Comparison of alternative methods of measuring the residual strength of a clay.

This paper describes a series of drained tests on Lias clay at various normal stresses in both a reversible shear box and a modified bromhead ring shear apparatus. The residual failure envelopes were found to be curved at normal stresses below 150 kN/sq m (22 lb/ sq in.). At normal stresses above this value, the modified bromhead ringshear tests produced lower values of residual shear strength than reversal shear box tests. The results indicate that residual failure surfaces are not developed at normal stresses below 30 kN/sq m (4.4 Lb/sq in.).