Jackleg - A percussion drill used for drifting or stopping that is mounted on a telescopic leg which has an extension of about 2.5 m. The leg and machine are hinged so that the drill need not be in the same direction as the leg. | |
Job Safety Analysis (J.S.A.) - A job breakdown that gives a safe, efficient job procedure. | |
Joint - A divisional plane or surface that divides a rock and along which there has been no visible movement parallel to the plane or surface. |
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