Hydrogeological Issues Concerning the Thar Lignite Prospect

Document Type: Research Paper

Authors

1 Nottingham Centre of Geomechanics, Department of Civil Engineering, Faculty of Engineering, University Park, Nottingham NG7 2RD, U.K.

2 Faculty of Computing, Engineering and Technology, Staffordshire University, Beaconside, Stafford, United Kingdom ST18 OAD

3 School of Mining, College of Engineering, University of Tehran, Iran

Abstract

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

Keywords