Closed-form solution for consolidation of three-layer soil with a vertical drain system

A closed-form solution for consolidation of three-layered soil with a vertical drain system is proposed in this paper. The solution is precise but has been proven to have some convergence problems. The use of double precision in the calculation program was found to be insufficient to guarantee convergence of the results. After symbolic operation was adopted in Matlab, the convergence was improved. Further study showed that the convergence problem still exists in cases when the calculation parameters for the different layers are significantly different. Hence, a new method is proposed to enlarge the controlling precision for the overall average degree of consolidation of the entire thickness of the soil and add controlling precision for the overall average degree of consolidation of each soil layer. Using this new method, the convergence problem is solved. An example case is presented of calculations for a three-layer embankment with a vertical drain system in Yueqing Bay in China. The pore pressure calculated along the depth of the embankment agrees well with in situ measurements.