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Casting design for bench blasting in surface coal mines is a new focus and a fairly recent success. This study aims at the development of a model to predict the throw of overburden material based on geological conditions of a bench and charges in blast holes. The model, derived on the basis of blasting theories and dynamics of the multiple-particle system, explores the mechanisms of casting rocks into pits. Implementing the model with a computer program is a part of the study. The execution of the computer program will result in quantitative data for evaluation of a blast round design. It serves the purposes of verification for the model and field applications. More specifically, the suggested model calculates the resultant forces exerted on the overburden material by the gas pressures in the blast holes. The trajectory velocity of the overburden material after the heave can be determined from the impulse-momentum theory. Ranges of throw for overburden material at different spacing-to-burden combinations are the results. Due to the fact that hypothetical assumptions are made and, further, that so many factors in the field can affect the outcome of a shot, the predictions are not recommended to be taken as absolute values but relative indications. The prediction, which is based on charge, geological condition of the bench, burden and spacing, can be used to determine the number of rows of blast holes to be drilled on the bench.