To study the relation between stress and rockburst during tunnel excavation at a hydro-power station, in-situ stress measurements are carried out by hydraulic fracturing method. the maximum compression stress and minimum compression stress within the tunnel cross—section are obtained by stress analysis. The possibility of rockburst is analyzed with rockburst criterion, and provided the scientific basis and technological support for the design and construction of the tunnel engineering.
As an important production increase measure for petroleum and natural gas, hydraulic fracturing origins from natural gas field in Kansas, the USA. Hubbert and Willis issued theoretical research result for relationship of tension fracture caused by hydraulic fracturing and surrounding stress in 1957 (Hubbert & Willis 1957). At present, it is an effective and practicable method to measure deep in-situ stress by theoretical and test research for tens of years. There are many inevitable difficulties during construction of deeply buried chamber and development of mineral resources. Secondary stress field will form due to stress adjustment in the rock during chamber excavation with concentrated stress near the chamber wall. Elastic strain energy stored in the rock mass will release suddenly with impetuous unstability damage for rock mass when stress exceeds breaking strength of rock mass. Broken rocks will eject on the chamberwall or a lot of rocks will outburst to generate violent blast of an explosion or shock wave. Such damage form of rock mass refers to rockburst. Rockburst will damage underground digging or project construction greatly so damage generation, development; prevention and control shall be researched with safe and economic significance for underground digging (Xu et al. 2002, Guo et al. 2006).
Northern landform is higher than southern one in the measurement zone.
