Construction method of underground excavation for large-span subway station in hard rock formation

Abstract

The underground excavation construction method of large-span subway stations in hard rock formations can effectively reduce the risk of excavation construction and improve the efficiency of excavation construction. The method comprises the following steps: excavating the middle of the arch of the station by two steps, first excavating the upper step in the middle of the arch of the tunnel, and applying the initial support arch cover; excavating the lower step in the middle of the arch of the tunnel; excavating the upper step of the tunnel arch On the left side of the tunnel arch and on the right side of the tunnel arch, lock-foot anchors are installed at the arch foot, and the initial support arch cover of the long vault is connected to complete the construction of the initial support arch cover; The rock mass at the lower part of the station is divided into three parts: left, middle and right, and three steps of upper, middle and lower. A total of 9 parts are excavated, and the corresponding section of the side wall is initially supported until the end of the excavation; The main structure of the station has been completed.

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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