Laboratory Validation of Ultra-Soft Soil Deformation Model

Abstract

Ultra-soft soil with high moisture content will experience large strain deformation under one-dimensional compression with little or no gain in effective stress. Such deformation behaviour does not comply with Terzaghi’s effective stress gain theory. The e-log \( \sigma_{v}^{\prime } \) relationship of ultra-soft soil is non-linear with large compression index in the first order of log cycle. This paper proposes three compression indices (\( C_{c1}^{*} \), \( C_{c2}^{*} \) and \( C_{c3}^{*} \)) for stresses covering three log cycles. Good prediction of settlement magnitude is possible with these newly proposed compression parameters for ultra-soft soil. In addition, implicit finite difference model applying the large strain theory is also proposed and validated with results from laboratory measurements. The time factor curves for ultra-soft soil with large strain compression are also proposed and validated.