Estimation of the Height of Complete Groundwater Drainage Above Mined Longwall Panels |
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| Authors: | Paul Tammetta |
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| Institution: | 1. Coffey Geotechnics, Level 18, Citadel Tower, 799 Pacific Highway Chatswood, NSW, 2067, Australia;2. paul_tammetta@coffey.com |
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| 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. |
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