The shear of clays of varying plasticity against interfaces of different ma
terials and varying roughness has been studied in the ring shear apparatus.
Results are compared with the shearing resistance of clay-on-clay. Particu
lar attention has been paid to shearing resistance with large displacements
, and the influence of the interface in changing the shearing mode. The eff
ect of corrosion of steel interfaces has been examined, as has the effect o
f fast shearing.