A double sidewall heading tunnel construction method

Abstract

The present application relates to a kind of double side wall guide tunnel construction method, the width ratio of two side guide pit and middle core soil width is 1.3-1.5:1, excavates upper and lower step portion of outer side guide pit, construction initial support, first two temporary strong support, and initial support and temporary strong support of outer side form one side guide pit steel frame structure;Excavate upper and lower step portion of inner side wall guide pit, construction initial support, first two temporary weak support, and initial support and temporary weak support of inner side form another side guide pit steel frame structure;Make the initial support of core soil upper step portion, remove first and second temporary weak support, form single side wall guide pit structure;Excavate core soil middle and lower step portion, remove first and second temporary strong support, construction inverted arch and inverted arch backfill, full-face pouring arch wall.When use, can use large mechanical equipment, improve construction efficiency, reduce surface subsidence, two sides use different temporary support, save material, facilitate recycling, reduce cost.

Description

Technical Field

[0001] This invention relates to the technical field of tunnel construction, specifically to a method for constructing a double-sided wall pilot tunnel, and more particularly to a method for constructing a double-sided wall pilot tunnel that reduces surface settlement. Background Technology

[0002] In existing technologies, the construction of large-section underground tunnels in cities can cause surface subsidence and tilting, which can damage surface structures in severe cases. Therefore, the double-sided wall pilot tunnel method is often chosen in conjunction with mechanical construction to control surface subsidence. However, the traditional double-sided wall pilot tunnel method has a slow construction progress and high cost.

[0003] Meanwhile, in order to facilitate the passage of construction machinery during the construction of both side pilot tunnels and the central core soil, the traditional double-sided wall pilot tunnel method tends to divide the tunnel into roughly three equal parts when dividing it laterally. This results in the narrow width and height of the three sections, which limits the machinery that can be selected during construction. Small excavators are often used in conjunction with breakers, single hook machines or milling machines. Large machinery cannot operate normally after entering the tunnel due to limited clearance, making it impossible to organize construction.

[0004] Therefore, there is an urgent need for a new tunnel construction method to improve construction efficiency and reduce surface subsidence. Summary of the Invention

[0005] The purpose of this invention is to provide an improved construction method for double-sided wall pilot tunnels. By improving the construction method and optimizing the structure of temporary support, the construction efficiency can be increased by more than 30%, and the temporary support can be reused, reducing costs.

[0006] To achieve the above objectives, the technical solution of the present invention is: a construction method for a double-sided pilot tunnel, characterized in that: the construction method includes the construction of the central core soil and the construction of pilot tunnels on both sides of the central core soil, wherein the ratio of the width of the two pilot tunnels to the width of the central core soil is 1.3-1.5:1, and the specific construction steps are as follows: a) excavating the upper step of the outer pilot tunnel, constructing the initial support, the first temporary strong support, and the outer temporary invert arch of the upper step; b) when the depth of step a reaches 6-8m, removing the outer temporary invert arch, and moving the removed outer temporary invert arch forward for subsequent reuse, excavating the lower step of the outer pilot tunnel, constructing the initial support and the second temporary strong support of the lower step, and the initial support of the upper and lower steps of the outer side cooperates with each other to form a closed steel frame structure for one side of the pilot tunnel; c) excavating the upper step of the inner side wall pilot tunnel, constructing the initial support of the upper step... d. When the depth of step c reaches 6-8m, remove the inner temporary invert arch and move it forward for subsequent reuse. Excavate the lower step of the inner side guide tunnel, construct the initial support and the second temporary weak support of the lower step. The initial support of the upper and lower steps on the inner side will cooperate to form a closed steel frame structure for the other side guide tunnel. e. Excavate the upper step of the core soil, construct the initial support of the upper step of the core soil, and then remove the corresponding first and second temporary weak supports on the inner side of the core soil to form a single-sided guide tunnel structure. f. Continue to excavate the middle and lower steps of the core soil, construct the initial support of the middle and lower steps of the core soil, so that the steel frame around the main tunnel is completely closed into a ring, and then remove the corresponding first and second temporary strong supports on the outer side of the core soil. g. Construct the invert arch and backfill the invert arch. h. Cast the arch wall across the entire section.

[0007] Preferably, in step a, when excavating 1-2 steel frame intervals each time, the initial support, the first temporary strong support, and the temporary invert arch of the outer upper step are constructed, and then the above process is repeated.

[0008] Furthermore, in step b, each time 1-2 steel frame gaps are excavated, the initial support and second temporary strong support of the outer lower step are constructed. The initial support of the outer upper and lower steps cooperates with each other to form a closed one-sided guide tunnel steel frame structure, and then the above process is repeated.

[0009] Furthermore, the front-to-back distance between the upper and lower steps of the outer pilot tunnel is 6-8m, the front-to-back distance between the upper and lower steps of the inner pilot tunnel is 6-8m, and the front-to-back distance between the upper steps of the two pilot tunnels is 14-16m.

[0010] Furthermore, the first and second temporary strong supports consist of several I-beams connected by steel bars, and the exterior of the I-beams is sprayed with a layer of concrete; the first and second temporary weak supports consist of several grid steel frames connected by steel bars, and the exterior of the grid steel frames and steel bars is sprayed with a layer of concrete.

[0011] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects:

[0012] 1. The improved scheme of the present invention has a width ratio of 1.3-1.5:1 between the width of the two side guide tunnels and the width of the central core soil, which allows the use of large-scale mechanical equipment during construction and improves construction efficiency. At the same time, the initial support of the upper and lower steps on the outer side cooperates with each other to form a closed steel frame structure of one side guide tunnel, and the initial support of the upper and lower steps on the inner side cooperates with each other to form a closed steel frame structure of the other side guide tunnel, which can effectively control surface settlement and ensure the safety of surface buildings.

[0013] 2. In the technical solution of the present invention, the upper step of the core soil is excavated, the initial support of the upper step of the core soil is constructed, and then the first and second temporary weak supports corresponding to the inner side of the core soil are removed to form a single-side wall guide tunnel structure. This not only orderly breaks down the super-large cross section into smaller parts, enhancing safety, but also effectively overcomes the impact of step-by-step small cross section on construction efficiency and solves the problem of inconvenience in the construction of the intermediate core soil in the past.

[0014] 3. This invention provides two different temporary support structures: temporary weak support and temporary strong support. Using different supports not only reduces construction costs but also improves construction efficiency. The temporary support and temporary invert can also be recycled and reused, saving on project costs.

[0015] 4. The construction method of this invention is economical and environmentally friendly. The materials removed during construction can be reused, which reduces construction costs. At the same time, the improved construction steps and optimized construction methods effectively improve construction efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the construction cross-section structure of the present invention.

[0017] Figure 2 This is a schematic diagram of the construction scheme for a section of the construction length of the present invention.

[0018] Figure 3 This is a schematic diagram of the temporary strong support structure of the present invention.

[0019] Figure 4 This is a schematic diagram of the temporary weak support structure of the present invention.

[0020] Figure 5 This is a partially enlarged schematic diagram of the grating steel frame of the present invention.

[0021] Figure 6 for Figure 5 A schematic diagram of the structure along the AA direction.

[0022] Figure 7 for Figure 5 A schematic diagram of the structure in the BB direction.

[0023] Figure 8 This is a partial structural schematic diagram of the prefabricated inverted arch of the present invention.

[0024] Figure label:

[0025] 1. The upper step of the outer guide tunnel; 11. The first temporary strong support;

[0026] 2. The lower step section of the outer guide tunnel; 21. The second temporary strong support;

[0027] 3. The upper step section of the inner side wall pilot tunnel; 31. The first temporary weak support;

[0028] 4. The lower step of the inner side wall pilot tunnel; 41. The second temporary weak support;

[0029] 5. Backfilling of the invert arch, 6. Arch wall, 7. Core soil in the middle, 8. Temporary invert arch on the outer side, 9. Temporary invert arch on the inner side;

[0030] 10. Grating steel frame, 101. Concrete layer, 102. Square steel support shell, 103. V-shaped support steel plate, 104. Reinforcing rib, 105. Left and right welded connecting plates;

[0031] 20 H-beams, 22mm steel bars;

[0032] 30 lifting rings, 32 angle steel. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention provides a method for constructing a double-sided pilot tunnel, see details below. Figure 1The difference between this method and existing technologies lies in the following: the construction method includes the construction of the central core soil and the construction of pilot tunnels on both sides of the central core soil. The width ratio of the pilot tunnels on both sides to the width of the central core soil is 1.3-1.5:1. The larger width of the pilot tunnels on both sides allows for the construction of large machinery and equipment, improving work efficiency and facilitating the transportation of various materials and equipment. The specific construction steps are as follows: a) Excavate the upper step section 1 of the outer pilot tunnel, and construct the initial support, the first temporary strong support 11, and the outer temporary invert arch 8 of the upper step section; b) When the depth of step a reaches 6-8m, remove the outer temporary invert arch 8 and move it forward for subsequent reuse. Excavate the lower step section 2 of the outer pilot tunnel, and construct the initial support and the second temporary strong support 21 of the lower step section. The initial supports of the upper and lower steps on the outer side cooperate to form a closed steel frame structure for one side of the pilot tunnel; c) Excavate the upper step section 3 of the inner side wall pilot tunnel. d. When the depth of step c reaches 6-8m, remove the inner temporary invert arch 9 and move it forward for subsequent reuse. Excavate the lower step section 4 of the inner side guide tunnel, construct the initial support and the second temporary weak support 41 of the lower step section. The initial support of the upper and lower steps of the inner side cooperates to form a closed steel frame structure of the other side guide tunnel. e. Excavate the upper step section of the core soil, construct the initial support of the upper step section of the core soil, and then remove the corresponding first and second temporary weak supports on the inner side of the core soil to form a single-sided guide tunnel structure. f. Continue to excavate the middle and lower steps of the core soil, construct the initial support of the middle and lower steps of the core soil, so that the steel frame of the main tunnel is completely closed into a ring. Then remove the corresponding first and second temporary strong supports on the outer side of the core soil. g. Remove the construction invert arch and backfill the invert arch 5. h. Cast the arch wall 6 in its entirety.

[0035] In practice, the construction method is applied to continuous construction length units, each unit being 60-90 meters long. The new method, based on the fact that the inner and outer temporary invert arches primarily serve as temporary support rings, innovatively proposes the use of precast segments. The longitudinal width of each precast segment is two construction length units, and the circumferential length is 2 meters. Connecting structures (such as...) are installed between the precast segments. Figure 8 (The angle steel structure at the end shown) Low-grade concrete post-cast sections are set between the inner and outer temporary invert arches and the initial support, and between the inner and outer temporary invert arches and the first temporary strong and weak support. During construction transition, the low-grade concrete post-cast sections are removed, and the inner and outer temporary invert arches are recovered and transported forward for reuse. This approach can significantly reduce project costs and achieve preliminary prefabrication of tunnel construction.

[0036] Example 1

[0037] The construction method described herein is applied to a series of continuous construction length units, each of which is 60-90 meters long. In this embodiment, a length of 70 meters is used. The construction method includes the construction of the central core soil and the construction of pilot tunnels on both sides of the central core soil. The ratio of the width of the pilot tunnels on both sides to the width of the central core soil is 1.3-1.5:1. The construction method is applied to a series of continuous construction length units, and the specific construction steps for each construction length unit are as follows: a) Excavate the upper step of the outer pilot tunnel, and construct the initial support, the first temporary strong support, and the outer temporary invert 8 for the upper step; b) When the depth of step a reaches 6-8m, remove the outer temporary invert 8 and move the removed outer temporary invert 8 forward for subsequent reuse. Excavate the lower step of the outer pilot tunnel, and construct the initial support and the second temporary strong support for the lower step. The initial supports of the upper and lower steps on the outer side cooperate with each other to form a closed steel frame structure for one side of the pilot tunnel; c) Excavate... d. When the depth of step c reaches 6-8m, the inner temporary invert arch 9 is removed and moved forward for reuse. The lower step of the inner guide tunnel is excavated, and the initial support and second temporary weak support are constructed. The initial supports of the upper and lower steps are coordinated to form a closed steel frame structure for the other side of the guide tunnel. e. The upper step of the core soil is excavated, and the initial support of the upper step of the core soil is constructed. Then, the first and second temporary weak supports corresponding to the inner side of the core soil are removed to form a single-sided guide tunnel structure. f. The middle and lower steps of the core soil are excavated, and the initial support of the middle and lower steps of the core soil is constructed to complete the closure of the main tunnel's steel frame. Then, the first and second temporary strong supports corresponding to the outer side of the core soil are removed. g. The invert arch is constructed and backfilled. h. The arch wall is poured in its entirety.

[0038] In specific construction, in step a, each time 1-2 steel frame gaps are excavated, the initial support, the first temporary strong support, and the outer temporary invert arch 8 of the outer upper step section are constructed. Then, the above process is repeated. Here, a low-grade concrete post-cast section is set between the initial support, the first temporary weak support, and the outer temporary invert arch to facilitate the subsequent dismantling and reuse of the temporary invert arch. The inner and outer temporary invert arches are composed of H-beams and concrete sprayed around the H-beams. A lifting ring is provided on one side of the H-beam. The inner and outer temporary invert arches can be dismantled and reused, reducing construction costs.

[0039] In step b, each time 1-2 steel frame gaps are excavated, the initial support and second temporary strong support of the outer lower step are constructed. The initial support of the outer upper and lower steps cooperates with each other to form a closed one-sided guide tunnel steel frame structure, and then the above process is repeated.

[0040] The front-to-back distance between the upper and lower steps of the outer pilot tunnel is 6-8m, the front-to-back distance between the upper and lower steps of the inner pilot tunnel is 6-8m, and the front-to-back distance between the upper steps of the two pilot tunnels is 14-16m, which is 15m in this embodiment.

[0041] The first and second temporary weak supports consist of several grid steel frames, which are connected by reinforcing bars. The grid steel frames and reinforcing bars are coated with a layer of sprayed concrete. The grid steel frames are made of a square steel support shell and V-shaped support plates inside. The connection between the V-shaped support plates and the steel support shell is reinforced with ribs and welded connecting plates on both sides. These connecting plates have upper and lower welded holes. During construction, the reinforcing bars on one side of the grid steel frame are connected to the upper welded holes, and the reinforcing bars on the other side are connected to the lower welded holes. This alternating arrangement enhances strength, ensures uniform stress distribution, and improves the load-bearing capacity of the support.

[0042] The first and second temporary strong supports consist of several I-beams, which are joined together by reinforcing bars. The I-beams and reinforcing bars are coated with a layer of sprayed concrete. Similarly, the reinforcing bars on one side of the I-beam are connected to the upper part of the I-beam, and the reinforcing bars on the other side are connected to the lower part of the I-beam, thus improving the overall strength and load-bearing capacity of the support.

[0043] In steps c and d, after completing the construction depth of one section of the upper guide tunnel, the inner and outer temporary invert arches are retrieved for use in the next construction length unit, each construction length unit being 60-90 meters.

[0044] Example 2

[0045] The construction method described herein is applied to a series of continuous construction length units, each unit being 60-90 meters long. The method includes the construction of the central core soil and the construction of pilot tunnels on both sides of the central core soil. The width ratio of the pilot tunnels to the width of the central core soil is 1.4:1. The specific construction steps for each continuous construction length unit are as follows: a) Excavate the upper step of the outer pilot tunnel, constructing the initial support, the first temporary strong support, and the outer temporary invert 8; b) When the depth of step a reaches 6-8 meters, remove the outer temporary invert 8 and move it forward for subsequent reuse. Excavate the lower step of the outer pilot tunnel, constructing the initial support and the second temporary strong support. The initial supports of the upper and lower steps cooperate to form a closed steel frame structure for one side of the pilot tunnel; c) Excavate the upper step of the inner side wall pilot tunnel. The construction process is as follows: 1. Initial support, first temporary weak support, and inner temporary invert arch 9 for the upper step section; 2. When the depth of step c reaches 6-8m, remove the inner temporary invert arch 9 and move it forward for reuse. Excavate the lower step section of the inner wall guide tunnel, construct the initial support and second temporary weak support for the lower step section. The initial support of the upper and lower steps on the inner side will cooperate to form a closed steel frame structure for the other side guide tunnel; 3. Excavate the upper step section of the core soil, construct the initial support for the upper step section of the core soil, and then remove the corresponding first and second temporary weak support on the inner side of the core soil to form a single-sided guide tunnel structure; 4. Continue to excavate the middle and lower steps of the core soil, construct the initial support for the middle and lower steps of the core soil, so that the steel frame around the main tunnel is completely closed into a ring, and then remove the corresponding first and second temporary strong support on the outer side of the core soil; 5. Construct the invert arch and backfill the invert arch; 6. Cast the arch wall across the entire cross section.

[0046] Specifically, the lengths of the pilot tunnels on both sides are 7m each, making it possible to choose large, efficient machinery for construction. Some large excavators and cantilever tunnel boring machines have enough room to maneuver, and the construction efficiency of the pilot tunnels on both sides is significantly improved.

[0047] To address the challenges of constructing the intermediate core soil, this construction method adjusted the construction sequence. One side of the temporary weak support was removed during the excavation of the intermediate core soil, while the other side of the temporary strong support was removed during the secondary lining construction. Once the upper bench excavation of the core soil was completed and the initial support for the main tunnel arch was installed, the temporary weak support on that side could be removed, thus resolving the construction issues of the intermediate core soil. After removing the temporary weak support on one side, the entire construction sequence effectively changed from the double-sided wall pilot tunnel method to the single-sided wall method. This not only improved safety by systematically breaking down the large cross-section into smaller sections but also effectively overcame the impact of step-by-step small-section construction on construction efficiency.

[0048] Meanwhile, the pilot tunnels on both sides of the large-section tunnel in this invention are often constructed in layers, with inner and outer temporary invert arches. The traditional method for constructing the inner and outer temporary invert arches is the same as that for temporary support, using I-beams and shotcrete. Although the traditional method provides good contact with the rock surface, significant waste occurs during dismantling due to material damage that prevents reuse.

[0049] This improved double-sided wall pilot tunnel method can effectively increase construction efficiency by more than 30% by adjusting construction procedures, optimizing pilot tunnel dimensions, and optimizing temporary support. It allows for faster and more efficient passage through control sections, which is of great significance for ensuring the safety of surface buildings. At the same time, this invention method can also significantly reduce costs.

[0050] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for constructing a double-sided pilot tunnel, characterized in that: The construction method includes the construction of the central core soil and the construction of pilot tunnels on both sides of the central core soil. The width ratio of the pilot tunnels on both sides to the width of the central core soil is 1.3-1.5:

1. The construction method is applied to a series of continuous construction length units. The specific construction steps for each construction length unit are as follows: a) Excavate the upper step of the outer pilot tunnel, and construct the initial support, the first temporary strong support, and the outer temporary invert arch of the upper step. The outer temporary support is strong support, and the inner support is weak support. The first and second temporary strong supports consist of several I-beams, which are spliced ​​together by steel bars. The I-beams and steel bars are sprayed with concrete. b) When the depth of step a) reaches 6-8m, remove the outer temporary invert arch and move it forward for subsequent reuse. Excavate the lower step of the outer pilot tunnel, and construct the initial support and the second temporary strong support of the lower step. The initial supports of the upper and lower steps of the outer side cooperate with each other to form a closed steel frame for one side of the pilot tunnel. Structure; c. Excavate the upper step section of the inner side wall pilot tunnel, construct the initial support, first temporary weak support, and inner temporary invert arch of the upper step section; d. When the depth of step c reaches 6-8m, remove the inner temporary invert arch and move the removed inner temporary invert arch forward for subsequent reuse, excavate the lower step section of the inner side wall pilot tunnel, construct the initial support and second temporary weak support of the lower step section, and the initial support of the upper and lower steps on the inner side cooperates to form a closed steel frame structure for the other side pilot tunnel; e. Open f) Excavate the upper step section of the core soil, construct the initial support for the upper step section of the core soil, and then remove the first and second temporary weak supports corresponding to the inner side of the core soil to form a single-sided guide tunnel structure; f) Continue excavating the middle and lower step sections of the core soil, construct the initial support for the middle and lower step sections of the core soil, so that the main tunnel's steel frame is completely closed into a ring, and then remove the first and second temporary strong supports corresponding to the outer side of the core soil; g) Construct the invert arch and backfill the invert arch; h) Cast the arch wall across the entire cross section to complete the construction of a precast segment.

2. The construction method for a double-sided pilot tunnel according to claim 1, characterized in that: In step a, each time 1-2 steel frame gaps are excavated, the initial support, the first temporary strong support, and the outer temporary invert arch of the upper step section are constructed, and then the above process is repeated.

3. The construction method for a double-sided pilot tunnel according to claim 1, characterized in that: In step b, each time 1-2 steel frame gaps are excavated, the initial support and second temporary strong support of the outer lower step are constructed. The initial support of the outer upper and lower steps cooperates with each other to form a closed one-sided guide tunnel steel frame structure, and then the above process is repeated.

4. The construction method for a double-sided pilot tunnel according to claim 1, characterized in that: The front-to-back distance between the upper and lower steps of the outer pilot tunnel is 6-8m, the front-to-back distance between the upper and lower steps of the inner pilot tunnel is 6-8m, and the front-to-back distance between the upper steps of the two pilot tunnels is 14-16m.

5. The construction method for a double-sided pilot tunnel according to claim 1, characterized in that: The first and second temporary weak supports consist of several grid steel frames, which are spliced ​​together by steel bars. The grid steel frames and steel bars are sprayed with a layer of concrete.

6. The construction method for a double-sided pilot tunnel according to claim 5, characterized in that: The grating steel frame is made of a square steel support shell and a V-shaped support steel plate inside it. The connection between the V-shaped support plate and the steel support shell is provided with reinforcing ribs and left and right welded connecting plates. The left and right welded connecting plates are provided with upper and lower welding holes.

7. The construction method for a double-sided pilot tunnel according to claim 1, characterized in that: In construction steps c and d, after completing the construction depth of one section of the upper guide tunnel, the inner and outer temporary invert arches are retrieved for use in the next construction length unit, each construction length unit being 60-90 meters.

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