Pore Distribution and Damage Evaluation of Modified Red Clay Based on NMR

Abstract

This study investigates the modification of red clay with calcium carbonate. The pore distribution was obtained using a combination of mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) techniques. The influence of calcium carbonate content, density, confining pressure, and shear strain on the pores was studied. Introducing pore classification to assess the extent of the damage under different conditions and the relationship between different types of pores. The results show that the content of added calcium carbonate has little effect on pore distribution when the density is low (1.4 and 1.5 g/cm³). The content of calcium carbonate has an influence on pore distribution when the density is high (1.6 g/cm³). With the density increases, the number of macropores and mesopores between soil particles decreases, while the small pores increase. The confining pressure results in the preferential drainage of free water from macropores. The porosity decreases as the confining pressure increases. Under the same confining pressure, as the shear strain increases, the large pores decrease while the small pores increase. Based on the analysis of damage degree, the shear strain is positively linearly related to the damage degree of intragranular mesopores, which forms a convex function relationship with intragranular macropores and intergranular mesopores (except under a confining pressure of 100 kPa).