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Abstract Uniaxial compression tests on naturally fractured marble samples taken from the transportation tunnels of Jinping II hydropower station were carried out using MTS815 rock testing system. And the acoustic emission (AE) activities were monitored by PCI-II AE system during the whole experimental process. According to the AE counts，the precise positioning and tracking on the time-space revolution processes of natural fractures with different spatial distributions characteristics have been successfully achieved. Experimental results clearly indicate that the failure of fractured marble is a locally progressive failure process. The progressive increasing curve of acoustic emission cumulative boll number is closely related with the experimental loading process and stress readjusts and redistribution in rock. Both of the spatial distributions of single and parallel natural fractures are relatively simple. For the two types of marbles，the strong AE events (count＞20) are increasing along the natural fracture surface with the progressive increasing compressive stress at low stress level. When the compressive stress is close to the peak failure strength，strong AE events progressively accumulate at the end of the fracture tip；and then along the final rupture direction. For marble including intersectant natural fractures，the distribution of strong AE events are relatively uniform in the initial compaction stage. In addition，with the continuing increase in the compressive stress，the AE events around the fracture surface gradually increase；and then accumulate around the intersection point of fractures. The distribution of AE events in marble including mixed natural fractures are most complex than those of marble including other types of fractures. It is still not difficult to determine the internal weakness parts and the corresponding stress field distribution law based on the special distribution of strong AE event. The above experimental and analytical results are significant for investigating rock mass failure and instability mechanism，and also provide guidance for microseismic monitoring in fields.
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Received: 12 October 2012
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2013, Vol. 32 
