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Abstract Columnar jointed basalt is a specially compositional rock mass by many prismatic rock blocks with the irregular polygon on the transverse section. For documenting the anisotropic properties and unloading failure mechanism of jointed basalt rock，detailed in-situ and laboratory investigation have been carried out. First，the geometrical anisotropy property of columnar jointed basaltic rock was summarized by detailed in-situ statistic for irregular polygon of its transverse section and the scanning electron microscope(SEM) analysis of different kinds of joint faces. Then，the deformational anisotropy property was checked by the ultrasonic testing with the direction which was parallel to the axis of the columnar block and the direction which was vertical to the axis of the columnar block in field. And，the strength anisotropy property was also tested by two ways，i.e. point load test for in-situ rock block with different directions and uniaxial compression test for standard cylindrical specimens with different loading directions. According to above resultant investigation，the basic failure mode of structure-stress control for columnar rock mass and its specific failure performances have been discussed，so as to provide helpful recognition and suggestion for reasonable excavation and supporting design for the underground caverns and tunnels in similar rock mass with columnar joint sets.
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Received: 28 May 2013
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2013, Vol. 32 
