A construction method for synchronous excavation of lower steps and inverted arches in large-section soft rock tunnels

Abstract

The invention provides a construction method for synchronous excavation of a lower step and an inverted arch of a large-section soft rock tunnel. Synchronous excavation of the lower step and the inverted arch is achieved through nine procedures, construction procedures of a traditional three-step method are simplified, the interference problem caused when the lower step and the inverted arch are synchronously excavated is effectively avoided, a primary support concrete structure of the large-section soft rock tunnel forms a quick closed loop, the stress state of the primary support concrete structure becomes reasonable easily as soon as possible, construction deformation of the large-section soft rock tunnel is effectively controlled, and construction safety of excavation of the large-section soft rock tunnel is guaranteed. Meanwhile, the nine procedures are reasonably linked, the interference problem existing in excavation of the inverted arch and a tunnel face is reduced, accordingly construction efficiency is effectively improved, and excavation construction process of the large-section soft rock tunnel is improved as a whole.

Description

【Technical field】 [0001] The invention belongs to the technical field of tunnel excavation, and in particular relates to a construction method for synchronously excavating lower steps and inverted arches of large-section soft rock tunnels. 【Background technique】 [0002] The three-step excavation method is one of the most common construction methods in tunnel engineering construction at present. It is generally applicable to the construction of weak surrounding rock sections of large-section tunnels with grades IV to V, and auxiliary advance support measures are determined depending on the surrounding rock conditions on site. . [0003] The so-called inverted arch refers to the inverted arch structure set at the bottom of the tunnel in order to improve the stress conditions of the upper support structure of the tunnel. combined with Figure 1-2 , in the construction scheme of the three-step excavation method, the excavation and initial support of the tunnel inversion genera...

AI Technical Summary

Problems solved by technology

combined with Figure 1-2 , in the construction scheme of the three-step excavation method, the excavation and initial support of the tunnel inversion generally exist as independent processes, which are not synchronized with the step excavation construction process. Considering the space of the ballast feed channel during the step excavation construction Inverted arch excavation construction and bench excavation construction will inevitably interfere with each other, which will adversely affect the connection of processes and the control of cycle time

[0004] In addition, because the excavation support of the inverted arch lags behind the lower steps, the initial support structure cannot be closed in time to form a ring, which is not conducive to the deformation control of the surrounding rock and the stability of the support structure

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