Abstract: To examine the evolution patterns of surrounding rock disturbance during deeply-burial soft rock tunnels under high geo-stress, a case study is conducted on the Muzhailing tunnel of the Weiyuan-Wudu expressway. Section ZK220 + 020 to ZK220 + 090 is selected as the monitoring section. Two parallel boreholes are drilled from the previous tunnel to the subsequent tunnel to monitor the wave velocity variation characteristics of the surrounding rock in the subsequent tunnel with the radial depth and the distance from the tunnel face using cross-hole acoustic wave monitoring technique. Finally, the spatial-temporal evolution of surrounding rock disturbance during tunneling and the influence patterns of tunneling procedures are inversely analyzed. Main findings are as follows: (1) In terms of time, the surrounding rock is significantly disturbed primarily within 5 days before excavation to 10 days after excavation, which reflects the influence of tunnel face distance on the disturbance of surrounding rock. (2) In terms of space, the influence range of the tunnel face excavation and supporting on the surrounding rock in the longitudinal direction is approximately 1.25D(15 m, where D is the tunnel excavation diameter), and approximately 2.08D (25 m) in the radial direction. (3) Construction procedures can be divided into two stages: the upper and middle bench excavation, and the lower bench and invert excavation, according to the disturbance degree to the surrounding rock. The upper and middle bench excavation causes the largest disturbance to the surrounding rock.

Key words: soft rock tunnel with high geo-stress, surrounding rock disturbance, cross-hole sonic wave testing technology, spatial-temporal evolution pattern, tunneling procedure, double-track tunnel