Open cut tunnel in frozen earth area and construction method

Abstract

The invention discloses an open cut tunnel in a frozen earth area and a construction method, and belongs to the technical field of open cut tunnel engineering, the open cut tunnel comprises a tunnel and protection walls built on a foundation, the protection walls are located on the two sides of the tunnel, the protection walls on the two sides are connected through a tensioning structure and filled with a filling body, and the filling body is located at the top of an open cut tunnel. A pressure-resistant body is arranged on at least one side of the tunnel; the filling body guides falling rocks and accumulated snow, the falling rocks and the accumulated snow are prevented from being accumulated at the top of the tunnel, the pressure of the tunnel is reduced, the stress of the protection wall is greatly improved through the action of the tension anchor rods, meanwhile, the thickness of the protection wall can be reduced, the compression-resistant body can buffer the accumulated snow generated by the falling rocks and avalanche, lateral protection is provided for the tunnel, and the service life of the tunnel is prolonged. The stability of the tunnel and the protection wall is improved.

Description

Technical Field

[0001] The invention relates to the technical field of open-cut tunnel engineering, and in particular to an open-cut tunnel in a frozen soil area and a construction method thereof. Background Art

[0002] Due to their unique geographical environment and climatic conditions, permafrost areas are often threatened by natural disasters such as avalanches, rockfalls, and ground collapses. The protective measures for open-cut tunnels built in ground-breaking areas mainly include the installation of physical protection facilities such as protective nets, anti-slip piles, and protective walls, but these facilities are often difficult to adapt to the complex environment of permafrost areas.

[0003] For example, the protective net may be covered by snow, the anti-slip piles may fail due to ground frost heave, and the protective wall may crack due to temperature changes. In addition, the construction method of the protective facilities is also an important issue. Due to the special ground structure in the permafrost area, the traditional construction method will cause damage to the ground, which will in turn aggravate the occurrence of geological disasters. At the same time, because the ground in these areas is frozen all year round, the construction of the Myeongdong is difficult, the construction period is long and the cost is high.

[0004] Therefore, it is necessary to design a protective structure and construction method for the open-pit tunnel in the ground-breaking area to prevent avalanches, falling rocks and collapse from threatening the open-pit tunnel. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides an open hole tunnel and a construction method for a frozen soil area, so as to achieve effective protection of the open hole in the frozen soil area and improve the safety of the open hole in the permafrost area.

[0006] The present invention is achieved through the following technical solutions: In the first aspect, the present application provides an open hole tunnel in a frozen soil area, comprising a tunnel and protective walls built on a foundation, wherein the protective walls are located on both sides of the tunnel, and the protective walls on both sides are connected by a tensioned structure and filled with a compacted body, wherein the compacted body is located at the top of the open hole, and a pressure-resistant body is provided on at least one side of the tunnel.

[0007] Furthermore, a cushion layer and a thermal insulation layer are provided at the bottom of the foundation.

[0008] Furthermore, the cushion layer includes a gravel and crushed stone cushion layer, and then a foaming agent is injected into the cushion layer to fill the gaps in the cushion layer to form a thermal insulation layer.

[0009] Furthermore, multiple layers of tension structures are arranged between the protection walls, and multiple tension structures in each layer are arranged at intervals along the direction of the tunnel. Both ends of the tension structure are respectively buried in the protection walls on both sides, and the tension structure is buried in the fill.

[0010] Furthermore, the tension structure is a tension anchor rod.

[0011] Furthermore, the lightweight aggregate concrete.

[0012] Furthermore, the top surface of the built-up body is a slope, and is consistent with the slope of the mountain.

[0013] Furthermore, a drainage network is arranged between the protection wall and the tunnel, the lower end of the drainage network is connected to the tunnel drainage ditch, and the upper end is located on the mountain surface.

[0014] Furthermore, the side wall and the protective wall of the tunnel are connected by embedded steel bars.

[0015] In a second aspect, the present application provides a method for constructing an open-cut tunnel in a frozen soil area, comprising the following steps: Step 1: Carry out foundation construction in the bedrock area, and wait for the concrete to solidify and meet the bearing requirements to form the foundation; Step 2: Set the steel structure of the tunnel body on the foundation, and set embedded steel bars extending to both sides in the side wall area of ​​the tunnel, and then cast the tunnel body; Step 3: Construct protective walls on both sides of the tunnel by using an integrated concrete pouring method, and bury the extended pre-buried steel bars in the protective walls and fix them; Step 4: Build a pressure-resistant body on the side of the tunnel away from the mountain.

[0016] Step 5: Set up a tension structure between two protection walls; Step 6: Fill the landfill between the protective walls. The landfill is located at the top of the tunnel. The top of the landfill is trimmed into a slope.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: The present application provides an open-cut tunnel in a frozen soil area. The tunnel is made on-site by integrally pouring reinforced concrete to increase the overall rigidity of the structure, improve the bearing capacity, and make it more adaptable to changes in the frozen soil environment. Protective walls are set on both sides of the tunnel and connected by a tensioning structure to protect the main structure from damage and ensure the reliability of the connection. The top of the tunnel is filled with lightweight aggregate concrete. The lightweight aggregate concrete is light in weight, which reduces the overall weight of the open-cut structure and avoids excessive pressure causing the frozen soil layer to melt or settle. The bottom of the foundation is provided with an insulation layer and a cushion layer. The insulation layer reduces the transfer of external heat to the frozen soil layer. The foundation uses a gravel and crushed stone cushion layer to absorb the frost heave pressure. An anti-avalanche retaining wall is set on the outside of the side wall of the structure to change the direction of avalanche movement and reduce the stress on the structure.

[0018] Furthermore, the drainage network is connected to the drainage ditch of the mountain to drain the snowmelt and rainwater to prevent the water pressure from affecting the stability of the structure. The accumulated water is quickly drained to prevent the water from entering the frozen soil layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is a schematic diagram of an open-cut tunnel in a frozen soil area according to the present invention.

[0021] In the figure: open hole 1, foundation 2, protection wall 3, drainage pipe 4, tension anchor rod 5, filling body 6, compression body 7. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0025] Open-cut tunnel refers to a tunnel structure built by open-cut method, which is used in sections with poor geology or shallow buried tunnel projects. Open-cut tunnel has the dual characteristics of ground and underground buildings. It can be used as a ground building to resist the collapse, rockfall, landslide, mud-rock flow and other diseases of the slope and back slope, and it can also be used as an underground building to replace tunnels when deep road cuttings and shallow buried sections are not suitable for dark tunnels.

[0026] Reference Figure 1 A permafrost area open hole tunnel comprises a tunnel built on a foundation 2, with protective walls 3 arranged on both sides of the tunnel, the protective walls on both sides are connected by a tensioning structure and filled with a compacted body 6, the compacted body 6 is located at the top of the open hole, and a compression-resistant body 7 is arranged on at least one side of the tunnel.

[0027] The backfill 6 is arranged on the top of the open hole structure 1 to reduce the impact damage of rocks falling directly from the top of the mountain on the open hole structure 1. The backfill material provides favorable reaction force support for the protection wall 3 to avoid damage to the protection wall 3 and reduce the stress on the top of the tunnel 1. The rocks falling on both sides of the top of the open hole structure 1 will be guided away from the open hole structure 1 by the backfill 6 to avoid accumulation on the top of the tunnel, reducing the pressure of the tunnel. The stress on the protection wall 3 is greatly improved through the action of the tension anchor 5, and the thickness of the protection wall 3 can also be reduced. The compression body 7 can buffer the snow generated by falling rocks and avalanches, and provide lateral protection for the tunnel, improving the stability of the tunnel and the protection wall.

[0028] In some embodiments, a cushion layer and an insulation layer are arranged at the bottom of the foundation. The insulation layer reduces the transfer of external heat to the permafrost layer, keeps the temperature of the permafrost layer constant, ensures the stability of the permafrost layer, and further improves the stability of the entire open tunnel.

[0029] The insulation layer is an insulation board or insulation foam; the cushion layer is a gravel and crushed stone cushion layer, which absorbs frost heave pressure. The foundation 2 is cast in one concrete and a steel mesh is buried inside; the foundation is cast on the cushion layer.

[0030] When the insulation layer uses insulation boards, the insulation boards are laid on the ground, and crushed stone cushion layers and gravel are laid on the top of the insulation boards in sequence, and finally the foundation is poured integrally on the top of the cushion layer.

[0031] When the insulation layer is a foaming agent, the gravel and crushed stone cushion layer is first laid during the construction process, and then the foaming agent is injected into the cushion layer to fill the gaps in the cushion layer, which can not only enhance the strength but also form a seamless insulation layer.

[0032] In some embodiments, the protective walls on both sides of the tunnel are cast concrete walls, the height of the protective walls is higher than a certain height of the tunnel vault, the tension structure is arranged at the top of the tunnel, and the two ends of the tension structure are respectively buried in the protective walls on both sides. Multiple tension structures are arranged at intervals along the direction of the tunnel, and can also be arranged in layers from top to bottom. Multiple tension structures in each layer are arranged at intervals along the direction of the tunnel, and backfill materials are filled between the two protective walls 3.

[0033] The heights of the two protection walls are different. The height of the protection wall on the side away from the mountain is lower than that of the protection wall on the side close to the mountain, so that the top of the filling body 6 forms a natural slope, which can guide fallen rocks and snow, avoid accumulation on the top of the tunnel, and reduce the pressure of the tunnel.

[0034] The tension structure is a tension anchor rod 5, and the spacing between the tension anchor rods is 5m.

[0035] Tension anchors are anchors that transfer and disperse loads through tension. Both ends of the anchors are connected to the protective wall. They use their own strength and rigidity to form a mechanical connection with the protective wall, thereby jointly bearing the load. The working principle of the tension anchor is mainly based on tension transmission and friction resistance. When the anchor is subjected to external loads, it transfers the tension to the protective wall through the friction or adhesion formed on the contact surface with the soil, so that the protective wall bears part of the load, thereby reducing the deformation and displacement of the tunnel. At the same time, the friction resistance between the anchor and the protective wall also increases the anti-slip property of the backfill material, preventing the backfill material from sliding under the action of external forces.

[0036] Tension anchor rods are generally composed of three basic parts: anchor head, rod body (tension rod) and anchor body (segment). The anchor head is the connecting part between the protection wall and the tension rod, the rod body is responsible for transmitting the tension, and the anchor body is closely connected to the protection wall to transmit the tension to the stable protection wall. Tension anchor rods include tension anchor rods, pressure anchor rods, etc. Tension anchor rods are preferred because they have better tensile properties.

[0037] The filling body 6 is made of lightweight aggregate concrete, which is also called lightweight aggregate concrete or lightweight aggregate concrete. It is a building material made of light coarse aggregate, light fine aggregate (or ordinary sand), cementitious materials, admixtures and water. Compared with conventional concrete, lightweight aggregate concrete has a lighter weight and can reduce the pressure on the tunnel. The filling body 6 forms a slope to guide fallen rocks and snow to avoid accumulation on the top of the tunnel.

[0038] In some embodiments, a drainage network 4 is provided on the side of the side wall away from the tunnel, the drainage network 4 is connected to the tunnel drainage ditch, and the upper end of the drainage network 4 is located on the surface of the mountain. Figure 1 In this embodiment, a drainage network 4 is set between the outside of the protective wall on the side of the tunnel close to the mountain and the mountain to divert the water flow on the tunnel surface to prevent rainwater from penetrating into the soil and freeze the soil in the tunnel area.

[0039] The open-cut tunnel provided by this application can avoid the impact of debris flow and avalanche and ensure the safety of highway traffic. There is no snow accumulation inside the open-cut structure, which avoids snow pressure and effectively prevents collapse. Prestressed concrete protection walls are set on both sides of the open-cut structure and equipped with tension anchor rods to effectively disperse and resist external impacts, protect the main structure from damage, and improve the structure's compression and shear resistance. The open-cut structure is constructed in sections, with each section being 300-500 meters long, which is convenient for construction machinery to enter and exit. The section construction operation area is small and has little impact on the stability of the roadbed. The compression-resistant body cast with lightweight aggregate concrete and open-cut slag reduces the impact on the environment and improves the durability of the structure. The support method combined with anchor rods and anchor rods can effectively restrain the surrounding rock and prevent the surrounding rock from loosening and collapsing.

[0040] Based on the above-mentioned Mingdong tunnel, the present application also provides a construction method of the Mingdong tunnel, including the following steps: Step 1: Remove loose soil and rocks at the corresponding position at the bottom of the open hole structure until the bedrock surface becomes stable; Step 2: Carry out foundation construction in the bedrock area. The foundation construction includes piling and pouring concrete. When the concrete solidifies and meets the bearing requirements, foundation 2 is formed.

[0041] The load requirement is 85% of the design strength.

[0042] Step 3: Set up the steel structure of the tunnel body on the foundation, and set up embedded steel bars extending to both sides in the side wall area of ​​the tunnel, and then cast the tunnel body.

[0043] Step 4: After the main body of the tunnel solidifies, a protective wall 3 is constructed on both sides of the tunnel. The protective wall is constructed by an integrated concrete pouring method, and the protruding embedded steel bars are embedded in the protective wall and fixedly connected.

[0044] Step 5: Arrange a drainage network 4 between the tunnel and the protection wall, wherein the lower end of the drainage network 4 is connected to the tunnel drainage ditch, and the upper end of the drainage network 4 extends to the surface of the mountain.

[0045] Step 6: Build a pressure-resistant body 7 on the side of the tunnel away from the mountain.

[0046] The tunnel waste and concrete pouring method are adopted to form a compression-resistant body 7 on the outside of the protective wall, forming lateral support for the tunnel to improve the stability of the tunnel.

[0047] Step 7: Set a tension anchor rod between the two protection walls and tighten and fix them by light pulling; Multiple layers of tension anchors are set up, with multiple tension anchors set up in each layer, and the spacing between adjacent tension anchors is 5m.

[0048] Step 8: Fill the lightweight aggregate concrete between the protection walls in layers. The lightweight aggregate concrete is located at the top of the tunnel. The top of the lightweight aggregate concrete is trimmed into a slope according to the height of the two protection walls.

[0049] Step 9: After the construction is completed, clean up the construction site and carry out commissioning and operation maintenance of the power generation equipment.

[0050] The open-cut tunnel constructed by this construction method is made on-site by integrally pouring reinforced concrete to increase the overall rigidity of the structure, improve the bearing capacity, and make it more adaptable to changes in the frozen soil environment. The thickness of the top plate and the walls on both sides of the open-cut tunnel structure meets the requirements of earthquake fortification in permafrost areas. The connection between the wall and the top plate adopts reinforced piling to effectively disperse and resist external impact, protect the main structure from damage, and ensure the reliability of the connection. A drainage system is set at the bottom of the open-cut tunnel structure to discharge snowmelt and rainwater to avoid water pressure affecting the stability of the structure. An anti-avalanche retaining wall is set on the outside of the side wall of the structure to change the direction of avalanche movement and reduce the stress on the structure. The construction method of excavating the frozen soil layer and artificial backfilling is adopted to avoid large-scale damage to the frozen soil layer and reduce the damage to the stability of the frozen soil layer. The construction is simple and reliable, no large-scale excavation equipment is required, the impact on the environment is small, and the traffic is not affected during construction. The proposed construction method is simple, the project cost is low, and the economic benefit is good.

[0051] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An open-cut tunnel in a frozen soil area, characterized in that: It includes a tunnel and protective walls built on a foundation. The protective walls are located on both sides of the tunnel. The protective walls on both sides are connected by a tensioning structure and filled with a compacted body. The compacted body is located on the top of the open hole. A compression-resistant body is provided on at least one side of the tunnel.

2. The open-cut tunnel in a frozen soil area according to claim 1, characterized in that: A cushion layer and a heat-insulating layer are arranged at the bottom of the foundation.

3. The open-cut tunnel in a frozen soil area according to claim 2, characterized in that: The cushion layer includes a gravel and crushed stone cushion layer, and then a foaming agent is injected into the cushion layer to fill the gaps in the cushion layer to form a heat-insulating layer.

4. The open-cut tunnel in a frozen soil area according to claim 1, characterized in that: Multiple layers of tension structures are arranged between the protection walls, and multiple tension structures of each layer are arranged at intervals along the direction of the tunnel. Both ends of the tension structure are respectively buried in the protection walls on both sides, and the tension structure is buried in the fill.

5. The open-cut tunnel in a frozen soil area according to claim 4, characterized in that: The tension structure is a tension anchor rod.

6. The open-cut tunnel in a frozen soil area according to claim 1, characterized in that: The lightweight aggregate concrete.

7. The open-cut tunnel in a frozen soil area according to claim 1, characterized in that: The top surface of the built-up body is a slope, which is consistent with the slope of the mountain.

8. The open-cut tunnel in a frozen soil area according to claim 1, characterized in that: A drainage network is arranged between the protection wall and the tunnel, the lower end of the drainage network is connected with the tunnel drainage ditch, and the upper end is located on the surface of the mountain.

9. The open-cut tunnel in a frozen soil area according to claim 1, characterized in that: The side wall and the protection wall of the tunnel are connected by embedded steel bars.

10. A construction method for an open-cut tunnel in a frozen soil area according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Carry out foundation construction in the bedrock area, and wait for the concrete to solidify and meet the bearing requirements to form the foundation; Step 2: Set the steel structure of the tunnel body on the foundation, and set embedded steel bars extending to both sides in the side wall area of ​​the tunnel, and then cast the tunnel body; Step 3: Construct protective walls on both sides of the tunnel by using an integrated concrete pouring method, and bury the extended pre-buried steel bars in the protective walls and fix them; Step 4: Build a pressure-resistant structure on the side of the tunnel away from the mountain; Step 5: Set up a tension structure between two protection walls; Step 6: Fill the landfill between the protective walls. The landfill is located at the top of the tunnel. The top of the landfill is trimmed into a slope.

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