Three-dimensional numerical simulation on interaction between double-shield TBM and surrounding rock mass in composite ground

3D numerical simulation with FLAC3D, was carried out to investigate the interaction between double shield TBM and composite ground. The real TBM geometry and the non-uniform annulus gap between ground and TBM shield were considered. The characteristics of surrounding rock deformation, the contact force and the frictional resistance acted on the shield of TBM in composite ground were studied at the following conditions:(1) weak rock layer occurs along the ground depth;(2) soft rock occurs along the axial direction of tunnel; and (3) different lengths of soft and hard rock alternating in the longitudinal direction. Meanwhile, the non-uniform annulus gap was introduced to the calculation of contact force acting on the shield as a function. In case (1), the curve of longitudinal displacement profile of surrounding rock came into contact with the TBM shield successively from bottom to top, which affected by the non-uniform annulus gap. The contact zone was mainly situated on the sidewall and below and the contact force was largely concentrated on the middle and tail end of both front shield and rear shield. The maximum magnitude of contact force occurred in the end of front shield. In case (2), the frictional resistance acting on the shield was increased and finally kept in steady state with the increasing length of soft rock. In case (3), the magnitude of the contact force acting on the shield was in periodic fluctuation and was basically in accordance with the variation of displacement. Moreover, the shapes of longitudinal displacement profile(LDP) curve in composite ground in cases (2) and (3) were absolutely different from that in homogeneous rock mass. © 2016, Science Press. All right reserved.