Studying The Behavior Of Unsaturated Soils Using Pore Scale Numerical Modeling With The Multiphase Lattice Boltzmann Method
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Studying the Behavior of Unsaturated Soils Using Pore-scale Numerical Modeling with the Multiphase Lattice Boltzmann Method
Advancements in unsaturated soil mechanics have historically lagged behind saturated soil mechanics, due to the complexities associated with the behavior of unsaturated soils. The presence of two fluid phases in the pore space of unsaturated soils gives rise to varying phase distributions and interfacial interactions, which play an important role in the mechanical and hydraulic behavior of the soil. Fundamental understanding of the behavior of unsaturated soils requires an understanding of the phase distributions at the pore scale. This dissertation presents early work on using pore-scale numerical modeling for studying the behavior of unsaturated soil. A code based on the multiphase lattice Boltzmann method (LBM) is developed for this purpose. Using this tool, two fundamental investigations are carried out. The first investigation is on the underlying source of soil-water characteristic curve (SWCC) hysteresis. Primary drainage and imbibition simulations are performed for a granular soil specimen. It is found that even in the absence of well-known contributors to SWCC hysteresis, such as contact angle hysteresis and air entrapment, SWCC is still hysteretic. The underlying source of this hysteresis is found by comparing phase distributions during drainage and imbibition. It is revealed that during imbibition narrow throats are filled by capillary condensation, while during drainage these narrow throats have to be emptied by high-curvature menisci pushing through them, therefore, requiring a higher suction at the same degree of saturation. The second investigation is on the hysteresis of the effective stress parameter as a function of degree of saturation. The effective stress parameter is measured at the base of a granular soil column during primary drainage and secondary imbibition. The independent contributions of suction and surface tension forces to the effective stress parameter are monitored throughout the simulation. It is found that the contribution of suction forces to the effective stress parameter is slightly lower during imbibition compared to drainage, however, the contribution of surface tension forces is much higher, resulting in a larger effective stress parameter during imbibition. The reason for this behavior is linked back to the differences between the phase distributions during imbibition and drainage
Proceedings of the 2nd International Symposium on Asia Urban GeoEngineering
This book contains the keynote presentations, invited speeches, and general session papers presented at the 2nd International Symposium on Asia Urban GeoEngineering, which will be held from 24 November to 27 November 2017 in Changsha, China. The contents will cover the topics of (i) Fundamental behavior and constitutive model of geomaterials, (ii) Excavation and slope engineering, (iii) Tunnel and underground engineering, (iv) Foundation and foundation treatment, (v) Environmental geotechnical engineering, (vi) Numerical methods in geotechnical engineering. It will provide an opportunity to share knowledge and experiences of the analysis, design, construction, and maintenance of urban geoengineering among engineers, researchers, and professors in Asian countries. It will improve our knowledge of requirements of geoengineering for a long-term sustainable urban development and the need to protect and preserve our environment.
Geotechnical Fundamentals for Addressing New World Challenges
This single-volume thoroughly summarizes advances in the past several decades and emerging challenges in fundamental research in geotechnical engineering. These fundamental research frontiers are critically reviewed and described in details in lights of four grand challenges our society faces: climate adaptation, urban sustainability, energy and material resources, and global water resources. The specific areas critically reviewed, carefully examined, and envisioned are: sensing and measurement, soil properties and their physics roots, multiscale and multiphysics processes in soil, geochemical processes for resilient and sustainable geosystems, biological processes in geotechnics, unsaturated soil mechanics, coupled flow processes in soil, thermal processes in geotechnical engineering, and rock mechanics in the 21st century.