Particle characteristics (particle shape and size), along with relative density, significantly influence the frictional characteristics and liquefaction behavior of granular materials, particularly sand. While many studies have examined the individual effects of particle shape, gradation, and relative density on the frictional characteristics and liquefaction behavior of sand, they have often overlooked the combined effects of these soil parameters. In this study, the individual effect of these three soil parameters on the strength characteristics (angle of internal friction) and liquefaction resistance has been quantified by analyzing the data available in the literature. A novel dimensionless parameter, the 'packing index (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document}),' was developed to account for the bulk characteristics (relative density - RD) and grain properties (gradation, represented by the coefficient of uniformity (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_u$$\end{document}), and particle shape represented by the shape descriptor regularity (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rho $$\end{document})) of the granular soils. Through statistical analysis, a power law-based equation was proposed and validated to relate the cyclic resistance ratio (CRR) and angle of internal friction (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document}) with the packing index. Finally, an approach to assess the liquefaction resistance was detailed considering the intrinsic soil parameters, aiming to bridge the gap between field observations and laboratory analysis to facilitate a comprehensive understanding of soil behavior under cyclic loading.

The present experimental study evaluates the overburden correction factor (K6) of different pond ash samples under earthquake loading for liquefaction analysis. A series of 54 stress-controlled cyclic simple shear tests was conducted on pond ash specimens at different overburden pressures and cyclic stress ratios. Cyclic resistance ratio (CRR) was evaluated for each pond ash sample at different overburden pressures using two criteria based on maximum excess pore water pressure and double amplitude shear strain to evaluate the K6. The K6 values obtained for the pond ash were compared with the K6 values for natural soils (clean sand and sand-silt mixtures). The cyclic resistance ratio (CRR) and K6 values were observed to decrease with an increase in overburden pressure from 50 kPa to 100 kPa, and a further increase in overburden pressure to 150 kPa led to an increase in CRR and K6 values for pond ash specimens with fine particles dominated matrix. However, an opposite trend was observed for pond ash specimens with coarse particles-dominated matrix. The unique response of K6 values for pond ash was found to be significantly different from the already available K6 response for natural cohesionless soil (clean sand and sand-silt mixtures) as it unavoidably included the effect of OCR and void ratio along with the vertical overburden pressure.

Seismic liquefaction is one of the most devastating natural hazards that can cause significant damage to structures and infrastructure. The liquefaction behaviour is simulated in the finite element code PLAXIS by the UBC3D-PLM constitutive model that is 3-D generalized formulation of the 2-D UBCSAND model developed at the University of British Colombia. The UBC3D-PLM model used in this work was successfully employed in many recent studies, e.g. to evaluate the liquefaction effects on the seismic soil-structure interaction, to assess the dynamic behaviour of earthen embankments built on liquefiable soil and to investigate the seismic performance of offshore foundations. Moreover, UBC3D-PLM model involves many input parameters to model the onset of the liquefaction phenomenon. Therefore, their determination becomes a crucial concern. Previous studies elaborated a specific formulation that requires the corrected Standard Penetration Test (SPT) blow counts as input. However, the Dilatometer Marchetti Test (DMT), compared to the SPT, is more sensitive to several factors that affect the liquefaction resistance such as aging, stress history, overconsolidation and horizontal earth pressure. For this reason, a new parameter selection procedure, which uses the horizontal stress index derived from DMT, was developed in this study. The new relationships were applied for determining the initial parameters of the UBC3D-PLM model to describe the behavior of several liquefiable deposits located in eastern Sicily (Italy) that experienced destructive earthquakes in the past. For each site, the model was calibrated to the DMT-based liquefaction triggering curve, developed by combining DMT correlations with the current method based on SPT test, by the simulation of cyclic direct simple shear tests (CDSS). Finally, CDSS tests were performed by means of the CDSS device at the Soil Dynamics and Geotechnical Engineering Laboratory of the University Kore of Enna (Italy). This allowed to validate the applicability of the proposed procedure in simulating the liquefaction behavior of sandy soils.

Laboratory and field tests were performed on sandy soils from six Pleistocene-age sites in the South Carolina coastal region to investigate the age-related resistance to liquefaction. Stress-controlled cyclic triaxial tests were used to determine the cyclic strength of soils with geologic ages ranging from approximately 59,000 to 1,200,000 years. Three sites have evidence of liquefaction in the form of sand blows that are 467 to 4,185 years old as determined from C14 dating of embedded organic material. The other three sites show no indications of liquefaction. Cyclic stress ratios ranging from 0.095 to 0.225 were applied to undisturbed and reconstituted soil specimens that were consolidated to an effective stress equal to 100 kPa. Soil specimen liquefaction was defined to occur when the excess pore pressure was equal to the confining effective stress. Estimates of the at-rest earth pressure coefficient were determined using measurements from the flat plate dilatometer and the cone penetrometer and were applied to the laboratory cyclic stress ratio occurring at the 15th loading cycle to determine the laboratory-field equivalent cyclic resistance ratio. The age-dependent liquefaction resistance was determined using additional data from the inner coastal plain of South Carolina and assessing the cyclic resistance ratios and their associated KDR ratios relative to the base data and applying one of the more recently developed liquefaction triggering model. It was found that the development of the aging factor should be independent of the liquefaction triggering model. Subsequently, the aging factor is developed using an offset that is constrained at 20 years and a KDR=1.0, and was found to range from 1.00 at 20 years to 1.45 at 1.0 Ma for the original deposition ages of the soils and 1.00 at 20 years to 1.51 at 1.0 Ma for the data set consisting of the last disturbance and original deposition ages of the soils.