At-Rest Lateral Earth Pressure of Consolidating Clay

Two clay slurries with different controlled chemistries (flocculated and dispersed) were consolidated in large-diameter rigid cylindrical slurry consolidometers. During two cycles of consolidation and rebound, the axial deformations, pore pressure, and both axial and radial stresses were measured directly, thereby providing a continuous record of the stress and strain history of each sample. The coefficient of lateral earth pressure at-rest, K_o, was found to remain essentially constant during the loading phase of a loading-unloading cycle, but its value increased gradually during unloading until it exceeded unity when the overconsolidation ratio was about 2. Several indirect approaches were used to compute K_o from shear strength parameters determined from triaxial compression tests on specimens trimmed from block samples of the same two clays for which direct measurements were obtained, and the results were found to be in good agreement. Within the scope of the test data, neither pore fluid chemistry nor the associated clay fabric exerted much influence of the measured (during loading) values of K_o, which were in the range of 0.70 ±0.05.