Blasting of cemented granular material and discrete element simulation of the process

Rock fall events at a cutting face during mountain tunnel excavation cause 1 or 2 fatalities per a year in Japan. In this study, we performed blasting tests on cemented granular specimens using a detonator and then used discrete element software to simulate the process. An explosion was initiated by passing a current through the detonator; this resulted in ejection of material from the side of the specimen which was the free boundary closest to the centre of the specimen. The discrete element analysis also demonstrated that blasting would eject material in the lateral direction. The simulation also indicated that tensile forces were generated in the specimen during the blasting and that some tensile forces remained after the blast. This leads us to conclude that the blasting process may lead to stress reduction in the rock mass near the tunnel face and so encourage rock falls.