THREE-DIMENSIONAL SEEPAGE ANALYSIS OF A COAL REFUSE PILE RECLAMATION

Abstract

Abstract. A coal refuse pile located in Greenbrier County, West Virginia was studied to restrict generation of acid mine drainage through the use of a cap and cover system. This paper presents results of a finite element method seepage analysis on a proposed reclamation design. The proposed reclamation incorporates a cap and cover system with a 0.3-m thick surface vegetation cap layer over a 0.6-m thick low permeability layer. The low permeability layer is directly above the coal refuse. Unsaturated soil mechanics was utilized, adopting the Fredlund and Xing equation for soil-water characteristic curve (SWCC) estimation. SWCC fitting parameters were calculated using the Zapata and the Hernandez estimation techniques. Different precipitation events were used to evaluate seepage throughout the reclamation area and assess the effectiveness of the cap and cover system. A steep area (>4H:1V) and a flat area were considered. The water balance analysis showed a 50% to 88% reduction in water volume at the coal refuse layer and a reduction in the time for the refuse to return to initial water content due to the cap and cover system implementation. Moisture detainment was observed in the growth layer and is important for supporting vegetation persistence.