Hydrogeological Issues Concerning the Thar Lignite Prospect

The paper is concerned with the hydrogeological appraisal of the proposed mining operations in theThar lignite field in Sindh, Pakistan. The Thar coalfield covers an area of approximately 9000km2 andcontains three lignite seams lying at depth of 130m to 250 m. In the Thar lignite field, the presence ofthree main aquifers induces pore pressure in the rock mass surrounding the lignite seams and makes highwall slopes potentially unsafe. It is, therefore, necessary to dewater the rock mass before commencingmining excavations. The paper describes the proposed mine dewatering scheme to facilitatedepressurising of the rock mass surrounding the mining excavations. Inflow prediction of groundwater tothe surface mining excavation was carried out using a SEEP/W finite element software package. Thesimulation results show that the ground water inflow from the Top aquifer is 114m3/d, from theIntermediate confined aquifer is 141m3/d and from the Bottom confined aquifer is 1.28 x 105 m3 /d. Theseresults were compared with the analytical solutions which indicated that the relative error of estimation ofinflow quantities varies from 3.4 % to 6.4%.