A LABORATORY STUDY OF THE STRENGTH OF 4 STIFF CLAYS

The results of oedometer and triaxial tests on high-quality intact sam ples of four natural stiff clays are presented and compared with the c orresponding results for reconstituted clays, By this means it has bee n possible to identify the influence of the micro-structure on the com pressibility and peak strength of the natural clays, All four clays ex hibit rapid loss of strength after peak with well-defined post-rupture strength envelopes, At low confining pressures the post-rupture angle s of shearing resistance are all close to the corresponding intrinsic critical state values, but for some of the clays there is a small cohe sive intercept, At higher confining pressures the post-rupture angles of shearing resistance are less than the corresponding critical state values, It is concluded that the strength reduction that takes place f rom peak to post-rupture strength is due primarily to breakage of inte rparticle bonds, but that at higher confining pressures some particle orientation also takes place.