Forecasting and prevention of water inrush during the excavation process of a diversion tunnel at the Jinping II Hydropower Station, China

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Table 1 Engineering geological properties of the rock masses in the #2 diversion tunnel

No.	Tunnel section (m)	Stratum	Rock type	Pressure head (m)	Infiltration rate	Permeability (m/d)
1	K0 + 000 ~ 0 + 115	T₁	Fine sandstone	76	0.15	0.008
2	K0 + 115 ~ 2 + 000	T_2z	Marble	237	0.38	0.004
3	K2 + 000 ~ 2 + 500	T₁	Chlorite schist	361	0.15	0.006
4	K2 + 500 ~ 3 + 316	T_2z	Marble	401	0.38	0.004
5	K3 + 316 ~ 4 + 414	T₃	Sandstone and slate	577	0.15	0.008
6	K4 + 414 ~ 8 + 265	T_2b	Marble and Limestone	945	0.5	0.004
7	K8 + 265 ~ 12 + 571	T_2b	Marble	876	0.38	0.004
8	K12 + 571 ~ 15 + 152	T_2y	Marble and limestone	624	0.5	0.005
9	K15 + 152 ~ 16 + 151	T_2y	Marble and slate	312	0.32	0.005
10	K16 + 151 ~ 17 + 291	T_2y	Marble, limestone and slate	220	0.35	0.006