Study of mechanical characteristics and strength deterioration of wide-graded sand under internal erosion

Internal erosion generally occurs in the pore structure of wide-graded granular materials in water-rich environments, which leads to strength deterioration and immediate deformation in hydraulic engineering foundations. To examine the mechanism of strength deterioration in sand influenced by fine particle content, consolidation pressure, and hydraulic gradient, triaxial seepage shear deterioration tests were performed utilizing a triaxial apparatus designed for internal erosion analysis. The control variable method was employed to analyze the impact of each factor on the strength deterioration of sand under internal erosion. The findings demonstrate that fine particle content, consolidation pressure, and seepage pressure substantially impact the erosion process, consequently influencing the strength mechanism of the sand. The increase of fine particle content and consolidation pressure diminishes soil deterioration, with the strength deterioration index ranging from 27.8% to 41.2% and 27.8% to 50.5%, respectively. In contrast, the increase of hydraulic gradient value markedly intensifies soil deterioration, with the index ranging from 27.8% to 54.3%. A hyperbolic function was employed to model the strength deterioration index, and a parameter formula for the deterioration index was established using MATLAB. The findings serve as a benchmark for assessing the deterioration of soil mechanical strength due to erosion failure and for the mitigation and management of erosion failure incidents in hydraulic engineering.