Preliminary bracing construction method for tunnel with surrounding rocks containing collapsible loess and soft rocks

Abstract

The invention discloses a preliminary bracing construction method for a tunnel with surrounding rocks containing collapsible loess and soft rocks. The method includes the following steps that a plurality of layers of advanced pipe sheds are arranged on a collapsible loess layer, and a single layer of advanced pipe shed is arranged on a soft rock layer; after the advanced pipe shed is set up, a working face is closed through sprayed concrete, a system anchor bolt is arranged on the soft rock layer, a foot locking small guide pipe is arranged at the arch springing position of the tunnel, and grouting is conducted on the rocks through permeation of the system anchor bolt and the foot locking small guide pipe; a pre-fabricated reinforcing mesh is paved on a concrete initial spraying layer formed by concrete initial spraying in a fluctuation mode, and a reinforcing mesh arranged at the collapsible loess layer is encrypted; a steel arch support is set on the collapsible loess layer, a reinforcing steel bar grid is set up at the soft rock layer, and the connecting position of the reinforcing steel bar grid and the steel arch support is welded; repeated spraying is conducted by adopting concrete spraying, and construction of tunnel preliminary bracing is finished. By means of the method, stress releasing and deformation coordination of two layers of surrounding rocks can be well controlled, operability is good, construction cost is low, and the safety is good.

Description

technical field [0001] The invention relates to a construction method for initial support of tunnels, in particular to a construction method for initial support of tunnels with collapsible loess and soft rock in the cross section. Background technique [0002] Compared with tunnel surrounding rocks of grades I to III, layered surrounding rocks containing collapsible loess and soft rocks have low strength, large deformation, and poor self-stabilization ability, and there are differences in the characteristics of the upper and lower rock and soil layers, especially It is because the excavation area of ​​the tunnel is greatly increased, and the construction difficulty increases sharply. The disturbance to the surrounding rock during construction may cause the surrounding rock to loosen or enter a stage of large deformation, resulting in an increase in the difficulty of the initial support of the tunnel. Therefore, a reasonable The initial support technology is particularly impo...

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Problems solved by technology

[0002] Compared with tunnel surrounding rocks of grades I to III, layered surrounding rocks containing collapsible loess and soft rocks have low strength, large deformation, and poor self-stabilization ability, and there are differences in the characteristics of the upper and lower rock and soil layers, especially It is because the excavation area of ​​the tunnel is greatly increased, and the construction difficulty increases sharply. The disturbance to the surrounding rock during construction may cause the surrounding rock to loosen or enter a stage of large deformation, resulting in an increase in the difficulty of the initial support of the tunnel. Therefore, a reasonable The initial support technology is particularly important

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