S40, where S The jacking distance when a relay space is required, in meters; 2) When the work is stopped and the jacking distance is L 1< S And the maximum top force of shutdown F 1≧0.8×controlled jacking force P c , the drag-reducing mud thixotropic performance recovery device is activated to destroy the gel structure of the mud; 3) When the jacking distance L 1≧ S When the first relay is applied, step S40 is directly executed.

7. The pipe jacking method for restarting after an intermittent stoppage according to claim 5, characterized in that: During the jacking construction of the pipe jacking structure, under the condition that the outer wall of the pipe jacking structure has a complete mud casing to effectively reduce drag, the layout position of the first relay room is calculated according to the following formula: （1） Where, S The jacking distance when a relay space is required, in meters; k is the jacking coefficient, which is 0.5~0.6; P c To control the top force, the unit is kN; R F is the head-on resistance of the pipe jacking machine, in kN; C is the outer perimeter of the top pipe; q f It is the average frictional resistance between the outer wall of the jacking pipe structure and the formation, i.e. the mud jacket, in kPa.

8. The pipe jacking method for restarting after an intermittent stoppage according to claim 5 is characterized in that: The performance weakening coefficient K of thixotropic mud after standing is: （2） Where, The starting jacking force when the actual pipe jacking project is restarted, in kN; The maximum jacking force required to stop the pipe jacking project, in kN; is the jacking distance, in m; is the average frictional resistance between the outer wall of the jacking pipe structure and the formation, i.e., the mud jacket, in kPa; is the outer perimeter of the jacking pipe, in m; is the unit weight of the pipe segment, in kN / m; is the friction coefficient of the pipe joint due to its own weight.

9. The pipe jacking method for restarting after an intermittent stoppage according to claim 5 is characterized in that: The recovery coefficient of thixotropic mud performance after the restart jacking method is used E for: （3） Where, The starting jacking force when the actual pipe jacking project is restarted, unit is kN; The maximum jacking force required to stop the pipe jacking project, in kN; is the jacking distance, in m; is the average frictional resistance between the outer wall of the jacking pipe structure and the formation, i.e., the mud jacket, in kPa; is the outer perimeter of the jacking pipe, in m; is the unit weight of the pipe segment, in kN / m; is the friction coefficient of the pipe joint due to its own weight.

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