See Launch SealA 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..
Angle to the ground surface at which the drill string enters or exits in forming the pilot bore in a directional drilling/guided boring system.
The surroundings or conditions (physical, chemical, mechanical) in which a material exists.
The susceptibility to crack or craze under the influence of specific chemicals stress and/or mechanical stress.
United States Environmental Protection Agency