Effects of Anisotropic Versus Isotropic Consolidation in Consolidated-Undrained Triaxial Compression Tests of Cohesive Soils.

摘要

The results of a series of consolidated-undrained (CU) triaxial compression tests performed on normally consolidated and overconsolidated specimes of two clays consolidated both isotropically (ICU tests) and anisotropically (ACU tests) are presented and analyzed in this report. The specimens were trimmed from samples of Vicksburg Buckshot clay (LL = 57) and a clay from the East Atchafalaya Basin Protection Levee (EABPL) project area (LL = 79), both of which had been consolidated from a slurry in large-diameter consolidometers under a maximum vertical consolidation pressure of 3.0 kg/sq cm. Data presented include stress-strain curves, pore pressure observations, final water content distributions within the specimens, and shear strength envelopes based on total and effective stresses. Test results indicate that the change in volume during consolidation and the water content at the end of consolidation are not a unique function of the vertical consolidation stresses but are related to the mean effective consolidation stress. Total stress envelopes based on Taylor's method of deriving strengths of anisotropically consolidated specimens from test results obtained from isotropically consolidated specimens slightly underestimate observed values. In this context, Taylor's method is an appropriate means of predicting strengths for various K sub c ratios from conventional ICU tests. Use of hyperbolic stress-strain relationships derived from ICU tests in finite element codes for ACU conditions will lead to erroneous results. Further testing of anisotropically consolidated soils under stress systems that better simulate in situ conditions is needed.