Summer-time face excavation construction method for high and cold permafrost ultra-long highway tunnel

Abstract

The invention discloses a summer-time face excavation construction method for a high and cold permafrost ultra-long highway tunnel. The summer-time face excavation construction method comprises the steps of tunnel portal excavation and side slope and heading slope protection, shallow-buried tunnel portal permafrost follow-pipe shed construction, shallow-buried tunnel trunk section permafrost excavation and supporting and frozen-earth-section tunnel trunk lining. Before a frozen-earth-section tunnel portal is excavated, a heat-preservation blind drain and a water retaining drive part are arranged in the outside 5 m away from the top of a heading slope and 2 m away from the tops of side slopes in a 'front-cut rear-drive' mode. A positive benching tunneling method is adopted at a frozen-earth tunnel portal section to perform layered and sectioned excavation and supporting, a tunnel portal is pre-reinforced by adopting a large advancing pipe shed, a mining method is adopted at a hidden hole shallow-buried section for construction, a three-bench seven-step excavation method is adopted for excavation, C30 low-temperature early-strength steel fiber sprayed concrete and primary-formwork-lining C30 low-temperature early-strength concrete are adopted to form a double-layer preliminary-supporting structure, and C45 concrete is adopted for secondary formwork lining. By means of the summer-time face excavation construction method, the hole forming difficulty problem can be solved, construction cost can be reduced, a construction period can be shortened, and the like.

Description

technical field [0001] The invention relates to a construction method of a permafrost extra-long road tunnel in a plateau cold area. Background technique [0002] Tunnel openings in alpine regions generally develop permafrost with a large area and depth, and its temperature and thickness are controlled by altitude. According to the research and analysis of the observation and test data of the existing permafrost section of the G214 line: the upper limit buried depth of permafrost in this section is generally 1.4~1.8m, and the ground temperature is -0.3℃~-1.5℃, which has the characteristics of high permafrost temperature. , faster degradation rate, more sensitive to thermal disturbance, worse thermal stability of permafrost, and strong vertical zonality. When the permafrost is frozen, the compressive strength is very high and it is not easy to blast, and it is easy to freeze after drilling. When the external environment temperature rises, the permafrost will melt and become ...

AI Technical Summary

Problems solved by technology

[0005] The technical problem to be solved by the present invention is to provide a low-cost, simple construction, reasonable stress, safe and reliable construction method for tunneling in summer for extra-long highway tunnels in alpine permafrost, so as to overcome the difficulties of tunneling in the prior art, High construction cost etc.

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