Abstract: Vertical drains including sand wells and prefabricated drains have been widely used to accelerate the consolidation of the ground consisting of soft clays. Various forms of analytical solutions have been proposed from time to time for evaluating the consolidation of homogeneous and isotropic ground with vertical drains under axisymmetrical conditions. In these solutions, however, the stress increases in the ground were assumed uniformly distributed along the depth of the vertical drain. It is evident that this assumption is not applicable to the cases where either the ratio of the depth of the vertical drain to the breadth of the surcharge-applied area is relatively high or the zone of influence of the vertical drain is in the vicinity of the edge of the surcharge-applied area. on the basis of an existing equal strain solution of radial and vertical coupled consolidation, this paper presents a solution for the situation that the stress increase in the ground is arbitrarily distributed along the depth of the vertical drain. In addition, the effects of the stress increase distribution and ramp loading rate on the ground consolidation are analysed. It has been found that the consolidation solution for a uniformly distributed stress increase underestimates the consolidation rate of the ground, whereas the solution for an instantaneously applied loading condition overestimates the consolidation rate.

Key words: consolidation, vertical drain, equal strain, stress increase, well resistance, smear, step loading, ramp loading