A method for replacing a tunnel pile foundation

Abstract

The application discloses a tunnel pile foundation underpinning construction method, and the construction method comprises the following steps: S100, construction preparation; S200, tunnel bench method construction to underpinning pile; S300, construction of advanced support; S400, pile body concrete removal, construction of initial support; S500, excavation of soil bodies on both sides of the lower part of the underpinning pile, and timely initial support closure; S600, pouring of side wall and arch part secondary lining; S700, removal of temporary cross brace after the secondary lining concrete reaches the design strength; S800, bottom plate construction; S900, repeating S200-S800 until all pile foundation underpinning is completed. The tunnel pile foundation underpinning construction method effectively utilizes the transformation of the initial support and the secondary lining of the tunnel to the load of the fire pool, guarantees the safety and normal use of the fire pool structure, and has small engineering quantity, and can save investment. By utilizing the mechanism of passive underpinning, the pile foundation bears the force by itself, the pile foundation intruding into the tunnel is removed and cut step by step and root by root, and the safety and normal use of the fire pool structure are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of underpinning construction, and particularly relates to a tunnel pile foundation underpinning construction method. BACKGROUND

[0002] Underpinning technology refers to a technology for solving the problems of needing to deal with the foundation of an existing building and needing to reinforce the foundation, and a technology for solving the problems of needing to build underground projects under the foundation of an existing building and needing to build new projects adjacent to the existing building and affecting the safety of the existing building. The underpinning technology can also be referred to as foundation underpinning.

[0003] In recent years, with the rapid development trend of urban subways, but due to the constraints of original urban planning, newly-built subway tunnels will inevitably conflict with the foundations of ground existing buildings during construction, and the column foundations of the existing buildings need to be safely and effectively underpinned. When a subway tunnel passes under the pile foundation of a ground building, the pile foundation is generally underpinned or reinforced on the ground.

[0004] However, various construction situations will be encountered in actual construction. When the tunnel construction encounters a fire pool, the existing underpinning technology cannot guarantee the safety and normal use of the structure of the fire pool, and the tunnel construction will cause damage to the ground building. In order to guarantee the safety and normal use of the structure of the fire pool, a large amount of construction and a large investment will be required. SUMMARY

[0005] The purpose of the present application is to provide a tunnel pile foundation underpinning construction method to solve the above problems in the prior art.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0007] A tunnel pile foundation underpinning construction method comprises the following steps:

[0008] S100: construction preparation;

[0009] S200: tunnel benching method construction to underpinning pile;

[0010] S300: construction of advanced support;

[0011] S400: pile body concrete removal, construction of initial support;

[0012] S500: excavation of the soil on both sides of the lower part of the underpinning pile, and timely initial support closure;

[0013] S600: pouring of side wall and arch two lining;

[0014] S700: after the two lining concretes reach the design strength, the temporary cross brace is removed;

[0015] S800: bottom plate construction;

[0016] S900: Repeat S200-S800 until all pile foundation replacements are completed.

[0017] In one possible design, step S200 includes: constructing an inclined shaft passage and excavating it to the pile foundation replacement section using a step method, wherein the step method forms an upper step above the corresponding replacement pile and a lower step below the corresponding replacement pile.

[0018] In one possible design, step S300 includes: constructing the pre-grouting small guide pipe and large pipe shed for the arch of the inclined shaft passage, and completing the pre-grouting reinforcement of the small guide pipe; excavating the upper part using the step method, constructing system anchor bolts and locking foot anchor bolts, laying steel mesh, and spraying 4cm thick C25 early strength concrete.

[0019] In one possible design, step S400 includes: cutting the pile foundation along the longitudinal direction of the tunnel according to the spacing of the dense steel frame (0.3m / pile); using a hand-held pneumatic pick to remove the pile foundation concrete and cut the exposed steel bars of the pile foundation; erecting the initial support steel frame of the arch, with vertical temporary support at the pile foundation location and temporary horizontal inverted arch in the transverse direction; erecting the initial support steel frame, vertical temporary support and temporary horizontal inverted arch for every 300mm thick pile foundation removed, until the entire pile foundation is replaced.

[0020] In one possible design, the vertical temporary support is selected as a support column, which includes an upper support plate, a support column body, a lower support plate and an outer cylinder. The support column body is inserted into the outer cylinder, and the two ends of the support column body and the outer cylinder are connected by the upper support plate and the lower support plate, respectively.

[0021] A receiving gap is formed between the support column body and the outer cylinder body. The support column body is equipped with a storage cylinder, which is located within the receiving gap and is detachably equipped with multiple additional support rods. The lower part of the storage cylinder is rotatably mounted on the support column body via a torsion spring. The outer cylinder body is equipped with a control rod, which is used to control the rotation of the storage cylinder.

[0022] Accordingly, the outer cylinder includes a main body and a disassembly plate part. The main body is provided with a pick-and-place slot for picking up and placing additional support rods, and the disassembly plate part is detachably mounted on the pick-and-place slot.

[0023] In one possible design, the storage tube includes a storage section, a middle plate and a rotating section arranged sequentially from top to bottom. The storage section includes an upper sleeve and several first partitions. The upper sleeve is rotatably mounted on the support column body. The first partitions are evenly distributed in the circumferential direction of the upper sleeve, and a slot for storing an additional support rod is formed between adjacent first partitions.

[0024] The rotating part includes a lower sleeve and several second partitions. The lower sleeve is rotatably mounted on the support column body by a torsion spring. The second partitions are evenly distributed in the circumferential direction of the lower sleeve, and a limiting groove is formed between adjacent second partitions.

[0025] Accordingly, the control rod includes an outer sleeve and a control rod body. The outer sleeve is fixed on the outer cylinder, and the control rod body is slidably disposed on the outer sleeve and can be inserted into the limiting groove.

[0026] In one possible design, the top surface of the upper support plate is provided with at least two connecting holes for connecting the pad plate. The bottom surface of the upper support plate is provided with a connecting rod and an annular cover. The connecting rod is located in the middle of the upper support plate and is connected to the support column body through a threaded connection. The annular cover is located outside the connecting rod and is inserted into the outer cylinder. A dynamic sealing structure is provided between the annular cover and the outer cylinder.

[0027] In one possible design, step S500 includes: excavating the soil on both sides of the lower step, retaining the core soil in the middle, and constructing the initial support steel frame, system anchor bolts, and locking foot anchor bolts on both sides.

[0028] In one possible design, step S600 includes: pouring the sidewalls and arch lining, wherein the vertical temporary supports and temporary horizontal arch suppressors shall not be removed during the pouring of concrete.

[0029] In one possible design, step S800 includes: after the secondary lining concrete reaches its design strength, excavating the lower half of the core soil and pouring the secondary lining of the channel bottom slab; after the bottom slab reaches its design strength, cutting off the vertical temporary supports and temporary horizontal arches outside the secondary lining.

[0030] Beneficial effects:

[0031] The described tunnel pile foundation underpinning construction method effectively utilizes the transfer of load on the fire water tank from the tunnel's initial support and secondary lining, ensuring the safety and normal use of the fire water tank structure. Moreover, it involves a smaller workload, saving investment. Utilizing the passive underpinning mechanism, relying on the bearing capacity of the piles themselves, the piles intruding into the tunnel are removed and cut step-by-step, ensuring the safety and normal use of the fire water tank structure and achieving effective transfer of the fire water tank's own load and dynamic load. Simultaneously, it has advantages such as low construction difficulty, flexible operation, low construction investment, quick and convenient adjustment of procedures, and low safety risks. The use of manual hand-held pneumatic picks to remove the pile foundation concrete reduces vibration and eliminates noise pollution to the surrounding environment. Attached Figure Description

[0032] Figure 1 This is a flowchart of a tunnel pile foundation underpinning construction method.

[0033] Figure 2 This is a structural diagram of the tunnel pile foundation replacement construction method at step S200.

[0034] Figure 3 This is a structural diagram showing the tunnel pile foundation replacement construction method at the start of step S300.

[0035] Figure 4 This is a structural diagram showing the tunnel pile foundation replacement construction method at the end of step S300.

[0036] Figure 5 This is a structural diagram of the tunnel pile foundation replacement construction method at step S600.

[0037] Figure 6 This is a structural diagram of the tunnel pile foundation replacement construction method at step S800.

[0038] Figure 7 This is a structural diagram of the supporting column.

[0039] Figure 8 for Figure 2 A cross-sectional structural diagram.

[0040] Figure 9 This is a structural diagram of the storage tube.

[0041] Figure 10 This is a schematic diagram of the assembly of the rotating part and the control lever.

[0042] Figure 11 This is a schematic diagram of the upper support plate.

[0043] In the picture:

[0044] 1. Upper support plate; 101. Connecting hole; 102. Connecting rod; 103. Annular cover; 2. Support column body; 3. Lower support plate; 4. Outer cylinder; 41. Main body; 42. Disassembly plate part; 43. Retrieval slot; 5. Storage cylinder; 51. Storage part; 52. Intermediate plate; 53. Rotating part; 511. Upper sleeve; 512. First partition plate; 513. Slot; 531. Lower sleeve; 532. Second partition plate; 533. 6. Limiting groove; 7. Additional support rod; 8. Control rod; 9. Outer sleeve; 10. Control rod body; 11. Upper step; 12. Lower step; 13. Small guide pipe; 14. Large pipe shed; 15. System anchor; 16. Locking foot anchor; 17. Vertical temporary support; 18. Temporary horizontal invert arch; 19. Central core soil; 20. Side wall lining; 21. Arch lining; 22. Bottom slab lining. Detailed Implementation

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0046] Example 1:

[0047] like Figures 1-6 As shown, a method for tunnel pile foundation underpinning includes the following steps:

[0048] S100: Construction preparation.

[0049] Specifically, construction preparations include, but are not limited to: closing the affected road sections, setting up monitoring points, and unloading the fire water tank. Closing the affected road sections creates a favorable construction environment and prevents construction from endangering the safety of surrounding personnel and buildings. Setting up monitoring points allows for real-time monitoring, timely detection and resolution of abnormal phenomena, and ensures construction safety. Unloading the fire water tank involves unloading the water stored in the fire water tank to reduce the load on the arch crown during the construction of the cut-off pile foundation and ensure the safety of tunnel construction.

[0050] At the same time, prepare multiple plastic buckets for holding water and connect them to the fire water tank through pipelines to serve as an external water storage source after the fire water tank lowers its water level, so as to ensure that the fire water tank can supply water normally in emergency situations.

[0051] Construction preparation also includes surveys of the surrounding environment and site conditions, as well as the preparation and review of construction plans. The former helps to understand in detail the underpass structures and site conditions of the construction section, while the latter formulates construction plans based on the information obtained from the former, striving to achieve scientific, reasonable, efficient, and safe construction.

[0052] S200: Tunnel bench construction to pile replacement.

[0053] Specifically, step S200 includes: constructing an inclined shaft passage and excavating using a bench method to the pile foundation replacement section, forming an upper bench 801 above the corresponding replacement pile and a lower bench 802 below the corresponding replacement pile. Based on this, underground tunnel excavation is achieved through the coordinated use of equipment such as tunneling machines and tracked excavators, and excess soil is removed using loaders. Figure 2As shown, when the tunneling reaches the vicinity of the replacement pile, an upper step 801 and a lower step 802 are formed using the step method. The upper step 801 is used for the replacement construction, and the tunneling progress of the lower step 802 lags behind that of the upper step 801. On the one hand, this reduces the amount of construction work, controls construction investment, and avoids directly cutting off the replacement pile. On the other hand, the lower step 802 is used to form support, and the bearing capacity of the pile foundation itself can be effectively utilized during the replacement process, ensuring the structural safety and normal use of the fire water tank.

[0054] S300: Implement advanced support.

[0055] Specifically, step S300 includes: constructing the pre-grouting small guide pipe 803 and large pipe roof 804 for the arch of the inclined shaft passage, completing the pre-grouting reinforcement of the small guide pipe 803; excavating the upper part using the bench method, constructing system anchors 805 and locking anchors 806, laying steel mesh, and spraying 4cm thick C25 early-strength concrete. Based on this, pipe roofs are installed at the tunnel arch and sidewalls, each consisting of multiple 108×8mm seamless steel pipes; several small guide pipes 803 are evenly distributed on the pipe roofs, connected to grouting equipment to inject cement slurry, and the small guide pipes 803 are made of 42×4mm seamless steel pipes. Multiple system anchors 805 are evenly distributed at the tunnel arch, and locking anchors 806 are installed at the bottom of the tunnel sidewalls. The system anchors 805 and locking anchors 806 together form a steel mesh to reinforce the tunnel, thereby improving its bearing capacity.

[0056] S400: Demolition of pile concrete and initial support construction.

[0057] Specifically, step S400 includes: cutting the pile foundation along the longitudinal direction of the tunnel according to the spacing of the densified steel frames (0.3m / pile); using a handheld pneumatic pick to remove the concrete of the pile foundation and cut the exposed steel bars of the pile foundation; erecting the initial support steel frame of the arch, with a vertical temporary support 807 at the pile foundation location and a temporary horizontal inverted arch 808 in the transverse direction; erecting the initial support steel frame, the vertical temporary support 807 and the temporary horizontal inverted arch for every 300mm thick pile foundation removed, until the entire pile foundation is replaced.

[0058] Based on this, utilizing the passive underpinning mechanism and relying on the bearing capacity of the pile foundation itself, the pile foundations intruding into the tunnel were removed and cut off step by step, ensuring the safety and normal use of the fire water tank structure and achieving effective transfer of the fire water tank's own load and dynamic load. At the same time, it has the advantages of low construction difficulty, flexible operation, low construction investment, quick and convenient adjustment of procedures, and low safety risk. The use of manual hand-held pneumatic picks to remove the pile foundation concrete reduces vibration and causes no noise pollution to the surrounding environment.

[0059] The initial support consists of a concrete layer, a steel mesh within the concrete layer, and a support frame. The concrete layer is a 28cm thick layered structure made of C25 shotcrete, covering the tunnel arch and sidewalls. Grouting is performed through grouting steel pipes spaced 1.0 x 0.5m (circular x longitudinal). The steel mesh is a full-ring structure composed of Φ8 steel pipes spaced 20 x 20cm.

[0060] like Figure 3 and Figure 4 As shown, a temporary vertical support and a temporary horizontal inverted arch 808 are connected to form a steel frame support. Multiple steel frame supports are provided at intervals along the pile foundation removal direction. The steel frame supports provide support to gradually complete the replacement of the entire pile foundation.

[0061] S500: Excavate the soil on both sides of the lower part of the replacement pile and promptly carry out initial support and sealing.

[0062] Specifically, step S500 includes: excavating the soil on both sides of the lower step 802, retaining the central core soil 809, and constructing the initial support steel frame on both sides, system anchor bolts 805, and locking anchor bolts 806.

[0063] Based on this, after step S300, the pile foundation of the upper step 801 has been replaced and supported by multiple steel frames. Then, construction proceeds to the lower step 802, i.e., step S400. This involves excavating the soil on both sides of the lower step 802 to create a construction space. Initial support steel frames, system anchors 805, and locking anchors 806 are then installed in the corresponding section of the lower step 802 to achieve closed-loop operation of the initial support and improve its structural strength. Based on the construction space created in the lower step 802, the central core soil 809 is retained. This central core soil 809 increases the bearing capacity, preventing overloading of the pile foundation at the lower step 802 and improving construction safety.

[0064] S600: Casting of the secondary lining for the side walls and arches.

[0065] Specifically, step S600 includes: pouring the secondary lining of the sidewalls 810 and the secondary lining of the arch 811. During concrete pouring, the vertical temporary supports 807 and the temporary horizontal arch suppressor must not be removed. Based on this, the secondary lining of the sidewalls and arch is poured after the tunnel is closed to further improve the tunnel's load-bearing capacity. Furthermore, the vertical temporary supports 807 and the temporary horizontal arch suppressor ensure that the secondary lining of the sidewalls and arch 811 reaches the design strength, guaranteeing construction quality.

[0066] The sidewall lining 810 is a 500mm thick layered structure made of C35 waterproof concrete, while the arch lining 811 is a 700mm thick layered structure made of C35 waterproof concrete. Both the sidewall lining 810 and the arch lining 811 are reinforced with steel mesh, and the parameters of the steel mesh are as follows: several Φ32 main bars spaced 100mm apart along the tunnel circumference, several Φ25 distribution bars spaced 150mm apart along the tunnel circumference, and several Φ16 tie bars spaced 150×100mm apart in a quincunx pattern along the tunnel circumference.

[0067] S700: After the secondary lining concrete reaches its design strength, the temporary cross bracing is removed. That is, to ensure the quality of the secondary lining construction, temporary cross bracing can be installed in the original construction space to improve load-bearing capacity. Once the secondary lining concrete meets the standards, the temporary cross bracing can be removed, restoring the construction space for the next stage of work.

[0068] S800: Base plate construction.

[0069] Specifically, step S800 includes: after the secondary lining concrete reaches its design strength, excavating the lower half of the core soil and pouring the secondary lining 812 of the tunnel floor slab; after the secondary lining 812 of the floor slab reaches its design strength, removing the external vertical temporary supports 807 and temporary horizontal arches. Based on this, the construction of the floor slab improves the bearing capacity of the tunnel bottom, facilitating the passage of heavy equipment later. The central core soil 809, the lower part of the underpinning piles, the vertical temporary supports 807, and the temporary horizontal arches all need to be removed, leaving the tunnel unobstructed and facilitating the passage of equipment and personnel.

[0070] Among them, the secondary lining 812 of the bottom plate is a 300mm thick layered structure made of C35 waterproof concrete. The secondary lining 812 of the bottom plate is also equipped with a steel mesh. Its parameters have been explained in step S600 and will not be repeated here.

[0071] S800: Repeat S200-S900 until all pile foundation replacements are completed.

[0072] Example 2:

[0073] This embodiment, based on Embodiment 1, provides a feasible solution for the vertical temporary support 807 used in Embodiment 1. Specifically, as follows: Figures 7-11 As shown, the vertical temporary support 807 is a support column, which includes an upper support plate 1, a support column body 2, a lower support plate 3 and an outer cylinder 4. The support column body 2 is installed inside the outer cylinder 4, and the two ends of the support column body 2 and the outer cylinder 4 are connected by the upper support plate 1 and the lower support plate 3, respectively.

[0074] A receiving gap is formed between the support column body 2 and the outer cylinder 4. The support column body 2 is provided with a storage cylinder 5, which is located in the receiving gap and is detachably provided with multiple additional support rods 6. The lower part of the storage cylinder 5 is rotatably mounted on the support column body 2 by a torsion spring. The outer cylinder 4 is provided with a control rod 7, which is used to control the rotation of the storage cylinder 5.

[0075] Accordingly, the outer cylinder 4 includes a main body 41 and a disassembly plate part 42. The main body 41 is provided with a pick-and-place slot 43 for picking up and placing the additional support rod 6, and the disassembly plate part 42 is detachably mounted on the pick-and-place slot 43.

[0076] The support column is mainly supported by the support column body 2, supplemented by upper support plate 1 and lower support plate 3, to avoid direct contact between the support column body 2 and the broken pile, thereby reducing wear on the support column body 2. Furthermore, an additional support rod 6 is installed on the support column body 2. In cases of large gaps or insufficient support, the additional support rod 6 forms a secondary support point to improve the stability of the support.

[0077] The storage tube 5 is used to store the additional support rod 6, and the storage tube 5 is rotatably mounted on the support column body 2 to achieve the connection between the additional support rod 6 and the support column body 2, eliminating the need to carry the additional support rod 6 separately. The outer cylinder 4 covers the outside of the storage tube 5, forming a receiving gap and acting as a barrier to protect the additional support rod 6 and prevent it from falling off.

[0078] The storage cylinder 5 rotates via the force of a torsion spring, aligning different auxiliary support rods 6 with the pick-up / placement slot 43 for easy access. The control lever 7 blocks the rotation of the storage cylinder 5 by contacting it. When the control lever 7 is removed, the storage cylinder 5 rotates under the action of the torsion spring, aligning the next auxiliary support rod 6 with the pick-up / placement slot 43. Simultaneously, a torsion spring with lower torsional force is selected to reduce the rotational speed of the storage cylinder 5, increasing the time required to rotate to the next auxiliary support rod 6, thus providing sufficient time for the operator to manipulate the control lever 7.

[0079] For the outer cylinder 4, the pick-up and put-down slot 43 is used to pick up and put down the additional support rod 6. The disassembly part 42 can control the opening and closing of the pick-up and put-down slot 43. That is, when the disassembly part 42 is installed into the pick-up and put-down slot 43, the pick-up and put-down slot 43 is closed. Conversely, when the disassembly part 42 is disengaged from the pick-up and put-down slot 43, the pick-up and put-down slot 43 is connected to the outside.

[0080] In this embodiment, the storage cylinder 5 includes a storage section 51, a middle plate 52, and a rotating section 53 arranged sequentially from top to bottom. The storage section 51 includes an upper sleeve 511 and a plurality of first partitions 512. The upper sleeve 511 is rotatably mounted on the support column body 2. The first partitions 512 are evenly distributed in the circumferential direction of the upper sleeve 511, and a slot 513 for storing an additional support rod 6 is formed between adjacent first partitions 512. The rotating section 53 includes a lower sleeve 531 and a plurality of second partitions 532. The lower sleeve 531 is rotatably mounted on the support column body 2 by a torsion spring. The second partitions 532 are evenly distributed in the circumferential direction of the lower sleeve 531, and a limiting groove 533 is formed between adjacent second partitions 532.

[0081] Based on this, the storage section 51 is used to store the additional support rod 6, that is, a slot 513 is formed by the first partition 512, and the additional support rod 6 is engaged in the slot 513. The rotating section 53 provides driving force through a torsion spring, and abuts against the control rod 7 through the second partition 532 to achieve rotation control. Optionally, as Figure 9 and Figure 10 As shown, there are four of each of the first partition 512 and the second partition 532.

[0082] Meanwhile, the first partition 512 and the second partition 532 are set one-to-one so that the slot 513 and the limiting slot 533 correspond one-to-one. Based on this, the control rod 7 is pulled out of the limiting slot 533. After the storage cylinder 5 starts to rotate, the control rod 7 can be retracted to the next limiting slot 533. When the control rod 7 abuts against one of the second partitions 532, one of the slots 513 and its additional support rod 6 are aligned with the pick-up and put-out slot 43.

[0083] like Figure 10 As shown, the control lever 7 includes an outer sleeve 71 and a control lever body 72. The outer sleeve 71 is fixed to the outer cylinder 4, and the control lever body 72 is slidably disposed on the outer sleeve 71 and can be inserted into the limiting groove 533. Based on this, the outer sleeve 71 is fixed to the outer cylinder 4, and the control lever body 72 is slidably disposed on the outer sleeve 71. When the control lever body 72 slides into the limiting groove 533, the control lever body 72 can abut against one of the second partitions 532 to form a block and prevent the rotation of the storage cylinder 5; when the control lever body 72 slides out of the limiting groove 533, the storage cylinder 5 will rotate under the action of the torsion spring.

[0084] In this embodiment, the top surface of the upper support plate 1 is provided with at least two connecting holes 101 for connecting the pad plate. The bottom surface of the upper support plate 1 is provided with a connecting rod 102 and an annular cover 103. The connecting rod 102 is located in the middle of the upper support plate 1 and is connected to the support column body 2 by a threaded connection. The annular cover 103 is located outside the connecting rod 102 and is inserted into the outer cylinder 4. A dynamic sealing structure is provided between the annular cover 103 and the outer cylinder 4.

[0085] In step S400, a handheld pneumatic pick is used to remove the concrete from the pile foundation. This results in an error in the height of the gap between the broken piles. Therefore, a shim plate is used to compensate for this height error, ensuring the support column abuts against the replacement pile. Simultaneously, the upper support plate 1 is connected to the support column body 2 via a connecting rod 102. Rotating the upper support plate 1 further adjusts its height, ensuring the support column firmly abuts against the replacement pile. A dynamic sealing structure of any suitable structure is installed between the annular cover 103 and the outer cylinder 4 to prevent the intrusion of dust, soil particles, and other impurities.

[0086] So, when the support column is working:

[0087] First, determine whether to connect a support plate to the upper support plate 1 based on the height of the gap between the broken piles. Second, insert the support column into the gap between the broken piles and rotate the upper support plate 1 to ensure that the support column is firmly against the replacement pile.

[0088] Then, when additional support points are needed, the disassembly plate 42 is removed to open the pick-and-place slot 43. If one of the additional support rods 6 is aligned with the pick-and-place slot 43, the additional support rod 6 is removed. If no additional support rod 6 is aligned with the pick-and-place slot 43, the control rod body 72 is held and pulled outward. The storage cylinder 5 rotates under the drive of the torsion spring, pushing the control rod body 72 in the opposite direction into the limiting slot 533, so that the additional support rod 6 is aligned with the pick-and-place slot 43. The additional support rod 6 is removed and placed in the gap between the broken piles, and the disassembly plate 42 is reinstalled onto the main body 41.

[0089] As is easily understood, the additional support rod 6 includes a threaded upper rod body and a lower rod body to facilitate the adjustment of the height of the additional support rod 6, so as to ensure that the additional support rod 6 is tightly pressed against the replacement pile.

[0090] When retrieving the additional support rod 6, if the support column is still in use, temporarily store the additional support rod 6 in any suitable storage box. If the support column is not in use, remove the upper support plate 1 and insert the additional support rod 6 into the slot 513 from above the support column. At the same time, twist the storage cylinder 5 to deform the torsion spring so that the additional support rod 6 can be taken out in sequence next time.

[0091] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for tunnel pile foundation underpinning construction, characterized in that, Includes the following steps: S100: Construction preparation; S200: Tunnel bench construction to pile replacement; S300: Implement advanced support; S400: Demolition of pile concrete, initial support construction; S500: Excavate the soil on both sides of the lower part of the replacement pile and promptly carry out initial support and sealing. S600: Casting the secondary lining of the side walls and arch; S700: After the secondary lining concrete reaches the design strength, the temporary cross bracing is removed; S800: Base plate construction; S900: Repeat S200-S800 until all pile foundation replacements are completed; Step S200 includes: constructing the inclined shaft passage and excavating it to the pile foundation replacement section using the step method, forming an upper step (801) above the corresponding replacement pile and a lower step (802) below the corresponding replacement pile using the step method; Step S300 includes: constructing the pre-grouting small guide pipe (803) and large pipe shed (804) of the inclined shaft passage arch, completing the pre-grouting reinforcement of the small guide pipe (803); excavating the upper part using the step method, constructing system anchor bolts (805) and locking foot anchor bolts (806), laying steel mesh, and spraying 4cm thick C25 early strength concrete; Step S400 includes: cutting the pile foundation along the longitudinal direction of the tunnel at a spacing of 0.3m / pile of densified steel frames; using a hand-held pneumatic pick to remove the concrete of the pile foundation and cut the exposed steel bars of the pile foundation; erecting the initial support steel frame of the arch, with a vertical temporary support (807) at the pile foundation location and a temporary horizontal inverted arch (808) in the transverse direction; erecting the initial support steel frame, the vertical temporary support (807) and the temporary horizontal inverted arch for every 300mm thick pile foundation removed, until the entire pile foundation is replaced.

2. The tunnel pile foundation replacement construction method according to claim 1, characterized in that, The vertical temporary support (807) is selected as a support column. The support column includes an upper support plate (1), a support column body (2), a lower support plate (3) and an outer cylinder (4). The support column body (2) is installed inside the outer cylinder (4), and the two ends of the support column body (2) and the outer cylinder (4) are connected by the upper support plate (1) and the lower support plate (3) respectively. A receiving gap is formed between the support column body (2) and the outer cylinder (4). A storage cylinder (5) is provided on the support column body (2). The storage cylinder (5) is located in the receiving gap and is detachably provided with multiple additional support rods (6). The lower part of the storage cylinder (5) is rotatably set on the support column body (2) by a torsion spring. A control rod (7) is provided on the outer cylinder (4). The control rod (7) is used to control the rotation of the storage cylinder (5). Accordingly, the outer cylinder (4) includes a main body (41) and a disassembly plate part (42). The main body (41) is provided with a pick-up and put-down groove (43) for picking up and putting down the additional support rod (6). The disassembly plate part (42) is detachably mounted on the pick-up and put-down groove (43).

3. The tunnel pile foundation replacement construction method according to claim 2, characterized in that, The storage tube (5) includes a storage section (51), a middle plate (52) and a rotating section (53) arranged sequentially from top to bottom. The storage section (51) includes an upper sleeve (511) and several first partitions (512). The upper sleeve (511) is rotatably mounted on the support column body (2). The first partitions (512) are evenly distributed in the circumferential direction of the upper sleeve (511). A slot (513) for storing an additional support rod (6) is formed between adjacent first partitions (512). The rotating part (53) includes a lower sleeve (531) and several second partitions (532). The lower sleeve (531) is rotatably mounted on the support column body (2) by a torsion spring. The second partitions (532) are evenly distributed in the circumferential direction of the lower sleeve (531), and a limiting groove (533) is formed between adjacent second partitions (532). Accordingly, the control lever (7) includes an outer sleeve (71) and a control lever body (72). The outer sleeve (71) is fixed on the outer cylinder (4), and the control lever body (72) is slidably disposed on the outer sleeve (71) and can be inserted into the limiting groove (533).

4. The tunnel pile foundation replacement construction method according to claim 2, characterized in that, The top surface of the upper support plate (1) is provided with at least two connecting holes (101), which are used to connect the pad plate. The bottom surface of the upper support plate (1) is provided with a connecting rod (102) and an annular cover (103). The connecting rod (102) is located in the middle of the upper support plate (1) and is connected to the support column body (2) by a threaded connection. The annular cover (103) is located outside the connecting rod (102) and inserted into the outer cylinder (4). A dynamic sealing structure is provided between the annular cover (103) and the outer cylinder (4).

5. The tunnel pile foundation replacement construction method according to claim 1, characterized in that, Step S500 includes: excavating the soil on both sides of the lower step (802), retaining the core soil in the middle (809), and constructing the initial support steel frame, system anchor bolts (805), and locking foot anchor bolts (806) on both sides.

6. The tunnel pile foundation replacement construction method according to claim 5, characterized in that, Step S600 includes: pouring the secondary lining of the side wall (810) and the secondary lining of the arch (811). During the pouring of concrete, the vertical temporary support (807) and the temporary horizontal arch suppressor shall not be removed.

7. The tunnel pile foundation replacement construction method according to claim 6, characterized in that, Step S800 includes: after the secondary lining concrete reaches the design strength, excavating the lower half of the core soil and pouring the bottom slab secondary lining (812); after the bottom slab secondary lining (812) reaches the design strength, cutting off the external vertical temporary support (807) and temporary horizontal arch.

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