Abstract
In excavating tunnels for subways and power cables, shield tunneling machines, which have many cutters, are used. The authors previously proposed an effective detection system, for the machines, which detected anomalous objects ahead, to prevent the cutters from getting damages and also to prevent the construction delay caused by the accident. The system has one sonic transmitting transducer and several sonic receiving transducers to get information on the anomalous objects. Not so many observations being available in the detection, optimal observation policy is of a practical importance. The paper discusses the optimal location of the transducers on the cutter plane of a shield tunneling machine and also the optimal observation policy which takes into account the rectlinear and revolving motions of the transducers caused by the movement of the tunneling machine.
