Pipe jacking construction method for soft clay layer pipeline

Abstract

The invention provides a pipe jacking construction method for a soft clay layer pipeline, which comprises the following steps: S1, arranging a working well and a receiving well at the starting point and the terminal point of the pipeline through open caisson construction, S2, splicing guide rails at the well bottoms of the working well and the receiving well, and installing a pipe jacking machine head and a jacking oil cylinder into the working well by using hoisting equipment; s3, the front end of the pipe jacking machine head is jacked into a hole inlet through a jacking oil cylinder, and S4, the pipe jacking machine head enters a soil layer after entering the hole, and jacking control and deviation correction are conducted according to parameters of a pipe jacking hydraulic system; s5, when the pipe jacking machine head is close to the well wall of the receiving well, the pipe jacking machine head penetrates through the outlet hole at a time; and S6, after acceptance inspection is qualified, the pipe jacking machine head and the guide rail are detached, and then the pipe jacking machine head is hoisted out. Jacking control and deviation correction are carried out according to parameters of the pipe jacking hydraulic system, deviation of the pipe jacking machine head can be found and corrected in time, it is ensured that the jacking direction of a pipe joint is accurate, and the construction quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of pipe jacking construction, and particularly relates to a pipe jacking construction method for pipelines in soft clay layers. Background Art

[0002] When constructing pipelines in soft clay layers, the traditional excavation construction method will cause great damage to the ground, affect the surrounding environment and traffic, and has high construction costs and long construction periods. As a trenchless construction technology, pipe jacking construction can reduce interference to the ground and has obvious advantages in pipeline construction in soft clay layers. However, soft clay layers have the characteristics of low strength, high compressibility, poor water permeability, etc., and problems such as soil collapse and pipe jacking machine deviation are likely to occur during pipe jacking construction, affecting construction quality and safety.

[0003] Therefore, an improved technical solution is needed to address the deficiencies of the above-mentioned existing technologies. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned existing technologies, and the present invention provides a pipe jacking construction method for pipelines in soft clay layers.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A pipe jacking construction method for pipelines in soft clay layers, comprising: Step S1, set up a working well and a receiving well at the starting point and the ending point of the pipeline through caisson construction, cut out-holes and in-holes on the well walls of the working well and the receiving well respectively according to the design drawings, and lift out the cut concrete blocks; Step S2, splice guide rails at the bottom of the working well and the receiving well, and extend the guide rails into the corresponding out-holes and in-holes; a rear seat corresponding to the jacking cylinder is provided in the working well, and the pipe jacking head and the jacking cylinder are installed into the working well by using a hoisting device; Step S3, use the jacking cylinder to push the front end of the pipe jacking head into the in-hole, lift in a pipe section and fixedly connect the pipe jacking head with the pipe section; Step S4, after the pipe jacking head enters the soil layer, carry out jacking control and deviation correction according to the parameters of the pipe jacking hydraulic system; Step S5, install pipe sections according to the jacking progress until the pipe jacking head is close to the well wall of the receiving well, retract the jacking cylinder and install a pipe section to enable the pipe jacking head to pass through the out-hole at one time, then remove the cylinder, and place steel supports between the pipe section and the rear seat to prevent the pipe section from retracting; Step S6, after passing the acceptance, remove the pipe jacking head and the guide rails and lift them out.

[0006] Preferably, in step S1, a water stop ring is arranged at the in-hole and the out-hole, and the water stop ring includes a pre-embedded casing, a steel flange, a steel pressure ring, and a rubber water stop belt; First, weld and fix the steel flange to the embedded casing, and fill the gap between the steel flange and the well wall tightly with high-strength mortar. Set a layer of rubber waterstop outside the steel flange. The bolt holes reserved on the rubber waterstop correspond to the bolt holes on the steel flange one by one. The outside of the rubber waterstop is tightly squeezed by a steel pressing ring. Set another layer of rubber waterstop outside the steel pressing ring. Corresponding bolt holes are set on the steel pressing ring and the outside rubber waterstop. Use bolts to pass through each component, and fix the whole waterstop device firmly through a steel pressing plate. Use cement mortar to seal the joints and stop water at the contact surface between the steel pressing ring and the concrete wall.

[0007] Preferably, in step S5, a gantry frame corresponding to the pipe jacking machine head is provided inside the receiving well. The gantry frame includes columns and a cross beam. The two ends of the cross beam are fixed on the columns to longitudinally limit the pipe jacking machine head.

[0008] Preferably, a telescopic rod is provided below the cross beam, and a roller corresponding to the outer wall of the pipe jacking machine head is provided at the end of the telescopic rod.

[0009] Preferably, grouting holes are preset on the pipe section, and grouting one-way valves are provided in the grouting holes. During the pipe jacking process in step S4, thixotropic slurry is injected between the pipe section and the soil through a grouting device.

[0010] Preferably, slurry outlet holes are also preset on the pipe section, and slurry outlet one-way valves are provided in the slurry outlet holes. In step S6, after the pipe jacking construction is completed, the pipe sections are divided into multiple groups. The grouting holes at one end of each group of pipe sections are connected to a grouting pump, and cement slurry is injected to discharge the thixotropic slurry from the slurry outlet holes. After the cement slurry is discharged from the slurry outlet, close the slurry outlet one-way valve, and keep the pressure for 30 minutes to complete the slurry replacement.

[0011] Preferably, the backseat includes reinforced concrete and embedded steel plates. A formwork is set on one side of the working well facing the inlet hole. The side of the formwork close to the inlet hole is a flat surface perpendicular to the axis of the inlet hole, and embedded bolts are provided on this flat surface to fix the embedded steel plates through the embedded bolts after pouring is completed.

[0012] Preferably, when the pipe jacking machine head is 30 m away from the receiving well, slow down the jacking speed, reduce the jacking pressure, comprehensively measure and review the attitude of the pipe jacking machine head. After the whole pipe jacking machine head exits the hole, separate the pipe sections by cutting.

[0013] Preferably, jet grouting piles are constructed around the working well to form a cylindrical curtain corresponding to the caisson, and a deviation correction device is provided inside the jet grouting piles to correct the deviation during the sinking process of the well wall.

[0014] Preferably, three parallel pipes are provided between the working well and the receiving well. First, jack the middle pipe according to steps S3 - S5. After the middle pipe jacking is completed, use the time for pipe connection and hoisting to carry out cross jacking operations on the two side pipes.

[0015] Beneficial effects: By controlling the jacking and deviation correction according to the parameters of the pipe jacking hydraulic system, it is possible to timely detect and correct the deviation of the pipe jacking machine head, ensure the accurate jacking direction of the pipe section, and improve the construction quality. A gantry is arranged inside the receiving well, and the pipe jacking machine head is supported and guided through the support rod and roller, which can ensure the smooth exit of the pipe jacking machine head from the hole, avoid the deviation or collision of the machine head during the exit process, and ensure the construction safety. Description of the Drawings

[0016] The schematic drawings in the specification that form a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. Among them: Figure 1 is the construction flow chart of pipe jacking in the specific embodiment provided by the present invention; Figure 2 is the installation schematic diagram of the gantry in the specific embodiment provided by the present invention; Figure 3 is the construction flow chart of the working well in the specific embodiment provided by the present invention; Figure 4 is the distribution schematic diagram of the deviation correction device in the specific embodiment provided by the present invention; Figure 5 is the structural schematic diagram of the deviation correction device in the specific embodiment provided by the present invention; Figure 6 is the schematic diagram of the sinking of the cutting edge in the specific embodiment provided by the present invention; Figure 7 is the schematic diagram of the heightening of the well wall in the specific embodiment provided by the present invention.

[0017] In the figures: 1, receiving well; 2, mixing pile; 3, pipe jacking machine head; 4, guide rail; 5, bottom plate; 6, gantry; 7, telescopic rod; 8, deviation correction device; 9, working well; 10, ring beam; 11, roller; 801, base; 802, installation pipe; 803, guide roller; 804, friction pad; 805, jacking rod; 901, cutting edge; 902, heightening; 903, backfill sand. Detailed Embodiments

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0019] In the description of the present invention, the orientation or positional relationship indicated by terms such as "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and does not require the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. The terms "connected" and "joined" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0020] The present invention will be described in detail below with reference to the drawings and in combination with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0021] As Figures 1-7 shown, a pipe jacking construction method for pipelines in soft clay layers uses a slurry balance pipe jacking machine for jacking. The slurry balance pipe jacking machine uses the slurry pressure in the slurry chamber to balance the earth pressure and water pressure on the jacking working face. By adjusting the slurry pressure in the discharge chamber, the excavation face is stabilized, including: Step S1, working wells 9 and receiving wells 1 are set at the starting point and the ending point of the pipeline through open caisson construction. During the sinking process of the open caisson, the sinking speed and verticality are strictly controlled to ensure the construction quality of the open caisson. After the construction of the working well 9 and the receiving well 1 is completed, according to the design drawings, an outlet hole and an inlet hole are respectively cut on the well walls of the working well 9 and the receiving well 1, and the cut concrete blocks are hoisted out. Step S2, guide rails 4 are spliced at the bottom of the working well 9 and the receiving well 1. The guide rails 4 are made of 25*15 cm square pipes with a wall thickness of 10 mm. The base 801 of the guide rails 4 is processed and manufactured from square pipes and channel steels. Steel plates are buried on the foundation 5 of the bottom plate of the working well 9, and an installation platform for the pipe jacking guide rails 4 is erected to firmly connect the working platform to the bottom plate 5. The guide rails 4 of the working well 9 or the receiving well 1 are extended into the corresponding outlet hole and inlet hole. The elevation of the guide rails 4 is controlled by a level, and the slope of the top surface of the track should be consistent with the designed slope of the pipe jacking.

[0022] A rear seat corresponding to the jacking cylinder is provided in the working well 9, and the pipe jacking head 3 and the jacking cylinder are installed in the working well 9 by using a hoisting device. Step S3, the front end of the pipe jacking head 3 is jacked into the inlet hole through the jacking cylinder, a pipe section is hoisted in, and the pipe jacking head 3 is fixedly connected to the pipe section. Between the steel pipe and the pipe jacking head 3 and between the steel pipes, shielded metal arc welding with carbon dioxide gas is used for welding and fixing. The pipe jacking welding process adopts the form of single-sided welding with double-sided forming.

[0023] Step S4. Before the jacking pipe machine advances, all equipment must be comprehensively inspected. After the jacking pipe machine head 3 enters the soil layer after entering the hole, jacking control and deviation correction are carried out according to the parameters of the jacking pipe hydraulic system. On the one hand, the main jacking speed should be slowed down, and on the other hand, the cylinder deviation correction should be continuously adjusted. The pipeline deviation is measured every 300 mm of jacking. In the initial stage of jacking, when the jacks retract, the jacking pipe machine may move backward. It is necessary to install profiled steel on the inner side of the track and connect it to the track with bolts. The profiled steel can hold the pipe joints to prevent backward movement and can be conveniently disassembled during the jacking process, so as to prevent the jacking pipe machine from bouncing back due to the action of the frontal soil pressure after the main jack retracts.

[0024] Step S5. Install the pipe joints according to the jacking progress until the jacking pipe machine head 3 approaches the well wall of the receiving well 1. Retract the jacking cylinders and install a pipe joint to enable the jacking pipe machine head 3 to pass through the exit hole at one time. After entering the receiving well 1 of the jacking pipe machine head 3, the tunneling machine head should quickly and continuously jack the pipe joints to shorten the exit time as soon as possible. Thereby, it is possible to avoid the deviation of the jacking pipe machine head 3 during the exit process, resulting in an unsuccessful exit caused by the deflection of the machine head. After the jacking pipe machine head 3 exits the hole, remove the cylinders, and place steel supports between the pipe joints and the backseat to prevent the pipe joints from retreating. During the pipeline jacking process, the dredged mud and slag should be collected in real time, and the consistency with the geological exploration description should be analyzed. During the jacking process, the dredging flow rate, mud feeding flow rate, and tunneling soil discharge volume should be checked to calculate whether the requirements of slurry balance are met, and the jacking pressure and speed should be adjusted in a timely manner to ensure the stability of the soil face against the incoming soil.

[0025] Step S6. Accept the construction quality of the pipeline, including the connection quality of the pipe joints, the deviation of the jacking direction, the water stop effect, etc. After passing the acceptance, remove the jacking pipe machine head 3 and the guide rail 4, and hoist them out of the working well 9 and the receiving well 1.

[0026] There are three parallel pipelines between the working well 9 and the receiving well 1. Each of the three pipelines is provided with corresponding inlet holes, outlet holes, guide rails 4, jacking equipment, gantry frames 6, and backseats. During actual construction, first, the middle pipeline is jacked according to steps S3 - S5. After the jacking of the middle pipeline is completed, cross-jacking operations are carried out on the two side pipelines during the pipeline connection and hoisting time. The distance between the two side pipelines during jacking is not greater than the length of two pipe joints.

[0027] During the jacking process of the two side pipelines, monitoring points are arranged in the middle pipeline, and the middle pipeline is monitored through the monitoring points, so as to control the construction of the two side pipelines according to the monitoring results and avoid affecting the middle pipeline. Further, strengthen the monitoring during the jacking process of the two side pipelines to ensure their construction quality.

[0028] In an optional embodiment, in step S1, waterstops are set at the entrance and exit of the cave, and the waterstops include embedded sleeves, steel flanges, steel pressure rings, and rubber waterstops. First, the steel flanges are welded and fixed to the embedded sleeves, and the gap between the steel flanges and the well wall is filled with high-strength mortar. A layer of rubber waterstop is set on the outside of the steel flange, and the bolt holes reserved in the rubber waterstops correspond to the bolt holes of the steel flanges. The outside of the rubber waterstops is tightly squeezed by the steel pressure rings. Another layer of rubber waterstops is set on the outside of the steel pressure rings. Corresponding bolt holes are set on the steel pressure rings and the outer rubber waterstops. Bolts are passed through each component, and the waterstop device is firmly fixed as a whole through the steel pressure plate. Cement mortar is used to seal the contact surface between the steel pressure ring and the concrete wall to stop water. By setting waterstops at the entrance and exit of the cave and adopting a combined structure of multiple layers of rubber waterstops and steel pressure rings, groundwater can be effectively prevented from seeping into the working well 9 and the receiving well 1, ensuring a dry and safe construction environment. The rubber water stop ring is 30mm thick, the inner diameter of the rubber flange should be about 40cm smaller than the outer diameter of the pipe, and one side should be turned inward by 20cm. The bolt spacing is 15cm, and the pressure plate should be tightly squeezed with the rubber flange by screws, and the screws must not be loose.

[0029] In an optional embodiment, in step S5, a gantry 6 corresponding to the pipe jacking head 3 is provided inside the receiving shaft 1. The gantry 6 includes a column and a crossbeam. The two ends of the crossbeam are fixed on the column. A driving device corresponding to the crossbeam is provided on the column to limit the pipe jacking head 3 in the longitudinal direction. After the pipe jacking head 3 passes through, the crossbeam can be used to limit the pipe jacking head 3 from tilting up, ensuring smooth exit from the hole. A telescopic rod 7 is provided under the crossbeam, and the end of the telescopic rod 7 is provided with a roller 11 corresponding to the outer wall of the pipe jacking head 3. In this way, the height of the roller 11 can be adjusted according to actual needs, so that the multiple rollers 11 are adapted to the outer curved surface of the pipe jacking head 3, thereby ensuring the limited stability, and the setting of the roller 11 allows the telescopic rod 7 and the pipe jacking head 3 to slide relative to each other without affecting the normal advancement of the pipe jacking head 3. And after tilting up, the telescopic rod 7 can be used to press down to correct the deviation. In this embodiment, the telescopic rod 7 is a hydraulic cylinder, and no fewer than two portal frames 6 can be provided. One portal frame 6 is located near the exit of the tunnel, and the remaining portal frames 6 are evenly spaced. The distance between any two adjacent portal frames 6 is one-quarter the length of the pipe jacking head 3. Preferably, three portal frames 6 are provided. The multiple portal frames 6 form a complete and defined track, thereby preventing the pipe jacking head 3 from deviating.

[0030] In an alternative embodiment, during the pipe jacking process, thixotropic slurry is injected against the outer wall of the pipe to reduce the frictional resistance between the outer wall of the pipe and the soil mass. Grouting holes are preset on the pipe section, and grouting check valves are provided in the grouting holes. During the pipe jacking process in step S4, thixotropic slurry is injected between the pipe section and the soil mass through a grouting device. Injecting thixotropic slurry between the pipe section and the soil mass can fill the gap between the pipe section and the soil mass, reduce the frictional force between the soil mass and the pipe section, reduce the risk of soil collapse, and at the same time can also play a lubricating role and improve the jacking efficiency.

[0031] For the 5m pipe section, 1 group of grouting holes is provided at the end; for the 9m pipe section, 2 groups of grouting holes are provided at the end and in the middle; for the 12m pipe section, 3 groups of grouting holes are provided at the end, at 4m, and at 8m. Each group is provided with 3 - 6 grouting holes evenly distributed along the circumferential direction of the pipe section.

[0032] In this embodiment, bleeding holes are also preset on the pipe section. After the pipe jacking construction is completed, injecting cement slurry into the pipe section to displace the thixotropic slurry can improve the stability of the soil mass around the pipe section and prevent the pipe section from settling or deforming during use. Specifically, a group of bleeding holes is provided at the rear end of the pipe section. Each group of bleeding holes includes 3 - 6 evenly distributed along the circumferential direction of the pipe section. Bleeding check valves are provided in the bleeding holes. In step S6, after the pipe jacking construction is completed, the pipe sections are divided into multiple groups. For each group of pipe sections, the grouting holes at one end are connected to a grouting pump, and cement slurry is injected to discharge the thixotropic slurry from the bleeding holes. After the cement slurry is discharged from the bleeding port, the bleeding check valve is closed. After maintaining the pressure for 30 minutes, the slurry replacement is completed. The grouting pressure during pressure maintenance is 1MPa. After the slurry replacement is completed, the main channel slurry pipe and the inner arc slurry pipe of the pipe should be removed and cleaned on the spot to prevent the slurry from solidifying and blocking.

[0033] In an alternative embodiment, the backseat includes reinforced concrete and embedded steel plates. The thinnest part of the reinforced concrete is 20cm thick and is poured with C35 concrete. A formwork is set on the side of the working well 9 facing the inlet hole. The side of the formwork close to the inlet hole is a flat surface perpendicular to the axis of the inlet hole. Embedded bolts are provided on this flat surface to fix the embedded steel plate through the embedded bolts after pouring. During installation, the steel backrest is lifted by a crane to the backrest position of the working well 9, and a theodolite and a plumb bob are used in cooperation to make the plane of the steel backrest perpendicular to the jacking axis.

[0034] The main jacking equipment consists of the following parts: jacking frame, jacking cylinder, oil pressure pumping station and pipe valves, and annular jacking iron. Installation sequence: installation of the jacking frame → installation of the jacking cylinder → installation of the oil pressure pumping station and pipe valves → installation of the annular jacking iron.

[0035] When the pipe jacking machine head 3 is 30m away from the receiving well 1, the jacking speed is slowed down and the jacking pressure is reduced. It is necessary to comprehensively measure and review the attitude of the pipe jacking machine head 3 through the ground control network and underground control points to ensure that the pipe jacking machine exits the hole with a good attitude. After the entire pipe jacking machine head 3 exits the hole, the pipe sections are separated by cutting.

[0036] In an optional embodiment, jet grouting piles 2 are constructed around the working well 9 to form a cylindrical curtain corresponding to the caisson, and a deviation correction device 8 is provided inside the jet grouting piles 2 to correct the deviation during the sinking process of the well wall. The construction steps of the working well 9 and the receiving well 1 are the same. Taking the working well 9 as an example, the specific method includes: Step S101, lofting according to the design drawings, and carrying out replacement filling and cushion construction in the area corresponding to the working well 9; the replacement filling area is an annular shape with a width of 2.7 m and a thickness of 1 m, and the concrete cushion is an annular shape with a width of 1.6 m and a thickness of 0.25 m. The replacement filling and cushion area is adapted to the well wall.

[0037] Step S102, erecting formwork to pour the cutting edge 901. After the concrete strength of the cutting edge 901 reaches the design strength, the cushion below the cutting edge 901 is chiseled off; after each group of construction personnel symmetrically removes a section, the cutting edge 901 should be immediately filled with original soil. Small soil piles with an appropriate height should be filled on the inner and outer sides of the cutting edge 901 and tamped layer by layer to transmit the sinking weight to the cushion. Observation should be strengthened during the removal.

[0038] Step S103, using excavation equipment to start from the middle of the caisson and excavate layer by layer towards the surrounding, and retaining the soil around the cutting edge 901 to form an earth embankment. Cut the soil layer towards the cutting edge 901 in a symmetric manner, so that the well wall sinks under its own weight. After each end well wall sinks, backfill sand 903 is filled for backpressure. After backfilling, the well wall is extended 902. The backpressure method of the backfill sand 903 is to increase the total frictional resistance during the fabrication and sinking process of the caisson by means of the internal frictional resistance of the caisson. Step S104, after cleaning the backfill sand 903, carry out multiple sinkings and extensions 902 until the excavation reaches the preset elevation; adopt the construction method of 6 fabrications and 6 sinkings. Each fabrication time is about 8 days. After the first section is fabricated, it needs to be cured to 100% according to the design requirements for about 20 days before the caisson sinking construction can be carried out.

[0039] The first sinking depth is 4.85 m respectively. When taking soil, start from the middle of the caisson and gradually dig layer by layer towards the surrounding. The thickness of each layer of soil excavation is 0.4 - 0.5 m. Reserve an earth embankment with a width of 1.5 - 2 m around the cutting edge 901. Then, along the caisson wall, in sections of 2 - 3 m each, gradually and uniformly thin the soil layer towards the cutting edge 901 in a comprehensive and symmetric manner (with the geometric centroid line of the plane as the axis of symmetry), with each excavation being 5 - 10 cm. When the soil layer can no longer withstand the extrusion of the cutting edge 901 and breaks, the caisson will sink vertically and uniformly under its own weight, without excessive inclination. If the sinking is very little or there is no sinking, 0.4 - 0.5 m can be dug down from the middle again, and continue to dig layer by layer and evenly towards the surrounding to make the caisson sink smoothly. During the soil excavation process, the soil at the lower part of the cutting edge 901 shall not be excavated. When the caisson is 1.0 m away from the design elevation, slow down the sinking speed. When the caisson finally sinks, leave 0.5 m from the top to the ground without taking soil for sinking; during backfilling, backfill layer by layer and evenly from the middle to the surrounding. After backfilling, the first height of the second connection 902 is 4.5 m.

[0040] During the sinking process of the caisson wall, monitor the water level in the caisson and supplement or drain water according to the water level change. The subsequent sinking is similar to the first sinking except for the different height. When each sinking is completed, leave 0.5 m from the top to the ground without sinking. Adopt non-draining sinking, and control the water level elevation at -6 m. If the groundwater level is not high enough, water needs to be supplemented.

[0041] Step S105, after the caisson is completed, arrange divers to go underwater to remove the floating mud at the bottom of the caisson, clean the underwater floating mud and the cutting edge 901, throw stones at the bottom of the well and level it, extend the concrete conduit into the bottom of the well, first pour from the middle to the surrounding in sequence, and then move from the well edge to the middle for layered pouring to form the bottom seal; Step S106, after the bottom seal concrete is poured, arrange the underwater tie bars. The underwater tie bars extend into the bottom seal concrete. After the bottom seal concrete reaches the preset strength, pump out the water; after pumping out the water, remove the loose layer on the concrete surface, level the concrete according to the design elevation, then bind the steel bars and pour the concrete to form the bottom plate 5.

[0042] In step S102, the mixing piles 2 are constructed synchronously outside the working well 9 to form a cylindrical curtain corresponding to the caisson. The bottom of the mixing piles 2 is higher than the pipeline elevation, so as not to affect the normal pipe jacking. There is a deviation correction device 8 inside the mixing piles 2 to correct the deviation of the caisson wall. When the axis of the caisson does not coincide with the design axis and there is a certain displacement phenomenon, control the caisson not to tilt in the offset direction, and intentionally make the caisson tilt in the direction opposite to the offset.

[0043] After entering the site, give priority to the construction of the caisson mixing piles 2, and then carry out the construction of the main structure of the caisson and the sinking construction, which can improve the bearing capacity of the soft soil.

[0044] In an alternative embodiment, deviation rectification starts after the first high connection 902. The deviation rectification device 8 includes a circular beam 10, a base 801, and a jacking rod 805. Among them, the circular beam 10 is a ring adapted to the mixing pile 2, and the width of the circular beam 10 is greater than the diameter of the mixing pile 2. First, the pile head of the mixing pile 2 is leveled. Then, excavation is carried out on both sides of the curtain formed by the mixing pile 2, and formwork is supported. Through steel bar binding, it is poured integrally with the upper end of the mixing pile 2 to ensure the stability of the circular beam 10 and provide a stable supporting force for deviation rectification. A base 801 is provided on the inner wall of the circular beam 10. The base 801 is anchored to the inner wall of the circular beam 10 by anchor bolts. Multiple bases 801 are evenly distributed circumferentially around the circular beam 10. Generally, the number of bases 801 is not less than 4, preferably 8. The jacking rod 805 is fixed on the base 801. When the shaft wall has a certain deviation, it is inclined along the radial direction of the circular beam 10 to squeeze the shaft wall in the direction opposite to the deviation of the caisson, so as to rectify the shaft wall.

[0045] In this embodiment, the base 801 is provided with an arc surface corresponding to the circular beam 10. On one side of the base 801 corresponding to the shaft wall, there is an installation pipe 802 with an opening pointing to the circular beam 10. The lower surface of the installation pipe 802 contacts the ground to provide a supporting force. Two guide grooves extending radially of the circular beam 10 are provided inside the installation pipe 802. The two guide grooves are distributed longitudinally. Sliders sliding along the guide grooves are provided in the guide grooves. Two jacking rods 805 are provided inside the installation pipe 802 to drive the two sliders respectively; one end of one slider corresponding to the shaft wall is provided with a guide roller 803 adapted to the shaft wall, and one end of the other slider corresponding to the shaft wall is provided with a friction pad 804 corresponding to the shaft wall.

[0046] Since the soil quality underground is not completely the same, the frictional forces received by each part of the shaft wall are different, so the problem of shaft wall deviation occurs frequently. In this application, a friction pad 804 is provided. The friction pad 804 is a rubber pad, which can generate frictional forces at different positions in the circumferential direction of the shaft wall through extrusion, so as to avoid the occurrence of deviation problems.

[0047] In this embodiment, the jacking pipe can be a hydraulic cylinder. The outer wall of the guide roller 803 is provided with an arc surface, which is mainly used to straighten the shaft wall; the frictional force distribution in the circumferential direction of the shaft wall is judged according to the settlement rate of the shaft wall. The friction pad 804 is a rubber pad, and the surface is an arc surface corresponding to the shaft wall. Under the extrusion action, the circumferential frictional force of the shaft wall is kept balanced through the friction pad 804, thereby improving the construction efficiency and quality.

[0048] A brick formwork corresponding to the cutting edge 901 is built inside the cutting edge 901. The outer side of the brick formwork is built into a bevel to form the cutting edge of the cutting edge 901. A plastering thickness of 25 mm should be reserved inside during construction. The cushion layer below the cutting edge 901 is divided into multiple pieces, and the cushion layer is demolished synchronously on both sides symmetrical to the cutting edge 901.

[0049] In an alternative embodiment, in step S5, the elevations of each point at the bottom of the pit are measured. During the bottom sealing, the pouring starts from the lower part and gradually proceeds in sequence around the well, and then moves from the well edge towards the middle, with layered pouring. The mixing pile 2 is constructed by a three-axis mixer, and the construction is carried out in a skip-type double-hole full-set re-mixing connection method. After the cement slurry at the pile top has passed the initial setting, the floating soil at the pile head is manually cleaned to ensure the integrity of the pile body and the cleanliness of the site.

[0050] In an alternative embodiment, the extension of the well wall 902 is carried out in a cast-in-place form. The working well 9 and the receiving well 1 are respectively provided with embedded sleeves of φ3060 and φ2600, so as to form an outlet and an inlet after the removal of the embedded sleeves. After the formwork of the caisson is removed, the reserved holes are blocked, and the blocking masonry is cured together with the main structure of the caisson.

[0051] The formwork of the well wall is assembled with wooden formwork. A scaffold is erected on the outside of the well wall, and a cantilever scaffold is installed on the inside according to the construction progress.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A pipe jacking construction method for pipelines in soft clay layers, characterized in that, Including: Step S1: Set up a working shaft and a receiving shaft at the starting point and the ending point of the pipeline through open caisson construction. Cut out-holes and in-holes on the shaft walls of the working shaft and the receiving shaft respectively according to the design drawings, and hoist out the cut concrete blocks. Step S2: Assemble guide rails at the bottom of the working shaft and the receiving shaft, and extend the guide rails into the corresponding out-holes and in-holes. There is a backseat corresponding to the jacking cylinders in the working shaft. Use hoisting equipment to install the pipe jacking machine head and the jacking cylinders into the working shaft. Step S3: Push the front end of the pipe jacking machine head into the in-hole through the jacking cylinders, hoist in pipe segments and fixedly connect the pipe jacking machine head with the pipe segments. Step S4: After the pipe jacking machine head enters the soil layer, conduct jacking control and deviation correction according to the parameters of the pipe jacking hydraulic system. Step S5: Install pipe segments according to the jacking progress until the pipe jacking machine head is close to the shaft wall of the receiving shaft. Retract the jacking cylinders and install a pipe segment so that the pipe jacking machine head can pass through the out-hole at one time. Then remove the cylinders and place steel supports between the pipe segment and the backseat to prevent the pipe segment from retracting. Step S6: After passing the acceptance, remove the pipe jacking machine head and the guide rails and hoist them out.

2. The pipe jacking construction method for pipelines in soft clay layers according to claim 1, characterized in that, In step S1, water stop rings are set at the in-hole and the out-hole. The water stop ring includes a pre-buried casing, a steel flange, a steel pressure ring, and a rubber water stop belt. First, weld and fix the steel flange to the pre-buried casing, and fill the gap between the steel flange and the shaft wall with high-strength mortar densely. Set 1 layer of rubber water stop belt outside the steel flange. The reserved bolt holes of the rubber water stop belt correspond to the bolt holes of the steel flange one by one. The outside of the rubber water stop belt is tightly squeezed by the steel pressure ring. Set 1 layer of rubber water stop belt outside the steel pressure ring. Corresponding bolt holes are set on the steel pressure ring and the outer rubber water stop belt. Use bolts to pass through each component, and fix the whole water stop device firmly through the steel pressing plate. Use cement mortar to plug the joints and stop water at the contact surface between the steel pressure ring and the concrete wall.

3. The pipe jacking construction method for pipelines in soft clay layers according to claim 1, characterized in that, In step S5, a gantry frame corresponding to the pipe jacking machine head is provided inside the receiving shaft. The gantry frame includes columns and crossbeams. The two ends of the crossbeam are fixed on the columns to longitudinally limit the pipe jacking machine head.

4. The pipe jacking construction method for pipelines in soft clay layers according to claim 3, characterized in that, An expansion rod is provided below the crossbeam, and a roller corresponding to the outer wall of the pipe jacking machine head is provided at the end of the expansion rod.

5. The pipe jacking construction method for pipelines in soft clay layers according to claim 1, characterized in that, Grouting holes are preset on the pipe segments, and grouting one-way valves are provided in the grouting holes. During the pipe jacking process in step S4, inject thixotropic slurry between the pipe segments and the soil through grouting equipment.

6. The pipe jacking construction method for pipelines in soft clay layers according to claim 5, characterized in that, Discharge holes are also preset on the pipe segments, and discharge one-way valves are provided in the discharge holes. In step S6, after the pipe jacking construction is completed, divide the pipe segments into multiple groups. Connect the grouting holes at one end of each group of pipe segments to a grouting pump, inject cement slurry to make the thixotropic slurry discharge from the discharge holes. After the cement slurry is discharged from the discharge port, close the discharge one-way valve, keep the pressure for 30 minutes, and then complete the slurry replacement.

7. The pipe jacking construction method for pipelines in soft clay layers according to claim 1, characterized in that, The backseat includes reinforced concrete and pre-buried steel plates. Set up a formwork on the side of the working shaft facing the in-hole. The side of the formwork close to the in-hole is a flat surface perpendicular to the axis of the in-hole. Embedded bolts are provided on this flat surface to fix the pre-buried steel plates through the embedded bolts after pouring is completed.

8. The pipe jacking construction method for pipelines in soft clay layers according to claim 5, characterized in that, When the pipe jacking machine head is 30 m away from the receiving well, slow down the jacking speed, reduce the jacking pressure, and conduct a comprehensive measurement and review of the attitude of the pipe jacking machine head. After the pipe jacking machine head exits the hole as a whole, separate the pipe sections by cutting.

9. The pipe jacking construction method for pipelines in soft clay layers according to claim 1, characterized in that, Carry out the construction of mixing piles around the working well to form a cylindrical curtain corresponding to the caisson, and a deviation correction device is provided inside the mixing piles to correct the deviation during the sinking process of the well wall.

10. The pipe jacking construction method for pipelines in soft clay layers according to claim 1, characterized in that, There are three parallel pipes between the working well and the receiving well. First, jack the middle pipe according to steps S3 - S5. After the jacking of the middle pipe is completed, use the pipe connection and hoisting time to carry out the cross-jacking operation on the two side pipes.

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