title: Estimation of the height of complete groundwater drainage above mined longwall panels.
abstract: The height of complete groundwater drainage above subsided longwall panels (referred to as H) at underground mines is determined using a data base of hydraulic head measurements made with multiple devices down the depth profile at each of a number of sites worldwide. H is shown to be relatively independent of most parameters except the geometry of the mined void and the overburden thickness. An empirical equation linking H to these parameters is developed using hydraulic head data, and confirmed using an independent data base of ground movement. H is shown to be the same as the height of the zone of major ground movement above a panel. H for special cases (above longwall chain pillars, above pillar extraction panels, and underneath significant water bodies) is invariably smaller than H above center panel for ordinary cases. A new caving model, from a groundwater perspective, is proposed for continuously sheared longwall panels at ordinary locations. It removes complexity and reduces the uncertainty in estimating H. The derived equation for H applies to a variety of strata types.
authors.affiliation: Coffey Geotechnics, Level 18, Citadel Tower, 799 Pacific Highway Chatswood, NSW, 2067, Australia; paul_tammetta@coffey.com.
authors.forename: Paul
authors.initials: P
authors.lastname: Tammetta
mesh_terms: D060587:Groundwater; D062070:Hydrology; D008906:Mining