Strength of Compacted Clay at High Pressure

Samples of clay were compacted wet of optimum to the same initial water content and density conditions, and tested in UU and CU triaxial tests at confining pressures up to 1000 psi to simulate loading conditions on elements of soil in earth dam. One series of samples was prepared by static compaction to produce an initially flocculated soil structure, and another series of samples was prepared by kneading compaction to produce a dispersed structure. The UU tests indicated that all confining pressures, samples prepared by static compaction were stronger and stiffer than those prepared by kneading compaction. The CU tests indicated that statically compacted samples were more plastic and were slightly weaker than otherwise initially identical samples prepared by kneading compaction and tested at the same consolidation pressures. This relative loss in strength was probably due to a difference in consolidation characteristics which produced different water contents at failure. On an effective stress basis, the behavior of both types of samples was the same.