Estimation of the Soil-Water Characteristic Curve of Fine-Grained Soils Form Moisture Profile in Response to a Controlled Temperature Gradient

Pedram Roshani, Julio Ángel Infante Sedano

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Unsaturated Soils

ABSTRACT: TION OF THE SOIL - WATER CHARACTERISTIC CURVE OF FINE-GRAINED SOILS FORM MOISTURE PROFILE IN RESPONSE TO A CONTROLLED TEMPERATURE GRADIENT Pedram Roshani, Julio Ángel Infante Sedano Department of Civil Engineering University of Ottawa, Ottawa, Ontario, Canada ABSTRACT In many regions, the ground water table is found at depth and soil is in an unsaturated condition. Implementing the mechanics of unsaturated soils in these regions requires the use of the soil-water characteristic curve (SWCC). Many unsaturated soil properties such as the coefficient of permeability, the shear strength, and the coefficient of water volume change are highly related to the SWCC. Furthermore understanding the changes in the SWCC under variable temperature can be important in circumstances where a temperature gradient imposed on the soil may result in an unwanted water migration. Much experimental evidence indicates that under the effect of a temperature gradient, the soil moisture is redistributed and migrates from the hot boundary towards the cold boundary. This is attributed mostly to changes of suction as a function of temperature. The aim of this paper is to develop a method based on considering effect of temperature on the SWCC and the obtained temperature and moisture profile at steady state under fixed temperature gradient. Relationships are estimated for the fixed parameters of the Fredlund and Xing (1994) equation. The proposed method will be verified for a fine-grained soil subjected to the same temperature gradients. This method of assessment of the SWCC can be used to provide a further look into the information provided by published experimental data for which temperature gradients and moisture profile data may have been available, among other measurements but for which no SWCC was determined. RÉSUMÉ Dans de nombreuses régions, la table de la nappe phréatique se trouve à une profondeur et le sol est dans un état non ation de la courbe caractéristique sol-eau (SWCC). De nombreuses propriétés des sols non saturés, tels que le coefficient de perméabilité, la résistance au cisaillement, et le coefficient de variation de volume de l'eau sont fortement liées à la SWCC. En outre comprendre les changements dans le SWCC sous température variable peut être important dans les cas où un gradient de température imposée sur le sol peut entraîner une migration de l'eau non désirée. Une grande partie des preuves expérimentales indiquent que sous l'effet d' un gradient de température , l' humidité du sol est redistribué et migre à partir de la limite chaude vers la limite froide. Ceci est attribué principalement aux variations de l'aspiration en fonction de la température. Le but de ce papier est de développer une méthode basée sur l'examen effet de la température sur la SWCC et le profil de température et d'humidité obtenu à l'état d'équilibre dans un gradient de température fixe. Les relations sont estimées pour les paramètres fixes de l'équation Fredlund et Xing (1994). La méthode proposée est vérifiée pour un sol à grains fins soumis aux mêmes gradients de température. Cette méthode d'évaluation de la SWCC peut être utilisée pour fournir un autre regard sur l'information fournie par les données expérimentales publiées pour lesquelles les gradients de température et des données de profil d'humidité peuvent avoir été disponible, entre autres 1 INTRODUCTION To state and mathematically simulate the behavior of the unsaturated soils many researchers have shown that the soil-water characteristic curve (SWCC) along with the saturated soil properties such as saturated hydraulic conductivity coefficient or saturated shear strength parameters ( and ) and one additional soil parameter is sufficient to accurately determine a number of unsaturated soil properties such as the coefficient of permeability (Mualem 1976; van Genuchten 1980), shear strength (Vanapalli et al. 1996), and coefficient of water volume change (Fredlund et al. 2012). Throughout the literature, the SWCC is widely defined as the relation between the capillary forces above the ground water table and the amount of water held within the soil (Buckingham 1907; Williams 1982). Several methods are vailable for determining the SWCC (Fredlund and Rahardjo 1993). Some of these methods measure the SWCC directly while the other techniques can estimate SWCC indirectly. In the case of the direct method, the experimental determination of the SWCC is laborious, and, depending on the soil type, may take from weeks to months to complete, and requires intricate testing equipment such as Tempe Cells and Pressure Plate apparatus (Vanapalli and Catana 2005). Moreover, many studies state that environmental factors such as the soil structure, initial water content, void ratio, stress history, compaction method, hysteresis, and temperature can also affect the SWCC shape (Vanapalli et al. 1999; Zhou and Yu 2005). Therefore, assuming a unique relationship of the SWCC for one type of soil in all geotechnical problems may not be reasonable. Due to above reasons, recent research efforts have been focused on the development of

RÉSUMÉ: STIMATION OF THE SOIL - WATER CHARACTERISTIC CURVE OF FINE-GRAINED SOILS FORM MOISTURE PROFILE IN RESPONSE TO A CONTROLLED TEMPERATURE GRADIENT Pedram Roshani, Julio Ángel Infante Sedano Department of Civil Engineering

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Pedram Roshani; Julio Ángel Infante Sedano (2014) Estimation of the Soil-Water Characteristic Curve of Fine-Grained Soils Form Moisture Profile in Response to a Controlled Temperature Gradient in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper446,author = Pedram Roshani; Julio Ángel Infante Sedano,title = Estimation of the Soil-Water Characteristic Curve of Fine-Grained Soils Form Moisture Profile in Response to a Controlled Temperature Gradient ,year = 2014}