A pipe jacking tunnel support structure and construction method

Abstract

The present invention provides a pipe jacking tunnel support structure and construction method, including a pipe jacking tunnel, a plurality of prefabricated pipe piles and locking steel pipes pressed into the ground below the pipe jacking tunnel; the prefabricated pipe piles extend underground and are arranged side by side and spaced apart along the axis of the pipe jacking tunnel, a pile top reinforcement body is provided around and above the upper end of the prefabricated pipe piles, and the locking steel pipe passes through the pile top reinforcement body and is located above the prefabricated pipe piles and is reinforced by grouting inside; the locking steel pipes are plugged into each other in a straight line arrangement and extend horizontally along the axis of the pipe jacking tunnel to form a portal structure with the prefabricated pipe piles. At the same time, a construction method for realizing the structure is also provided. The concrete prefabricated pipe pile structure and the locking steel pipe structure are jointly formed into a portal structure, which supports the upper pipe jacking tunnel, blocks soil deformation and stress transfer caused by the planned tunnel construction, and plays a good protective role for the pipe jacking tunnel.

Description

Technical Field

[0001] The invention belongs to the technical field of pipe jacking tunnels, and in particular relates to a pipe jacking tunnel support structure and a construction method, which are suitable for pre-protecting a pipe jacking tunnel under construction under the condition that the pipe jacking tunnel under construction crosses a planned tunnel. Background Art

[0002] Before the construction of the pipe jacking tunnel, it is known that a subway tunnel will pass under the pipe jacking tunnel in the future according to the underground space planning. It can be expected that the construction of the planned tunnel will inevitably disturb the surrounding strata, causing deformation of the surrounding strata and transmitting upward, resulting in a reduction in the bearing capacity or support conditions of the upper pipe jacking tunnel structure or structural deformation. When the additional stress caused by the deformation of the strata exceeds the strength limit of the structure, it will cause damage to the upper structure and affect the construction of the lower structure, and even cause serious safety accidents. This impact will be particularly serious for soft soil foundations. In the past, due to delayed planning, the upper tunnel could only be passively protected when the lower subway passed through the upper tunnel. Now, according to the subway planning, proactive protection measures can be taken for the pipe jacking tunnel to avoid the impact of the planned subway tunnel construction in the future.

[0003] The pre-protection of the top pipe tunnel above can be achieved by full cement soil reinforcement. The soft soil in the area where the top pipe passes can be reinforced into cement soil through cement soil mixing piles, rotary jet piles or grouting, which can protect the top pipe tunnel to a certain extent. However, this method will greatly increase the resistance of the tunnel, require higher construction conditions, and require more funds for construction. In addition, the use of full-area cement soil reinforcement will generate a lot of unnecessary material consumption. Therefore, it is extremely necessary to adopt a safe, efficient and conducive pre-support scheme for top pipe tunnel construction. Summary of the invention

[0004] One of the purposes of the present invention is to overcome the shortcomings of the prior art and provide a jacking tunnel support structure, which achieves a pre-support effect on the jacking tunnel under construction by means of a gantry structure formed by grouting reinforcement of locking steel pipes and prefabricated pipe piles.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A pipe jacking tunnel support structure comprises a pipe jacking tunnel, a plurality of prefabricated pipe piles pressed into the ground below the pipe jacking tunnel, and locking steel pipes; the prefabricated pipe piles extend underground and are arranged side by side and spaced apart along the axis of the pipe jacking tunnel; pile top reinforcement bodies are arranged around and above the upper ends of the prefabricated pipe piles; the locking steel pipes pass through the pile top reinforcement bodies and are located above the prefabricated pipe piles and are reinforced by grouting inside; the locking steel pipes are plugged into each other and arranged in a straight line and extend horizontally along the axis of the pipe jacking tunnel to form a portal structure with the prefabricated pipe piles.

[0007] Furthermore, the locking steel pipes are filled with steel pipe reinforcement bodies formed by cement-water glass slurry.

[0008] Furthermore, an exhaust pipe with a steel pipe exhaust hole is provided close to the inner wall of the locking steel pipe, one end of the exhaust pipe is closed, and the other end extends out of the locking steel pipe.

[0009] Furthermore, a steel pipe male lock buckle with a protrusion on the outer end is provided on the outer side wall of the locking steel pipe, and a steel pipe female lock buckle with a sliding groove is provided on the other opposite side. The sliding groove cooperates with the protrusion and is correspondingly located on the cross-sectional diameter of the locking steel pipe.

[0010] Furthermore, a steel pipe grouting pipe is provided near the inner wall of the locking steel pipe, and a steel pipe grouting hole penetrating the side wall of the locking steel pipe is provided on the steel pipe grouting pipe; the steel pipe grouting pipe is distributed up and down based on the plug-in position.

[0011] Furthermore, jacking pipe segments are continuously pushed into the jacking pipe holes of the jacking pipe tunnel, and thixotropic mud is evenly injected into the outer walls of the jacking pipe segments.

[0012] Furthermore, the upper end of the prefabricated pipe pile is provided with a hollow interior; a plurality of pile wall grouting holes are provided on the side wall surface of the hollow interior and a transverse partition is provided at the bottom, a steel cage is provided on the transverse partition, and a pipe pile air outlet hole is provided on the transverse partition.

[0013] Beneficial effects of the above technical solution:

[0014] 1. The prefabricated concrete pile structure and the locking steel pipe structure are combined to form a portal structure, which supports the upper jacking tunnel, blocks soil deformation and stress transfer caused by the planned tunnel construction, and plays a good protective role for the jacking tunnel;

[0015] 2. The locking steel pipe passes through the pile top reinforcement body at the top of the prefabricated pipe pile. The steel pipe reinforcement body and the pile top reinforcement body are integrated with each other, making the connection between the prefabricated pipe pile structure and the locking steel pipe structure very firm and tight, so that the force of the locking steel pipe structure can be better transmitted to the prefabricated pipe pile;

[0016] 3. The supporting layer composed of cement mortar injected into the locking steel pipe, cement-water glass reinforcement around the locking steel pipe and the locking buckles between the locking steel pipes has high rigidity, which is very beneficial for controlling the deformation of the jacking tunnel;

[0017] 4. The grouting liquid injected into the soil around the locking steel pipe is cement-water glass slurry, which solidifies quickly and can solidify quickly in a short time with high strength. There is an exhaust pipe inside the locking steel pipe, which can discharge the air in time when the cement mortar is injected into the locking steel pipe, which is conducive to the cement mortar completely filling the inside of the locking steel pipe.

[0018] 5. The combined structure of locking steel pipe and prefabricated pipe piles is safe, efficient and saves materials.

[0019] Another object of the present invention is to provide a construction method for a pipe jacking tunnel support structure, comprising the following steps:

[0020] (1) Strengthen the departure well and receiving well and carry out corresponding foundation pit excavation;

[0021] (2) preparing the prefabricated pipe pile: installing a conical concrete pipe pile tip at the bottom of the prefabricated pipe pile, casting a layer of diaphragm inside the upper end of the prefabricated pipe pile by drilling and embedding reinforcement, and reserving pipe pile vent holes on the diaphragm; placing a steel cage on the diaphragm, and drilling pile wall grouting holes on the upper part of the diaphragm;

[0022] (3) Installing the prefabricated pipe piles: After the prefabricated pipe piles are pressed into the determined foundation position by static pressure construction, the pressed piles and grouting pipes are connected to grout the upper part of the diaphragm and grout the surrounding soil through the grouting holes of the pile wall. The grouting liquid is a cement slurry with a retarder added, and finally a pile top reinforcement body is formed;

[0023] (4) Excavating the jacking tunnel hole and the steel pipe groove required for inserting the locking steel pipe through the wall of the starting well;

[0024] (5) preparing the locking steel pipe: welding a steel pipe grouting pipe and an exhaust pipe in the locking steel pipe, and opening a steel pipe grouting hole and a steel pipe exhaust hole;

[0025] (6) The locking steel pipe is pushed in a straight line through the broken groove by the jacking method. The jacking sequence of the locking steel pipe is symmetrically carried out from the middle to both ends based on the locking steel pipe on the central axis of the cross section, and the locking steel pipe is pressed into the designed position by means of a press-in pipe so that the locking steel pipe passes through the pile top reinforcement body. The locking steel pipe is connected to the prefabricated pile through the pile top reinforcement body to form a portal structure;

[0026] (7) using a grouting pump and injecting cement-water glass slurry into the soil around the locking steel pipe through the steel pipe grouting pipe, and forming a steel pipe reinforcement body in the foundation;

[0027] (8) One end of the exhaust pipe of the locking steel pipe is closed, and the other end extends from the inner cavity of the pressure-injection pipe into the departure well, and cement mortar is injected into the locking steel pipe, and air is discharged through the exhaust pipe of the locking steel pipe; after the locking steel pipe is filled with cement mortar, the pipe is pulled out while injecting cement mortar into the pressure-injection pipe to fill the soil densely;

[0028] (9) Install the jacking equipment such as the back wall, guide rails and jacks, determine the measurement axis and level point, and start jacking the jacking tunnel. While jacking, continuously inject thixotropic mud on the outer wall of the jacking tunnel segment, and monitor and correct the deviation in a timely manner.

[0029] Furthermore, cement mixing piles are used to construct end reinforcement bodies around the departure well and the receiving well, and the cement mixing piles are constructed using the "two spraying and four mixing" method; then prefabricated sheet piles are inserted into the foundation closely against the inner side of the end reinforcement bodies of the cement mixing piles to form a protective sheet pile wall, thereby reinforcing the departure well and the receiving well.

[0030] Furthermore, a waterproof board is installed around the hole in the top pipe.

[0031] The construction method is overall simple and convenient, low in cost and the formed support structure is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a plan layout diagram of the present invention.

[0033] Figure 2 It is a cross-sectional view of the working well of the present invention.

[0034] Figure 3 It is a schematic diagram of the connection relationship between the locking steel pipe and the pile top reinforcement body of the present invention.

[0035] Figure 4 It is a schematic diagram of the structure of the jacking tunnel hole and the locking steel pipe broken groove of the present invention.

[0036] Figure 5 It is a schematic structural diagram of the prefabricated pipe pile of the present invention.

[0037] Figure 6 It is the arrangement diagram of the grouting holes of the pipe pile of the present invention.

[0038] Figure 7 It is a schematic diagram of the locking steel pipe structure of the present invention.

[0039] Figure 8 This is a layout diagram of the exhaust holes of the locking steel pipe of the present invention.

[0040] In the figure: 1-pipe jacking tunnel; 2-locking steel pipe; 3-long-term planned tunnel; 4-prefabricated pipe pile; 5-steel pipe grouting pipe; 6-steel pipe reinforcement body; 7-pile top reinforcement body; 8-steel pipe grouting hole; 9-pile tip; 10-reinforcement cage; 11-steel pipe female lock buckle; 12-steel pipe male lock buckle; 13-pipe pile vent; 14-pile wall grouting hole; 15-diaphragm; 16-exhaust pipe; 17-steel pipe vent; 18-artificial fill; 19-silty silty clay; 20-end reinforcement body; 21-pipe jacking hole; 22-steel pipe broken groove; 23-enclosing sheet pile wall; 24-pile top grouting pipe; 25-pressed pipe; 26-mortar body in the pipe. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] Refer to the accompanying drawings. The pipe jacking tunnel support structure of this embodiment includes a pipe jacking tunnel 1, a plurality of prefabricated pipe piles 4 pressed into the ground below the pipe jacking tunnel 1, and a locking steel pipe 2. Among them, the prefabricated pipe piles 4 are made of concrete, and the upper end thereof has a hollow interior, and the lower end is a pointed cone with a diameter that shrinks downward. The bottom of the hollow interior is a layer of diaphragm 15 with air vents 13 for pipe piles, and a steel cage 10 is cast on the diaphragm 15. A plurality of pile wall grouting holes 14 are provided on the side wall surface of the hollow interior. Specifically, the side wall surface of the hollow interior is evenly provided with 6 pile wall grouting holes 14 at cross sections every 30 cm in the height direction.

[0043] The locking steel pipe 2 is closed at one end and open at the other end. The upper radial direction of the two opposite wall surfaces of the outer wall of the locking steel pipe 2 is respectively provided with a steel pipe male lock buckle 12 with a raised outer end face and a steel pipe female lock buckle 11 with a slide groove on the outer end face. The raised end face and the slide groove cooperate to realize the plug-in connection between the locking steel pipes 2 and ensure that the locking steel pipes 2 are in the same horizontal line. The inner wall of the locking steel pipe 2 is also welded with an exhaust pipe 16 and a steel pipe grouting pipe 5. Four steel pipe exhaust holes 17 are symmetrically distributed on the exhaust pipe 16 at intervals of 1.5m along the axial direction. One end of the exhaust pipe 16 is closed and the other end extends out of the locking steel pipe 2. There are two steel pipe grouting pipes 5, which are distributed at 45° above and below the radial straight line connecting the steel pipe male lock buckle 12 and the steel pipe female lock buckle 11 as the reference. The steel pipe grouting pipe 5 is provided with a steel pipe grouting hole 8 that penetrates the side wall of the locking steel pipe 2.

[0044] The prefabricated pipe piles 4 are arranged side by side and spaced apart along the axis of the top pipe tunnel 1. The spacing in the length direction can be specifically adapted according to the long-term planned tunnel 3 below the top pipe tunnel 1. In particular, the spacing between adjacent prefabricated pipe piles 4 is three times the pile diameter. A pile top reinforcement body 7 is provided around and above the upper end of the prefabricated pipe pile 4. The pile top reinforcement body 7 is formed by the cement-retarder overflowing the pile wall grouting hole 14. The locking steel pipe 2 passes through the pile top reinforcement body 7 and is located above the prefabricated pipe pile 4 and is reinforced by cement grouting inside. The locking steel pipes 2 are plugged into each other in a straight line arrangement and extend horizontally along the axis of the top pipe tunnel 1 to form a portal structure with the prefabricated pipe piles 4, that is, the horizontally arranged locking steel pipes 2 are supported by multiple pairs of prefabricated pipe piles 4 arranged side by side. Specifically, the portal structure is symmetrical on the left and right, thereby ensuring good structural stability. The locking steel pipes 2 are also filled with steel pipe reinforcement bodies 6 , which are formed by cement-water glass slurry overflowing from the grouting holes of the steel pipe grouting pipe 5 .

[0045] Pipe jacking segments are continuously pushed into the pipe jacking holes 21 of the pipe jacking tunnel 1, and the outer walls of the pipe jacking segments are uniformly injected with thixotropic mud.

[0046] The construction method of this embodiment is as follows:

[0047] The pipe jacking tunnel support structure and construction method include the following steps:

[0048] 1) Cement mixing piles are used to construct the end reinforcement body 20 around the starting well and the receiving well. The cement mixing piles are constructed by the "two spraying and four mixing" method. In this embodiment, the starting well and the receiving well are 12m deep.

[0049] 2) Use sheet pile wall for support, insert prefabricated sheet piles into the foundation closely against the inner side of the cement mixing pile end reinforcement body to form a retaining sheet pile wall 23, and excavate the starting well and receiving well foundation pits.

[0050] 3) A conical concrete pile tip 9 is installed at the bottom of the prefabricated pipe pile 4, and a layer of pipe pile diaphragm 15 is cast inside the pipe pile by drilling and embedding reinforcement method. The diaphragm 15 is reserved with pipe pile vent holes 13, and a steel cage 10 is placed on the pipe pile diaphragm 15. Six grouting holes are evenly and symmetrically drilled on the upper pile wall of the diaphragm 15 every 30cm of the cross section.

[0051] 4) The surveyor uses the axis control network to control the points, accurately places the pile position, takes the distance between the pipe piles to three times the pile diameter, installs the grouting pipe, and vertically points the pile tip downward. The prefabricated pipe pile 4 is pressed into the foundation by static pressure construction, and the air in the pipe pile is discharged from the vent hole on the pipe pile diaphragm 15. Connect the pressed pile, place the pile top grouting pipe 24 into the pressed pile, and continue static pressure to the designed elevation. Pull out the pressed pile, leave the grouting pipe in the pipe pile, add a retarder to the cement slurry, grout into the surrounding soil through the grouting holes on the pile wall, and grout into the upper part of the diaphragm 15 inside the pile, and finally form the pile top reinforcement body 7. In this embodiment, the pre-branched pipe pile is 8m long and pressed 10m from the bottom surface, with a pile diameter of 550mm.

[0052] 5) Determine the insertion position of the locking steel pipe 2 and the jacking pipe, and artificially dig the jacking pipe hole 21 required for the jacking pipe and the steel pipe broken groove 22 required for the locking steel pipe 2 on the wall of the departure well. Install waterproof panels around the jacking pipe hole. In this embodiment, the cross section of the jacking pipe hole 21 is square, with a size of 3.5m*3.5m, and the cross section of the steel pipe broken groove 22 is rectangular, with a size of 5m*0.7m, to facilitate the jacking of the locking steel pipe 2 and the jacking pipe.

[0053] 6) Select a locking steel pipe 2 with an appropriate diameter according to the project conditions, install the steel pipe grouting pipe 5 and the exhaust pipe 16 in the locking steel pipe 2, and open the steel pipe grouting hole 8 and the steel pipe exhaust hole 17. In this embodiment, a locking steel pipe 2 with a diameter of 500 mm is selected, and the length along the top pipe tunnel 1 is 30 m.

[0054] 7) Before the pile top reinforcement body 7 solidifies, the locking steel pipe 2 is arranged and pushed in in a straight line by the jacking method. The jacking sequence of the steel pipe is symmetrical from the middle to both ends based on the steel pipe on the central axis of the cross section. One end of the steel pipe is closed and the other end is connected to a grouting pump. The steel pipe is pushed in to a suitable position and connected to a pressing pipe 25. The locking steel pipe 2 is pressed in to the designed position with the help of the pressing pipe 25, so that the locking steel pipe 2 passes through the pile top reinforcement body 7. The locking steel pipe 2 is connected to the precast pile through the grouting reinforcement body to form a portal structure.

[0055] 8) A grouting pump is used to inject cement-water glass slurry into the soil around the steel pipe through the grouting pipe inside the steel pipe. The cement-water glass slurry is injected into the foundation from the grouting hole 8 of the steel pipe to form a steel pipe reinforcement body 6.

[0056] 9) One end of the steel pipe exhaust pipe 16 is closed, and the other end extends from the inner cavity of the push-in pipe 25 to the departure well, and cement mortar is injected into the locking steel pipe 2. The air is discharged through the exhaust pipe 16. After the locking steel pipe 2 is filled with cement mortar, cement mortar is injected into the push-in pipe 25 to form a mortar body 26 in the pipe while the pipe is pulled out to fill the soil densely.

[0057] 10) Install the jacking equipment such as the back wall, guide rails and jacks, determine the measurement axis and level point, and start jacking the jacking segments. While jacking, continuously inject thixotropic mud on the outer wall of the jacking segments, and monitor and correct the deviation in time. The soil layer for jacking is silty clay 19, and it is covered with artificial fill 18. The size of the jacking segments is 3m*3m. On the one hand, thixotropic mud can convert the dry friction between the pipe wall and the soil into wet friction, reducing the jacking friction resistance. On the other hand, it can also form a complete mud sleeve in the gap of the hollowed-out outer wall of the pipe, reducing the deformation of the soil and making the pipeline more stable.

[0058] It should be noted that the above describes the embodiments of the present invention. However, those skilled in the art should understand that the present invention is not limited to the above embodiments, which are only used to illustrate the principles of the present invention. The present invention may be subject to various changes and modifications without departing from the scope of the present invention, and these changes and modifications all fall within the scope of the present invention to be protected.

Claims

1. A pipe jacking tunnel support structure, characterized in that The invention comprises a pipe jacking tunnel, a plurality of prefabricated pipe piles and locking steel pipes pressed into the ground below the pipe jacking tunnel; the prefabricated pipe piles are arranged side by side and spaced apart along the axis of the pipe jacking tunnel, a pile top reinforcement body is arranged around and above the upper end of the prefabricated pipe piles, the locking steel pipe passes through the pile top reinforcement body and is located above the prefabricated pipe piles and is reinforced by grouting inside; the locking steel pipes are plugged into each other and arranged in a straight line and extend horizontally along the axis of the pipe jacking tunnel to form a portal structure with the prefabricated pipe piles; the portal structure is formed by the following steps: (1) Strengthen the departure well and receiving well and carry out corresponding foundation pit excavation; (2) preparing the prefabricated pipe pile; installing a conical concrete pipe pile tip at the bottom of the prefabricated pipe pile, casting a layer of diaphragm inside the upper end of the prefabricated pipe pile by drilling and embedding reinforcement, and reserving pipe pile vent holes on the diaphragm; placing a steel cage on the diaphragm, and drilling pile wall grouting holes on the upper part of the diaphragm; (3) installing the prefabricated pipe piles; after the prefabricated pipe piles are pressed into the determined foundation position by static pressure construction, the pressed piles and grouting pipes are connected to grout the upper part of the diaphragm and grout the surrounding soil through the grouting holes of the pile wall, the grouting liquid is cement slurry with a retarder added, and finally a pile top reinforcement body is formed; (4) Excavating the jacking hole for the jacking tunnel and the steel pipe groove required for inserting the locking steel pipe through the wall of the starting well; (5) Preparation of the locking steel pipe: (6) The locking steel pipe is pushed in through the broken groove in a straight line by using the jacking method, and the locking steel pipe is connected to the prefabricated pipe pile through the pile top reinforcement to form a portal structure.

2. A pipe jacking tunnel support structure as claimed in claim 1, characterized in that A steel pipe reinforcement body formed by cement-water glass slurry is also filled between the locking steel pipes.

3. A pipe jacking tunnel support structure as claimed in claim 2, characterized in that An exhaust pipe with a steel pipe exhaust hole is provided close to the inner wall of the locking steel pipe. One end of the exhaust pipe is closed, and the other end extends out of the locking steel pipe.

4. A pipe jacking tunnel support structure as claimed in claim 2, characterized in that A steel pipe male lock buckle with a protrusion on the outer end is provided on the outer side wall of the lock steel pipe, and a steel pipe female lock buckle with a slide groove is provided on the other opposite side. The slide groove cooperates with the protrusion and is correspondingly located on the cross-sectional diameter of the lock steel pipe.

5. A pipe jacking tunnel support structure as claimed in claim 2, characterized in that A steel pipe grouting pipe is also provided near the inner wall of the locking steel pipe, and a steel pipe grouting hole penetrating the side wall of the locking steel pipe is provided on the steel pipe grouting pipe; the steel pipe grouting pipe is distributed up and down based on the plug-in position.

6. A pipe jacking tunnel support structure as claimed in claim 5, characterized in that Pipe jacking segments are continuously pushed into the pipe jacking holes of the pipe jacking tunnel, and thixotropic mud is evenly injected into the outer walls of the pipe jacking segments.

7. A pipe jacking tunnel support structure as claimed in any one of claims 1 to 6, characterized in that The upper end of the prefabricated pipe pile is provided with a hollow interior; a plurality of pile wall grouting holes are provided on the side wall surface of the hollow interior and a transverse partition is provided at the bottom, a steel cage is provided on the transverse partition, and a pipe pile air outlet hole is provided on the transverse partition.

8. A construction method for a pipe jacking tunnel support structure as claimed in any one of claims 1 to 7, characterized in that The steps include: (1) Strengthen the departure well and receiving well and carry out corresponding foundation pit excavation; (2) preparing the prefabricated pipe piles: installing a conical concrete pipe pile tip at the bottom of the prefabricated pipe pile, casting a layer of diaphragm inside the upper end of the prefabricated pipe pile by drilling and embedding reinforcement, and reserving pipe pile vents on the diaphragm; placing a steel cage on the diaphragm, and drilling pile wall grouting holes on the upper part of the diaphragm; (3) Installing the prefabricated pipe piles: After the prefabricated pipe piles are pressed into the determined foundation position by static pressure construction, the pressed piles and grouting pipes are connected to grout the upper part of the diaphragm and grout the surrounding soil through the grouting holes on the pile wall. The grouting liquid is cement slurry with a retarder added, and finally a pile top reinforcement body is formed; (4) Excavating the jacking hole for the jacking tunnel and the steel pipe groove required for inserting the locking steel pipe through the wall of the starting well; (5) preparing the locking steel pipe: welding a steel pipe grouting pipe and an exhaust pipe in the locking steel pipe, and opening a steel pipe grouting hole and a steel pipe exhaust hole; (6) The locking steel pipe is pushed in through the broken groove in a straight line by the jacking method. The jacking sequence of the locking steel pipe is symmetrically carried out from the middle to both ends based on the locking steel pipe on the central axis of the cross section, and the locking steel pipe is pressed into the designed position by means of a press-in pipe so that the locking steel pipe passes through the pile top reinforcement body. The locking steel pipe is connected to the prefabricated pipe pile through the pile top reinforcement body to form a portal structure. (7) using a grouting pump and injecting cement-water glass slurry into the soil around the locking steel pipe through the steel pipe grouting pipe, and forming a steel pipe reinforcement body in the foundation; (8) One end of the exhaust pipe of the locking steel pipe is closed, and the other end extends from the inner cavity of the pressure-injection pipe to the departure well, and cement mortar is injected into the locking steel pipe, and air is discharged through the exhaust pipe; after the locking steel pipe is filled with cement mortar, cement mortar is injected into the pressure-injection pipe to form a mortar body in the pipe while the pipe is pulled out to fill the soil densely; (9) After installing the back wall, guide rails and jacks, determine the measurement axis and level point, and start jacking the tunnel. While jacking, continuously inject thixotropic mud into the outer wall of the tunnel segment, and monitor and correct the deviation in a timely manner.

9. A construction method for a pipe jacking tunnel support structure as claimed in claim 8, characterized in that Cement mixing piles are used to construct end reinforcement bodies around the departure well and the receiving well. The cement mixing piles are constructed using the "two spraying and four mixing" method. Then, prefabricated sheet piles are inserted into the foundation closely against the inner side of the end reinforcement bodies of the cement mixing piles to form a protective sheet pile wall, thereby reinforcing the departure well and the receiving well.

10. The construction method of a pipe jacking tunnel support structure according to claim 8, characterized in that A waterproof board is installed around the jacking pipe hole.

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