Controlling factors decreased of granite rock masses quality on Bangka island

Abstract The Granite rock covered almost one-fifth of the land on Bangka Island. The construction of settlements and various infrastructures on granite formations has increased. This research intended to analyze the parameters controlling the granite quality (S-type and I-type), which are widespread on Bangka Island. The Rock Mass Rating (RMR) and Geological Strength Index (GSI) methods measure the rock quality and their controlling factors. As a result, granite has RMR and GSI variation quality from fair to very good. Granite at the coastline tends to be of lower quality than those further from the coastline. Geological structure and weathering are the main factors causing a decreasing rock mass quality. The sea water entering the rock fractures is thought to have accelerated the weathering along the coastline.