Rock burst is one of the most serious geologic hazards, adversely affecting the safety, economy and productivity of underground engineering construction. High ground stress and its induced frequent rock bursts are major influences of tunnel instability during the survey and design and construction stages. As a major construction of the Jinping II Hydro-power Station on the Yalongjiang River, the deep-buried water transfer tunnels face the problems of rock bursts in hard rock under high geostress. According to the characteristic of the rock bursts in Jinping II Hydro-power Station, the method of preventing the rock burst by rapid stress releasing was put forward, and the scheme of stress releasing hole was selected through numerical simulation by using FLAC (Fast Lagrangian Analysis of Continua) 3D explicit finite-difference software. Through the testing and application in water transfer tunnels of Jinping II Hydro-power Station, the rapid stress release method by blasting has proven to be an effective method for preventing and treating rock burst.
The rock mass in west China has been influenced by horizontal squeezing of the Indian Ocean tectonic plate and the rising of QingZang plateau. It suffered seriously from tectonic distortion and ground surface remodeling resulting in complicated geological conditions with deep valleys, high field stress, many active faults, frequent earthquakes, and slope disasters around the peripheral area of QingZang Plateau. Under such circumstances, underground construction usually is subject to engineering geology hazards, such as rock bursts, large deformations, and leakage of underground water or mud and marsh gas. With the development of underground construction, rock bursts have become a serious engineering geological hazard in west China. Rock burst is one of the most serious underground construction hazards, adversely affecting the safety, economy and productivity of underground constructions. It is a sudden manifestation of the release of strain energy stored in the rock mass. At present, there is no universally accepted method for predicting and preventing of the rock burst.
Rock bursts is one of the disasters can occur in deep mining and rock excavation. It is a kind of dynamic fracture excited by the released elastic energy previously stored in the rock mass (Paul Singh 1989, Dowing & Andersson 1986, Cai et al. 2001). High ground stress and its induced frequent rock bursts are major influences of tunnel instability during the survey and design and construction stages. In the past few years, many methods of preventing rock bursts have been proposed, including controlling blasting charge, rock mechanics assessment, watering rock surface and effective protection measures. Need has stimulated demand for research in this field, but the outcome is still unsatisfactory due to the complexity of the problem. As an important construction of the Jinping II Hydropower Station on the Yalongjiang River, Sichuan Province, diversion tunnels have the condition of rock bursts occurrence, due to the deep buried, high in situ stress and intact rock with high strength, there frequently occurred plenty of rock bursts when the diversion tunnels were excavated, which restricted the development of construction.
This paper gives the basic idea for preventing the rock bursts by rapid stress releasing. Through the testing and application in water transfer tunnels of Jinping II Hydro-power Station, the method of preventing the rock bursts by rapid stress releasing is validated.
