A method for segmented construction of large tunnels

Abstract

This invention relates to a segmented construction method for large tunnels, comprising the following steps: Step S101: Dividing the entire foundation pit into a preliminary section and several subsequent sections, and constructing a partition wall at the junction of the preliminary and subsequent sections; Step S103: First excavating the preliminary section, then constructing support components and the main structure sequentially within the preliminary section, and finally constructing a force transmission strip between the main structure and the partition wall; Step S105: Constructing the several subsequent sections sequentially until the entire foundation pit is completed; The construction steps for the subsequent sections are the same as those in Step S101 (construction of the preliminary section and partition wall) and Step S103 (construction of the preliminary section and force transmission strip). The partition wall in this construction method adopts the same type as the foundation pit retaining structure, ensuring the integrity of the closed retaining structure of the divided small foundation pits and improving the construction quality of the retaining structure of the small foundation pits; and according to different types of partition walls, different structures are used for the force transmission strip, allowing for flexible coordination and diverse construction methods, thus improving the construction effect.

Description

Technical Field

[0001] This invention belongs to the field of tunnel construction technology, and relates to large open-cut tunnels, especially a method for segmented construction of large tunnels. Background Technology

[0002] The main construction process of cut-and-cover tunnels is to first construct the retaining structure, then excavate and support the foundation pit, and finally construct the main tunnel structure. However, in the process of urban municipal road construction, due to factors such as underground pipelines, traffic and land acquisition and demolition, long and large tunnel foundation pits cannot be constructed at the same time as a whole. They need to be constructed in sections according to the time of resolution of the above-mentioned influencing factors, which inevitably divides the entire tunnel foundation pit into several small foundation pits.

[0003] Traditional segmented tunnel excavation construction involves completing the foundation slab of the first segment, then pouring a concrete force-transfer strip between the foundation slab and the sealing wall of the segment, and finally erecting steel pipe supports above the foundation slab to balance the earth pressure behind the sealing wall. This approach has the following problems:

[0004] 1. Traditional segmented construction methods use the same treatment method for foundation pits of different depths and with different retaining structures. The construction methods are monotonous, the construction effect is not good, the construction efficiency is low, and the construction cost is high.

[0005] 2. The traditional segmented construction method uses a whole concrete force transmission strip, which leads to serious damage to the construction of the main tunnel structure and the waterproofing of expansion joints during later demolition. This requires secondary repairs, which is costly and inefficient. In addition, there is a risk of water leakage in the later stage, resulting in poor construction quality.

[0006] To address these issues, we propose a segmented construction method for large tunnels. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple, efficient, and safe method for segmented construction of large tunnels.

[0008] To solve the above problems, the technical solution of the present invention is as follows:

[0009] A method for segmented construction of large tunnels includes the following steps:

[0010] Step S101: Construction of the partition wall

[0011] The entire foundation pit is divided into a preliminary section and several subsequent sections. Separation walls are constructed at the junctions of the preliminary and subsequent sections.

[0012] Step S103, Construction Pre-construction Section and Force Transmission Belt

[0013] First, the pilot section is excavated, then the supporting components and main structure are constructed sequentially within the pilot section, and finally the force transmission strip is constructed between the main structure and the partition wall.

[0014] Step S105, subsequent construction section

[0015] The subsequent sections are constructed sequentially until the entire foundation pit is completed.

[0016] The construction steps for the subsequent sections are the same as those for step S101 (constructing the partition wall) and step S103 (constructing the pilot section and force transmission strip).

[0017] In a further embodiment, in step S101, during the construction of the enclosure wall, a retaining structure is constructed around the perimeter of the preliminary section, and the enclosure wall and the retaining structure are of the same type.

[0018] In a further embodiment, the sealing wall is a diaphragm wall, pile bank, or SMW method pile.

[0019] In a further embodiment, in step S103, the support components in the construction pilot section and force transmission belt include concrete supports and steel supports. The concrete supports are fixedly installed at the top of the pilot section, and the steel supports are fixedly installed inside the pilot section.

[0020] In a further embodiment, in step S103, the main structure includes a bottom plate and a top plate. The bottom plate is constructed first, and then the steel support between the bottom plate and the top plate is removed. The side walls and the top plate are constructed from the bottom plate upwards. Finally, the steel support and concrete support above the top plate are removed.

[0021] In a further embodiment, a waterstop is provided at one end of the bottom plate and the top plate near the force transmission strip, and a force transmission strip is provided between the bottom plate, the top plate and the partition wall.

[0022] In a further embodiment, the partition wall is a diaphragm wall, and the force transmission band includes an installation plate and a support rod. The installation plate is pre-embedded in the partition wall by anchor bars. One end of the installation plate is located outside the partition wall, and one end of the support rod is fixedly installed in the bottom plate or top plate, while the other end of the support rod abuts against the installation plate.

[0023] Several support rods are located on the upper and lower sides of the waterstop.

[0024] In a further embodiment, the partition wall is a pile wall or an SMW method pile, and the force transmission strip includes force transmission strip steel bars and force transmission strip concrete. One end of the force transmission strip steel bars is embedded in the bottom plate or top plate, and the force transmission strip concrete is poured on the force transmission strip steel bars.

[0025] The top surface of the force transmission strip concrete is located below the waterstop strip.

[0026] In a further embodiment, the cross-sectional area of ​​the reinforcing bar in the force transmission band is calculated using formulas (1), (2), and (3):

[0027] A s =M / f y γ s h0 (1)

[0028]

[0029]

[0030] In the formula, A s Let f be the cross-sectional area of ​​the reinforcing steel in the load-transfer band, M be the maximum bending moment of the cantilever beam under its own weight, and f be the cross-sectional area of ​​the reinforcing steel in the load-transfer band. y γ is the design value of the tensile strength of the reinforcing steel in the load-bearing band. s α is the internal arm coefficient of the internal moment, h0 is the effective height of the section, and α is the internal arm coefficient of the internal moment. s α1 is the ground resistance coefficient of the cross section, α1 is the ratio of the stress value of the rectangular stress diagram of the concrete in the compression zone to the design value of the axial compressive strength of the concrete, and f is the ground resistance coefficient of the cross section. c denoted as , where b is the design value of the axial compressive strength of the concrete, and b is the width of the force transmission band section.

[0031] In a further embodiment, during the construction of the subsequent section in step S105, when the foundation pit of the subsequent section is excavated, the sealing wall is dismantled from top to bottom along with the foundation pit excavation, and the force transmission belt is dismantled together with the sealing wall.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. The enclosure wall of this construction method adopts the same type as the foundation pit retaining structure, such as diaphragm wall, pile wall or SMW method pile, to ensure the integrity of the enclosure structure of the divided small foundation pits and improve the construction quality of the retaining structure of the small foundation pits; and according to the different types of enclosure walls, the force transmission strip adopts different structures, which can be flexibly combined and the construction methods are diverse, thus improving the construction effect.

[0034] 2. In this construction method, force transmission strips are installed on both the bottom and top slabs, eliminating the need for steel pipe supports and improving the support quality. Waterstops are installed at the ends of the bottom and top slabs near the force transmission strips. Both types of force transmission strip structures avoid the waterstops during construction, ensuring that the waterproof nodes of the tunnel main structure are not damaged during later removal, eliminating the need for secondary repairs, avoiding leakage risks, and resulting in high construction quality.

[0035] 3. The force transmission belt of this construction method has two structures: one is a support rod with a steel plate, and the other is a reinforced concrete structure. Both use common components, requiring no additional customization, resulting in low material costs, quick and convenient construction, short construction period, and improved construction efficiency.

[0036] 4. After the first section is completed using this construction method, the subsequent section is constructed. When excavating the foundation pit of the subsequent section, the sealing wall of the first section is removed from top to bottom along with the foundation pit. The force transmission strip of the first section is also removed. The force transmission strip formed by the support rod is removed by gas cutting, and the force transmission strip formed by the concrete of the force transmission strip is removed by pneumatic hammer. There is no need for a separate force transmission strip removal step, which shortens the construction period and improves construction efficiency. Attached Figure Description

[0037] Figure 1 A flowchart of a segmented construction method for a large tunnel;

[0038] Figure 2 This is a side view of a segmented construction method for large tunnels;

[0039] Figure 3 One of the schematic diagrams of a force transmission belt in a segmented construction method for large tunnels;

[0040] Figure 4 This is the second schematic diagram of a force transmission belt in a segmented construction method for large tunnels.

[0041] In the diagram: 1. Subsequent section; 2. Preliminary section; 3. Support components; 31. Concrete support; 32. Steel support; 4. Top slab; 5. Bottom slab; 6. Force transmission band; 61. Anchor bar; 62. Mounting plate; 63. Support rod; 64. Force transmission band reinforcement; 65. Force transmission band concrete; 7. Partition wall; 8. Waterstop. Detailed Implementation

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] Example 1:

[0044] A method for segmented construction of large tunnels, such as Figures 1 to 4 As shown, it includes the following steps:

[0045] Step S101, Construction of the partition wall 7

[0046] Based on the pipelines, traffic and other influencing factors on site, the positions of the pilot section 2, the subsequent section 1 and the sealing wall 7 are reasonably divided, and the foundation pit of the entire large tunnel is divided into several small foundation pits; the retaining structure is constructed around the pilot section 2. After the retaining structure is completed, the sealing wall 7 is constructed at the predetermined position. The sealing wall 7 is spaced 0.8m to 1.2m from the construction joint or deformation joint of the tunnel main structure, and is used for the construction of the force transmission belt 6.

[0047] The retaining structure is determined based on the depth of the foundation pit and the surrounding geological environment, and can be either pile walls or SMW piles. The form of the partition wall 7 is determined by calculation based on the depth of the foundation pit and the surrounding environment, and can be a diaphragm wall, pile walls, SMW piles, etc. Generally, SMW piles are used when the foundation pit is shallow, and diaphragm walls or pile walls are used when the foundation pit is deep. The type and depth of the partition wall 7 are the same as the retaining structures on both sides of the foundation pit to ensure the closed integrity of the retaining structure of each small foundation pit.

[0048] Step S103, Construction Pre-construction Section 2 and Force Transmission Belt 6

[0049] like Figure 2 As shown, the soil at the top of the first section 2 is excavated to below the predetermined position of the concrete support 31. Several concrete supports 31 and capping beams are constructed at intervals at the predetermined positions. The capping beams form a whole with the concrete supports 31. After the capping beams and the concrete supports 31 reach 85% of their design strength, the excavation continues downward until it reaches 0.5m below the predetermined position of the first layer of steel support 32. The first layer of steel support 32 is assumed at the predetermined position. After the axial force is pre-applied to the steel support 32, the steps of excavation and erection of steel support 32 continue until the foundation pit is excavated to the bottom elevation.

[0050] After excavating the foundation pit to the design elevation of the base, the concrete cushion layer, waterproof layer, and base slab 5 are constructed in sequence. Then, a force transmission strip 6 is constructed between the base slab 5 and the partition wall 7. After the base slab 5 and the force transmission strip 6 reach 100% of their design strength, the steel support 32 between the base slab 5 and the top slab 4 at the preset position is removed. The side walls and top slab 4 are constructed upwards from the base slab 5. A waterstop 8 is installed at one end of the base slab 5 and the top slab 4 near the force transmission strip 6. After the top slab 4 is constructed, the force transmission strip 6 is constructed between the top slab 4 and the partition wall 7. After the top slab 4 and the force transmission strip 6 both reach 100% of their design strength, the steel support 32 and concrete support 31 above the top slab 4 are removed. The soil at the top of the foundation pit is backfilled, and the pipelines and traffic are relocated to the top of the pilot section 2 to facilitate the construction of the subsequent section 1.

[0051] The force transmission strip 6 extends from the top slab 4 or bottom slab 5 to the partition wall 7, with its length determined based on the actual construction conditions on site, generally ranging from 0.8m to 1.2m. The force transmission strip 6 can be constructed using two methods:

[0052] Construction method 1 for force transmission belt 6: Figure 3 As shown in the figure, the top slab 4 is taken as an example; the partition wall 7 is a diaphragm wall, and the force transmission band 6 includes anchor bars 61, mounting plates 62 and support rods 63. When the steel cage of the diaphragm wall is installed, one end of the anchor bar 61 is fixedly installed on the steel cage, and the other end of the anchor bar 61 is fixedly installed on the mounting plate 62. When the diaphragm wall is poured, one end of the mounting plate 62 is located outside the diaphragm wall. When the steel bars of the bottom slab 5 or the top slab 4 are tied, one end of the support rod 63 is welded to the steel bars of the bottom slab 5 or the top slab 4, and the other end of the support rod 63 is pressed against the mounting plate 62 to form the force transmission band 6. Finally, the bottom slab 5 or the top slab 4 is poured.

[0053] The mounting plate 62 can be rectangular or square. The side length of the mounting plate 62 is determined according to the model of the support rod 63. Each side of the mounting plate 62 needs to be 0.5m longer than the support rod 63, and the thickness of the mounting plate 62 is greater than or equal to 1cm. The support rod 63 is embedded in the bottom plate 5 or top plate 4 for a length of not less than 30cm, avoiding the waterstop 8 of the construction joint during installation. The support rod 63 is set in one row above and one row below the waterstop 8, with a spacing of greater than or equal to 3m between adjacent support rods 63, and is evenly and symmetrically arranged on each partition wall 7. Preferably, the mounting plate 62 is a steel plate; the anchoring bars 61 are HRB steel bars, with a length of 30cm and a diameter of 14mm, and a total of eight bars are evenly distributed; the model of the support rod 63 is greater than or equal to I28, and the support rod 63 can be I-beam, angle steel, H-beam, steel pipe, etc.

[0054] Construction method two for force transmission belt 6: Figure 4As shown in the figure, the top slab 4 is used as an example; the partition wall 7 is in the form of pile foundation or SMW method piles, etc. The force transmission band 6 includes force transmission band steel bars 64 and force transmission band concrete 65. When the reinforcement of the bottom slab 5 or the top slab 4 is tied, one end of the force transmission band steel bar 64 is fixed together with the reinforcement of the bottom slab 5 or the top slab 4. The length of the force transmission band steel bar 64 anchored into the bottom slab 5 or the top slab 4 is greater than or equal to 25 times the diameter of the force transmission band steel bar 64. The side of the force transmission band steel bar 64 near the partition wall 7 is provided with a 90° bend, and the bend length is large. The diameter of the force-transfer strip reinforcement 64 is equal to 15 times that of the reinforcement 64. The force-transfer strip concrete 65 is poured to form the force-transfer strip 6, and finally the bottom slab 5 or top slab 4 is poured. The bottom end of the force-transfer strip 6 is flush with the bottom end of the bottom slab 5 or top slab 4, and the top end of the force-transfer strip 6 is located 5cm to 10cm below the waterstop 8, ensuring that the top surface of the force-transfer strip 6 is below the waterstop 8 to prevent damage to the waterstop 8 when the force-transfer strip 6 is removed later. The force-transfer strip reinforcement 64 is a negative moment reinforcement, set at the top of the force-transfer strip 6 to facilitate bearing negative bending moments and its own weight.

[0055] The cross-sectional area of ​​the 64-strength reinforcing bar can be calculated using formulas (1), (2), and (3):

[0056] A s =M / f y γ s h0 (1)

[0057]

[0058]

[0059] In the formula, A s Let f be the cross-sectional area of ​​the reinforcing bar 64 in the load-transfer band, M be the maximum bending moment of the cantilever beam under its own weight, and f be the maximum bending moment of the cantilever beam under its own weight. y γ is the design value of the tensile strength of the 64mm reinforcing bar in the load-bearing band. s α is the internal arm coefficient of the internal moment, h0 is the effective height of the section, and α is the internal arm coefficient of the internal moment. s α1 is the ground resistance coefficient of the cross section, α1 is the ratio of the stress value of the rectangular stress diagram of the concrete in the compression zone to the design value of the axial compressive strength of the concrete, and f is the ground resistance coefficient of the cross section. c denoted as , where is the design value of the axial compressive strength of the concrete, and b is the width of the force transmission band section 6.

[0060] Step S105, Construction of Subsequent Section 1

[0061] After the foundation pit and main structure of the first section 2 are completed, the retaining structure, partition wall 7, foundation pit and main structure of the subsequent section 1 are constructed in sequence. The construction steps are the same as steps S101 and S103. When the foundation pit of the adjacent subsequent section 1 is excavated, the partition wall 7 is removed from top to bottom as the foundation pit is excavated. The corresponding force transmission belt 6 is also removed. The force transmission belt 6 formed by the support rod 63 is removed by gas cutting, and the force transmission belt 6 formed by the force transmission belt concrete 65 is removed by pneumatic pick. Steps S101, S103 and S105 are repeated until the entire tunnel foundation pit is completed.

[0062] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for segmented construction of a large tunnel, characterized in that, Includes the following steps: Step S101, Construction of the partition wall (7) The entire foundation pit is divided into a preliminary section (2) and several subsequent sections (1), and a partition wall (7) is constructed at the junction of the preliminary section (2) and the subsequent sections (1). Step S103, Construction Preliminary Section (2) and Force Transmission Belt (6) First, the pilot section (2) is excavated, and then the support components (3) and the main structure are constructed in sequence within the pilot section (2). Finally, a force transmission strip (6) is constructed between the main structure and the partition wall (7). The main structure includes a bottom plate (5) and a top plate (4). A waterstop strip (8) is provided at one end of the bottom plate (5) and the top plate (4) near the force transmission strip (6). Step S105, Construction of the subsequent section (1) The subsequent sections (1) are constructed sequentially until the entire foundation pit is completed. The construction steps of the subsequent section (1) are the same as those of the construction of the sealing wall (7) in step S101, the construction of the preliminary section (2) and the force transmission belt (6) in step S103; The partition wall (7) is a diaphragm wall. The force transmission strip (6) includes an installation plate (62) and a support rod (63). The installation plate (62) is pre-embedded on the partition wall (7) by anchor bars (61). One end of the installation plate (62) is located outside the partition wall (7). One end of the support rod (63) is fixedly installed in the bottom plate (5) or the top plate (4). The other end of the support rod (63) abuts against the installation plate (62). Several support rods (63) are located on the upper and lower sides of the waterstop strip (8). Alternatively, the partition wall (7) can be a pile or a SMW method pile. The force transmission strip (6) includes a force transmission strip steel bar (64) and a force transmission strip concrete (65). One end of the force transmission strip steel bar (64) is embedded in the bottom plate (5) or the top plate (4). The force transmission strip concrete (65) is poured on the force transmission strip steel bar (64). The top surface of the force transmission strip concrete (65) is located below the waterstop strip (8).

2. The method for segmented construction of a large tunnel according to claim 1, characterized in that, In step S101, the enclosure wall (7) is constructed. A retaining structure is constructed around the perimeter of the preliminary section (2). The enclosure wall (7) is of the same type as the retaining structure.

3. The method for segmented construction of a large tunnel according to claim 2, characterized in that, The enclosure wall (7) is a diaphragm wall, a pile bank, or a SMW method pile.

4. The method for segmented construction of a large tunnel according to claim 3, characterized in that, In step S103, the construction pilot section (2) and the force transmission belt (6) include a support component (3) comprising a concrete support (31) and a steel support (32). The concrete support (31) is fixedly installed at the top of the pilot section (2), and the steel support (32) is fixedly installed inside the pilot section (2).

5. The method for segmented construction of a large tunnel according to claim 4, characterized in that, In step S103, the construction pilot section (2) and the force transmission belt (6) are constructed first, the base plate (5) is constructed first, then the steel support (32) between the base plate (5) and the top plate (4) is removed, the side wall and the top plate (4) are constructed from the base plate (5) upwards, and finally the steel support (32) and the concrete support (31) above the top plate (4) are removed.

6. The method for segmented construction of a large tunnel according to claim 5, characterized in that, The force transmission belt (6) is respectively provided between the bottom plate (5), the top plate (4) and the partition wall (7).

7. The method for segmented construction of a large tunnel according to claim 6, characterized in that, The cross-sectional area of ​​the force-transfer reinforcing bar (64) is calculated using formulas (1), (2), and (3): （1） （2） （3） In the formula, The cross-sectional area of ​​the force-transfer reinforcing bar (64) is... The cantilever beam of the force transmission belt (6) bears the maximum bending moment under its own weight. This is the design value of the tensile strength of the force-transfer reinforcing bar (64). This is the internal lever arm coefficient of the internal moment. The effective height of the cross section, Let be the georesistivity coefficient of the cross section. This represents the ratio of the stress value in the rectangular stress diagram of the compression zone concrete to the design value of the axial compressive strength of the concrete. This is the design value of the axial compressive strength of concrete. The width of the cross section of the force transmission belt (6) is given.

8. A method for segmented construction of a large tunnel according to claim 7, characterized in that, In step S105, during the construction of the subsequent section (1), when the foundation pit of the subsequent section (1) is excavated, the sealing wall (7) is dismantled from top to bottom along with the excavation of the foundation pit, and the force transmission belt (6) is dismantled together with the sealing wall (7).

Images