Author(s): M. Mavroulidou; R. I. Woods; M. J. Gunn
Linked Author(s):
Keywords: Numerical modelling; Trench drains; Variably saturated soil; Transientresponse; Storage coefficient
Abstract: Most of the existing solutions for trench drainage systems, assume saturated soil theories. It can be anticipated however, that trench drainage involving lowering of the water table might produce desaturation of the soil. The influence of the unsaturated zone on the rate at which the transient seepage develops can be significant when shallow groundwater table movement is involved and should be considered by the trench drainage model. Due to complications involved with unsaturated hydraulic property calculations, simplified forms of these properties have often been used in the geotechnical engineering literature, for the numerical solution of flow in variably saturated porous media. The writers assess the performance of some of these simplifying assumptions, applied to the numerical modelling of trench drainage. Comparisons are made with sandbox model results found in the literature, as well as results derived by the writers’model, that incorporates possible desaturation of the materials based on data from real soils, rather than simplified forms of the unsaturated hydraulic properties. It is shown that the rate at which the transient seepage develops might be considerably underestimated when simplifying assumptions about the storage coefficient are made, and especially in coarse soils. Thus, the importance of using realistic values for the storage term variation, when modelling transient drainage conditions, is demonstrated.
Year: 1999