A Meso-Macro Method of Evaluating Water Content Effect on Direct Tensile Fracture in Brittle Rocks

Abstract

Tensile stress is one of the primary forms of loading triggering the fracture in brittle rocks. Water content strongly affects the fracture process induced by meso-crack extension under the direct tensile loading of brittle rocks. Due to limitation of current equipments, the experiment of direct tensile fracture considering water content effect of brittle rocks is hardly implemented. Furthermore, the meso-macro model simultaneously considering the influence of water content and tensile loading on fracture behaviours of brittle rocks is also rarely studied. This paper proposes a meso-macro mechanical model to evaluate the water content effect on the fracture process under direct tensile loading of brittle rocks. This model is developed by combining the suggested model of meso-crack extension under direct tensile loading, the correlation of macroscopic strain and meso-crack extension, and considering the effect of water content on fracture toughness KIC and initial damage D0. This meso-macro model is linking the development process of meso-crack initiation, extension and coalescence to macroscopic fracture. The axial stress-strain curves during progressive tensile fracture under different water contents were studied, and the rationality of the suggested theoretical model was validated by the test results. The influences of water content on the relation between wing crack length and axial stress, the relation between wing crack length and stress intensity factor KI, crack initiation stress, peak stress, and elastic modulus were analyzed. The influences of the model parameter β and the initial crack angle φ on the peak stress and crack initiation stress under the different water contents are also discussed.