ABSTRACT
The construction of the second block cave mine at Rio Tinto’s Northparkes Mines, known as Lift 2, commenced in March 2001 with forecast project completion by December 2004. Construction of the mine includes 14 647 linear metres of development, all of which are supported with fibre reinforced shotcrete (FRS). The Lift 2 Project was one of the first users of synthetic fibres and was perhaps the first mine anywhere to specify structural synthetic fibres for reinforcement of all shotcrete applied. When the mine wrote the specification for FRS for Lift 2 in 2000, synthetic reinforcing fibres were just beginning to appear on the market. It is forecast that approximately 31 000 cubic metres of FRS will be sprayed in the Lift 2 area by the end of Project construction. Since inception, the Lift 2 Project has encountered higher than predicted ground stresses, resulting in strainbursts and seismic events. The underground openings in certain areas will also be subjected to abutment stress as the block cave progresses. The drawpoints will be subjected to abrasion and blasting damage over their five year life. The ground support systems for these various conditions have been developed over the life of the Project, with different FRS mix designs trialled to suit. This paper discusses the issues associated with specifying a new and largely (at the time) unproven product and the mine’s experiences in using this type of reinforcement in the various underground environments.
