Energy Release Analysis of a Severe Rockburst in a Headrace Tunnel Crossing a Tectonic Stress Zone

Table 1

Composition of sandstone in the N-J headrace tunnel.

Quartz (%)	Potassium feldspar (%)	Albite (%)	Calcite (%)	Dolomite (%)	Hematite (%)	Clay mineral (%)
38.9	0.4	3.7	33.8	6.6	1.2	15.4