Geosynthetics International: Vol.8, No. 6, 2001

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Note of Appreciation to Paper Reviewers
T.S. Ingold, R.J. Bathurst, J.P. Giroud

The quality of the technical journal Geosynthetics International and, hence, its reputation as the premier peer-reviewed journal on geosynthetics and related topics depends on the dedication of the many reviewers who donate their time and expertise to assess submissions to the Journal. The Editor, Co-Editor, and Chair of the Editorial Board would like to thank the following individuals for completing manuscript reviews in 2001. If we have missed your name below please let us know and we will be sure to include you in the reviewers list to appear in the last issue of Volume 9 in 2002.

M. Adams, S.R. Allen, T.M. Allen, J. Atmadja, D.T. Bergado, J.D. Bray, B.R. Christopher, P.J. Fox, K. Hatami, D.J. Hoare, R.D. Holtz, J.S. Horvath, Y. Hsuan, M. Kamon, R.M. Koerner, J. Lafleur, A. Lee, W.F. Lee, D. Leschinsky, H. Ling, R. Lohnes, S.M. Merry, M. Othman, E.M. Palmeira, R.K. Rowe, A. Sawicki, E.T. Selig, C.D. Shackelford, A.J. Valsangkar, D. Walters, J. Zornberg

Technical Paper by V.C. Xenaki and G.A. Athanasopoulos

Experimental Investigation of the Interaction Mechanism at the EPS Geofoam-Sand Interface by Direct Shear Testing

ABSTRACT: The results of laboratory direct shear tests conducted at the expanded
polystyrene (EPS) geofoam-sand interface are presented in this paper. The sands used
in the tests were composed of rounded to subangular particles with values of mean particle
size ranging from 0.28 to 2.17 mm and void ratios ranging from 0.51 to 0.72. The
EPS geofoam was of two different densities: 10 and 20 kg/m3. The test results are
expressed in the form of shear stress versus normal stress in direct shear failure envelopes,
which were found to be nonlinear. The curved interface failure envelopes were
approximated by piecewise linear envelopes composed of three linear segments corresponding
to three types of phenomenological interaction mechanism, which develop
successively for increasing values of normal interface stress: purely frictional, frictional-
adhesional, and purely adhesional. A simple conceptual framework is proposed
that qualitatively explains the observed interface behavior in terms of the normal interface
stress, EPS geofoam hardness (or density), interface relative roughness (which
incorporates the mean particle size), shape of sand particles, and void ratio of sand.
The experimental results are compared to similar results reported in the literature for
HDPE geomembrane-sand interfaces. Apparent values of interface friction angle, d,
and adhesion, ca , are proposed in the paper for the tested sands and for specific ranges
of normal interface stresses and the two EPS geofoam densities.

KEYWORDS: Expanded polystyrene, Geofoam, Sand, Direct shear test, Interface,
Interface friction angle, Interface adhesion.

AUTHORS: V.C. Xenaki, Graduate Student and G.A. Athanasopoulos, Professor,
Department of Civil Engineering, University of Patras, Greece, Telephone: 30/610-
997677, Telefax: 30/610-997274, E-mail: gaa@upatras.gr.

DATE: Original manuscript submitted 6 November 2000, revised version received 1
November 2001, and accepted 7 November 2001. Discussion open until 1 September
2002.

REFERENCE: Xenaki, V.C. and Athanasopoulos, G.A., 2001, “Experimental Investigation
of the Interaction Mechanism at the EPS Geofoam-Sand Interface by Direct
Shear Testing”, Geosynthetics International, Vol. 8, No. 6, pp. 471-499.

Technical Paper by N. Kotake, F. Tatsuoka, T. Tanaka, M.S.A. Siddiquee, and C.C. Huang

FEM Simulation of the Bearing Capacity of Level Reinforced Sand Ground Subjected to Footing Load

ABSTRACT: To obtain a better understanding of the bearing capacity characteristics
of reinforced sand subjected to a footing load and the associated reinforcing mechanisms,
results from plane strain laboratory model tests were simulated using a nonlinear elastoplastic
finite element model (FEM). The following factors, which affect the strength and
deformation of sand, were considered in the simulations: (i) confining pressure; (ii)
anisotropy; (iii) nonlinear strain-hardening and strain-softening; (iv) dilatancy; and (v)
strain localization into a shear band(s) having a width proportional to the particle size.
Simulated load-settlement relationships were generally in good agreement with the physical
experimental results. The strain and stress fields obtained from the FEM analysis
clearly reveal that the ground failure is extremely progressive. The peak strength is never
mobilized simultaneously along the potential failure planes.

KEYWORDS: Bearing capacity, Finite element method, Shear band, Stress path.

AUTHORS: N. Kotake, Engineer, Toyo Construction Co. Ltd., Japan, 3-7-1
Kandanishiki-cho, Chiyoda-ku, Tokyo 101-8463 Japan, Telephone: 81/3-3296-4623,
Telefax: 81/3-3296-4633, E-mail: kotake-nozomu@toyo-const.co.jp; F. Tatsuoka, Prof.,
Dept. of Civil Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-
8656, Japan, Telephone: 81/3-5841-6120, Telefax: 81/3-5841-8504, E-mail:
tatsuoka@geot.t.u-tokyo.ac.jp; T. Tanaka, Prof., Dept. of Biological & Environmental
Engineering, University of Tokyo, Japan, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657,
Japan, Telephone: 81/3-5841-5346, Telefax: 81/3-5841-8170, E-mail:
atanak@mail.ecc.u-tokyo.ac.jp; M.S.A. Siddiquee, Assoc. Prof., Dept. of Civil
Engineering, Bangladesh University of Engineering and Technology, Bangladesh,
Dhaka-1000, Bangladesh, E-mail: sid@bangla.net; and C.-C. Huang, Prof., Dept. of
Civil Engineering, National Cheng Kung University, No.1, Ta-Hsueh Road, Tainan,
Taiwan, 70101 ROC, E-mail: samhcc@mail.ncku.edu.tw.

DATE: Original manuscript submitted 10 November 2001, revised version received 14
December 2001, and accepted 5 January 2002. Discussion open until 1 September 2002.

REFERENCE: Kotake, N., Tatsuoka, F., Tanaka, T., Siddiquee, M.S.A., and Huang,
C.C., 2001, “FEM Simulation of the Bearing Capacity of Level Reinforced Sand Ground
Subjected to Footing Load”, Geosynthetics International, Vol. 8, No. 6, pp. 501-549.

Technical Paper by G.J. Foose, C.H. Benson, and T.B. Edil

Analytical Equations for Predicting Concentration and Mass Flux from Composite Liners

ABSTRACT: Composite liners, consisting of a geomembrane overlying a soil liner,
are often required as bottom liners for waste containment systems. In many applications,
regulations prescribe the type of liner that must be installed. However, regulations
often have provisions that permit an alternative liner design, provided that the
alternative liner is equivalent to, or as effective as, the prescriptive liner. The current
approach for demonstrating equivalency is based on comparing leakage rates for the
alternative and prescriptive liners. This approach is too simplistic because leakage rate
is not always indicative of the mass of contaminants discharged from the liner. In this
paper, practical equations are presented for predicting the discharge of contaminants
from composite liners and for designing alternative liners. The equations can be implemented
using hand-held calculators or computer spreadsheet applications. Some of
these equations are shown to provide predictions of mass flux and contaminant breakthrough
that are similar to predictions made with more complex one- and three-dimensional
numerical models for composite liners having perfect contact, circular defects, a
constant source concentration, and relatively simple boundary conditions.

KEYWORDS: Composite, Liner, Leachate, Equivalency, Leakage, Geosynthetic,
Clay, Landfill, Contaminant, Transport.

AUTHORS: G.J. Foose, Assistant Professor, Department of Civil and Environmental
Engineering, University of Cincinnati, Cincinnati, Ohio 45221, USA, Telephone: 1/
513-556-3781, Telefax: 1/513-556-2599, E-mail: gary.foose@uc.edu; C.H. Benson,
Professor, Department of Civil and Environmental Engineering, University of Wisconsin-
Madison, Madison, Wisonsin 53706, USA, Telephone: 1/608-262-7242, Telefax:
1/608-263-2453, E-mail: benson@engr.wisc.edu; and T.B. Edil, Professor, Department
of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison,
Wisconsin 53706, USA, Telephone: 1/608-262-3225, Telefax: 1/608-264-2453, Email:
edil@engr.wisc.edu.

DATE: Original manuscript submitted 22 February 2001, revised version received 11
February 2002, and accepted 12 February 2002. Discussion open until 1 September 2002.

REFERENCE: Foose, G.J., Benson, C.H., and Edil, T.B., 2001, “Analytical Equations
for Predicting Concentration and Mass Flux from Composite Liners”, Geosynthetics
International, Vol. 8, No. 6, pp. 551-575.

Technical Paper by J.D. Frost and S.W. Lee

Microscale Study of Geomembrane-Geotextile Interactions

ABSTRACT: This paper summarizes the results of a study that used quantitative
measures of surface roughness as the basis for investigating the role of topography on
the interface shear mechanism of geomembrane-geotextile interfaces. The results show
that the interface strength and mechanisms can be quantitatively related to the surface
roughness of the geomembrane. The peak and residual interface strengths increase dramatically
through the use of textured geomembranes. For textured geomembranes, the
peak interface strength is due to the micro-texture of the geomembrane, however, the
residual interface strength is primarily attributed to macro-scale surface roughness that
pulls and breaks the filaments of the geotextile. The effect of geomembrane wear on
the stress-strain response is quantified. The findings of this study provide a quantitative
framework that can lead to a significantly improved basis for the selection of geotextiles
and geomembranes in direct contact.

KEYWORDS: Geomembrane, Geotextile, Surface roughness, Interface strength,
Wear.

AUTHORS: J.D. Frost, Professor, School of Civil and Environmental Engineering,
Georgia Institute of Technology, Atlanta, Georgia 30332-0355, USA, Telephone: 1/
404-894-2280, Telefax: 1/404-894-2281, E-mail: david.frost@ce.gatech.edu; and S.W.
Lee, Senior Researcher, Civil Engineering Research Division, Korea Institute of Construction
Technology, Ilsan, Koyang, Kyunggi, 411-712, Korea, Telephone: 82/31-
910-0230, Telefax: 82/31-910-0211, E-mail: slee@kict.re.kr.

DATE: Original manuscript submitted 14 May 2001, revised version received 9 November
2001, and accepted 9 November 2001. Discussion open until 1 September 2002.

REFERENCE: Frost, J.D. and Lee, S.W., 2001, “Microscale Study of Geomembrane-
Geotextile Interactions”, Geosynthetics International, Vol. 8, No. 6, pp. 577-597.