Numerical analysis of surcharge preloading consolidation of layered soils via distributed sand blankets

Abstract

Surcharge preloading consolidation of soft soils often implements a layer of fully arranged aggregate materials. The volume of drained water is abundant at the early stage of consolidation, but it reduces at middle and later stages, during which the fully arranged sand blanket will be a waste. In this investigation, a concept of distributed sand blankets is proposed to save aggregate materials. A series of finite element analyses have been performed on layered soils with distributed sand blankets. A mixed type of drainage boundary is assigned to a representative model, where a half sand blanket is perfectly pervious and a half width of soil among sand blankets is impervious. From parametric study, it has been found that a pave ratio between sand blankets and the total soil width can be selected in a range of 40%–60%, which will save aggregates by approximately 50% but cause an increase of consolidation time by less than 10%. For a fixed pave ratio, more evenly spaced sand strips with smaller width should be employed to optimize the design. The effectiveness of distributed sand blankets is not influenced by the anisotropy of hydraulic conductivity, elastic modulus, Poisson’s ratio, and thickness in multiple soil layers.