The influence of temperature on shear strength at a soil-structure interface

Thermal heat exchanger piles combine the requirements of a traditional pile foundation with the energy harvesting/dissipating potential of a ground source heat pump. Such installations are becoming increasingly popular as a means of reducing the energy demands of buildings. Behaviour of the soil-pile interface is central to predicting the shear response of floating piles; yet understanding of the effects of thermal loading on soil-structure interaction remains uncertain. In this paper, heated interface shear tests have conducted using a specially adapted direct shear apparatus; to mimic the behaviour of a thermal pile interface. Testing was undertaken at various over-consolidation ratios, normal stresses and temperatures. This investigation observed the interface friction angle to remain unaffected by heating until its thermal yield is reached and thermal consolidation takes place, at which point there is a reduction in the friction angle which remains when the soil is cooled. There is also an observed increase in apparent adhesion at the interface in response to heating which also remains after cooling.