The Effect of Weathering on the Mineral Grains and Macroscale Young’s Modulus of Granites

Weathering process leads to changes in mineral composition, microdefects and mechanical properties of mineral grains, which has a significant impact on the macroscale mechanical properties of granitic rocks. In this paper, four granitic samples with different weathering degrees were investigated using microscale rock mechanics experiments (micro-RME), macroscale rock mechanics experiments (macro-RME) and accurate grain-based model (AGBM). The following conclusions can be achieved. First, quartz is erosionally resistant compared to feldspar and biotite. The weathering products of feldspar and biotite are sericite and chlorite, respectively. Second, with the increasing of weathering degree, the volume fractions of quartz and weathering products increase, meanwhile the volume fractions of feldspar and biotite decrease. Third, during the weathering process, Young’s modulus of quartz and feldspar almost keep constant, however, Young’s modulus of biotite decreases significantly. Fourth, the weathering process significantly increases the volume of microdefects, including pores and microcracks. Finally, from the viewpoint of the weathering effect, we discovered a negative correlation between quartz content and the macroscale Young's modulus of granites.