Experimental and numerical investigation into the mechanical degradation of clayey gravel under internal erosion

The mechanical response of clayey gravel after prescribed fines removal was investigated using triaxial tests and discrete element method (DEM) simulations. Four laboratory states were examined at confining pressures of 30, 60 and 100 kPa. A corrected erosion degree, ξD, expressed the relative decrease in the grading fractal dimension along the prescribed removal sequence. Relative to the initial compacted reference, failure strength at 30 kPa decreased from 295.9 to 35.4 kPa in the most severely treated state, a reduction of 88.0%. Apparent total-stress cohesion decreased from 60.5 to 12.9 kPa, and the apparent friction angle decreased from 34.6° to 6.8°. The stress–strain curves exhibited lower peaks and reduced peak prominence as the prescribed loss level increased. DEM simulations using one final parameter set reproduced the principal response trends. At 30 kPa, the fine–fine contact population decreased by approximately 49%, while the coarse–coarse contact population increased. The contact counts and force distributions show that additional coarse–coarse contacts do not compensate for the loss of fines-related interactions. The combined assessment relates measured strength changes to contact redistribution in the numerical assemblies and provides a material-scale basis for evaluating clayey gravel subjected to fines removal and associated conditioning.