Abstract The anchoring of floating platforms is one of many processes in the oil industry that requires innovative strategies. In this respect, there is interest in developing techniques that improve the shear strength of soft soils in order to increase the bearing capacity of offshore foundations anchored in these soils. Normally consolidated clay soil is known to undergo thermal consolidation when submitted to temperature cycles. The present study aimed to assess the impact of a temperature cycle on soft kaolin clay using a reduced-scale physical model submitted to heating at maximum temperatures of 85 °C and 65 °C, followed by cooling. Variables such as pore pressure, temperature at different soil depths and displacement were monitored during the thermal cycle to better understand the phenomenon. The strength profile before and after heating was determined via T-bar tests conducted in different positions in relation to the heat source. The temperature variation increased the undrained shear strength of the soil directly proportional to the temperature applied and inversely proportional to the radial distance from the heat source, reaching improvements of 123%. In this respect, it is believed that applying a temperature cycle to normally consolidated soft clayey soil can improve the pullout capacity of offshore foundations.

Abstract Knowledge of the soil-temperature relation and its peculiarities have been widely discussed in Geotechnics. Previous studies show that heated fine-grained soil induces pore pressure, and as a result, the soil exhibits a consolidation effect similar to that of conventional consolidation when pore pressure is dissipated. The outcome of this process depends on soil characteristics such as the overconsolidation ratio and plasticity. Consolidated soil typically induces positive pore pressure while overconsolidated one induces negative pore pressure when heated. The phenomenon described was explored in this study aimed at the thermal consolidation product regarding the decrease in void ratio and consequent increase in undrained shear strength (Su) of a soil submitted to heating. These aspects were investigated using physical models at 1g gravity field, built on a laboratory scale. The heat source was placed inside a driven torpedo pile model in a medium consisting of a kaolin and metakaolin mixture. The undrained shear strength profile was defined by T-Bar tests involving different effective stresses and consolidation temperatures. The results show that for both mediums (normally consolidated and overconsolidated), undrained shear strength tends to grow proportionally to the temperature variation and permanent volume change is reached after a heating-cooling cycle. On the other hand, undrained shear strength indicates less significant variations for higher overconsolidation ratios.