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.

Understanding the deformation characteristics of soft and fractured rock masses is crucial for the rational design and safe construction of underground engineering projects. Based on the diversion tunnel project of the Guzhen Hydropower Station, where undisturbed rock samples were collected to conduct passive triaxial compression tests. Deformation curves of the soft fractured rock mass in the tunnel site area under graded loading were obtained. The study analyzed the time-dependent deformation characteristics using both empirical rheological models and the viscoelastic rheological model proposed by Sun Guangzhong. The results indicate that: (1) Under passive triaxial compression, the soft fractured rock mass exhibits three-stage deformation characteristics, including initial significant compaction deformation during the loading stage, relatively elastic deformation in the middle stage, and significant plastic deformation after yielding. The stable pressure stage shows accelerated deformation under relatively small axial stresses. (2) Both rheological models can effectively describe the stable pressure deformation process of the soft fractured rock samples. The parameters of the viscoelastic rheological model vary with axial loading pressure, revealing differences in time-dependent deformation characteristics during the closure-compaction stages of internal fissures within the sample.