Quantitative evaluation of rock brittleness based on crack initiation stress and complete stress–strain curves

Brittleness is an important rock material property, and its accurate evaluation has guiding significance in construction as well as in disaster prevention and reduction. Considering the limitations of the existing brittleness indices, a new brittleness index based on the overall stress–strain process of a rock mass is established that considers both the stress growth rate between the peak stress and the crack initiation stress before the peak, as well as the stress descent rate after the peak. Uniaxial and triaxial compression tests were conducted to evaluate the new index. The results of the tests show that the new index can accurately determine the rock brittleness according to the prepeak stress–strain curve under uniaxial loading system conditions, which compensates for the limitation of inaccurate postpeak curves for brittle rock. Under triaxial compression conditions, the new index more clearly represents the influence of the confining pressure on the brittleness of marble. The reliability and comprehensiveness of the new index are verified, and these research results may improve the existing evaluation of rock brittleness.