@thesis{thesis,
		author={KUSUMA  GDE WIJAYA},
		title ={ANALISIS PENGARUH MASSA BATUAN, PELEDAKAN,
DAN METODE SCALING TERHADAP OVERBREAK
PADA DEVELOPMENT DI LEVEL EKSTRAKSI,
GRASBERG BLOCK CAVING (GBC)
PT. FREEPORT INDONESIA},
		year={2017},
		url={http://eprints.upnyk.ac.id/11753/},
		abstract={PT. Freeport Indonesia (PTFI) is a copper and gold mining company.
Grasberg Block Cave (GBC) is one of the underground mine site located at PT.
Freeport Indonesia. The mining method in underground mines Grasberg Block
Cave using Caving method.
The Extraction Level 2830 GBC is a level where ore will be mucking after
caving process. Blasting is used to rock excavation during development. The
location rock type is Tgdfa (andesit) with average density 2.72 ton/m3. Tunnel
dimension that planned is 4.4 x 4 m. PTFI applies same geometry for all blasting
in the Extraction Level, using 59 blast holes.
Overbreak often occur at Extraction Level. There are three factors that cause
overbreak : rock mass condition, blasting, and scaling. Overbreak will make rock
mass around the tunnel more unstable so it?s dangerous. This Research was done
to know the influence of rock mass condition (RMR), blasting, and scaling
method to overbreak in the extraction level.
Based on research, known that the reduction of RMR value will increasing
the overbreak, obtained the formula for determining the value is overbreak = 0,45
? 0,006 x (RMR). Increasing the PPV value will increasing overbreak. Jumbo
scaling method will increasing overbreak and RQD have contribution when jumbo
scaling is used. Based on Jimeno (1995), known that number of blast holes should
use is 38 holes. Rock mass condition (RMR) and blasting (PPV) make some
influences to overbreak. The obtained formula to determine overbreak is y = 0,06
x2 ? 0,005 x1. This formula is suitable for fair-good rock (RMR 41-79).}
		}