Blasting Effects on Coal Refuse Impoundment Structures

Currently, mining water impacts (streams, creeks, etc) are very sensitive topics for the mining industry, the public and the government agencies. An impoundment slope failure can be catastrophic involving human lives as well as environmental losses. Independent of the impoundment stage of life, it is necessary to determine the hazard potential rating of the impoundment. This assessment is made through the evaluation of the impoundment slope failure and its consequences on the surrounding areas. Usually those evaluations are performed downstream of the impoundment site. Since 1972, after the Buffalo Creek failure, several regulations were promulgated to avoid new disasters. Currently in the stage of impoundment design it is recommended, in some specific conditions, to evaluate the seismic instability of the impoundments under dynamic conditions as a co nsequence of earthquake motion. This evaluation assumes that the main source of ground motion that will impact the impoundment is generated by an earthquake source. There are no references to evaluate the stability when ground motions are generated by blasting activity. The hypothesis that blasting doesn't generate enough vibration levels to affect the impoundment facilities must be tested and the question about the influence of blasting activity in this type of facility still remains. The general objective of the project is the analysis of slope stability of impoundments (coal refuse/slurry) over time under static and specifically under dynamic conditions produced as consequences of the blasting activity in a surface coal mine. Several specific objectives support the general objective with a combination of field measurement and study, computational and numerical modeling of the impoundment structures, validation of the models with field measurements, and development of simulations for highly dynamic blast events that could cause failure ofthe impoundment structures. The specific objectives follow: • Study of the generation ofwater pore pressure excess and particle velocity/acceleration in two impoundments due to dynamic loads produced by the mining production blasting activity in a surface coal mine. • Computational evaluation of coal refuse impoundments subject to dynamic activity produced by production blasting in a surface coal mine. • Determination of the best practices for blast design in a surface coal operation when impoundments are the structures under protection or close to the production area. The end result should be a guide to determine stability ratings or factors to consider when blasting near impoundment structures. As a result of the analyses described above the primary deliverable will be a design guide tool created to assist with blast design near impoundment structures. Several nomograms will be developed involving the main variables of the problem. The nomograms will include safety factors against failure for slope stability analysis under dynamic conditions due to mining blast vibrations. The monitoring proposed, will allow for measured time series from mining blast events to be used for calibration of the models. The University of Kentucky Explosives Research Team (UKERT) is requesting $200,000 from OSM to complete this study. Teco Coal Corporation has offered $205,000 in in-kind match to facilitate completion ofthe project, including blasting supply, labor, and drilling cost.