A construction method for adding static pressure piles inside a shield tunnel in the central urban area of soft soil

Abstract

The present invention relates to a construction method for adding static pressure piles in a shield tunnel in the central urban area of soft soil, and the steps are as follows: pre-bury a steel casing at the center position of the arc bottom of the segment, and place a threaded steel female head inside the segment; insert a PE plastic cylinder into the steel casing, and paste a temperature sensing optical fiber at the bottom to make a standard block, which is assembled at the bottom of the shield tunnel; connect the temperature measuring optical fiber in the tunnel to a data acquisition instrument, connect the two ends of the vertical steel pipe inside the segment to a refrigeration unit, and introduce a low-temperature refrigerant into it, connect an air compressor to the one-way ventilation valve inside the PE plastic cylinder, inject high-pressure air into it, jack up the PE plastic cylinder to the inner side of the tunnel and pull it out; screw in the reaction frame steel column with a male head, and install a reaction beam, etc.; press the pile segments with precast pile tips into the target depth in sections; remove the reaction frame, etc., pour fine aggregate concrete into the threaded female head and the hollow steel pipe duct, and continuously pour concrete above the pile top to form an integral body of the pile and the segment.

Description

Technical Field

[0001] The present invention relates to an inner lining structure of a shield tunnel in soft soil based on improvement, and in particular to a construction method for adding static pressure piles in a shield tunnel in soft soil. Background Art

[0002] At present, the construction of shield tunnels in the soft soil central urban area is booming, the geological conditions are becoming increasingly complex, the environmental protection requirements around the city are constantly improving, and the precise control of tunnel settlement has become an inevitable requirement in the industry.

[0003] At present, the settlement control technology of shield tunnels mainly controls tunnel settlement by filling the gap between the lining and the soil body. However, its grouting accuracy and parameters are easily affected by conditions such as the consolidation and deformation of the surrounding soil, and the dynamic control is difficult. This includes grouting materials, grouting pressure, grouting volume, etc. In addition, the grouting method does not change the essential constraint characteristics of shield tunnel settlement control, and the grouting method cannot completely solve the problem of long-term settlement of shield tunnels.

[0004] To solve the above problems, static pressure piles can be driven at the bottom of the tunnel, and the bearing friction resistance of the pile body is used to control the long-term settlement deformation of the tunnel. This method needs to solve three key technical difficulties:

[0005] 1. Different from the static pressure piles in ground construction, there are high water and soil pressures outside the lining of the shield tunnel. Therefore, sealing measures need to be added to prevent external water and soil from entering the tunnel during the process of the pile passing through the shield segment and entering the soil body.

[0006] 2. A device that can reasonably provide pile pressing force in the tunnel.

[0007] 3. A structure that can firmly connect the static pressure pile and the tunnel lining.

[0008] Therefore, it is necessary to provide a bottom lining structure and construction method of a shield tunnel with static pressure piles, which changes the segment structure at the bottom of the shield tunnel, enables it to meet the sealing requirements of pile pressing, and through reasonable structural design, proposes a pile pressing device and the connection structure form between the pile body and the lining. Summary of the Invention

[0009] The purpose of the present invention is to provide a construction method for adding static pressure piles in a shield tunnel in the soft soil central urban area, improve the control accuracy of tunnel settlement in the urban central area, and further reduce its impact on ground buildings.

[0010] To achieve the above purpose, the technical solution of the present invention is: a construction method for adding static pressure piles in a shield tunnel in the soft soil central urban area, and the steps are as follows:

[0011] Step 1: When fabricating the steel reinforcement cage of the shield segment, a steel casing with the same height as the segment thickness is pre-buried at the center of the segment's arc bottom. An annular groove is provided at the center height on the inner side of the steel casing, and flange steel rings protruding outward are provided at both ends and the middle height of the steel casing;

[0012] Step 2: Around the steel casing, continuously buried horizontal involute spiral hollow steel pipes are provided, and vertical steel pipes are connected to both ends of the hollow steel pipes so that their ports extend to the inner plane of the segment. The innermost side of the hollow steel pipe is closely attached to the steel casing wall;

[0013] Step 3: A pair of threaded steel female heads are symmetrically placed inside the segment and welded to the main reinforcement bars of the steel reinforcement cage, and their tops are sealed with plastic protective covers;

[0014] Step 4: An annular rubber water stop ring is embedded in the annular groove on the inner side of the steel casing, and a prefabricated PE plastic cylinder with the same inner diameter as the steel casing is inserted into the steel casing. A pore passage with a one-way ventilation valve is provided at the axis of the PE plastic cylinder;

[0015] Step 5: A temperature sensing optical fiber is pasted at the bottom of the PE plastic cylinder, tied along the outer side of the segment and extended for a certain length and then passed out from the inner side of the segment. Subsequently, the steel reinforcement cage is hoisted into the formwork, concrete is poured and cured to make a standard block that can be used for pile pressing in the tunnel, and it is assembled at the bottom of the shield tunnel;

[0016] Step 6: In the tunnel, connect the temperature measurement optical fiber to the data acquisition instrument, connect the two ends of the vertical steel pipes inside the segment to the refrigeration unit, and continuously pass low-temperature refrigerant into it until the frozen wall monitored by the optical fiber reaches the designed thickness. Then connect the air compressor to the one-way ventilation valve inside the PE plastic cylinder and inject high-pressure air into it to lift the PE plastic cylinder to the inner side of the tunnel and pull it out;

[0017] Step 7: Uncover the protective cover of the threaded female head, screw in the reaction frame steel column with a male head, and install the reaction beam, hydraulic jack, pile hoisting pulley and pile body clamp;

[0018] Step 8: Press the pile segments with precast pile tips into sections to the target depth;

[0019] Step 9: Remove the reaction frame, hydraulic jack, pile hoisting pulley and pile body clamp, pour fine aggregate concrete into the threaded female head and the hollow steel pipe pore passage, and continuously pour concrete above the pile top to form a cushion with the designed thickness at the pile top, so that the pile and the segment form an integral body.

[0020] Furthermore, in Step 2, the distance between the hollow steel pipe and the steel casing wall increases uniformly along the spiral line to the designed range.

[0021] Furthermore, in Step 3, the threaded steel female head is fully welded to the main reinforcement bars of the steel reinforcement cage.

[0022] Further, in the eighth step, full welding connections are used between the pile segments.

[0023] The beneficial effects of the present invention are as follows:

[0024] The present invention uses precast concrete segments with a special structure, enabling the construction of jacked piles after the completion of the tunnel. The cylindrical steel casing can reserve a pile jacking duct during the precast segment stage. The flange steel ring can effectively prevent leakage at the joint between the steel casing and the concrete under the action of groundwater pressure. The PE plastic cylinder and the rubber water stop ring can serve as effective temporary plugging structures, resisting both external soil pressure and water pressure, and being easy to disassemble for subsequent pile jacking. The spiral hollow steel pipe and the refrigeration unit can effectively form a temporary frozen area outside the reserved hole of the segment, serving as a temporary water stop and solidifying body during pile jacking, creating construction conditions convenient for pile jacking. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic connection diagram of the precast segment structure and construction equipment in the present invention;

[0026] Figure 2 It is the connection of the pile jacking equipment and the segment in the present invention;

[0027] Figure 3 It is a schematic diagram of the ninth step in the present invention;

[0028] In the figure: 1 - cylindrical steel casing, 2 - annular groove, 3 - flange steel ring, 4 - spiral hollow steel pipe, 5 - vertical steel pipe, 6 - threaded steel female head, 7 - rubber water stop ring, 8 - PE plastic cylinder, 9 - one-way ventilation valve, 10 - temperature sensing optical fiber, 11 - data acquisition instrument, 12 - refrigeration unit, 13 - air compressor, 15 - reaction frame steel column, 16 - reaction beam, 17 - hydraulic jack, 18 - pile hoisting pulley, 19 - pile body clamp, 20 - pile segment, 21 - cushion layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described below in conjunction with the drawings and embodiments.

[0030] For the construction method of adding jacked piles in the shield tunnel in the soft soil central urban area of this embodiment, the connection between the segment structure and the construction equipment is as shown in Figure 1 , Figure 2, and its steps are as follows:

[0031] The first step: When fabricating the reinforcement cage of the shield segment, a cylindrical steel casing 1 with the same height as the segment thickness is pre-buried in the reinforcement cage at the center position of the crown of the segment. An annular groove 2 is provided at the center height inside the cylindrical steel casing 1. Flange steel rings 3 with outward extensions are provided at both ends and the middle height of the cylindrical steel casing 1.

[0032] Step 2: On the plane at a distance of 10 cm from the outer side of the segment, continuously buried horizontal involute spiral hollow steel pipes 4 are arranged inside the steel reinforcement cage outside the cylindrical steel casing 1, and vertical steel pipes 5 are connected to both ends of the spiral hollow steel pipes 4 so that their ports extend to the inner plane of the segment. The innermost side of the spiral hollow steel pipe 4 is closely attached to the wall of the cylindrical steel casing 1, and the distance between the spiral hollow steel pipe 4 and the wall of the cylindrical steel casing 1 increases uniformly along the spiral line to the design range.

[0033] Step 3: A pair of threaded steel female heads 6 are symmetrically placed inside the segment and are fully welded to the main reinforcement bars of the steel reinforcement cage, and their tops are sealed with plastic protective covers.

[0034] Step 4: The annular rubber water stop ring 7 is embedded in the annular groove 2 inside the cylindrical steel casing 1, and a prefabricated PE plastic cylinder 8 with the same inner diameter as the cylindrical steel casing 1 is inserted into the cylindrical steel casing 1. The axis of the PE plastic cylinder 8 is a through hole, and a one-way ventilation valve 9 is provided at its top.

[0035] Step 5: The temperature sensing optical fiber 10 is pasted at the bottom of the PE plastic cylinder 8, tied along the outer side of the segment and extended for a certain length and then passed out from the inner side of the segment. Subsequently, the steel reinforcement cage is hoisted into the formwork, concrete is poured and cured to make a standard block for pile pressing in the tunnel, which is assembled at the bottom of the shield tunnel.

[0036] Step 6: Inside the tunnel, the temperature measuring optical fiber 10 is connected to the data acquisition instrument 11, and both ends of the vertical steel pipe 5 inside the segment are connected to the refrigeration unit 12, and low-temperature refrigerant is continuously introduced into it until the frozen wall monitored by the optical fiber reaches the design thickness. Then, the air compressor 13 is connected to the one-way ventilation valve 9 inside the PE plastic cylinder 8, and high-pressure air is injected into it to lift the PE plastic cylinder 8 to the inner side of the tunnel and pull it out.

[0037] Step 7: Uncover the protective cover 14 of the threaded female head, screw in a pair of reaction frame steel columns 15 with male heads, and install the reaction beam 16, hydraulic jack 17, pile hanging pulley 18 and pile body fixture 19.

[0038] Step 8: The pile segments 20 with precast pile tips are pressed into the target depth in sections, and full welding connections are used between the pile sections.

[0039] Step 9: As Figure 3 shown, remove the pile pressing equipment such as the reaction frame, pour fine aggregate concrete into the steel female head and the spiral steel pipe hole, and continuously pour concrete above the pile top to form a cushion layer 21 with the design thickness at the pile top, so that the pile and the segment form an integral whole.

Claims

1. A construction method for adding static pressure piles in a shield tunnel in the central urban area of soft soil, characterized in that, The steps are as follows: First step: When fabricating the steel reinforcement cage of the shield segment, a steel casing with the same height as the segment thickness is pre-buried at the center of the arc bottom of the segment. An annular groove is provided at the center height on the inner side of the steel casing, and flange steel rings protruding outward are provided at both ends and the middle height of the steel casing; Second step: Around the steel casing, continuous horizontally involute spiral hollow steel pipes are buried, and vertical steel pipes are connected to both ends of the hollow steel pipes so that their ports extend to the inner plane of the segment. The innermost side of the hollow steel pipe is closely attached to the steel casing wall; Third step: A pair of threaded steel female heads are symmetrically placed inside the segment and welded to the main reinforcement bars of the steel reinforcement cage, and their tops are sealed with plastic protective covers; Fourth step: An annular rubber water stop ring is embedded in the annular groove on the inner side of the steel casing, and a prefabricated PE plastic cylinder with the same inner diameter as the steel casing is inserted into the steel casing. A pore passage with a one-way ventilation valve is provided at the axis of the PE plastic cylinder; Fifth step: A temperature-sensing optical fiber is pasted at the bottom of the PE plastic cylinder, tied along the outer side of the segment and extended for a certain length and then passed out from the inner side of the segment. Subsequently, the steel reinforcement cage is hoisted into the formwork, concrete is poured and cured to make a standard block that can be used for pile pressing in the tunnel, and it is assembled at the bottom of the shield tunnel; Sixth step: In the tunnel, the temperature-measuring optical fiber is connected to a data acquisition instrument, and both ends of the vertical steel pipes inside the segment are connected to a refrigeration unit, and low-temperature refrigerant is continuously introduced into it until the frozen wall monitored by the optical fiber reaches the designed thickness. Then, an air compressor is connected to the one-way ventilation valve inside the PE plastic cylinder, and high-pressure air is injected into it to lift the PE plastic cylinder to the inner side of the tunnel and pull it out; Seventh step: Uncover the protective cover of the threaded female head, screw in the reaction frame steel column with a male head, and install the reaction beam, hydraulic jack, pile-hoisting pulley and pile body clamp; Eighth step: Press the pile segments with precast pile tips into the target depth in sections; Ninth step: Remove the reaction frame, hydraulic jack, pile-hoisting pulley and pile body clamp, pour fine aggregate concrete into the threaded female head and the hollow steel pipe pore passage, and continuously pour concrete above the pile top to form a cushion with the designed thickness at the pile top, so that the pile and the segment form an integral body.

2. The construction method of adding static pressure piles in the shield tunnel of the soft soil central urban area according to claim 1, characterized in that: In the second step, the distance between the hollow steel pipe and the steel casing wall increases uniformly along the spiral line to the designed range.

3. The construction method of adding static pressure piles in a shield tunnel in the soft soil central urban area according to claim 1, characterized in that: In the third step, the threaded steel female head is fully welded to the main reinforcement bars of the steel reinforcement cage.

4. The construction method of adding static pressure piles in the shield tunnel of the soft soil central urban area according to claim 1, characterized in that: In the eighth step, full welding connections are adopted between the pile sections.

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