Strength-dilatancy relation of sand containing non-plastic fines

Bolton's stress-dilatancy equation is mainly used for clean sands. It needs to be investigated whether this equation could be used for sand with non-plastic fines or not. A series of drained triaxial compress tests were conducted for the sand with non-plastic fines. It was observed from these tests that the peak-state and critical-state friction angles increased with increasing the fines content. The peak-state friction angle and maximum dilatancy angle increased with decreasing the confining pressure. It was also found that the relationship between the excess friction angle (i.e. the difference between the peak-state and critical-state friction angles) and maximum dilatancy angle was unchanged with the non-plastic fines content. This has illustrated that the Bolton's stress-dilatancy equation proposed for clean sands could still be applied to sands with non-plastic fines.