Radial-clearance measuring system between tunnelling shield and tubing exterior - uses three measuring sensors on shield with rays inclined rearwards and outwards to inner surfaces of shield and tubing

摘要

On the rear surface of a wall, e.g. the thrust wall (9), stiffening the casing (2) of the shield in the radial direction, are three or more distance-measuring sensors (11), fixed in position. The measuring rays (12) emanating from them are inclined against the working direction and at a known angle ( alpha ) to the shield travel axis (4). As the tunnel is driven, the distance (LS) to the internal surface of the shield casing (13) and to that of the tubing (14) are measured. From the known thickness of the tubing, the radial clearance (delta) is then calculated. USE/ADVANTAGE - The system measures the clearance between the internal surface of the rear part of the tunnelling shield and the external surface of the tubing on encountering an underground chamber. It is simple, continuous and provides accurate control of air-supply to rear of shield.