Experimental investigations on discrepancy in consolidation degrees with deformation and pore pressure variations of natural clays

Degrees of consolidation can be determined by two different methods using deformation and excess pore pressure variations for reconstituted and natural clays in laboratory tests and engineering practice. Theoretically, the relationship between the degrees of consolidation determined using the two methods should be unique. However, this study finds the experimental results from fifteen one-dimensional incremental load consolidation tests on five kinds of natural clays deviated from the theoretical line. The experimental relationships correlating the degrees of consolidation determined by the two methods are also found not unique, instead, consisting of a cluster of curves depending on different step stress increments. Two key causes are found to be responsible for the substantial discrepancy between experimental and theoretical results: (1) the nonlinear development of deformation during the dissipation of excess pore pressure; (2) the degree of consolidation determined by excess pore pressure measurements lower than 100% when the degree of consolidation determined based on the deformation-time curve becomes 100%. It is also found that the experimental relationships correlating the degrees of consolidation determined by the two methods are significantly affected by the values of degree of consolidation with excess pore pressure dissipation at 100% of consolidation degree with deformation observations.