The resilient modulus, M R , of subgrade soil is an important stiffness parameter for analysing fatigue cracking in either the asphalt or concrete layer of a pavement. Although subgrade soil is often unsaturated and subject to seasonal variations of moisture content and hence suction in the field, effects of soil suction on the resilient modulus are generally not accounted for in existing testing methods. In this study, M R values of a subgrade soil under various stress and suction conditions were investigated using a suction-controlled cyclic triaxial apparatus. To enhance the accuracy of measurements, Hall-effect transducers were employed to monitor the local axial and radial deformation of each specimen. It was found that M R increases with number of load applications when a soil contracts, but decreases slightly when a soil dilates. When suction increases, the soil response tends to change from contractive to dilative due to suction-induced dilatancy. Moreover, the measured M R is highly dependent on the stress state. It decreases with cyclic stress due to the nonlinearity of the soil stress-strain behaviour, but increases significantly with suction due to the presence of water tension. At the same stress and suction conditions, M R measured along the wetting path is generally larger than that measured along the drying path. A new semi-empirical equation representing the stress-dependency of M R is proposed and was verified using experimental results of four different soils.Résumé : Le module de résilience, M R , du sol de fondation est un paramètre important de la rigidité pour l'analyse des fissures de fatigue dans l'asphalte ou la couche de béton d'une chaussée. Même si le sol de fondation sur le terrain est souvent non saturé et soumis aux variations saisonnières de teneur en eau, et conséquemment de succion, les effets de la succion du sol sur le module de résilience ne sont généralement pas considérés dans les méthodes d'essais existantes. Dans cette étude, les M R d'un sol de fondation soumis à différentes conditions de contraintes et succion ont été étudiés à l'aide d'un appareil triaxial cyclique contrôlé par la succion. Pour améliorer la précision des mesures, des capteurs à effet de Hall ont été utilisés pour suivre les déformations axiales et radiales de chaque échantillon. Il a été observé que M R augmente avec le nombre d'applications de charges lorsque le sol se contracte, mais diminue légèrement lorsque le sol se dilate. Quand la succion augmente, le comportement du sol tend à changer de contractif à dilatant en raison de la dilatation induite par la succion. De plus, le M R mesuré est fortement dépendant de l'état des contraintes. Il diminue avec les contraintes cycliques en raison de la non-linéarité du comportement en contrainte-déformation du sol, mais augmente significativement avec la succion à cause de la présence de la tension de l'eau. Pour les mêmes conditions de contrainte et succion, le M R mesuré en mouillage est généralement plus grand que celui mesuré en séchage. Une nouvelle éq...

Although the small-strain shear modulus of saturated soils is known to be significantly affected by stress history, consisting of the overconsolidation ratio (OCR) and recent stress history, the effects of suction history on the small-strain shear modulus of unsaturated soils have rarely been reported. In this study, the effects of suction history, which refers to current suction ratio (CSR) and recent suction history, on both the very-small-strain shear modulus (G0) and shear modulus reduction curve of an unsaturated soil, are investigated by carrying out constant net mean stress compression triaxial tests with bender elements and local strain measurements. In addition, the effect of suction magnitude on G0 and the shear modulus reduction curve is also investigated. At a given suction, G0, elastic threshold strain (εe), and the rate of shear modulus reduction all increase with CSR. On the other hand, the effect of recent suction history on G0 is not significant. The effect of direction of recent suction path (θ) on the shear modulus reduction curve is not distinct. However, the magnitude of recent suction path (l) affects the shear modulus reduction curve significantly when θ = –90°.

This paper presents a hybrid teaching approach, a new Web Security course as well as how to use the hybrid approach to teach the Web Security course to practice information assurance. The hybrid teaching approach contains three key issues that are keeping the lecture materials up-to-date, assigning former research projects as comprehensive team projects, and connecting classroom knowledge with real world web applications. We have applied this approach to the teaching a Web Security course and achieved excellent results. Our experience exhibits that integrating education, research and web applications into the Web Security course to practice information assurance are essential for a sound security education. Using this approach instructors connect knowledge in the classroom to real world applications, attract students to the security area, and train students to become information assurance professionals.