Experimental investigations of the soil–concrete interface: physical mechanisms, cyclic mobilization, and behaviour at different temperatures

Abstract

Behaviour of the pile–soil interface is important to correctly predict the response of floating piles in terms of displacement and lateral friction. Regarding energy piles, which couple the structural roles of deep foundations with the principle of shallow geothermal energy, the response of pile–soil interfaces is influenced by seasonal and daily cyclic thermal variations. Accordingly, the goal of this paper is to experimentally investigate the response of the pile–soil interface at different temperatures. This experimental campaign aims to analyse (i) the cyclic mobilization of the shear strength of the soil–pile interface that is induced by thermal deformation of the pile and (ii) the direct influence of temperature variations on the soil and soil–pile interface behaviour. In this study, a direct shear device was developed and calibrated for nonisothermal soil–structure interface testing. It appears that the sand–concrete interface was affected by cyclic degradation but not affected directly by temperature. Conversely, the response of the clay–concrete interface changed at different temperatures, showing an increase of strength with increasing temperature, presumably due to the effects of temperature on clay deformation.

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

“…The main conclusions of Reference [225] were that the sand-concrete interface was affected by cyclic shear strength degradation but not directly by temperature. The concrete-clay interface appeared to be sensitive to thermal variations, showing an increase of clay-pile interface strength upon thermal loading, probably because of thermally induced compaction strength with increasing temperature (thermal consolidation).…”

“…In Reference [225], a direct shear device developed and calibrated for non-isothermal soil-structure interface testing was used, adopting a heating system composed by an electrical resistance, an electrical power supplier, an insulation system, and a thermocouple.…”

“…More recently, with the specific aim of studying SGE applications, the response of a natural silty clay soil to thermal loading in drained conditions was investigated by means of oedometer tests by References [228] and [225]. The devices employed for the experiments are oedometer cells that were adapted to include temperature control (see Reference [204], and Figure 1 therein).…”

Influence of Number of Geosynthetic Layers on the Performance of Geosynthetic-reinforced Pile-supported Earth Platforms on Soft Soil: Numerical Study

“…The frictional behavior was created on the interface between the external surface of the pile and the surrounding soil. The interface friction angle (δ) was determined based on the equation as: tan tan     , in which  is the friction angle of the neighboring soil; and  is the interaction coefficient, typically in a range from 0.6 to 1.0 (Di Donna et al, 2015). In the numerical modeling, the interaction coefficient was assumed to be 0.7.…”

Influence of Dilation on the Strength of Sand – Steel Interfaces

“…The stress-strain-displacement response of interface plays an important role in the behaviour of deep foundations, retaining walls and reinforcement of soils, which was extensively investigated experimentally and theoretically [1][2][3][4][5][6][7][8][9]. The mechanical behaviour of interfaces is a function of solid material roughness; soil state and stress level [10][11][12][13].…”