Abstract: The cutterhead of tunnel boring machine(TBM) working in jointed rock mass is likely to be jammed. In order to reduce the loss, risk assessment is necessary. Whether the cutterhead is jammed or not depends on the relationship between torque and resistance torque. The magnitude of resistance torque depends on the height of collapse. According to the randomicity of collapse height and the theory of probability, a formula for calculating the probability of cutterhead jamming is established. Meanwhile, according to the magnitude of resistance torque and cutterhead’s parameters, the consequences of cutterhead jamming is divided into five ranks. On the basis of probability and consequence ranks, risk assessment matrix for TBM cutterhead is proposed. The research results are verified reasonable by practical example.

Key words: tunnel collapse, risk assessment, TBM cutterhead, resistance torque, risk assessment matrix