Wall Quality, Cost, and Environmental Impact Assessment of Wall Control Blasting – A Case Study

Problems of crest damages and toe deviations render the results of wall control blasting unsatisfactory, gradually leading to a deviation between the asbuilt and the designed geometry of the pit. From explosives economy, the only to evaluate accurately the cost of explosives is to examine its effects on blasting (that is the purpose for which it was used for). This, therefore, arises the need to assess results of wall control blasting. This project assessed the current practices of wall control blasting aiming at the wall quality, cost of unsatisfactory control blasting results, and, the environmental impact. Wall quality and Cost assessment was done by comparing the asbuilt and actual pit geometry and estimating the cost incurred from hauling rock materials generated from crest damages on the 980, 1000 and 1020 Reduced Levels (RL). Environmental impact assessment was done by comparing measured air blast and ground vibration value from selected pre-split shots to the accepted values. Superimposition of the as built berm on the designed berm on the 980 RL, 1000 RL and the 1020 RL gave a loss percentage of berm area of 58.86 %, 39.48 % and 39.96 % respectively as compared to the allowable loss percentage of berm area of 20 %. A cost of $ 32,234.14 was incurred from hauling waste rock generated from crest damage from 980 – 1020 RL. The analysis of blast monitoring results of the randomly selected pre-split shots showed pre-splitting is environmentally successful.