Underground excavation construction method of large-span subway station in flexible-top and hard-bottom stratum

Abstract

The invention provides an underground excavation construction method of a large-span subway station in a flexible-top and hard-bottom stratum, and aims at effectively reducing the construction risk and increasing the excavation construction efficiency. The method comprises the steps of constructing an arch part by the left part and the right part; constructing a temporary partition wall in the middle of the arch part constructing a first initial support for the arch part; removing the temporary partition wall in the middle within a short circulation after excavating the arch part; constructing a second initial support; gradually thickening from the top to the bottom of the arch to form a structural form that large arch feet are formed at the end parts; connecting the first initial support and the second initial support through reinforcing steel bars to form overlapped initial support arch covers; excavating the rest rock by a pulling trough step method under the protection of the double-layer overlapped initial support arch covers until reaching the bottom part of the tunnel; sequentially constructing a two-lining structure and the inner structure of the station from bottom to top.

Description

technical field [0001] The invention relates to tunnel engineering, in particular to a construction method for underground excavation of a large-span subway station in upper soft and lower hard strata. Background technique [0002] In cities such as Chongqing, Dalian, Xiamen, and Qingdao, the bedrock is buried shallowly, and the construction of subway stations avoids the problems caused by conventional open cut or cover excavation construction, which cause a large number of problems such as pipeline relocation, greening relocation, and traffic congestion. Controlled by the depth of burial, the main structure of many subway stations is located in rock strata that are soft at the top and hard at the bottom, that is, the vaults are located in strongly weathered and moderately weathered rocks, and the arch feet are located in moderately or slightly weathered rocks. The structure is mostly in moderately and lightly weathered rock. [0003] The traditional underground excavation ...

AI Technical Summary

Problems solved by technology

Both the double-side-wall pilot-pit method and the hole pile (column) method are suitable for weak surrounding rock conditions. The use of the double-side-wall pilot-pit method in medium and slightly weathered rocks has the following disadvantages: First, the blasting excavation impact damage has been completed temporarily support and initial support; second, the construction period is long, the risk is high, and the abandoned project is large; the third is that the risk of removing the temporary support before the construction of the second lining is relatively high

The use of hole pile (column) method in medium and slightly weathered rocks has the following disadvantages: one is to use conventional blasting to excavate and impact and destroy the completed permanent structures such as columns, arches, and middle plates, and to use weak blasting, which will result in high costs and long construction periods; Second, the construction risk of artificial and blasting excavated piles is high; third, the quality of structure and waterproof construction is poor

The two-lined arch cover method has the following disadvantages: first, the settlement of the vault is large when the temporary support is removed, and the settlement control is difficult and the risk is high; second, the waterproof layer and structural integrity at the interface between the arch foot and the top of the wall are not good, and the project quality is affected ; The third is that the blasting construction of the lower part of the tunnel may cause impact damage to the completed second lining of the vault

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