Dense Granular Columns in Liquefiable Ground. II: Effects on Deformations

Dense Granular Columns in Liquefiable Ground. I: Shear Reinforcement and Cyclic Stress Ratio Reduction

“…Dense granular columns may also continue to provide support for overlying structures, reducing their settlement relative to the unimproved case. These aspects of granular columns are investigated in a companion manuscript (Rayamajhi et al 2016).…”

Performance of embankments on liquefiable soil deposits improved with with dense granular columns

“…Base motion underestimated total volumetric strains (primarily due to sedimentation), leading to an underestimation of net surface settlements (s) by one order of magnitude (e.g., at R = 2.5 m: sexperimental = 15 cm; snumerical = 1.8 cm). These shortcomings have been known and documented in prior studies (Elgamal et al 2003;Rayamajhi et al 2016b;Ramirez et al 2018;Karimi et al 2018).…”

“…Prior numerical parametric studies representing DGCs as unit cells have demonstrated their effectiveness in reducing lateral displacements owing to a combination of drainage and shear reinforcement (e.g., Elgamal et al 2009;Asgari et al 2013;Rayamajhi et al 2016b). They have also provided valuable insight into shear deformations between the columns and their surrounding soil (e.g., Rayamajhi et al 2016a), and have shown that DGCs can significantly improve site performance, particularly for Ar values ranging from about 20% to 30% (which is greater than the range reported in successful case histories).…”

“…They have also provided valuable insight into shear deformations between the columns and their surrounding soil (e.g., Rayamajhi et al 2016a), and have shown that DGCs can significantly improve site performance, particularly for Ar ranging from about 20% to 30% (again greater than the range reported in successful case histories). Nevertheless, the final settlements predicted by these studies may not be reliable, particularly in thicker liquefiable profiles, because of the limitations in the available soil constitutive models and, in general, the use of a continuum framework to capture volumetric strains (Rayamajhi et al 2016b;Ramirez et al 2018). Further, prior numerical studies have typically not been validated against physical modeling of granular columns, particularly in the presence of embankments.…”

“…The state-of-practice for the design of DGCs is currently limited to simplified approaches that consider, separately or in a de-coupled manner, the three primary liquefaction-mitigation mechanisms provided by columns: (i) installation-induced densification; (ii) enhanced drainage; and (iii) shear reinforcement (e.g., Baez and Martin 1993;Baez 1995;Rayamajhi et al 2014;Rayamajhi et al 2016a;Rayamajhi et al 2016b). Critical factors, such as the impact of structuresoil-mitigation interaction, site characteristics and layer-to-layer interaction, evolutionary characteristics of the ground motion, and importantly, uncertainties around predicting key engineering demand parameters (e.g., peak excess pore water pressure and shear strain in each layer or seismic ground deformations) are not included in the existing engineering design procedures.…”