Evaluation of Liquefaction Potential of Saturated Granular Soils under Partial Drainage Conditions

Southern Methodist University, Dallas TX

Investigators

Abstract

The U.S. and other seismically active areas around the world have sustained considerable damage resulting from earthquake-induced site liquefaction that was associated with very costly damage to port facilities, bridges, dams, buried pipes, and buildings of all types. The Earthquake Engineering Research Institute reports that the direct cost of losses in the built environment and the indirect economic cost of a major earthquake that strikes a major urban area could easily exceed 100 billion dollars. Such losses could be significantly reduced if the performance of soil systems could be reliably predicted and current design and remediation measures improved. This project addresses a critical gap in engineering knowledge related to the evaluation of the liquefaction potential of soil deposits under realistic drainage conditions. This undertaking will help in reducing the uncertainty and large costs associated with site liquefaction hazards. The research and education activities fall within the national interest. They have the potential to achieve increased economic competitiveness through better assessment of liquefaction potential. The knowledge gained from this research would prevent future loss of lives and contribute to the welfare of the American public. The research will contribute to the progress of earthquake engineering and science. The activities would also lead to a globally competitive American STEM workforce equipped with the latest development in high-performance computational modeling. Liquefaction is a result of water pressure build-up due to squeezing of pore space during rapid earthquake loading that, in turn, reduces soil strength. The mechanism of pore-pressure development during cyclic loading has been mainly explained based on the analogy between cyclic contraction of fully drained sands and pore pressure generation in undrained conditions. However, depending on several factors such as external loading rate, soil permeability and in-situ pore-pressure boundary conditions, different drainage conditions are expected in the field. These conditions may lead to a partial drainage situation in which simultaneous change in pore volume and in pore water pressure may occur during shearing. Under these conditions, soils originally believed to be non-liquefiable such as dense sand, may actually experience instability. This project aims at providing accurate characterization of pore fluid migration during seismic loading of a soil deposit and assessing liquefaction potential under realistic drainage conditions. The high-performance computing (HPC) resources of the cyberinfrastructure component of the NSF-supported NHERI enable the development of a universal predictive tool capable of seamless modeling of soil systems at an unprecedented resolution. High-fidelity fully-coupled micromechanical computational simulations utilizing parallel computing are planned in this effort to provide much-needed answers to questions related to understanding the mechanical processes that control the evolution of pore pressure during seismic loading.