FAILURE CHARACTERISTICS OF ROCK MASS WITH INTERMITTENT JOINTS OF DIFFERENT CONNECTING RATES UNDER DIRECT SHEAR TEST

Rock bridges with different shapes, connectivity rates and arrangements, play a decisive role during slope stability evaluation. Indoor direct shear test combined with the characteristic parameters of acoustic emission is carried out. The test results reveal the failure law of rock mass containing intermittent joints with different connectivity rates and different normal stress states.The results show that: under the condition of direct shear, with the changes of normal stress and connectivity rate, failure surfaces of rock mass appear as "A-line-shaped", "X-shaped", "serration-shaped", "Z-shaped" and their combinations, which are somewhat smooth. The crack coalescences of rock mass resulting in failure happen at the same time. When normal stress is constant, with the increase of connectivity rate in intermittent rock bridges, AE cumulative counts grow linearly, while the peak value of AE counts increases generally. When the connectivity rate is constant, with the improvement of normal stress, the peak values of AE counts and AE cumulative counts both reach their peaks under the middle normal stress. Study on the failure and deformation characteristics of rock bridges with intermittent joints is not only useful to the analysis of the mechanical properties of rock mass, but also is good to the evaluation and prediction in slope engineering.