Construction method of under cutting excavation supporting of of deeply buried soft-rock large tunnel

Abstract

The invention relates to a construction method of the under cutting excavation supporting of a deeply buried soft-rock large tunnel. The invention aims to provide a construction method of the under cutting excavation supporting of the deeply buried soft-rock large tunnel, thus ensuring safe and stable structure of the tunnel in the construction process. The technical scheme of the invention is asfollows: the construction method comprises the following steps: 1) upper cross section grouted anchor bars, an upper cross section steel arch centering and a concrete spraying layer are arranged in an excavated upper cross section cavern in turn; 2) prestressed anchor bars are arranged on the spandrel, waist and arch springing of the upper cross section cavern respectively; 3) foundation piles with anchors are arranged on the arch springing parts of the two sides of the upper cross section cavern; 4) under cutting excavation is performed to the lower cross section cavern in a left-right framing mode to form an integral annular supporting; and 5) the above steps are repeated until the whole tunnel is completed. The invention is mainly used in various hydraulic and hydroelectric engineerings, in particular the deeply buried soft-rock tunnel with large cross section.

Description

technical field [0001] The invention relates to a construction method for deep-buried soft-rock large-scale tunnel excavation and support at the bottom, which is mainly applicable to various water conservancy and hydropower projects, especially deep-buried soft-rock large-section tunnels. Background technique [0002] In recent years, with the needs of social development, the number of deep-buried tunnel projects has gradually increased. Existing research and engineering practices have shown that rock masses will undergo many failure phenomena different from those under conventional shallow-buried conditions under high buried depth conditions. Such as rockburst, stress-type relaxation and collapse, continuous deformation, etc. Large plastic deformation of surrounding rock is the most common damage phenomenon in deep soft rock caverns, often accompanied by tunnel collapse, crown sinking, bottom heaving and abnormality of surrounding rock In the event of deformation, etc., the...

AI Technical Summary

Problems solved by technology

For the soft rock cave section excavated by the step method, during the construction process of the lower step, there must be a stable and balanced state of the surrounding rock after breaking the support of the upper half section, especially the system steel arch foundation of the upper half section will follow the lower half section Due to the excavation of the section, the suspension loses its support and bearing capacity, which makes the

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