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Abstract A series of triaxial compressive tests and CT scanning tests on dense sandstones were carried out. The CT images of failure cracks in rocks under different confining pressures were obtained. Using the image processing technique and the statistic principle，three-dimensional geometric models of failure cracks are established. Based on these three-dimensional models，the influences of confining pressure on geometric form and distribution features of failure cracks were analyzed. The energy theory was employed to reveal the intrinsic energy mechanism of crack growth characteristics in rocks subjected to triaxial stress. The results show that the confining pressure had great effects on the forms，the quantity and the special distribution features of failure cracks in rocks. When the confining pressure value is lower，the great number of the failure cracks occurs with complex formation. When rocks are completely fractured，the main cracks and secondary cracks cross each other forming a crack network. When the confining pressure is higher，the number of main cracks decreases and secondary cracks disappear. The cracks network with complicated geometrical form is replaced by linear failure cracks in similar. The confining pressure has significant influences on the characteristics of energy dissipation and energy release of the failure cracks. With the increase of the confining pressure，the releasable elastic strain energy increases linearly and the dissipation energy gradually decreases. Under the lower confining pressures，rocks have more dissipated energy leading to a large number of failure microcracks with complex geometric formations. While under the higher confining pressures，rocks have less dissipation energy leading to less failure cracks with the regular geometric formations.
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Received: 02 July 2013
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2014, Vol. 33 
