Therewas a hydropower in the transition zone between Qinghai-Tibet plateau and Sichuan Basin, while excavating the traffic tunnel towards its underground structure at about 631m horizontal depth, many rock burst happened at right arch, and the hydraulic fracturing three dimensional stress measurement was adopt at the place immediately. The paper introduced the process and the result of this measurement, analyzed the spatial distribution of crustal stress and the maximum tangential stress σθmax in tunnel excavation. It found that the direct mechanical cause of the rock burst was that the σθmax at the site of right arch reached 39MPa, which have greatly exceeded the rock burst critical stress σlcr 29MPa.
The hydropower is located in Ganzi Tibetan autonomous prefecture, a transition zone of Qinghai- Tibet plateau and the Sichuan Basin, is a high mountain canyon. In the zone, mountains and the ditches stagger each other, and the whole terrain is from west to east, the local faults are not developed, and no regional active faults pass through. While excavating the traffic tunnel of diversion routes, rock burst happened at about 631m Horizontal depth. It occurs during the smoke cleaning after blasting, and occasionally happened after the tunnel have finished for 1 to 2 months, It mostly occurred at right arch on the wall, mainly medium-sized peeled off. To identify the crustal stress at the location of rock burst, a three dimensional stress measuring point was conducted in the traffic tunnel which is about 635m away from the entrance. The measuring point includes of three 25m depth boreholes with diameter ∅76 mm, two are horizontal boreholes named ZKD01 and ZKD02 with 80° angle each other, they are about 0.85m high to the bottom, and the other vertical borehole named ZKD03 at the bottom.