Physical modeling of thermal improvement in normally consolidated and overconsolidated soil

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.