Waste rock dump capping strategy and soil moisture probe research for closure at Chatree Gold Mine

摘要

A trial was established at Chatree Gold Mine, Thailand, in May 2005 to investigate the use of different capping treatments (depth, permeability and type of material) to encapsulate Potentially Acid Forming waste rock to aid the minimisation of rainfall infiltration and therefore Acid and Metalliferous Drainage. Chatree Gold Mine has a Tropical Savannah type climate with the majority of rainfall received over the monsoonal wet season (1,315 millimetres average per year). Numerical modelling was undertaken to determine the design of capping treatments that were most likely to minimise water infiltration. Soil moisture probes were then installed in two capping treatments on the sides (slope profiles) of a waste rock dump trial and one on the top (flat profile) of a waste rock dump to field test the infiltration of rainfall through these treatments. Monitoring of the soil moisture probes has occurred over approximately 2 years to December 2006 and will continue to obtain long term data. Results to date show that the capping strategies on the sides of the waste rock dump have been successful in excluding rainfall infiltration to the Potentially Acid Forming materials. Although further data is required to confirm the trend, soil moisture results from the top of the waste rock dump have shown some rainfall infiltration through the capping treatment. Therefore as a precautionary measure, mine designs for future capping of the top of waste rock dumps will be modified to include thicker layers of low permeability materials, with strict engineering controls during construction to obtain maximum compaction.