An Excavation Method Applicable to Two Steps of a Tunnel with Soft Surrounding Rock and Rapidly Closing and Forming a Ring at One Time

Abstract

The invention discloses a two-step one-time rapid closing and ring-forming excavation method suitable for a tunnel in soft and weak surrounding rock. The two-step tunnel comprises an upper step, a lower step and an inverted arch. The excavation method comprises the following steps that an advance geological prediction on the surrounding rock in front of a working face of the tunnel is carried out,and a geological prediction result is obtained; based on the geological prediction result, pre-grouting reinforcement is carried out on the surrounding rock in front of the working face; the workingface is excavated along an excavation contour line of the tunnel according to excavation circulating footage of the upper step, at the same time of excavating, concrete closed for the working face andinitial support for the upper step are carried out until the upper step with predetermined length is formed; a trestle is laid, and the junction of the tail end of the upper step and the trestle areexcavated to a slope for setting up the trestle; the lower step and a concave pit of the inverted arch are excavated according to excavation circulating footage of the lower step, at the same time, initial support for the lower step is carried out until the initial support of the upper step and the initial support of the lower step are closed into a ring; and the method is executed circularly until the excavation of the two-step tunnel is completed.

Description

technical field [0001] The invention relates to the technical field of tunnel construction, in particular to an excavation method suitable for one-time rapid sealing and ring formation of two steps of tunnels with weak surrounding rocks. Background technique [0002] With the continuous improvement of national strength, the country's infrastructure construction is constantly increasing. Due to the complex and diverse address conditions in our country, it is necessary to build bridges and roads under various road conditions, especially in the south. Due to the terrain, there are various mountain or hilly landforms. Tunneling is required. [0003] In the technical field of tunnel construction, a variety of mature tunnel construction methods have emerged, such as arch first and then wall method, funnel scaffolding method, step method, full section method, upper and lower pilot pit first wall and then arch method, mushroom method, Side wall pilot pit first wall then arch metho...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the technical problems of narrow working space, low construction efficiency and low construction safety in the tunnel excavation method in the prior art, the present invention provides an excavation method suitable for one-time rapid closure of two steps of tunnels with weak surrounding rocks to form a ring. By adopting two-step construction and the construction method of excavating and supporting the lower steps and the inverted arch together, the working space is increased and the working safety is improved

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