A construction method for pile foundation replacement structure in a shallow buried tunnel

Abstract

The invention provides a construction method for a pile foundation underpinning structure in a tunnel using a shallow buried dark excavation method, which is applicable to the technical field of pile foundation underpinning in tunnel engineering. The construction method for a pile foundation underpinning structure in a tunnel using a shallow buried dark excavation method comprises pre-construction preparation, advanced support construction, step excavation, secondary lining side wall and arch construction, tunnel area pile truncation, secondary lining invert construction and tertiary lining construction. The invention connects piles that conflict with the tunnel in the tunnel area with the reinforced secondary lining structure, and then truncates the original piles in the tunnel, and the load borne by the original piles is transmitted to the soil layer under the tunnel through the tunnel secondary lining structure, and the tertiary lining structure is added to ensure the safety of the upper structure of the original pile and the tunnel itself, thereby solving the problems of noise pollution, dust pollution, additional abandoned soil, large engineering quantity and long construction period in the traditional pile foundation underpinning construction method.

Description

Technical Field

[0001] The invention relates to a construction method for a pile foundation underpinning structure in a shallow buried tunnel using a dark excavation method, and is applicable to the technical field of pile foundation underpinning in tunnel engineering. Background Art

[0002] In the process of building urban underground transportation networks, shallow buried tunnel projects often encounter underground obstacles, especially tunnel lines often conflict with the pile foundations of buildings or structures. In the early planning and design stage of the project, the line planning can be used to bypass the influence range of the pile foundations of buildings or structures, but this method usually leads to longer lines and higher project costs. Therefore, the traditional pile foundation replacement construction method was produced. This method conducts large-scale excavation on the ground, adds new supporting structures on both sides of the tunnel to transfer the load, and then cuts off the original piles.

[0003] The traditional pile foundation underpinning construction method has a great impact on the surrounding environment, especially in densely populated and busy urban areas. The noise and dust generated by this method will cause great inconvenience to residents. On the other hand, the traditional pile foundation underpinning construction method expands the construction area, increases the additional excavation workload, and the underpinning structure engineering is large, which increases the equipment rental and maintenance as well as earth excavation and transportation costs. Moreover, the ground construction is affected by weather factors, which increases the risk of delays in the construction period. And because the operation affects a large area, it often involves traffic diversion, which has a certain adverse impact on the traffic in the area.

[0004] Therefore, there is an urgent need for a pile foundation underpinning structure construction method that is friendly to the surrounding environment, saves construction costs, does not delay the construction period, and has little impact on surrounding traffic. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of noise pollution, dust pollution, large workload of earth excavation and transportation and structural construction, and great impact on surrounding traffic caused by traditional pile foundation underpinning construction methods. A shallow buried tunnel excavation method pile foundation underpinning structure construction method is proposed, which has the advantages of being friendly to the surrounding environment, saving construction costs and not delaying the construction period, and can be widely used in the field of tunnel engineering pile foundation underpinning technology.

[0006] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0007] S1, preparation before construction;

[0008] The pre-construction preparation includes the preparation of emergency plans, storage of materials and emergency supplies, completion of construction condition acceptance, arrangement of monitoring points, recording of initial monitoring values ​​of the monitoring points, and arrangement of technical personnel to make detailed geological records during the excavation process;

[0009] S2, advanced support construction;

[0010] The advanced support construction includes closing the tunnel face, drilling holes to install grouting pipes, closing pipe openings, pipe connection tests and grouting into the pipes;

[0011] S3, bench excavation;

[0012] The step method excavation includes upper step excavation, upper step initial support construction, lower step excavation, reserved core soil and lower step initial support construction. The upper step initial support construction includes tunnel area pile drilling, installation of through-core steel rods, erection of upper step initial support steel frame, upper step steel frame foot locking anchor rod construction, and installation of protective nets and spraying protection on the steps on the face. The lower step initial support construction includes erection of lower step initial support steel frame, lower step steel frame foot locking anchor rod construction, and installation of protective nets and spraying protection on the steps below the face.

[0013] S4, secondary lining side wall and vault construction;

[0014] The secondary lining side wall and vault construction includes roughening and planting of piles in the tunnel area, tying the secondary lining side wall and vault steel bars, inserting the planting bars in the piles in the tunnel area into the secondary lining vault steel mesh, then installing the secondary lining support formwork, pouring the secondary lining side wall and vault concrete, and finally proceeding to the next step after the concrete curing reaches the strength requirement;

[0015] S5, pile truncation in tunnel area;

[0016] The tunnel area pile cutting includes safety preparation before pile cutting, then cutting piles in stages, cutting single piles in batches, and after each cutting is completed, lifting the broken piles to the ground for crushing, and finally transporting the crushed broken piles out with the slag;

[0017] S6, secondary lining invert construction;

[0018] The secondary lining invert construction includes core soil excavation, tunnel bottom stratum reinforcement, erection of invert steel frame, hanging of protection net and spraying, tying of invert steel bars, pouring of invert concrete and proceeding to the next step after the concrete reaches the strength requirement;

[0019] S7, tertiary lining construction;

[0020] The three-tier lining construction includes waterproof layer construction, tying of three-tier lining invert arch steel bars, pouring of three-tier lining invert arch concrete, tying of three-tier lining side wall and arch top steel bars, installation of three-tier lining support formwork, pouring of three-tier lining side wall and arch top concrete and other forced formwork removal and maintenance, completing the pile foundation replacement operation in the tunnel.

[0021] Furthermore, in step S3, the tunnel area pile drilling includes drilling a hole at the center of the pile width direction just above the primary support steel frame, the bottom of the hole is flush with the top of the primary support steel frame, and the hole diameter is more than 10 mm larger than the diameter of the through-core steel rod.

[0022] Furthermore, in step S3, the installation of the through-steel rod includes passing through the tunnel area pile perpendicular to the face, and welding the through-steel rod to the primary support steel frame after the installation of the primary support steel frame is completed. It also includes further advancing the face along the tunnel direction until the soil around the tunnel area pile is excavated, and then welding the through-steel rod on the other side to the primary support steel frame on the other side symmetrically of the tunnel area pile.

[0023] Furthermore, in step S3, the steel frame locking anchor construction includes cement slurry reinforcement of the stratum along the direction of the locking anchor and welding of the locking anchors at the footings on both sides of the primary support steel frame to the primary support steel frame.

[0024] The beneficial effects of the present invention are: solving the problems of noise pollution, dust pollution, additional excavation workload and potential delays in the traditional pile foundation replacement construction method. First, the piles that conflict with the tunnel in the tunnel area are connected to the reinforced secondary lining structure, and then the original piles in the tunnel are partially cut off. The load borne by the original piles is transferred to the soil layer under the tunnel through the tunnel secondary lining structure, and the tertiary lining structure is added to ensure the safety of the original pile superstructure and the tunnel itself. This method is carried out on the original face, does not increase the additional excavation workload, does not require open-air operations, has little impact on the surrounding environment and residents, and avoids interference from natural factors such as weather, ensuring the continuity and stability of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a construction method of a pile foundation underpinning structure in a shallow buried tunnel by dark excavation method of the present invention;

[0026] Figure 2 This is a schematic diagram of the tunnel before excavation of the present invention;

[0027] Figure 3 It is a schematic diagram of the upper step excavation and the initial support steel frame of the present invention;

[0028] Figure 4 This is a schematic diagram of the reserved core soil for excavation of the lower step of the present invention;

[0029] Figure 5 It is a schematic diagram of the secondary lining vault reinforcement and side wall construction of the present invention;

[0030] Figure 6 is a schematic diagram of the tunnel area pile cutoff of the present invention;

[0031] Figure 7It is a schematic diagram of the construction of the primary steel frame and the secondary lining invert of the present invention;

[0032] Figure 8 It is a schematic diagram of the three-tier lining construction of the present invention;

[0033] Fig. 9 is a top view of the completed tunnel of the present invention;

[0034] Reference numerals in the figure: 1-grouting pipe, 2-tunnel area piles, 3-in-situ soil to be excavated, 4-primary support steel frame, 5-connecting steel plate, 6-locking anchor rod, 7-through steel rod, 8-reserved core soil, 9-secondary lining vault, 10-secondary lining side wall, 11-embedded reinforcement, 12-secondary lining invert, 13-primary support steel frame invert, 14-tertiary lining side wall, 15-tertiary lining vault, 16-tertiary lining invert, 17-secondary lining vault reinforcement densification area. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings; it should be understood that the specific embodiments given here are only used to illustrate and explain the present invention and cannot be used to limit the present invention.

[0036] The following is a specific embodiment of a construction method for a pile foundation underpinning structure in a shallow buried tunnel.

[0037] like Figure 1 The figure is a flow chart of a construction method of a pile foundation underpinning structure in a shallow buried tunnel according to the present invention.

[0038] This project is based on the Chengdu Rail Transit Line 30 Phase I Civil Construction Zone 3 Project. The standard dark excavation section has a rough width of 8.4m, a height of 7.2m, and a length of 89.884m; the bridge pile underpinning dark excavation section has a rough width of 9.4m, a height of 8.143m, and a length of 9.666m. The shallow buried dark excavation tunnel passes under the Chengren Interchange A ramp approach bridge on the north side of the South Third Ring Road Section 2. The passage conflicts with the four bridge piles of the approach bridge. The pile diameter is 1m, the pile length is 16m, and the pile bottom is located at the designed bottom plate position of the tunnel structure. Due to the heavy traffic on the main road of the Third Ring Road, there are no conditions for pile foundation underpinning on the ground, and the approach bridge piles need to be underpinned in the tunnel. The specific construction process of the pile foundation underpinning structure in the tunnel is as follows:

[0039] S1, preparation before construction;

[0040] Since the project is a sub-project that uses new technologies, new processes, new materials and new equipment that may affect the safety of the project construction, and there are no national, industry or local technical standards for the sub-project, a special plan was prepared for the construction process and expert demonstration, and a corresponding emergency plan for danger was prepared;

[0041] According to the specifications and plan requirements, various types of measuring points were arranged and the initial data of each measuring point was recorded;

[0042] Completed advanced geological forecast and construction condition acceptance;

[0043] According to the design requirements, the initial support adopts a steel frame + shotcrete structure. The preparation work such as steel frame and steel bar preparation and processing has been completed, and relevant emergency materials are in place;

[0044] Arrange specialized technicians to record the full process measurement point data of the pile foundation underpinning structure construction;

[0045] S2, advanced support construction;

[0046] Use shotcrete to seal the face, then use a YT-28 pneumatic drill to drill a hole 3-5mm larger than the diameter of the catheter. After drilling, use a blowpipe to remove the gravel in the hole, or use a hook to manually clean the sand and gravel in the hole, and insert the catheter into the cleaned drilled hole to form a grouting pipe 1. The opening of the grouting pipe 1 and the gaps around it need to be sealed with plastic mud. Use shotcrete to spray a 5 to 10 cm thick concrete layer on the working surface to ensure that the slurry will not leak out during grouting. Use a YSH-3 grouting machine for grouting. During the grouting process, closely monitor the grouting volume and grouting pressure, and determine the appropriate grouting duration based on these parameters;

[0047] S3, bench excavation;

[0048] Each time the excavation advances one steel frame, the upper step is excavated to the pile foundation surface, and the center of the tunnel area pile 2 on the preset primary support steel frame 4 is drilled with a hole diameter of 100mm and a depth of 1400mm. A through-hole steel rod 7 with a size of 80mm×1800mm is installed in the hole. Two primary support steel frames 4 are erected side by side on the tunnel area pile perpendicular to the outer side of the heading surface, and the primary support steel frame 4 is welded to the through-hole steel rod 7. Then the locking anchor rod 6 is constructed, and the stratum along the direction of the locking anchor rod 6 is injected with cement slurry for reinforcement. The locking anchor rods 6 at the footings of both sides of the primary support steel frame 4 are welded to the primary support steel frame 4, and a protective net is hung on the step on the heading surface and sprayed for protection. The upper step is continued to be excavated, and then two primary support steel frames 4 are erected side by side on the tunnel area pile perpendicular to the inner side of the heading surface, and through-hole welding, locking anchor rod 6 construction and net spraying are also carried out.

[0049] The core soil 8 is reserved, and the lower step and the upper step are also excavated, the initial support steel frame 4 is erected, the locking foot anchor rod 6 is constructed, and the net spraying operation is performed;

[0050] S4, construction of secondary lining side wall 10 and secondary lining vault 9;

[0051] The tunnel area piles are roughened and rebars are planted, and the secondary lining side walls 10 and the secondary lining vault 9 steel bars are tied. The rebars 11 in the tunnel area piles 2 are inserted into the secondary lining vault 9 steel mesh, and then the secondary lining support formwork is installed, and the secondary lining side walls 10 and the secondary lining vault 9 concrete are poured. Finally, the next step is carried out after the concrete curing reaches the strength requirements;

[0052] S5, tunnel area pile 2 truncation;

[0053] The pile cutting is carried out from late night to early morning. The road is temporarily closed during the cutting period. The four tunnel area piles 2 are cut in two stages. When the monitoring values ​​of the previous stage are stable and the changes do not exceed the thresholds of the specifications and the plan, the next stage of construction is carried out. The tunnel part of a single tunnel area pile 2 is cut 8 times. After each cutting is completed, the broken piles are hoisted to the ground for crushing, and finally the crushed broken piles are transported out with the slag.

[0054] S6, construction of secondary lining invert 12;

[0055] The construction of the secondary lining invert 12 includes core soil excavation, tunnel bottom stratum reinforcement, erection of the primary steel frame invert 13, installation of the protective net and spraying, tying of the invert steel bars, pouring of the invert concrete, and the next step after the concrete reaches the strength requirement.

[0056] S7, tertiary lining construction;

[0057] The tertiary lining construction includes waterproof layer construction, tying of tertiary lining invert arch 16 steel bars, pouring of tertiary lining invert arch 16 concrete, tying of tertiary lining side wall 14 and tertiary lining arch 15 steel bars, installation of tertiary lining support formwork, pouring of tertiary lining side wall 14 and tertiary lining arch 15 concrete, and other forced demolition and maintenance to complete the pile foundation replacement operation in the tunnel.

[0058] In the above embodiment, the present invention discloses a construction method for a pile foundation underpinning structure in a tunnel using a shallow buried and dark excavation method, including pre-construction preparation, advance support construction, step excavation, secondary lining side wall and arch construction, tunnel area pile truncation, secondary lining invert arch construction and tertiary lining construction; the construction method for a pile foundation underpinning structure in a tunnel using a shallow buried and dark excavation method proposed by the present invention does not increase additional excavation workload, does not require open-air operations, has little impact on the surrounding environment and residents, ensures the safety of construction personnel and structures, and at the same time avoids interference from natural factors such as weather, thereby ensuring the continuity and stability of construction.

[0059] The above description is a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A construction method for a pile foundation underpinning structure in a shallow buried tunnel, characterized in that: The method comprises the following steps: S1, preparation before construction; The pre-construction preparation includes the preparation of emergency plans, storage of materials and emergency supplies, completion of construction condition acceptance, arrangement of monitoring points, recording of initial monitoring values ​​of the monitoring points, and arrangement of technical personnel to make detailed geological records during the excavation process; S2, advanced support construction; The advanced support construction includes closing the tunnel face, drilling holes to install grouting pipes, closing pipe openings, pipe connection tests and grouting into the pipes; S3, bench excavation; The step method excavation includes upper step excavation, upper step initial support construction, lower step excavation, reserved core soil and lower step initial support construction. The upper step initial support construction includes tunnel area pile drilling, installation of through-core steel rods, erection of upper step initial support steel frame, upper step steel frame locking foot anchor rod construction, and installation of protective nets and spray protection on the steps on the face. The lower step initial support construction includes erection of lower step initial support steel frame, lower step steel frame locking foot anchor rod construction, and installation of protective nets and spray protection on the steps below the face. The installation of the through-steel rod includes passing through the tunnel area pile perpendicularly to the tunnel face, welding the through-steel rod to the upper step primary support steel frame after the installation of the upper step primary support steel frame is completed, and further advancing the tunnel face along the tunnel direction until the soil around the tunnel area pile is excavated, and then welding the through-steel rod on the other side to the upper step primary support steel frame on the other side on the other side of the tunnel area pile; S4, secondary lining side wall and vault construction; The secondary lining side wall and vault construction includes roughening and planting of piles in the tunnel area, tying the secondary lining side wall and vault steel bars, inserting the planting bars in the piles in the tunnel area into the secondary lining vault steel mesh, then installing the secondary lining support formwork, pouring the secondary lining side wall and vault concrete, and finally proceeding to the next step after the concrete curing reaches the strength requirement; S5, pile truncation in tunnel area; The tunnel area pile cutting includes safety preparation before pile cutting, then cutting piles in stages, cutting single piles in batches, and after each cutting is completed, lifting the broken piles to the ground for crushing, and finally transporting the crushed broken piles out with the slag; S6, secondary lining invert construction; The secondary lining invert construction includes core soil excavation, tunnel bottom stratum reinforcement, erection of invert steel frame, hanging of protection net and spraying, tying of invert steel bars, pouring of invert concrete and proceeding to the next step after the concrete reaches the strength requirement; S7, tertiary lining construction; The three-tier lining construction includes waterproof layer construction, tying of three-tier lining invert arch steel bars, pouring of three-tier lining invert arch concrete, tying of three-tier lining side wall and arch top steel bars, installation of three-tier lining support formwork, pouring of three-tier lining side wall and arch top concrete and other forced formwork removal and maintenance, completing the pile foundation replacement operation in the tunnel.

2. The method for constructing a pile foundation underpinning structure in a shallow buried tunnel according to claim 1 is characterized by: In step S3, the tunnel area pile drilling includes drilling a hole at the center of the pile width direction just above the upper step primary support steel frame, the bottom of the hole is flush with the top of the upper step primary support steel frame, and the hole diameter is more than 10 mm larger than the diameter of the through-core steel rod.

3. The method for constructing a pile foundation underpinning structure in a shallow buried tunnel according to claim 1, characterized in that: In step S3, the locking anchor rod construction of the upper step steel frame includes injecting cement slurry to reinforce the stratum in the direction of the upper step locking anchor rods at the feet of both sides of the upper step primary support steel frame, and welding the upper step primary support steel frame to the upper step locking anchor rods; the locking anchor rod construction of the lower step steel frame includes injecting cement slurry to reinforce the stratum in the direction of the lower step locking anchor rods at the feet of both sides of the lower step primary support steel frame, and welding the lower step primary support steel frame to the lower step locking anchor rods.

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