Coupled Flow And Deformation In Unsaturated Soils Based On Random Field Theory

Actually, soils are unsaturated under normal circumstances. Inprevious studies on unsaturated soils, the soil is assumed to behomogenous. In reality, soils have been subject to various stresses, porefluids, physical and chemical changes, its properties vary spatially evenwithin the same soil layer. Natural soils at an unsaturated state are morecomplicated considering coupled flow and deformation.When a vertical load is applied on a layer of unsaturated soil, thestudy on the uncertaintis caused by the spatial variation of soil propertieshas certain theoretical meaning and guiding significance. In this study,spatial random soils are investigated based on the random field theory. Thespatial variability of soil properties is simulated using the covariancematrix decomposition method together with the Monte Carlo simulationmethod. The main research findings are summarized as follows:(1) A parametric study of coupled unsaturated consolidation in spatialrandom soils to investigate the influence of elastic modulus, saturatedpermeability and unsaturated hydraulic properties. The results showthat the mean and standard deviation of the settlement are significantlyaffected by the coefficient of variation of elastic modulus. Theuncertainty of the settlement is increased due to the spatial variabilityof elastic modulus. In general, the effect of spatial variability ofsaturated permeability is much less significant than that of elasticmodulus and it mainly affects the unsaturated consolidation in process.For a finer soil, the dissipation of excess pore water pressure and thedisplacement during consolidation is much slower than that in a coarse soil.(2) A random finite element analysis is carried out to examine the effectsof spatial variability of shear modulus, soil permeability and degree ofsaturation on seabed responses. The results indicate that the pore waterpressure and stress distribution in the seabed are affected by spatialvariability of shear modulus significantly. The uncertainty of oscillatedpore pressure is increased due to the spatial variability of shearmodulus. The effect of spatial variability of soil permeability on seabedresponse is less significant than that of shear modulus. The spatialvariability of soil permeability increases the uncertainty of oscillatedpore pressure at shallow depth of the seabed. The influence of degreeof saturation is less significant, but it effects the whole porous seabed.