EXPERIMENTAL-VERIFICATION OF CRS CONSOLIDATION THEORY

The paper presents and analyzes results from nine constant rate of str ain (CRS) consolidation tests on resedimented Boston blue clay (BBC) u sing a specially instrumented, computer-automated hydraulic consolidat ion device. Specimens were loaded using one of three vertical strain r ates (0.1, 1, and 3%/h), and pore pressures were measured at three poi nts through the specimen height and at the base. The CRS results were compared to the end of primary states in four incrementally loaded (IL ) oedometer tests performed using standard procedures. At the two fast er CRS rates, excess pore pressures (Delta u) developed and two method s were used to compute vertical effective stress (sigma(v)'): nonlinea r CRS theory of Wissa et al. that depends in part on Delta u measured only at the base; and direct integration of the measured Delta u distr ibution through the specimen (the ''isochrone method''). The results s how that at the two faster rates, the CRS tests based on nonlinear CRS theory are consistent with those obtained using the isochrone method; results from CRS tests at all three rates compare well with the IL te st results, despite base Delta u values exceeding 70% of applied verti cal stress in the 3%/h CRS tests. The CRS behavior of resedimented BBC is virtually independent of strain rate across the range tested; the value of preconsolidation pressure (sigma(p)') is rate independent as is the virgin compressibility. At sigma(v)' levels at and above sigma( p)', CRS tests loaded at 1 and 3%/h yielded coefficients of consolidat ion and hydraulic conductivity values that agreed well with IL test va lues. The paper supports the validity of nonlinear CRS theory and sugg ests that less structured clays such as those tested may have less rat e dependence during consolidation than soils with strong interparticle bonding and structure.