Axisymmetric numerical modeling of a unit cell in geosynthetic-reinforced, column-supported embankments

Abstract

Rational design of geosynthetic-reinforced, column-supported embankments requires realistic estimates of the portion of the embankment load that acts vertically downward on the geosynthetic in the area underlain by the foundation soil located between columns. This vertical load can then be used to calculate the strain and tension that develops in the plane of the geosynthetic reinforcement. Several simplified methods are available for calculating the vertical load acting on the geosynthetic, but these methods produce dramatically different results, and there is not agreement regarding which method produces the best estimates. Axisymmetric numerical modeling provides an alternative approach for determining the vertical stresses that develop in the embankment and act on the geosynthetic reinforcement. In this research, axisymmetric numerical modeling is verified against: (1) instrumentation data from a full-scale column-supported test embankment, albeit without geosynthetic reinforcement, at the I-95/Route 1 Interchange project in Virginia, USA; (2) an analytic solution for a disk of membrane material that is pinned at its outer edge and subject to a vertical stress; (3) instrumentation data from a pilot-scale test of a geosynthetic-reinforced, column-supported embankment conducted at the University of Kassel in Germany; and (4) three-dimensional numerical analyses. The results demonstrate that drained axisymmetric numerical analyses using a mesh of linear elastic zones to represent the geosynthetic reinforcement produce results in good agreement with instrumentation data, the analytic solution, and three-dimensional analyses.

Numerical study of the effect of geosynthetic encasement on the behaviour of granular columns

“…More complex group loading behaviour, such as that observed in pile-supported embankments where settlement and stress arching occurs between columns (e.g. Smith and Filz 2007;Huang and Han 2009;Yoo and Kim 2009), is beyond the scope of this work. As vertical displacements were applied to the top of the column, the resultant stress was recorded, allowing the stress-settlement curve to be drawn accordingly.…”

“…Alexiew et al (2005) documented that design values of tensile modulus (J) between 2000 and 4000 kN/m were required for the geosynthetic used to encase granular columns on a number of different projects (the tensile modulus of the encasement, J, is also commonly referred to as the geosynthetic stiffness, e.g. Murugesan and Rajagopal 2006;Smith and Filz 2007). Consequently, a value of J ¼ 3000 kN/m was used in the numerical analyses.…”

“…A circumferential elastic modulus (E c ) of 600 MPa was used for the geosynthetic, which was derived from the relationship E c ¼ J/t (e.g. Murugesan and Rajagopal 2006;Smith and Filz 2007). The thickness of the geosynthetic (t ) was assumed to be 5 mm for all of the numerical analyses that were performed; this value is in accordance with the range of 3 to 7 mm thickness that is typically used for modelling this material (e.g.…”

Two-dimensional parametric study of geosynthetic-reinforced column-supported embankments by coupled hydraulic and mechanical modeling

“…However, due to limited understanding of this complex system, comprised of columns, soil, and geosynthetic, various assumptions were made to develop these design methods, which lead to great variations among them [1]. To better understand this embankment system and eliminate the uncertainty in use of these methods, experimental and numerical studies have been conducted [2][3][4][5][6][7][8].…”

Extensible geosynthetics and stone-column-reinforced soil

“…Han and Gabr (2002) conducted a numerical study to investigate the behaviour of geosynthetic-reinforced and pilesupported earth platforms resting on soft soil by considering the effects of the height of the fill, tensile stiffness of the geosynthetic and elastic modulus of the pile on settlement response, stress concentration and soil arching phenomena. Smith and Filz (2007) conducted axisymmetric numerical modelling for geosynthetic-reinforced and column-supported embankments to determine the vertical stresses acting on the embankment and geosynthetic reinforcement.…”