Abstract:

Jinping Ⅱ hydropower station, located in Yalong river, will generate electricity by employing low gate interception and long-distance diversion,with tunnel length of 17 km, the maximum depth of 2,525 m, the maximum geostress of 70 MPa and water pressure of 10.2 MPa. Therefore, the surrounding rock classification methods are beyond the present specification standard. Based on the engineering geological background,the key factors influencing the rock classification are extracted,including rock strength,rock structure,integrity,geostress, and high water pressure. Then, in combination with the field statistical data, a rapid assessment method is established for Jinping Ⅱ hydropower station under the high geostress and high water pressure. Field application shows that its prediction accuracy is more than 88%,which can provide a reliable basis for the further reinforcement of tunnel geological disasters.

Key words: high depth tunnel, high water pressure, high geostress, rock mass quality classification, fast evaluation method, Jinping, Sichuan