Supporting structure for tunnel under complex unfavorable geological conditions and construction method of supporting structure

Abstract

The invention relates to the technical field of tunnel construction, in particular to a supporting structure for a tunnel under complex unfavorable geological conditions and a construction method of the supporting structure, the supporting structure comprises protection arch foundations arranged at the bottoms of two side walls of the tunnel and protection arches arranged on the protection arch foundations and located above a tunnel entering excavation line; the protective arch comprises two super-long pipe shed layers and a cast-in-place concrete layer arranged between the two super-long pipe shed layers. According to the method, higher supporting force and stability can be provided under complex unfavorable geological conditions, and the foundation is effectively prevented from sinking.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a supporting structure for tunnels in complex and adverse geological conditions and a construction method thereof. Background Art

[0002] The tunnel entrance section is generally a shallow buried section with poor geological conditions. When selecting the route, it is generally avoided to cross the bad geological section. However, in recent years, with the vigorous development of domestic transportation and the increase in speed target values, the straightness requirements of the route conditions have been continuously improved. At the same time, in order to save land, the open-cut method is not allowed for the buried section, making it more difficult for the tunnel entrance to avoid bad geology. The entrance of the bad geological section is very prone to collapse during construction, which often affects and restricts whether the tunnel can enter the hole smoothly.

[0003] For the construction of tunnels in poor geological conditions, the conventional technical means is to use single-layer advanced pipe shed grouting to reinforce the surrounding rock. However, for shallow buried tunnel openings, single-layer large pipe shed advanced support construction may cause overall sinking due to insufficient bearing capacity of the foundation. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the first aspect of the present invention aims to provide a support structure for tunnels under complex and adverse geological conditions, which can provide stronger support and stability under complex and adverse geological conditions and effectively prevent foundation sinking.

[0005] The second aspect of the present invention aims to provide a construction method for a support structure of a tunnel in complex and adverse geological conditions.

[0006] According to the purpose of the first aspect of the present invention, there is provided a supporting structure for tunnels in complex and adverse geological conditions, comprising a protective arch foundation arranged at the bottom of the two side walls of the tunnel and a protective arch arranged on the protective arch foundation and located above the entrance excavation line; the protective arch comprises two extra-long pipe shed layers and a cast-in-place concrete layer arranged between the two extra-long pipe shed layers.

[0007] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: the super-long pipe rack layer includes a plurality of arched steel frames arranged in sequence along the length direction of the tunnel and a plurality of steel pipes evenly spaced along the arched surfaces of the arched steel frames, and the length direction of the steel pipes extends along the longitudinal direction of the tunnel.

[0008] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: the steel pipes include guide pipes evenly spaced along the arched surface of the arched steel frame and pipe support pipes arranged inside the guide pipes.

[0009] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: the front end of the guide tube is welded to one of the arched steel frames, and the rear end of the guide tube is raised by 7-9 cm and welded to another of the arched steel frames.

[0010] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: the pipe-roof pipes include odd-numbered pipes and even-numbered pipes, the odd-numbered pipes are perforated pipes, and the even-numbered pipes are non-perforated pipes.

[0011] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: the pipe-roof pipe is composed of a number of pipe segments connected in sequence, the connection node between one pipe segment and another pipe segment forms a joint, the number of the joints in any section in the longitudinal direction of the tunnel is not more than 50%, and the joints of two adjacent pipe-roof pipes are staggered by at least 1m in the longitudinal direction of the tunnel.

[0012] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: it also includes back slope protection, and the back slope protection includes a number of small pipes and a hanging net connected to the several small pipes.

[0013] Furthermore, the support structure for tunnels with complex and adverse geological conditions provided by the present invention may also have the following characteristics: it also includes an initial support layer and a secondary lining layer located below the entry excavation line and arranged in sequence from the inside to the outside.

[0014] According to the purpose of the second aspect of the present invention, a construction method for a supporting structure for a tunnel with complex and unfavorable geological conditions is provided, which is used to construct the supporting structure for a tunnel with complex and unfavorable geological conditions as described above, comprising the following steps: Back slope protection: Drill several holes on the back slope, insert small tubes into the holes, fill the small tubes with mortar, and finally connect several small tubes to the hanging net; Arch protection foundation treatment: excavate the arch protection foundation, and after the excavation is completed, set steel pipe piles in a staggered manner in a plum blossom shape and perform grouting treatment on them. After the grouting treatment is completed, pour concrete to form the arch protection foundation; Arch protection construction: The arch protection is constructed on the arch foundation. First, an arch steel frame is set above the entrance excavation line, and then a number of guide pipes are evenly spaced along the arch surface of the arch steel frame. The length direction of the guide pipe extends along the longitudinal direction of the tunnel. Holes are then drilled in the guide pipes and pipe rack pipes are installed in the holes to form an extra-long pipe rack layer. After installing two extra-long pipe rack layers, concrete is poured between them to form a cast-in-place concrete layer.

[0015] Furthermore, the construction method of the support structure for a tunnel with complex and adverse geological conditions provided by the present invention may also have the following characteristics: the arch protection construction further includes the following steps: When drilling holes in the guide pipe and installing the pipe-roofing pipe in the holes, first drill odd-numbered holes and install the perforated pipes, inject cement slurry into the perforated pipes, and then drill even-numbered holes and install the non-perforated pipes.

[0016] The beneficial effects of the present invention are: 1. The support structure provided in this application forms a multi-layer support structure by combining two super-long pipe shed layers and a cast-in-place concrete layer. It has high stability and can cope with various adverse terrains for tunnel construction.

[0017] 2. In this application, through the construction method of back slope protection, arch foundation treatment and arch construction layer by layer, when facing adverse geological conditions, it can effectively reduce soil erosion and improve the overall stability of the support. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated into the specification and constitute a part of the specification, illustrate embodiments of the present invention and are used together with the description to explain the principles of the present invention. In these drawings, similar reference numerals are used to represent similar elements. The drawings described below are some embodiments of the present invention, but not all embodiments. For those of ordinary skill in the art, other drawings can be obtained from these drawings without paying creative work.

[0019] Figure 1 It is a structural schematic diagram of the first viewing angle of the present invention; Figure 2 It is a structural schematic diagram of the second viewing angle of the present invention; Figure 3 It is a structural schematic diagram of the grouting layer of the steel pipe pile of the present invention; Figure 4 It is a partial schematic diagram of the super-long pipe shelf layer of the present invention; Figure 5 It is a schematic structural diagram of the perforated tube of the present invention.

[0020] In the figure: 1. Inverted arch foundation; 11. Concrete pedestal; 12. Ribbed steel mesh; 13. First steel pipe pile; 2. Arch foundation; 3. Extra-long pipe shed layer; 31. Arched steel frame; 32. Steel pipe; 33. Guide pipe; 34. Pipe shed pipe; 35. Fixed steel bar; 36. Perforated pipe; 37. Grouting hole; 38. Pipe head; 39. Stiffening hoop; 4. Cast-in-place concrete layer; 51. Small guide tube; 52. Hanging mesh; 6. Initial support layer; 7. Secondary lining layer; 8. Open hole lining layer; 9. Excavation line into the hole. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The present invention provides a support structure for tunnels with complex and unfavorable geological conditions, comprising an invert foundation 1 arranged at the bottom of the tunnel, a protective arch foundation 2 arranged at the bottom of the two side walls of the tunnel, and a protective arch arranged on the protective arch foundation 2 and located above the tunnel entry excavation line 9; the protective arch comprises two super-long pipe shed layers 3 and a cast-in-place concrete layer 4 arranged between the two super-long pipe shed layers 3. Compared with the traditional single-layer advanced pipe shed grouting, the support structure provided by the present invention forms a multi-layer support structure by combining the two super-long pipe shed layers 3 and the cast-in-place concrete layer 4, which can provide more stable support when facing the construction of tunnels with complex and unfavorable geological conditions.

[0023] The inverted arch foundation 1 includes a steel pipe pile grouting layer and a concrete replacement layer. Specifically, when the fully weathered covering layer is greater than 1m, the open hole foundation includes a steel pipe pile grouting layer, which includes a C20 concrete cap 11 and a steel pipe pile grouting part arranged below the concrete cap 11. The bottom of the concrete cap 11 is provided with a φ12mm ribbed steel mesh 12. The steel pipe pile grouting part includes a number of φ108×6mm first steel pipe piles 13 arranged in a staggered manner in a plum blossom shape. The spacing between the two first steel pipe piles 13 is 60×60cm. The length of the bottom of the first steel pipe pile 13 driven into the strongly weathered rock layer is not less than 30cm, and the top of the first steel pipe pile 13 is not less than 40cm driven into the concrete cap 11; when the fully weathered covering layer is less than 1m, the open hole foundation includes a concrete replacement layer, and the concrete replacement layer is replaced with C15 rubble concrete.

[0024] The arch protection foundation 2 includes a plurality of φ108×6mm second steel pipe piles arranged in a plum blossom shape, with a lateral spacing of 40cm and a longitudinal spacing of 60cm between two second steel pipe piles, and the bottoms of the second steel pipe piles are embedded in the medium-weathered rock layer; the arch protection foundation 2 also includes a concrete casting part formed by C15 rubble concrete casting and arranged above the plurality of second steel pipe piles.

[0025] The super-long pipe scaffolding layer 3 includes a plurality of arched steel frames 31 arranged in sequence along the length direction of the tunnel and a plurality of steel pipes 32 evenly spaced along the arched surface of the arched steel frames 31. The length direction of the steel pipes 32 extends along the longitudinal direction of the tunnel. The arched steel frames 31 are preferably 5 18-gauge I-steel arched steel frames.

[0026] The steel pipe 32 includes φ159 guide pipes 33 evenly spaced along the arched surface of the arched steel frame 31 and φ108 pipe support pipes 34 arranged inside the guide pipes 33. The circumferential spacing between two adjacent guide pipes 33 along the arched surface of the arched steel frame 31 is at least 0.4m.

[0027] The front end of the guide tube 33 is welded to an arched steel frame 31, and the rear end of the guide tube 33 is raised by 7-9 cm and welded to another arched steel frame 31. The raising process is used to prevent the drill rod from sinking during the drilling operation before the guide tube 33 is set, causing the drill hole to invade other parts. In order to ensure the stability of the connection, the guide tube 33 and the arched steel frame 31 are fixed and welded by φ16 fixing steel bars 35, and the fixing steel bars 35 and the arched steel frame 31 are double-sided welded and fully welded.

[0028] The pipe 34 is preferably a φ108×6mm hot-rolled seamless steel pipe. For ease of installation, the pipe head 38 at the front end of the pipe 34 is made into an arrow-shaped or bamboo-shaped shape. In addition, a φ10 stiffening hoop 39 is provided on the pipe 34, and the stiffening hoop 39 is at least 10 cm away from the tail end of the pipe 34.

[0029] The pipe support pipes 34 include odd-numbered pipes and even-numbered pipes. The odd-numbered pipes are perforated pipes 36 for grouting operations. The stability of the support can be enhanced through grouting. The even-numbered pipes are non-perforated pipes for providing more direct physical support. The alternating arrangement of perforated pipes 36 and non-perforated pipes can achieve better mechanical distribution.

[0030] A plurality of φ10 grouting holes 37 are staggeredly arranged in a plum blossom shape on the perforated pipe 36 , and the spacing between two grouting holes 37 is 30 cm. No grouting hole 37 is arranged within at least 4 m from the tail end of the perforated pipe 36 .

[0031] The pipe-roof pipe 34 is composed of several pipe sections connected in sequence. Each pipe section of the perforated pipe 36 is 6m, the first section of the non-perforated pipe is 3m, and the remaining pipe sections are 6m. By adjusting the number of pipe sections and the length of the pipe sections, the overall length of the pipe-roof pipe 34 can be easily controlled. The connection node between one pipe section and another pipe section forms a joint. In order to avoid too many joints concentrated in the same position and reduce the risk of damage to the integrity of the structure, the number of joints in any section in the longitudinal direction of the tunnel is not more than 50%, and the joints of two adjacent pipe-roof pipes 34 are staggered by at least 1m in the longitudinal direction of the tunnel, which can effectively prevent local stress concentration and improve the overall bearing capacity and stability of the super-long pipe-roof layer 3.

[0032] In some embodiments, the cast-in-place concrete layer 4 is preferably cast using C30 concrete.

[0033] In some embodiments, the support structure further includes back slope protection, which includes a plurality of small conduits 51 and a hanging net 52 connected to the plurality of small conduits 51. The small conduits 51 are preferably φ42×4 grouting small conduits, and the hanging net 52 is preferably an E6 steel mesh.

[0034] In some embodiments, the support structure further includes an initial support layer 6 and a secondary lining layer 7, which are arranged from the inside to the outside and are located below the tunnel excavation line 9. The initial support layer 6 is preferably a sprayed anchor initial support layer, and the secondary lining layer 7 is preferably a reinforced concrete secondary lining layer.

[0035] In some embodiments, the support structure further includes an open hole lining layer 8 located in the open cut section. Since the open cut section lacks rock mass, initial support cannot be performed, and the open hole lining layer 8 includes a reinforced concrete open hole lining layer for connecting the secondary lining layer 7.

[0036] The present invention also provides a construction method for a supporting structure for a tunnel with complex and unfavorable geological conditions, which is used to construct the supporting structure for a tunnel with complex and unfavorable geological conditions as described above, and comprises the following steps: Back slope protection: Drill several holes on the back slope, use high-pressure air to remove rock debris in the holes, insert small tubes 51 into the holes, fill mortar into the small tubes 51, and finally connect several small tubes 51 to the hanging net 52; Invert foundation treatment: when the fully weathered covering layer is greater than 1m, the first steel pipe piles 13 are staggered in a plum blossom shape and grouting treatment is performed on them to form a steel pipe pile grouting part, and a concrete cap 11 is arranged on the steel pipe pile grouting part, and the top of the first steel pipe pile 13 extends into the cap by at least 40cm; when the fully weathered covering layer is less than 1m, replacement concrete is used for treatment to form a concrete replacement layer; Arch protection foundation treatment: excavate the arch protection foundation 2, after the excavation is completed, arrange the second steel pipe piles in a staggered manner in a plum blossom shape and perform grouting treatment on them, after the grouting treatment is completed, pour concrete to form the arch protection foundation 2; Arch protection construction: The arch protection is constructed on the arch protection foundation 2. First, an arch steel frame 31 is set above the tunnel excavation line 9, and then a number of guide pipes 33 are evenly spaced along the arch surface of the arch steel frame 31. The length direction of the guide pipe 33 extends along the longitudinal direction of the tunnel. Then, holes are drilled in the guide pipes 33 and pipe shed pipes 34 are installed in the holes to form an extra-long pipe shed layer 3. After the two extra-long pipe shed layers 3 are installed, concrete is poured between them to form a cast-in-place concrete layer 4.

[0037] Initial support and secondary lining: After the guard arch is established, a mesh is hung below the tunnel excavation line 9 to spray concrete to form an initial support layer 6; after waterproofing, concrete is poured to form a secondary lining layer 7; to connect the secondary lining layer 7, an open hole lining layer 8 is set in the open excavation section.

[0038] Furthermore, the arch protection construction also includes the following steps: When drilling holes in the guide tube 33 and installing the pipe-supporting pipe 34 in the holes, first drill the odd-numbered holes and install the perforated pipe 36, inject cement slurry into the perforated pipe 36, then drill the even-numbered holes and install the non-perforated pipe. The intervals between the drilling holes help to ensure the quality of the holes and prevent the completed holes from collapsing due to drilling into adjacent holes. When the diameter of the guide tube 33 is set to 159 mm, the diameters of the odd-numbered holes and the even-numbered holes are not less than 128 mm to facilitate the installation of the pipe-supporting pipe 34.

[0039] Furthermore, injecting cement slurry into the perforated pipe 36 comprises the following steps: Insert the grouting pipe into the grouting hole 37 until it is 20 cm from the bottom of the hole, connect all pipelines including the grouting pipe, and after the connection is completed, use the anchoring agent to seal the gap around the grouting hole 37 to prevent leakage. Close the orifice valve of the grouting hole 37, turn on the grouting pump, and conduct formal grouting after the pipeline water pressure test is correct. After the formal grouting reaches the design pressure, stabilize the pressure for 15 minutes. If the pressure remains unchanged, the grouting can be stopped. Otherwise, the grouting needs to be continued until the pressure stabilizes. In the above process, the grouting water-cement ratio is 0.8:1, and the pressure conditions are initial pressure 0.5-1.0MPa and final pressure 2.0Mpa.

[0040] The contents described above may be implemented individually or in combination in various ways, and these variations are all within the protection scope of the present invention.

[0041] In the description of the invention, it should be noted that relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements.

[0042] In the description of the invention, it is also necessary to explain that the terms "center", "upper", "lower", "front", "back", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the invention. In the description of the invention, unless otherwise specified, "several" means two or more.

[0043] The above contents are further detailed descriptions of the present invention in combination with specific preferred implementation modes, and it cannot be determined that the specific embodiments of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A support structure for tunnels with complex and adverse geological conditions, characterized in that: It comprises a protective arch foundation (2) arranged at the bottom of the two side walls of the tunnel and a protective arch arranged on the protective arch foundation (2) and located above the tunnel entry excavation line (9); the protective arch comprises two extra-long pipe shed layers (3) and a cast-in-place concrete layer (4) arranged between the two extra-long pipe shed layers (3).

2. The support structure for tunnels with complex and adverse geological conditions according to claim 1 is characterized in that: The super-long pipe shed layer (3) comprises a plurality of arched steel frames (31) arranged in sequence along the length direction of the tunnel and a plurality of steel pipes (32) arranged at even intervals along the arched surfaces of the arched steel frames (31), wherein the length direction of the steel pipes (32) extends along the longitudinal direction of the tunnel.

3. The support structure for tunnels in complex and adverse geological conditions according to claim 1 is characterized in that: The steel pipe (32) comprises guide pipes (33) arranged at even intervals along the arched surface of the arched steel frame (31) and a pipe support pipe (34) arranged inside the guide pipe (33).

4. The construction method of the support structure for tunnels with complex and adverse geological conditions according to claim 3 is characterized in that: The front end of the guide tube (33) is welded to one of the arched steel frames (31), and the rear end of the guide tube (33) is raised by 7-9 cm and welded to the other of the arched steel frames (31).

5. The support structure for tunnels in complex and adverse geological conditions according to claim 3 is characterized in that: The pipe rack pipes (34) include odd-numbered pipes and even-numbered pipes, the odd-numbered pipes are perforated pipes (36), and the even-numbered pipes are non-perforated pipes.

6. The supporting structure for tunnels in complex and adverse geological conditions according to claim 3 is characterized in that: The pipe-roof pipe (34) is composed of a plurality of pipe segments connected in sequence, wherein a connection node between one pipe segment and another pipe segment forms a joint, the number of the joints located in any section in the longitudinal direction of the tunnel is not greater than 50%, and the joints of two adjacent pipe-roof pipes (34) are staggered by at least 1 m in the longitudinal direction of the tunnel.

7. The support structure for tunnels in complex and adverse geological conditions according to claim 1 is characterized in that: It also includes back slope protection, which includes a plurality of small ducts (51) and a hanging net (52) connected to the plurality of small ducts (51).

8. The supporting structure for tunnels in complex and adverse geological conditions according to claim 1 is characterized in that: It also includes an initial support layer (6) and a secondary lining layer (7) which are arranged in sequence from the inside to the outside and are located below the tunnel excavation line (9).

9. A construction method for a support structure of a tunnel with complex and adverse geological conditions, characterized in that: The method for constructing a supporting structure for a tunnel in complex and adverse geological conditions as claimed in any one of claims 1 to 8 comprises the following steps: Back slope protection: drilling a plurality of openings on the back slope, inserting a small conduit (51) into the openings, then filling the small conduit (51) with mortar, and finally connecting the plurality of small conduits (51) to the hanging net (52); Treatment of the arch protection foundation: excavating the arch protection foundation (2), after the excavation is completed, staggeredly arranging steel pipe (32) piles in a plum blossom shape and grouting them, after the grouting is completed, pouring concrete to form the arch protection foundation (2); Arch protection construction: The arch protection is constructed on the arch protection foundation (2). First, an arch steel frame (31) is arranged above the tunnel excavation line (9). Then, a plurality of guide pipes (33) are evenly arranged along the arch surface of the arch steel frame (31). The length direction of the guide pipe (33) extends along the longitudinal direction of the tunnel. Then, holes are drilled in the guide pipes (33) and pipe shed pipes (34) are installed in the holes to form an extra-long pipe shed layer (3). After two extra-long pipe shed layers (3) are installed, concrete is poured between them to form a cast-in-place concrete layer (4). Initial support and secondary lining: After the arch is built, a mesh is hung below the tunnel excavation line (9) to spray concrete to form an initial support layer (6); after waterproofing, concrete is poured to form a secondary lining layer (7).

10. The construction method of the support structure for tunnels with complex and adverse geological conditions according to claim 9 is characterized in that: The arch protection construction also includes the following steps: When drilling holes in the guide tube (33) and installing the pipe support tube (34) in the holes, firstly drill odd-numbered holes and install the perforated tube (36), inject cement slurry into the perforated tube (36), then drill even-numbered holes and install the non-perforated tube.

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