Mechanical mechanism of large deformation and support control for jointed thin soft rock tunnel in Southwest China

Abstract

This study analyzes the large deformation failure mode and mechanical mechanism of tunnel surrounding rock, with an aim to lessen the damage of high ground stress soft rock tunnel support structure and large deformation of surrounding rock in southwest mountainous area, with Yunnan Changning Tunnel as example for analysis, This paper investigates NPR anchor cable stress compensation support for soft rock tunnel.First, we analyzed the geological conditions and causes of failure of the tunnel through field survey and indoor test.Then, we looked at the main control factors affecting the stability of surrounding rock and the failure mode of surrounding rock of Changning Tunnel.Next, this study proposed the stress compensation support technology with NPR anchor cable as the core.Finally, we analyzed the control effect of surrounding rock of Changning Tunnel under the condition of NPR anchor mesh coupling support through field test.Results show that the main failure modes of the surrounding rock of Changning Tunnel are the compression bending of rock strata and the shear slip between layers.The stress compensation support technology with NPR anchor cable as the core works to effectively control the large deformation of the tunnel surrounding rock in the initial support.The maximum deformation of the tunnel surrounding rock is controlled from 2 150 mm to less than 100 mm, which demonstrates significant control effect.The research results can provide reference for the prevention and control of large deformation of soft rock tunnel.

Keywords

• soft rock tunnel
• failure mode
• negative poisson's ratio anchor cable (npr anchor cable)
• excavation compensation