Modelling Suctions in a Cutting with a Bimodal Soil Water Characteristic Curve and Hydraulic Conductivity Function

Abstract

With future summers in the United Kingdom forecast to be warmer and drier the extent of desiccation cracking is expected to increase, with reciprocal effects on the hydraulic conductivity of the soil. This paper proposes a new method of implementing the effects of desiccation cracking into a hydrological slope model. The technique uses a bimodal soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF) that reflect the new water retention properties and increase in hydraulic conductivity that occurs when desiccation cracks form in the soil. An infrastructure slope model is created in the finite element software VADOSE/W. The modelled slope is the A34 Newbury bypass cutting, constructed in London Clay in south England. The cutting has been extensively monitored since January 2003 by researchers at Southampton University. This paper details the comparability of the calculated pore water pressures from the simulation with observed data from the cutting. The results from this initial analysis show that the proposed SWCC and HCF can predict winter suctions in the VADOSE zone better than the traditional unimodal functions.