A thermodynamic model to simulate the thermo-mechanical behavior of fine-grained gassy soil

Fine-grained gassy soil is a special kind of unsaturated soil, with the gas in the form of discrete big bubbles within the saturated matrix. These gas bubbles are sealed and considerably larger than the normal particle size. Based on the conceptual model of soil containing large gas bubbles proposed by Wheeler (Geotechnique 38(3):389-397, 1988a) and the granular solid hydrodynamics (GSH) theory, a thermodynamic model is presented to describe the mechanical properties and temperature effect of fine-grained gassy soil in this paper. The model assumes that the gas pressure is related to total stress and pore water pressure of soil, and the behavior of saturated matrix is controlled by "quasi-effective stress." In addition, the effect of gas on the plastic deformation of soil skeleton is considered. Comparing with the experimental results, the ability of the model to describe the consolidation and undrained shear properties of fine-grained gassy soil is verified. What is more, the effect of temperature on fine-grained gassy soil considering the various responses for different drainage conditions and overconsolidation ratios is discussed and simulated by the proposed model. It is concluded that for fine-grained gassy soil with different overconsolidation ratios, the increase of temperature can increase the compressibility and thermal contraction under drained conditions, as well as the pore water pressure under undrained conditions, while the temperature effect on undrained shear properties depends on the initial conditions.