Conference Paper 3D numerical analysis of time-dependent behavior of a tunnel constructed with conventional support system

Arima, H  ,  Sainoki, A  ,  Fukuda, Daisuke  ,  Kodama, Jun-ichi  ,  Fujii, Yoshiaki

In Hokkaido prefecture, Japan, a number of road mountain tunnels constructed with conventional support systems are still in use. In one of the tunnels, the progressive damage evolution and large deformation of the tunnel wall were observed. The present study investigates its mechanism and the effectiveness of the conventional support system. In order to simulate the time-dependent behavior of the target tunnel, a variable-compliance-type constitutive equation is employed and implemented into FLAC3D. A 3D numerical model reproducing the actual ground surface topography is constructed. Using the numerical model and constitutive equation, the time-dependent damage evolution and resultant deformational behavior are simulated whilst considering combinations of the conventional support system members, namely steel sets, concrete lining and invert concrete. The analysis results show that concrete invert installation is the most effective measure to suppress and control the damage evolution and deformation of the tunnel wall. The concrete lining is the second effective, alleviating the deformation taking place on the tunnel wall and crown. It is then revealed that steel sets do not significantly contribute to suppressing the damage evolution. The analysis result also indicates that axial stresses originally acting on the steel sets are re-distributed to the concrete lining and invert concrete, proving that the two support members can work more effectively than steel sets in the aspect of controlling the time-dependent damage evolution of the surrounding rock mass.

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