Study on Safety Benchmark Value of Monitoring and Early Warning for Large Section Highway Tunnels

Abstract

Taking several tunnels under construction of a highway as the research object, the ultimate displacement of four buried depth sections of 0-50, 50-100, 100-300, 300-500 m in the surrounding rock of grade III, IV and V is numerically simulated by three-step and seven-step excavation method, middle-wall method, cross-middle-wall method and double-side-wall guide pit method for initial support of large-section highway tunnels. Through analysis, the deformation law of tunnel surrounding rock is obtained: under the same buried depth, the displacement ultimate displacement of the two-sided guide pit method and the cross-middle-wall method is the largest, the middle-wall method is the second, and the three-step seven-step excavation method is the smallest. Through the analysis and collation of the measured data obtained by monitoring and measurement of each construction method in the construction site, the surrounding rock deformation datum values of large-span and large-section tunnel under each construction method are obtained.