Abstract: In order to study the interaction between double shield TBM and the surrounding rock affected by the LDP relax ratios, overcut, conicity of the shield, length of shield and lateral pressure coefficient, a completely three-dimensional TBM model usingFLAC^3D has been adopted to investigate the features of the surrounding rock deformation, the contact force and the frictional resistance act on the shield based on the above influence factors considering the non-uniform gap between shield and surrounding rock. Moreover, the LDP curve relax ratios has also been defined in this paper. The simulation result has indicated that the LDP curve release rate and the resistance act on the shield of TBM have been affected significantly when the stress release rate exceeds a specific value, therefore a sensitivity analysis should be conducted under the specific engineering geological conditions. The nonuniform gaps between the shield and ground will gradually close from invert to crown and subsequently contact the shield surface and the most significant contact areas occur at the end of the front shield and rear shield. Both the friction force acting on the front shield and rear shield and the total friction force will increase linearly with the increasing overcut and appropriate increasing of overcut can effectively reduce the shield resistance; the total friction force acting on the shield will increase linearly with the increasing of the length of shield as well; with the increasing shield conicity, the friction force acting on cutterhead and front shield and the total friction force will increase slowly while the force acting on rear shield will decrease obviously. The frictional resistance acting on the front and rear shield is remarkable when the lateral pressure coefficient is more than 1.2. The above achievements have important reference significance for further understanding the interaction between TBM and surrounding rock and for forecasting TBM entrapment subsequently.

Key words: double shield TBM, non-uniform gap, LDP relax ratio, overcut, shield conicity, shield length, lateral pressure coefficient