GEOLOGICAL PROBLEMS ENCOUNTERED IN ROCK TUNNEL AT JINPING|ⅡHYDROELECTRIC POWER STATION AND THEIR TREATMENT MEASURES

Gravitational collapse, brittle failure and wedge falling are key geological problems that occurred during the construction of a rock tunnel at Jinping Ⅱ hydroelectric power station. The gravitational collapse mainly occurred in the Ⅳ and Ⅴ rock mass. The brittle failure mainly occurred in the Ⅰ and Ⅱ rock mass. The wedges falling mainly occurred in the Ⅱ, Ⅲ and Ⅳ rock mass. Three failure modes are common in the rock tunnel. They would bring about severe danger for workers and construction equipments , and greatly affect the construction schedule. This paper analyzes the geological causes of the threefailure modes and puts forward corresponding excavating and supporting measures. The proposed measures obtained favorable engineering results.