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An isogeometric analysis (IGA) based numerical model is presented for simulation of thermo-hydro-mechanically (THM) coupled processes in ground freezing. The momentum, mass and energy conservation equations are derived based on porous media theory. The governing equations are supplemented by a saturation curve, a hydraulic conductivity model and constitutive equations. Variational and Galerkin formulation results in a highly nonlinear system of equations, which are solved using Newton-Raphson iteration. Numerical examples on isothermal consolidation in plane strain, one-dimensional freezing and heave due to a chilled pipeline are presented. Reasonably good agreements were observed between the IGA based heave simulations and experimental results.

Summary The mechanical behavior of expansive soils varies according to the chemical composition of the pore fluid. It is well known that electrochemical phenomena on the surface of clay mineral crystals considerably affect their macrostructural behavior. In particular, a change in the pore fluid composition causes osmotic consolidation or swelling. In this study, a model is constructed to describe the characteristic behavior of expansive soils by coupling the interlaminar behavior of clay mineral crystals and the soil skeleton behavior. The interlaminar behavior is derived from the electro‐chemo‐mechanical coupling equilibrium of mineral crystals, and the soil skeleton behavior is given by a general elastoplastic constitutive model for soils. This modeling approach extends a general model to consider the electro‐chemo‐mechanical phenomena of mineral crystals. Oedometer tests with the replacement of the cell fluid and the swelling pressure and deformation tests on expansive clays are simulated with the proposed model. The simulation results indicate that the proposed method can reasonably represent the typical behavior of expansive soils.

A simple and uniˆed constitutive model for soils, considering various eŠects such as the in‰uences of density, bonding, time dependent behavior and others, is presented in this paper. The elastoplastic behavior of over consolidated non-structured soils under a one-dimensional stress condition isˆrstly presented by introducing a state variable that represents the in‰uence of density (stage I). To describe the one-dimensional stress-strain behavior of structured soils, attention is focused on density and bonding as the main factors that aŠect the response of this type of soil, because it can be considered that soil a skeleton structure which is in a looser state than that of a normally consolidated soil is formed by bonding eŠects (stage II). Furthermore, a simple method is presented which allows for other soil characteristics to be considered, such as time and temperature dependency, and the eŠect of suction in unsaturated soils. Experimental observations show that the normally consolidated line (NCL) in the void ratio-stress relation (e.g., e-ln s curve) shifts depending on the change of strain rate, temperature, suction and others (stage III). The validation of the model at stages I and II is demonstrated by simulating one-dimensional consolidation tests for normally consolidated, over consolidated and natural clays. The applicability of the model at stage III is veriˆed not only by the simulations of time-dependent behavior of clays in one-dimensional element tests but also by the soil-water coupledˆnite element analysis of oedometer tests as a boundary value problem. The extension from one-dimensional models to three-dimensional models is easily achieved by deˆning the yield function using stress invariants instead of one-dimensional stress s' and by assuming an appropriate ‰ow rule in stress space. The details of the modeling in general three-dimensional stress conditions will be described in another paper (Nakai et al., 2011).

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