Abstract
The mechanical behaviour of the soil-structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermo-active structures, due to non-isothermal 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 soil-structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on soil and soil-structure interface in a direct shear device at temperatures of 5, 22 and 60 °C. Kaolin clay was used as proxy for clayey soils. The results showed that, in clay samples the temperature increase, 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.
Highlights
The soil-structure interactions at the interface are of primary importance in foundation designs
In the literature constant normal load (CNL) and constant normal stiffness (CNS) tests on sand-steel interface is performed [3] and the results showed that the effect of the normal stiffness (K) on the mobilized shear resistance of the interfaces in CNS tests depends on the volumetric response exhibited by the interfaces in the Constant normal load (CNL) tests
The results showed that, the shear strength of the clay samples was higher than that of the clay-concrete interface, and the effects of temperature on the shear strength and friction angle were negligible in the sand, clay and clay-concrete interface
Summary
The soil-structure interactions at the interface are of primary importance in foundation designs. In energy geostructures the mechanical loads applied to the structure on one hand, and the effect of heat exchange between structure and surrounding soil on the other hand, modify the behaviour of the soil-structure interface. These thermal variations and mechanical loads affect the bearing capacity and frictional resistance of these thermo-active structures. The effects of temperature on the soil-structure interface mechanical parameters should be investigated. An important concept to aid in understanding the interface behaviour is the constant normal stiffness (CNS). Depending on the volumetric response of the soil at the interface during shearing, the surrounding soil stiffness constrains the volumetric response of the interface and acts as a virtual spring with a given stiffness [1]
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