Abstract
Block Caving is a mining mechanism in which ore collapse due to its own weight in a controlled form into draw bells. Block caving is usually used to mine large ore bodies that have dependable grade throughout. The Deep Mill Level Zone (DMLZ) block cave mine in PT Freeport Indonesia continues to ramp up production since initial undercutting began in 2015. At approximately 1,500 m down from surface, the DMLZ is one of the world’s deepest caving operations. The DMLZ is part of the Grasberg mine complex located in Papua, Indonesia, operated by PT Freeport Indonesia (PTFI). Underground with hard rock mining environment represent challenges requiring all stake holder to make improvement for facing challenges occurred. With dominant geological is diorite which competent, massive and includes as limited persistence vein system and widely spaced large scale faulting. In term of caving operational, the hard and massive rock mass could inhibit cave propagation leading because brittle failure behaviour generally occurred at hard rock in deep mine, challenges occurred with significances of hung-up event in draw bell. Currently, DMLZ are working for analysing implementation of extension hole on undercut called “High Undercut Design” which become preliminary preconditioning to create early crack before natural propagation. The first ring drill and blast trial started on September 2020 and still progressing. The preliminary result was convincing with 35% increasing of undercut swelling tonnage and 38% decreasing of hung-up blasting event on draw bell.