Influence of temperature on residual strength of clayey soils

Abstract

This paper presents the influence of temperature on the residual strength by analyzing shearing tests carried out in a temperature- and velocity-controlled ring shear apparatus. Temperature was applied in steps of cooling and heating ranging between 6 °C and 50 °C at a constant shearing velocity of 0.442 mm/min. Additional tests include the evaluation of the strength at 0.890 mm/min before and after the imposed temperature change. Six basic soil types characterized by different mineralogy, grain size and plasticity, as well as, mixture soils having different proportions of sand and clay, are evaluated and the results are interpreted in terms of their properties. The experimental results reveal that the temperature effect becomes relevant when fine particles and plasticity increase being negligible in the case of the sandy soil. Shear strength reacts immediately to temperature changes and a new residual strength establishes soon. The temperature effect is symmetric. An increase in temperature leads to a decrease in strength, and an equal and opposite trend is observed when temperature decreases. The magnitude of the strength variation is significant in clayey soils. For the case of high plasticity soils, the residual friction angle variation observed during cooling and heating (±50 °C) is around 2°. The strain rate effect evaluated in a smaller number of tests indicated a strain rate strengthening in all the materials tested except for the case of the sandy soil, which also was not reactive to temperature changes. The experiments are calibrated with a velocity, state, and temperature-dependent friction model.