Effects of overconsolidation ratios on the shear strength of remoulded slip surface soils in ring shear

The drained shear strength of clay soils is independent of stress history, though there have been instances in the geotechnical literature of studies that have suggested some dependence of stress history on the drained shear strength. Accordingly, the effect of artificial overconsolidation ratios (OCR) on the drained shear behaviour and shear strength of a high plasticity clay soil and a loess soil has been discussed from an experimental point of view. The slip surface materials of two landslides were remoulded and consolidated from slurry and were subjected to drained shear tests. Four overconsolidation ratios (OCR 1, OCR 2, OCR 4 and OCR 6) were tested under constant effective normal stress in a ring shear apparatus. The overconsolidated specimens achieved peak friction coefficients at relatively lesser shear displacements in contrast to the normally consolidated specimens in the Kamenose soil. The fully softened friction coefficient and the residual friction coefficient showed stress dependency in the OCR 1 bloc of both soils. However, between the two soils, although dissimilar patterns of variation of these two shear strength parameters in the overconsolidated state compared to the normally consolidated state was evident, significant differences in the residual friction coefficient attributable to overconsolidation were not found.

► Shear behaviour of Kamenose and Miaowan soils reflects grain size and mineralogy.
► Fully softened and residual friction coefficients are stress dependent in OCR1.
► Differences in the residual friction coefficient at all tested OCR are non significant.