Horizontal well dewatering systems in mining: Experience and prospects

Abstract

Almost all mineral deposits being currently mined occur in the zones of risk governed by difficult geology, geomechanics, hydrogeology and engineering geology. The main complication factor is often groundwater. The choice of a dewatering system depends on the natural conditions and mining technology at each specific deposit. The article addresses issues of waterproof at an open pit mine of AGD Diamonds; the critical point here is pitwall rock mass dewatering. The performance of a horizontal well dewatering system as the internal pit drainage facility is described. The scope of the analysis embraces the current technology used in construction of horizontal wells of the optimized ‘telescopic’ structure and the size of stricken water influxes. The visual effectivity of pitwall drainage using the horizontal dewatering wells consists in the reduced seepage of groundwater on the pitwall and in the decreased gravity moisture of overburden rocks. The horizontal dewatering wells create conditions for the controllable groundwater removal from the Pandun rock mass at the drainage depth to 150–200 m, which greatly reduces the overall number of flowing water sources on pitwall in the test surface mine of AGD Diamonds. The concept is formulated for the efficient use of the horizontal well dewatering system as the permanent water protection of ultimate pitwall. The horizontal dewatering wells can be used as independent drainage elements and can be included in more complex systems generating an extended horizontal drainage at a certain depth from ground surface.