Drilling, Blasting and Mucking
The work of drilling and blasting rock is done in cycles known as ‘the round’. It comprises of: drilling, blasting, smoke time, mucking and supporting. Holes are drilled by using pneumatically operated rock drills with wet drilling. The typical drilling pattern, sequence of blasting and quantum of charge used recently for heading and benching operations in a tunnel worked through hard rock on the Bombay-Nasik section of the Central Railway. In hard rock the progress of excavation is directly proportional to time to drill out a round cycle. A number of safety precautions are imperative while drilling and charging the holes and blasting. ‘Mucking’ is the term used for removal of the spoil. In the early days mucking was done by running small trolley trucks or open top wagons over narrow tracks laid on the floor. Soil mucking is done by loading the spoil through large-diameter pipes, mixing with compressed air and pumping outside the tunnel.