EXPERIMENTAL AND MESO-SCALE NUMERICAL MODELING OF SPLITTING TENSILE BEHAVIOR OF WEATHERED GRANITES FROM SOUTH CHINA

This paper presents an investigation into the splitting tensile damage and fracture behavior of granite rocks from South China showing various levels of weathering. The rock samples were selected from Conghua, Guangdong Province, and can be sub-divided into three series, namely, fresh, slightly weathered and moderately weathered granite rocks. Mineral composition tests and Brazilian tension tests were conducted to study the difference in mineral compositions and its effect on the fracture failure patterns. Two types of pre-processing approaches were adopted to represent the meso-scale structure of weathered granites, one using a statistical method considering spatial correlation character and the other using digital image processing technique. Comprehensive numerical analyses of the Brazilian tests were then carried out using bonded-particle discrete element method. The test results show that the feldspar minerals in granite will progressively change into clay minerals with the increasing weathering levels, which leads to a decrease of the strength of crystallization, an increase of void defects, and in turn the degradation of the macro-scale mechanical properties of granites. It is also found that the single crack failure pattern is dominant in fresh granites whilst the moderately weathered granite samples present multiple crack branching, and that the brittleness of granite rocks decreases with the weathering levels. The numerical results from the two types of meso-scale numerical models both compare well with the test observation that the tensile strength decreases with the weathering levels, and similar fracture failure patterns are also given. Moreover, the present numerical study can provide an in-depth investigation into the meso-scale cracking mechanism in the granite rocks with respect to the weathering induced internal deterioration.