Effect of plastic fine particles on shear strength at the critical state of sand–clay mixture

A large number of engineering cases have shown that there is significant presence of the sand–clay mixtures during the engineering geological accidents. Static liquefaction or loss of bearing capacity is frequently observed due to the rise in pore water pressure from large deformation in such engineering geology. This study investigates the static behavior of sand–clay mixtures with varying fines contents and various plasticity indices of fines by means of the monotonic drained consolidation triaxial shear tests in conjunction with the binary packing model. Factors influencing the active fines content ( b) of the sand–clay mixtures are examined based on the mixtures’ critical state. This study also discusses the reasons for variations in the critical friction angle ( M) of the sand–clay mixtures using environmental scanning electron microscope tests. Results indicated that the changes of fines content and the plastic index of fines have a certain effect on the static behavior, active fines content ( b), and the friction angle ( M) of the sand–clay mixture. This study presents an equation with reliable predictive results. These findings hold considerable importance for a deeper understanding of the mechanical properties of the sand–clay mixture with and the influencing mechanisms of different plasticity index of fines.