Real-time Discriminant Analysis of Surrounding Rock Features for Double Shield TBM Tunnel in High Geostress Zone

Numerous long and deep tunnels would be constructed for the development of transport and energy resources in the high mountains along the Qinghai-Tibet plateau and its eastern margin. The TBM tunneling method has significant advantages. Based on the double-shield TBM project of DXL tunnel in Brahmaputra grand canyon, Tibet, the engineering geological conditions of tunnel site, the tail ballastless-dependent instant acquisition and real-time features of surrounding rock were presented. The results show that (1) the main reason for jamming TBM was that the fracture of cracked and hard rock mass led to large deformation of surrounding rock under high geostress. (2) Valuable information and parameters of real-time lithology, rock mass structure and deformation near the tunnel face could be obtained immediately by comprehensive observation of tail ballastless and segment grouting holes. (3) Based on the real-time information and index of surrounding rock, the real-time discriminant analysis index and criterion of engineering geological features of surrounding rock was proposed, which can quantificationally evaluate the real-time engineering geological features of surrounding rock at the double-shield TBM face. The thoughts described in the paper can provide a simple, effective and real-time geology forecast supplementary method for double-shied TBM and traditional tunnel excavation.