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Mechanical behaviour of the soil–structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermoactive structures, due to nonisothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and the soil–structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on the soil and soil–structure interface in a direct shear device at temperatures of 5, 22, and 60 °C. Fontainebleau sand and kaolin clay were used as proxies for sandy and clayey soils. The sandy soil was prepared in a dense state and the clayey soil was prepared in a normally consolidated state. Results show that the applied thermal variations have a negligible effect on the shear strength of the sand and sand–structure interface under CNL and CNS conditions, and the soil and soil–structure interface behaviour could be considered thermally independent. In clay samples, an increase in the temperature increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay–structure interface than in the clay samples. The adhesion of the clay–structure interface is less than the cohesion of the clay samples. [ABSTRACT FROM AUTHOR]

The permanent deformation of the road subgrade soil accumulated during passage of the cyclic loads is mainly due to the post-compacting and plastic flow mechanisms according to a study by the National Cooperative Highway Research Program in 2004. The main objective of the paper is to develop a relationship between the parameters a an d b of a power model and the usual physical properties of subgrade soils. The parameters a and b are assumed to represent the post-compacting and plastic deformation, respectively. Highlighting the link between the parameters a and b and the mechanisms of permanent deformation was the basic assumption which helped developing correlations. Data collected on nine different samples of soils characterized and having undergone cyclic triaxial tests permanent deformation were used to develop relationships. A distinction was made between the relationship parameter for clay and sandy soils. Indeed, clay soils with lower air permeabilities behave differently when compared to post-compaction sandy soils. However, a single relationship was developed for the parameter b, because the observed behavior appears similar for clay and sandy soils. Both correlations have coefficients of determination about 0.6. Also, comparison of the measured and predicted permanent deformation was done on the clay of St-Narcisse and sand of Fossambault. The results are generally good, despite a case of discrepancy observed. [ABSTRACT FROM AUTHOR]

Some peculiarities of water retention in a tropical lateritic soil of clayey nature are presented and discussed. The typical soil microstructure is shown through thin-layer plates emphasizing soil microaggregation and pore distribution and their repercussion on the soil-water retention curve and on hysteresis. It is shown that the clayey soil has a behavior that to a large extent resembles sandy soil, which is characterized by the relatively high saturated hydraulic conductivity, low air-entry value, and small suction range at which water drainage takes place. The severe weathering processes that originated this soil have produced an altered soil that seems to be homogeneous in terms of physical indices, hydraulic conductivity, and soil-water retention characteristics, up to 4.5 m in depth. [ABSTRACT FROM AUTHOR]

This study examined the effect of soil type on burrowing behaviour and cocoon formation during aestivation in the green-striped burrowing frog, Cyclorana alboguttata (Günther, 1867). Given a choice, frogs always chose to burrow in wet sand in preference to wet clay. Frogs buried themselves faster and dug deeper burrows in sandy soil. However, under my laboratory conditions, there was little difference in the pattern of soil drying between the two soil types. Frogs in both sand and clay soil experienced hydrating conditions for the first 3 months and dehydrating conditions for the last 3 months of the 6-month aestivation period, and cocoons were not formed until after 3 months of aestivation. After 6 months, there were more layers in the cocoons of frogs aestivating in sand than those aestivating in clay. Frogs were able to absorb water from sandy soil with water potentials greater than –400 kPa, but lost water when placed on sand with a water potential of –1000 kPa. [ABSTRACT FROM AUTHOR]