A case study on improvement of powder factor and fragmentation in quarry blasting

Abstract

Firing pattern exerts tremendous influence on the fragment size and the heave of the muckpile. Similarly, the stemming column also assists rock fragmentation by retaining the blasthole pressure for a considerable period of time, in order to make best use of explosive energy. The present paper is a case study in the limestone quarry where major problems in terms of improper fragmentation (large boulder count, and poor front end loader (FEL) performance), poor wall control, and poor heave characteristics of the muckpile were witnessed on the 6m high limestone benches. The paper highlights the marked improvements in fragmentation results by changing the diagonal firing pattern to V-type firing pattern, and also, by making suitable adjustments in the stemming column. Looking at the modifications and the improvements thereof, advantage of the said modifications were implemented on 9m high benches of the same quarry to reap the benefit of reduced bench stiffness, by way of expanding the mesh area in the subsequent blast rounds. The increase in mesh area (SxB) was done incrementally from the existing 8.96 Sq.m. to 12 sq. m. The results were meticulously registered in the field, and clearly depicted definite improvements in the blast performance in terms of fragment size, increased P.F., reduced boulder count, reduced FEL cycle time etc.