Unsaturated soil mechanics has rapidly become a part of geotechnical engineering practice as a result of solutions that have emerged to a number of key problems (or challenges). The solutions have emerged from numerous research studies focusing on issues that have a hindrance to the usage of unsaturated soil mechanics. The primary challenges to the implementation of unsaturated soil mechanics can be stated as follows: (1) The need to understand the fundamental, theoretical behavior of an unsaturated soil; (2) the formulation of suitable constitutive equations and the testing for uniqueness of proposed constitutive relationships; (3) the ability to formulate and solve one or more nonlinear partial differential equations using numerical methods; (4) the determination of indirect techniques for the estimation of unsaturated soil property functions, and (5) in situ and laboratory devices for the measurement of a wide range of soil suctions. This paper explains the nature of each of the previous challenges and...

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Unsaturated Soil Mechanics in Engineering Practice

The range of problems that geotechnical engineers must face is increasing in complexity and scope. Often, complexity arises from the interaction between the soil and the environment – the topic of this lecture. To deal with this type of problem, the classical soil mechanics formulation is progressively generalised in order to incorporate the effects of new phenomena and new variables on soil behaviour. Recent advances in unsaturated soil mechanics are presented first: it is shown that they provide a consistent framework for understanding the engineering behaviour of unsaturated soils, and the effects of suction and moisture changes. Building on those developments, soil behaviour is further explored by considering thermal effects for two opposite cases: high temperatures, associated with the problem of storage and disposal of high-level radioactive waste; and low temperatures in problems of freezing ground. Finally, the lecture examines some issues related to chemical effects on soils and rocks, focusing i...

Soil–environment interactions in geotechnical engineering

The mathematical representation of freezing and thawing processes in variably-saturated, non-deformable soils

/pdf/climate-change-impacts-on-groundwater-and-soil-temperatures-25dym3s0vc.pdf

Climate change impacts on groundwater and soil temperatures in cold and temperate regions: Implications, mathematical theory, and emerging simulation tools

A fully coupled thermo-hydro-mechanical (THM) finite element (FE) formulation is presented that considers freezing and thawing in water-saturated soils. The formulation considers each thermal, hydraulic and mechanical process, and their various interactions, through fundamental physical laws and models. By employing a combination of ice pressure, liquid pressure and total stress as state variables, a new mechanical model has been developed that encompasses frozen and unfrozen behaviour within a unified effective-stress-based framework. Important frozen soil features such as temperature and porosity dependence of shear strength are captured inherently by the model. Potential applications to geotechnics include analysis of frost heave, foundation stability or mass movements in cold regions. The model's performance is demonstrated with reference to the in situ pipeline frost heave tests conducted by Slusarchuk et al. Detailed consideration is given to FE mesh design, the influence of hydraulic parameters, an...

/pdf/thm-coupled-finite-element-analysis-of-frozen-soil-1ywlcklggq.pdf

THM-coupled finite element analysis of frozen soil: formulation and application

This paper presents an approach for predicting heat and mass transfer in freezing unsaturated soil when frost heave does not occur. The theoretical formulation uses soil-freezing and soil-water characteristic curve data to combine the heat and mass transfer relationships into a single equation for freezing or frozen regions of the soil. Numerical simulations were compared with the results of freezing tests for a closed system of fine silica flour where large moisture redistribution occurred without frost heave. Accurate predictions of ice content and water content were obtained using a single permeability versus suction function with no impedance factor. The permeability function was obtained using a recently developed method for predicting permeability functions for unsaturated soils using the soil-water characteristic curve. (A)

/pdf/heat-and-mass-transfer-in-unsaturated-soils-during-freezing-5augv9v1mt.pdf

G W Wilson

Papers

Heat and mass transfer in unsaturated soils during freezing