Excavation and preliminary bracing method for soft rock tunnel

Abstract

The invention discloses an excavation and preliminary bracing method for a soft rock tunnel. The excavation and preliminary bracing construction for the soft rock tunnel are performed in sections from back to front. When any section is subjected to excavation and preliminary bracing construction, the method comprises the following steps: 1) confirming basic mechanical parameters of the surrounding rock; 2) confirming the reserved excavated volume of the tunnel: confirming the reserved excavated volume of the currently constructed section according to a theoretical value of inward displacement of the surrounding rock of the soft rock tunnel after being braced; 3) excavating the tunnel; 4) confirming a preliminary bracing structure of the tunnel; 5) constructing the preliminary bracing of the tunnel; 6) performing the excavation and preliminary bracing construction of the next section; and 7) repeating the step 6) till all the processes of the excavation and preliminary bracing construction of the soft rock tunnel are completed. The method disclosed by the invention has the advantages of simple steps, reasonable design, convenience in realization and good use effect; the reserved excavated volume is confirmed according to the surrounding rock deformation condition of the soft rock tunnel; and the steel bracket and the anchoring net sprayed preliminary bracing structure are coordinated for performing all-section preliminary bracing on the tunnel.

Description

technical field [0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a soft rock tunnel excavation and primary support method. Background technique [0002] In recent years, with the rapid development of my country's highway and railway construction, the construction of soft rock tunnels under the conditions of large buried depth and high ground stress has become one of the inevitable trends in the development of the transportation field. Wushaoling Tunnel, Zhongnanshan Tunnel and Xiakou Tunnel, etc. Due to the harsh engineering geological conditions, the self-supporting capacity of the surrounding rock is poor, and the deformation of the soft rock tunnel is severe. If the support is not timely or the plan is unreasonable, large deformation of the surrounding rock and damage to the lining structure will easily occur. For this reason, a large number of experts, scholars and on-site engineering technicians have carried out in...

AI Technical Summary

Problems solved by technology

In fact, for large-deformation soft rock tunnels under specific geological conditions, even the 120mm upper limit reserved deformation allowed by the code cannot meet the requirements of continuous deformation of soft rock after initial support, and the strain energy of surrounding rock cannot be fully released. Eventually lead to the failure of the steel arch and the instability of the surrounding rock

So far, there is still a lack of comprehensive theoretical research on the reserved deformation system for excavation of large-deformation soft rock tunnels.

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