Analysis of rock burst in critical section of second part of Karaj- Tehran Water Supply Tunnel

摘要

One of the geotechnical hazards in the tunnels under high overburden and high in siturnstresses is the phenomenon of rock burst. Rock burst is a typical geologic phenomenon caused by excavationrnin rock masses. In this phenomenon, because of stress released and explosion in rock masses, theyrnare broken as large and small pieces and are distributed, so that leads to damage of peoples or equipments.rnTherefore, familiar with this phenomenon and its mechanism of occurrence, is need to analyze thisrnissue. The second part of water supply Karaj-Tehran tunnel with a length of 14 km and about 4.5 m diameterrnis located in Tehran province. Rock burst analysis has been carried out in the tunnel from kilometerrn6 to 9.5 that is critical section because of high overburden (up to 800 m) and presence of faults andrncrushed zones. In this paper, for predicting rock burst in the critical section of second part of Karaj-rnTehran tunnel, four criteria including, Strain energy, Rock brittleness, Seismic energy and Tangentialrnstress criterion are used. Analysis results show that units with high overburden have high possibility ofrnrock burst.