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Uncoupled and coupled solutions of volume change problems in expansive soils
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In this paper, the authors apply the general theory of consolidation/swelling for unsaturated soils to provide a reliable, practical technique for the prediction of one-, twoor three-dimensional volume change associated with unsaturated, expansive soils.Abstract:
Lightly loaded structures constructed on expansive soils are often subjected to severe distress subsequent to construction, as a result of changes in the pore-water pressures in the soil. The structures most commonly damaged are roadways, airport runways, small buildings, irrigation canals, spillway structures and all near ground surface structures associated with infrastructure development. Changes in the pore-water pressure can occur as a result of variations in climate, change in depth to the water table, water uptake by vegetation, removal ofvegetation or the excessive watering of a lawn. An analytical tool for the prediction of heave is extremely valuable to geotechnical engineers. There has been little advancement in the development of such a tool for solving engineering problems. There does not appear to be a computer program that has been written and widely accepted for solving this problem. It is important that such an analytical tool be developed and that it be developed for both oneand two-dimensional problems. The primary objective of this research study is to apply the general theory of consolidation/swelling for unsaturated soils to provide a reliable, practical technique for the prediction of one-, twoor three-dimensional volume change associated with unsaturated, expansive soils. The void ratio constitutive surface of an unsaturated, expansive soil was estimated from volume change indices obtained from conventional oedometer tests. Mathematical equations, which can be applied over a wide range of stress conditions, are proposed to describe the constitutive surfaces for both soil structure and water phase. The elastic parameter functions that are required for the volume change analysis are calculated from the constitutive surfaces with an assumed value ofPoisson's ratio. The solutions to the volume change problems associated with an unsaturated, expansive soil are obtained using both an uncoupled and a coupled approach. In the uncoupled approach, the continuity equation for the water phase and the equilibrium equations are solved independently. Uncoupled solutions are obtained using a partial differential equation solver, called FlexPDE. In the coupled approach, the continuity equation and the equilibrium equations are solved simultaneously. Coupled solutions are obtained using a finite element program, called COUPSO. The examples presented in this study represent typical volume change problems that are often encountered in engineering practice (i.e., influence of vegetation on light engineering structures, water leakage under floor slab,read more
Citations
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The prediction of one-, two-, and three-dimensional heave in expansive soils
Hung Q Vu,Delwyn G. Fredlund +1 more
TL;DR: In this paper, the prediction of heave in unsaturated, expansive soils has been studied primarily as a one-dimensional type analysis, and a methodology that can be used for the predic...
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Numerical analysis of an experimental pipe buried in swelling soil
TL;DR: In this article, the pipe-soil interaction for pipes buried in expansive soil when subjected to swelling soil movement due to increase in moisture content is investigated, and a three dimensional numerical model is developed to analyse the pipe response, using FLAC3D computer program.
Journal ArticleDOI
A simple analytical solution to one-dimensional consolidation for unsaturated soils
TL;DR: In this paper, a simple analytical solution to the one-dimensional consolidation theory for unsaturated soils is presented, where the coefficients of permeability and volume change are assumed to remain constant throughout the consolidation process and two new variables are introduced to transform the two coupled governing equations of porewater and pore-air pressures into an equivalent set of partial differential equations.
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