Abstract:

Rock-burst is a very complicated dynamical instability phenomenon. High ground stress and its induced frequent rockbursts are major influences of tunnel instability during the survey and design and construction stages. As an important and casual construction of the Jinping Second Level Hydropower Station on the Yalongjiang River, Sichuan Province, when the drain tunnel was excavated at the depth of 1600m, there frequently occurred plenty of rockbursts, which  restricted the development of construction. Aiming to investigate the relationship between the rock-burst mechanism and high ground stress, and to effectively predict the location of rock-bursts in the drain tunnel, a progressive failure progress numerical analysis code-RFPA was used to analyze the stress, and the fitting curves of the initial stress were obtained corresponding to the site measurement. Meanwhile, on the basis of RFPA simulation, the disturbed zones in the surrounding rock mass induced by stress redistribution resulting from excavation agreed with the  rock-burst fields, which indicated that RFPA can virtually simulate the mechanism of rock-burst. 

Key words: Jinping second level hydropower station, surroundingrock, rockburst, stress distribution, numerical simulation