Stability Monitoring and Analysis of Core Rock in a Tunnel with Extra-large Cross Section and Low Flat-ratio during Construction

摘要

Different from normal tunnels, the mechanical behaviors of super large section tunnel with two bores and eight lanes are more complex and the construction methods are also diversified. Based on the maximum rock tunnel with extra-large cross section and low flat-ratio in China, the convergence and anchor bolts stress of core rock are monitored in detail. The deformation and stress characteristic of core rock under different construction stages are analyzed. Some conclusions have been drawn. Compared with the upper part, the bolt's axial stress of the middle part in the core rock is greatly affected by the construction process. The excavation of the upper-stage and down-stage has a great effect on the anchor bolt stress of core rock and those procedures are the main point to control the stability of core rock. The longitudinal incidence of the excavation of the extra-large cross section and low flat-ratio tunnel is about half time of the tunnel span, which is about 10 to 11 m. The result presented in the paper can be refereed in the design, construction and research of similar tunnel.