Primary support structure suitable for high-ground-stress high-temperature tunnel and construction method

Abstract

The invention belongs to the field of high-crustal-stress geological construction, and particularly relates to a primary supporting structure suitable for a high-crustal-stress high-temperature tunnel and a construction method.The position, close to surrounding rock, in the primary supporting structure is a layer of high-performance concrete, the outer layer of the high-performance concrete is high-porosity foam concrete, and the outer layer of the high-performance concrete is high-porosity foam concrete; the outer layer of the high-porosity foam concrete is an erected steel frame and a reinforcing mesh, the inner layer and the outer layer of the steel frame and the reinforcing mesh are re-sprayed high-performance concrete, and the re-outer layer of the high-performance concrete is low-heat-conductivity-coefficient foam concrete. The layered composite structure is provided, the inner layer is made of high-porosity foam concrete (an energy release layer), the outer layer is made of low-heat-conduction foam concrete (a heat insulation layer), a rigid-flexible coupling supporting system is formed by combining slidable joints of the steel frame, the initial supporting waterproof performance is improved, the energy release-yielding-heat insulation function is achieved, and meanwhile mechanical matched construction is adapted.

Description

Technical Field

[0001] The present invention belongs to the field of high geostress geological construction, and particularly relates to an initial support structure and construction method applicable to high geostress and high-temperature tunnels. Background Art

[0002] Under high geostress conditions, an appropriate yielding and energy-releasing space is required. The deformation of the traditional support system is very small, resulting in many on-site cracks, encroachments, and replacements. With large-scale mechanized support, the steel frames and steel bar meshes are erected synchronously. It is difficult to fill the concrete sprayed behind the steel frames and steel bar meshes densely, and voids are easily formed, leading to defects in the force transmission system of the initial support and further increasing the degree of support damage. The thickness of the concrete sprayed each time in the traditional construction is generally about 5 cm. During large-scale mechanized construction, the over-excavation amount is large, and the initial spraying cannot reach the position of the steel frame erection at one time. Spraying high-performance concrete for over-excavation backfill results in high construction costs. Most of the thermal insulation layer processes in high-temperature tunnels use thermal insulation boards, which are added between the initial support and the secondary lining, and the initial support structure is not thermally insulated. Summary of the Invention

[0003] The purpose of the present invention is to provide an initial support structure and construction method applicable to high geostress and high-temperature tunnels to solve the problems existing in the above background art.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] An initial support structure applicable to high geostress and high-temperature tunnels, with a layer of high-performance concrete near the surrounding rock. The outer layer of the high-performance concrete is high-porosity foam concrete. The outer layer of the high-porosity foam concrete is the erected steel frames and steel bar meshes. Inside and outside the steel frames and steel bar meshes is the re-sprayed high-performance concrete. The outermost layer of the high-performance concrete here is low-thermal-conductivity foam concrete.

[0006] Further, steel fibers are added to the high-performance concrete.

[0007] Further, microcapsule repair agents are added to the low-thermal-conductivity foam concrete.

[0008] Further, the high-performance concrete near the surrounding rock is 5 cm.

[0009] A construction method of an initial support structure applicable to high geostress and high-temperature tunnels. First, initially spray high-performance concrete, then erect the steel frames and steel bar meshes, and at the same time reserve the pumping pipes. Then re-spray high-performance concrete. After several cycles, pump high-porosity foam concrete through the pre-buried pumping pipes. Finally, before the secondary lining construction, spray low-thermal-conductivity foam concrete to the outer contour of the secondary lining.

[0010] Further, the pumping of high-porosity foamed concrete is carried out 24 hours after the spraying of high-performance concrete for the second time, when the strength of the high-performance concrete reaches more than 15 MPa. When pumping the high-porosity foamed concrete, the plum blossom shape or pumping from low to high in sequence is adopted, and the adjacent pumping pipes are used as exhaust pipes.

[0011] The beneficial technical effects of the present invention are as follows:

[0012] By using foamed concrete as the heat insulation - energy release - pressure yielding material, the present invention solves the problems of energy release and heat insulation in high in-situ stress and high-temperature tunnels. The original high-performance shotcrete is replaced with foamed concrete for over-excavation backfilling, reducing the project cost. On the one hand, a layered composite structure is proposed: high-porosity foamed concrete (energy release and energy absorption) is adopted on the side close to the surrounding rock, and low-thermal-conductivity foamed concrete (heat insulation) is adopted on the outer layer. Combining with the slidable joints of the steel frame forms a "rigid-flexible coupling" support system. Utilizing its dry shrinkage, large porosity, and low elastic modulus, energy release is realized, and impact loads are absorbed and dispersed to protect the primary support structure, achieving the synergistic effect of "gradient energy release - heat insulation"; on the other hand, self-healing materials are introduced: microcapsule repair agents are added to the foamed concrete, and repair substances are automatically released when cracks occur, improving the durability of the support structure. Finally, the low water permeability of the foamed concrete is utilized to further improve the waterproof performance of the primary support. At the same time, it is adapted to mechanized supporting construction. Description of the Drawings

[0013] Figure 1 It is a schematic cross-sectional structure diagram of the tunnel in the embodiment of the present invention;

[0014] Figure 2 is Figure 1 the large-scale drawing of the A-A section in

[0015] Reference numerals in the drawings: 1 - high-performance concrete, 2 - high-porosity foamed concrete, 3 - steel frame and steel mesh, 4 - low-thermal-conductivity foamed concrete, 5 - pumping pipe, 6 - microcapsule repair agent. Detailed Embodiments

[0016] The technical solutions provided by the present invention will be further described below by combining the drawings and embodiments.

[0017] Embodiment:

[0018] As Figure 1 and Figure 2 shown, an initial support structure is located between the surrounding rock and the secondary lining, and its structure is 5 cm of high-performance concrete 1 - high-porosity foamed concrete 2 (the thickness adapts to the over-excavation by itself) - steel frame and steel mesh 3 - high-performance concrete 1 - low-thermal-conductivity foamed concrete 4.

[0019] The construction method of the above initial support includes the following steps:

[0020] Initially spray 5cm high-performance concrete 1 to form a "shell"-like constraint on the surface to prevent key blocks and wedges from loosening and falling, destroying the overall surrounding rock force transmission system. Use early high-strength shotcrete and add steel fiber or other fiber materials to increase toughness.

[0021] Set up steel frame and steel mesh 3, reserve pumping pipe 5, spray high-performance concrete 1 again, flexibly arrange pre-buried pumping pipe 5 according to the location of over-excavation, blasting pit and falling blocks on site to ensure that the pumped foam concrete is thick and dense backfill.

[0022] After 24 hours, when the strength of the re-sprayed high-performance concrete 1 reaches above 15MPa, high-porosity foamed concrete 2 is pumped through the pre-buried pumping pipe 5. When pumping the foamed concrete, a plum blossom shape or pumping from low to high is adopted, and the adjacent pumping pipes 5 are used as exhaust pipes to achieve the compaction of pumping backfill. The strength of the foamed concrete adopts a higher grade to meet the energy consumption requirements.

[0023] Before the secondary lining construction, low thermal conductivity foam concrete 4 is sprayed to the outer contour of the secondary lining (replacing the original reserved deformation backfill concrete), and microcapsule repair agent 6 is added to the low thermal conductivity foam concrete 4.

[0024] High-performance shotcrete is C30 shotcrete with a strength of no less than 10Mpa in 8h and 15Mpa in 24h; high-porosity foam concrete: porosity 70%-90%, density 300-600kg / m 3 , compressive strength 1-4MPa; low thermal conductivity foam concrete: thermal conductivity ≤0.12W / (m·K), density 150-500kg / m 3 , porosity 60%-85%.

[0025] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An initial support structure suitable for high-stress and high-temperature tunnels, characterized in that: A layer of high-performance concrete (1) is provided near the surrounding rock. The outer layer of the high-performance concrete (1) is high-porosity foamed concrete (2). The outer layer of the high-porosity foamed concrete (2) is a steel frame and steel mesh (3). The inner and outer layers of the steel frame and steel mesh (3) are sprayed high-performance concrete (1). The outer layer of the high-performance concrete (1) is low-thermal conductivity foamed concrete (4).

2. The initial support structure suitable for high-stress and high-temperature tunnels according to claim 1 is characterized in that: Steel fibers are added to the high performance concrete (1).

3. The initial support structure suitable for high-stress and high-temperature tunnels according to claim 2 is characterized in that: A microcapsule repairing agent (6) is added to the low thermal conductivity foam concrete (4).

4. The initial support structure suitable for high-stress and high-temperature tunnels according to claim 3 is characterized in that: The thickness of high performance concrete (1) close to the surrounding rock is 5 cm.

5. A construction method for an initial support structure suitable for a high-in-situ stress and high-temperature tunnel according to any one of claims 1 to 4, characterized in that: First, high-performance concrete (1) is sprayed, then a steel frame and a steel mesh (2) are erected, and a pumping pipe (5) is reserved. Then, high-performance concrete (1) is sprayed again. After several cycles, high-porosity foam concrete (2) is pumped through the pre-buried pumping pipe (5). Finally, before the secondary lining construction, low-thermal conductivity foam concrete (4) is sprayed to the outer contour of the secondary lining.

6. The construction method of the initial support structure applicable to high-stress and high-temperature tunnels according to claim 5 is characterized in that: The high-porosity foamed concrete (2) is pumped 24 hours after the high-performance concrete (1) is sprayed, and when the strength of the high-performance concrete (1) reaches 15 MPa or above. When the high-porosity foamed concrete (2) is pumped, it is pumped in a plum blossom shape or from low to high, and the adjacent pumping pipes (5) serve as exhaust pipes.

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