Interactions of Four Tunnels Driven in Squeezing Fault Zone of Wushaoling Tunnel

摘要

Wushaoling Tunnel comprised of two parallel separate tunnels, which has a length of 22.05km, is the longest tunnel in China at present and has been completed. NATM was adopted in the construction and several regional fault zones were encountered during excavation. Especially, the Fault Zone No. 7 has a width of about 785 m, and the most complex geological conditions such as squeezing strata. During the construction of the left and right main tunnel in the Fault Zone No. 7, excessive deformations occurred. In order to speed up the tunnel construction in Fault Zone No.7, another two advancing drifts were made to go through the collapsed regions. There existed four tunnels within the fault zone, and the distances between every two tunnels were 40m (centre-to-centre). The evaluation of the interactions between the four closely spaced tunnels in the squeezing fault zones with highly insitu stresses has become an essential part of the construction of Wushaoling Tunnel. Based on actual layouts and construction sequences of the four tunnels within Fault Zone No.7, and field measurements of in-situ stresses, deformation and pressure monitoring, the interactions during the construction of four tunnels were conducted in this paper. The commercial software of FLAC was adopted to simulate the actual interactions. The stability of the rock pillar between two tunnels, the stresses and deformations of the surrounding rocks and linings of the four tunnels were obtained. This paper describes the details of evaluation of the interactions between the four closely spaced tunnels in the squeezing Fault Zone No.7 of Wushaoling Tunnel.