A mechanical seal, usually consisting of a rubber flange that is mounted to the wall of the jacking shaft. The flange seal is distended by the MTBM as the machine passes through the shaft. The seal is intended to prevent the flow of groundwater, soils, slurry, and lubrication into the shaft during tunneling operations.
US customary units for weight per unit length. One lb/ftUS customary units for weight per unit length. One lb/ft equals 1.488 kilograms per meter. equals 1.488 kilograms per meter.
The leading pipe designed to fit the rear of a jacking shield and over which the trailing end of the shield is fitted.
Nominal length of drill rod.
(1) The specified direction of the proposed bore in a horizontal plane. (2) (Path) The shortest distance between two points as laid out by a survey crew for the installation of pipelines and their bores and tunnels.