Blast Impact Prediction Studies at Ghana Manganese Company (GMC) Ltd, Nsuta, Ghana

Abstract

Ghana Manganese Company (GMC) Limited has its mining operations currently concentrated in the Pit C area, and the company intends to re-develop the northern extension known as Pit C North, close to Tarkwa-Banso community. Mining of the pits involve both free digging and drilling and blasting of the overburden and the fresh competent rocks respectively. To conduct safe blasting operations in the Pit C North, studies were undertaken to assess the environmental impacts of blast associated with ground vibration, air blast and fly rock at 400 m from the pit periphery. It is however envisage that settlements within 400 m from the pit periphery should be resettled by the Company. Various models were used to predict the blast impact in terms of ground vibration, air blast and fly rock distance. The ground vibration at 400 m from the pit periphery predicted with the USBM model is 0.67 mm/s but predicted with Gustaffson’s model is 1.15 mm/s. Both predicted ground vibration values are below the Ghanaian’s regulatory threshold of 2 mm/s. Similarly, at 400 m from the pit periphery, the predicted maximum air blast based on current drill and blast design parameters of the Mine is 52.17 dB (L). This predicted air blast values is lower than Ghanaian’s regulatory threshold of 117 dB (L). The estimated maximum fly rock throw from Pit C North using the current drill and blast design parameters is 194 m. By adhering to best blasting practices and current drill and blast design parameters for Pit C North, impacts of ground vibration, air blast and fly rock on the neighbouring Tarkwa-Banso community are within the acceptable regulatory requirement for residential areas.