Abstract:

The construction period for long tunnel can be effectively reduced if tunnel boring machine (TBM) works well.  However, TBM also can be embedded or out of work if complicated geological structure is encountered, and bypass tunneling is often used for helping TBM restart. The influence of bypass to pilot tunnel are unclear and worthy to investigate . The 10th TBM embedded case in Hsuehan pilot tunnel is simulated by using the three dimensional numerical code FLAC3Din the study. Pilot tunnel is circular with diameter 5m and bypass tunnel is square with width 2m.
　　　The analytic results show that compression zone was developed around the sidewall of breakage boundary when breakage tunneling is perpendicular to pilot tunnel, and the stress increment can be 10% to 22% higher than prior breakage. The stress increment of maximum, intermediate, and minimum principal stresses σ1、σ2、σ3 of perpendicular breakage in the studying case is（20%、18%、6%）.  The two side breakage stresses of 45° inclined bypass tunnel entering pilot tunnel are different. The stress increment of σ1、σ2、σ3 of breakage in the studying case are 47%、40%、-33.5%）respectively at the acute sidewall, and （21%、11%、-45%）at the obtuse sidewall . These results can be provided engineers a reference for intersection support design.