Automatic shield control systems have been developed based on empirical relationships during the past decade. But they do not have a precise theoretical background. Therefore, it is difficult to predict the shield behavior. The theoretical shield model was developed to cope with that problem. Taking into account the equilibrium condition on the shield model to simulate the shield behavior. The shield position, the cutter face rotating direction and the state of earth pressure at the face and around the shield periphery were the factors affecting to the shield behavior. The overall agreement between the simulation results and the observation suggested that the shield model could be applied to simulate the shield behavior.
Closed type shield tunneling methods together with computer aided automatic control of shield and tunneling operations have recently developed to minimize the ground surface settlement. However, some automatic control systems are based on empirical relationships and the precise theoretical background has not yet been studied. Therefore, it is difficult to control the shield particular in the complicated geological structure. A theoretical approach is necessary to cope with the above mentioned problems. A theoretical model of loads acting on a shield, taking account of the ground displacement around the skin plate was developed to evaluate the quantitative effect of the copy cutter (Sugimoto et al., 1999). In this model, the force acting at the face is given by a function of the shield velocity, the cutter face rotation speed and the state of earth pressure, and the force acting on the skin plate is given by a function of the ground displacement around the skin plate. The definitions of rotation angles are illustrated in Figure 1. The comparison of shield behavior between the simulation results and the observation are reported.