Collaborative Research: Experimental and Computational Investigation of Multiphase Consolidation for Partially Saturated Soils

Partially saturated soils are three-phase earth materials that contain both air and water in the void space between the solid grains. Such soils are commonly encountered in field construction for a wide range of civil engineering works, including foundations, landfills, slopes, retaining walls, compacted fills, and highways. The mechanical behavior of partially saturated soils is not well understood because of complex interactions of the three phases. This award supports fundamental research, using both experimental and computer modeling methods, to provide needed knowledge of the mechanisms by which partially saturated soils undergo deformation and volume change (i.e., consolidation) under various loading conditions. This work has the potential to transform current understanding of partially saturated soils, which has relevance to sampling, testing, characterization, and monitoring, as well as design and construction of sustainable civil infrastructures using these materials.

The objective of this research program is to conduct a comprehensive experimental and computational investigation of multiphase consolidation for partially saturated soils, and then assess the significance of these findings for relevant applications in geotechnical and geoenvironmental engineering. This work has both intrinsic scientific merit in terms of advancing the current understanding of a widespread physical process, as well as practical utility in terms of developing improved prediction methods for settlement, fluid flow, effective stress, and final material property profiles for a wide range of engineering applications. The experimental program will include multiphase consolidation tests conducted for a variety of soils with changing stress and hydrologic conditions. Measured data will be interpreted using a new and consistent framework based on unified effective stress theory and the suction stress characteristic curve. The computational program will develop new models using a novel tri-lagrangian (solid-water-air) discretization method to track movements of each phase while accounting for geometric and material nonlinearities, compressible non-Darcy gas flow, coupled flow effects, phase discontinuities, and mechanical and hydrologic hysteresis. Once validated, the new models will be used to perform numerical simulation studies to assess the significance of multiphase soil consolidation for a variety of engineering applications and highlight the importance of these effects to the broader geotechnical and geoenvironmental engineering community.