Saturated soil consists of a solid phase and a fluid phase. Individual solid grains form a deformable solid skeleton with interconnected pores filled with fluids. When saturated soil undergoes shear wave excitations, the relative motion between the two phases has two effects on the dynamic behavior of saturated soil: pore fluid induced damping (i.e., energy dissipation) and effective soil density. The effective soil density is related to the fraction of pore fluid that moves with the solid skeleton during shear wave propagation, and is always smaller or equal to the saturated density. Due to a lack of quantitative assessment of these two effects in published literature, they are generally neglected in current geotechnical engineering research and practice. However, recent research indicates that these two effects are important for soils with high permeability (e.g., sands and gravels) and/or under high-frequency excitations. The objective of this research is to provide fundamental understanding, quantitative assessment, and practical solutions to pore fluid induced damping and effective density in saturated soil. This research is primarily motivated by the wide spread and increasing popularity of geotechnical laboratory and field tests involving high-frequency shear waves (e.g., centrifuge, bender elements, seismic CPT).
The objective of this research will be achieved through analytical study and experimental testing. In the proposed analytical study, analytical solutions of pore fluid induced damping and effective density will be derived based on a framework that considers both Biot flow and squirt flow. The proposed experimental testing will use resonant column tests to provide validation of the analytical work and examine the effects of shear strain and specimen size.
This research will serve to bridge the gap between theory and practice by developing solutions that can be easily used by researchers and practitioners. It has the potential to transform the way in which researchers and engineers interpret data and perform analyses relating to soil dynamics and geotechnical earthquake engineering. Ultimately, the benefits will be the reduction of losses to society as a result of earthquakes. Broader impacts also include improving educational opportunities in the area of geotechnical engineering at Clarkson University. A soil dynamics testing laboratory is currently being developed to conduct research and educate students at both the undergraduate and graduate levels. This research project will foster that effort and spark students? interest in this profession.
