DETERMINATION OF DISPOSAL MATERIAL DENSITY IN OPEN-PIT COAL MINE DISPOSAL AREA

Abstract

This study proposes a method for determining the density of disposal material in open-pit coal mines using undisturbed sampling with a large sampler tube (LST). The disposal materials in the studied area are mostly mixed between sandstone and claystone from the coal overburden and/or interburden material in the coal open pit. The materials belong to the Warukin Formation in the southeast area of Kalimantan Island. Determination of disposal material density has become necessary since it is related to the planning of the material disposal process in the disposal area and the desire to optimize disposal capacity. The material sampling was conducted at several points in the Kusan and Girimulya disposal areas, and each point was taken at various depths. Sampling locations were also selected based on disposal age: less than 3 months (active disposal), approximately 6 months (slightly active disposal), 12 months and more (old disposal), and mining road to disposals. Additionally, the CBR test was conducted at a location near the material sampling point, where the results will be used for comparison with the density values obtained.  The undisturbed sampling of disposal material was conducted using a sampler tube made of galvanized iron with a diameter of 13.3 cm. The natural bulk density is determined by following the procedure of ASTM D2937. The results show that the active Kusan disposal area has low-density material because only 10% of samples have a density equal to or greater than the optimum density, while the active Girimulya disposal area has high-density material because 70% of samples have a density equal to or greater than the optimum density. The results of the study also show that natural compaction with the existing dumping procedure can be achieved after a disposal age of approximately six months. Compared to the CBR values along its depth, the density values obtained from this method are in good trend; the proposed method can be used for monitoring the density of disposal material.