A new methodology to estimate the powder factor of explosives considering the different lithologies of volcanic lands: A case study from the island of Tenerife, Spain

Abstract

Many populations live on small islands where there are no naturally occurring rivers and lakes. Therefore, they need to look for underground water sources that involves the use of complex, expensive civil engineering operations which normally use explosives. An adequate prediction of the amount of explosive and performance of blasts is essential for a proper drilling plan. In the present work, a new methodology is proposed to estimate the consumption of explosives with respect to each type of rock drilled, based on a regression model that relates the geomechanical characteristics of the rocks with the progress made with each blast. The model is obtained using real data from the drilling of 85.70 m in a water tunnel with a cross section of 4 m2 on a volcanic island. The blast used gelatin-based explosives based on nitroglycol, placed according to the drilling and blasting pattern for tunnels (structure to capture groundwater). The extracted rocks were mechanically characterized (density, porosity and point load strength index) and correlated with the powder factor. A methodology based on a regression model was constructed with this information that allows predictions of the powder factor, number of blasts and the amount of explosive needed as a function of the geomechanical properties of the tested rocks. The blasting progress had a non-linear relationship with the geomechanical parameters of the different lithotypes. The data show that advance is strongly non-linearly correlated with the porosity and the point load strength index of the rock. The regression model will be useful in the design of tunnel construction projects, as it can provide a better estimation of duration and costs of civil works than those used at present.