Effect of mineral compositions on mechanical properties of granite residual soil

Mineral composition has an important effect on the mechanical properties of granite residual soil under the influence of hot and humid climate. In this paper, different minerals including red clay, kaolinite, montmorillonite and illite powder were used to reconstruct the soil samples. A series of mechanical experiments including compressive, shear, tensile and disintegration tests were carried out to study the influence of different minerals on the mechanical strength of soil. And the influencing mechanism was revealed from macro-, meso- and micro-perspectives. The results show that the influence of the four minerals on tensile strength is kaolinite > illite > montmorillonite > red clay. From the meso-perspective, the disperse soil particles will become tight and occlusive after improvement with the mineral. And the particles will be surrounded by the minerals and form a bridge connection between the soil particles. If the cementing capacity of the sample is stronger, the ability to withstand the external force is more positive. From the microscopic perspective, the mechanical improvement of soil with mineral is not only to reduce the porosity of sample mass, but also to form more particle aggregates with higher strength, and the particle aggregates should be connected by skeleton structures. With the strengthened structure formed by mineral, the soil has certain properties of compressive, shear, tensile and disintegration resistance. The finding can provide some engineering guidance for the granite residual soil areas.