Large-span subway station underground excavation construction method for hard rock stratum

Abstract

Disclosed is a large-span subway station underground excavation construction method for a hard rock stratum. The large-span subway station underground excavation construction method for the hard rock stratum is used for effectively reducing the excavation construction risk and improving the excavation construction efficiency. The large-span subway station underground excavation construction method for the hard rock stratum comprises the following steps that the arch portion middle of a station is divided into two steps to be excavated, a tunnel arch portion middle upper step is excavated, and an initial support arch cover of the tunnel arch portion middle is constructed; a tunnel arch portion middle lower step is excavated; a tunnel arch portion left side portion and a tunnel arch portion right side portion are excavated, feet-lock bolts are constructed at the arch foot positions, the initial support arch cover on the arch top is lengthened through connection, and construction of the initial support arch cover is accomplished; a rock mass arranged below the station is excavated in a slot broaching mode under the protection action of the initial support arch cover, nine portions including upper steps on the left portion, the middle portion and the right portion, middle steps on the left portion, the middle portion and the right portion and lower steps on the left portion, the middle portion and the right portion are excavated, and side wall initial supports of corresponding sections are constructed until the rock mass is excavated to the bottom; and a station body structure is sequentially constructed from bottom to top, and station construction is accomplished.

Description

technical field [0001] The invention relates to tunnel engineering, in particular to a construction method for underground excavation of large-span subway stations suitable for hard rock formations. Background technique [0002] In order to avoid problems such as massive pipeline relocation, greening relocation, and traffic congestion caused by conventional open-cut or cover-excavation construction, Chongqing, Dalian, Xiamen, Qingdao and other urban areas with shallow bedrock burial depth have appropriately lowered the rail surface elevation to make some The main structure of the subway station is basically located in the hard rock stratum, and then the underground excavation method was chosen for construction. [0003] Traditionally commonly used underground excavation methods for large-section tunnels include the sub-step method, the three-step seven-step excavation method, the double-side-wall pilot pit method, the hole pile (column) method, and the two-lined arch-cover m...

AI Technical Summary

Problems solved by technology

Among them, the double-side wall pilot pit method and the hole pile method (PBA method) are suitable for weak surrounding rock formations; there are the following disadvantages in the use of hard rock: First, blasting and excavation impact damage to completed temporary supports or completed columns , arch, and permanent structure of the middle plate, the cost will be high if the weak explosion is used; second, the construction period is long, the risk is high, and the abandoned project is large

The sub-step method is suitable for tunnels with deep burial and good surrounding rock conditions. The three-step seven-step excavation method is suitable for tunnels with general surrounding rock conditions and low requirements for settlement control. The two methods are generally suitable for mountain tunnels; There are hidden dangers in the use of underground excavation stations in urban subways, such as difficult control of ground subsidence, affecting pipelines under the road and traffic safety on the road surface, etc.

The two-lining arch cover method is suitable for large-section excavation stations with upper soft and lower hard surrounding rocks, but it has the following disadvantages: when the temporary support is removed, the settlement of the vault is large, the settlement control is difficult, and the risk is high; the second is the position of the interface between the arch foot and the top of the wall The integrity of the waterproof layer and structure is not good, and the quality of the project is affected; the third is that the blasting construction of the lower part of the tunnel may cause impact damage to the completed vault second lining structure

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