New Approach to Analysis of Consolidation Data at Early Times

If ${\overline{U}}_v>0.50$, Asaoka’s method can be used to evaluate $c_v(s)$ and $s_{cf}$ from settlement data, but the method leads to unsafe results when the data are measured when ${\overline{U}}_v<0.50$ (i.e., $c_v$ much too high and $s_{cf}$ much too low). For field conditions where all data have $({\overline{U}}_v)<0.50$, one cannot predict $s_{cf}$ or estimate $c_v(s)$ solely on the basis of measurements of surface settlement. These conditions require analysis of both piezometer and settlement data together with knowledge of the initial excess pore pressure ($u_0$). With proper instrumentation, Johnson’s incremental time ($\mathrm{\Delta }t$) graphical method can be used to estimate $c_v$ and $s_{cf}$, but this technique tends to be cumbersome and imprecise. Two new techniques (EFM-1 and EFM-2) based on the Laplace Transform are proposed. The accuracy of $c_v$ and $s_{cf}$ estimates using EFM-1 and EFM-2 are evaluated as functions of piezometer location, time, and uncertainty in $u/u_0$.