Consolidation in spatially random unsaturated soils based on coupled flow‐deformation simulation

Abstract

This paper integrates random field simulation of soil spatial variability with numerical modeling of coupled flow and deformation to investigate consolidation in spatially random unsaturated soil. The spatial variability of soil properties is simulated using the covariance matrix decomposition method. The random soil properties are imported into an interactive multiphysics software COMSOL to solve the governing partial differential equations. The effects of the spatial variability of Young's modulus and saturated permeability together with unsaturated hydraulic parameters on the dissipation of excess pore water pressure and settlement are investigated using an example of consolidation in a saturated-unsaturated soil column because of loading. It is found that the surface settlement and the pore water pressure profile during the process of consolidation are significantly affected by the spatially varying Young's modulus. The mean value of the settlement of the spatially random soil is more than 100% greater than that of the deterministic case, and the surface settlement is subject to large uncertainty, which implies that consolidation settlement is difficult to predict accurately based on the conventional deterministic approach. The uncertainty of the settlement increases with the scale of fluctuation because of the averaging effect of spatial variability. The effects of spatial variability of saturated permeability k sat and air entry parameters are much less significant than that of elastic modulus. The spatial variability of air entry value parameters affects the uncertainties of settlement and excess pore pressure mostly in the unsaturated zone. Figure 6. Effect of δ lnE on (a) mean and (b) standard deviation of surface settlement (COV E = 150%, WT = 6 m). COUPLED FLOW AND DEFORMATION IN SPATIALLY RANDOM UNSATURATED SOILS 691 Figure 7. Influence of δ lnE on mean of pore water pressure (COV E = 150%, WT = 6 m): (a) t = 1 s; (b) t = 1 min; (c) t = 10 min; (d) t = 1 d. [Colour figure can be viewed at wileyonlinelibrary.com] 692 Y. CHENG ET AL.Figure 10. Effect of COV E (WT = 6 m) on (a) mean and (b) standard deviation of surface settlement (Solid line: COV E = 50%; Dotted line: COV E = 150%). 694 Y. CHENG ET AL.Figure 11. Influence of δ ln(ks) on mean of pore water pressure (COV ks = 150%, WT = 6 m): t = 1 s; (b) t = 1 min; (c) t = 10 min; (d) t = 1 d. [Colour figure can be viewed at wileyonlinelibrary.com] COUPLED FLOW AND DEFORMATION IN SPATIALLY RANDOM UNSATURATED SOILS 695 Figure 13. Effect of δ ln(ks) on settlement (COV ks = 150%, WT = 6 m): mean settlement; (b) standard deviation of settlement.Figure 14. Comparison of settlement with different COV ks (Solid line: COV ks = 50%; Dotted line: COV ks = 150%, WT = 6 m). 698Y. CHENG ET AL.

Advances in Gaussian random field generation: a review

“…19). Cheng et al (2017) [15] integrated the random field simulation with numerical modeling of coupled flow and deformation to study the consolidation in spatially random unsaturated soils. The spatial variability of soil properties following the lognormal distribution, such as Young's modulus, saturated permeability, and unsaturated hydraulic parameters, were simulated using matrix decomposition method.…”

Effect of the Water-Air Coupling on the Stability of Rainfall-Induced Landslides Using a Coupled Infiltration and Hydromechanical Model

“…Many rainfall infiltration analysis methods for unsaturated soil slopes consider pore-air pressure to be equal to zero by using Richards' equation [11] to model the subsurface fluid flow [12][13][14][15][16]. These models ignored the coupling with airflow in pores assumed that the airflow is much freer compared with water flow.…”

An approach for modelling spatial variability in permeability of cement-admixed soil

“…Random finite element study on consolidation problems for soil with variable permeability and coefficient of volume change has been reported widely (e.g. [1,3,14]). However, the soil is assumed to behave in a linear elastic manner and does not undergo yielding.…”