Analysis of nonlinear rheological consolidation with vertical drains: large or small strain

Given the importance of vertical drainage systems in facilitating the stability of soft ground, this paper presents a feasibility study of small-strain consolidation solutions with vertical drains and a quantitative comparison with large-strain consolidation solutions. This solution incorporates essential factors, such as non-Darcian vertical and radial flows, nonlinear void ratio and permeability relationship, initial self-weight stress, elastic viscoplastic constitutive equation, and time-dependent loading. In the design of vertical drains for large and small deformation consolidation equations are comprehensively addressed. The numerical results obtained by the finite difference method demonstrate that the conventional small-strain consolidation method for soft clay has the potential to overestimate the dissipation of excess pore pressure and underestimate the settlement at the later stage, yet correctly assess the effective stress reduction during the initial loading period. Based on the comparison of consolidation data, the relative difference in settlement between large-strain and small-strain consolidation theories will exceed 5% as the accumulated vertical strain reaches about 13%. Another threshold exists for the ratio of the soil thickness to the influence radius (H / r(e)) to affect the consolidation rate, whether or not the self-weight stress is captured.