Inﬂuence of geomembrane on the deformation behaviour of clay-based landﬁll covers P.V. Divya a,1 , B.V.S. Viswanadham a, * , J.P. Gourc b, 2 a Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India b LTHE, University of Joseph-Fourier, Grenoble F-38041, France article info Article history: Received 19 August 2011 Received in revised form 24 February 2012 Accepted 3 June 2012 Available online Keywords: Geosynthetics Clay barrier Geomembrane Landﬁlls Centrifuge modelling Differential settlements abstract Clay-based landﬁll covers often have a geomembrane (GM) layer sandwiching between the clay barrier and the cover soil. The knowledge pertaining to the deformation behaviour of a clay barrier along with geomembrane subjected to differential settlements is very limited. Hence, the main objective of this paper is to examine the inﬂuence of GM on the integrity of clay-based landﬁll covers subjected to differential settlements in a geotechnical centrifuge. First, scaling considerations required for model- ling geomembrane in a centrifuge are presented. A series of centrifuge tests were performed at 40 gravities using a 4.5 m radius beam centrifuge having a capacity of 2500 g-kN available at IIT Bombay on model clay-based landﬁll covers with and without GM. By maintaining type moist-compacted conditions of the clay barrier as constant, the thickness of the clay barrier was varied as 0.6 m and 1 m. The performance of the clay barrier with and without GM was monitored by measuring water breakthrough at the onset of differential settlements. The analysis and interpretation of centrifuge test results reveal that with the provision of a GM and an overburden pressure equivalent to that of a landﬁll cover, the sealing efﬁciency of the cover system was found to be maintained even after the formation of full-depth cracks within 0.6 m and 1 m thick clay barriers subjected to a maximum distortion level of 0.125. This observed behaviour is attributed to the downward thrust exerted by the deformed geomembrane at the zone of maximum curvature which hinders the inﬁltration of water through cracks. This indicates the signiﬁcant inﬂuence of GM in maintaining the sealing efﬁciency of a landﬁll cover system. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction In most of the countries, engineered landﬁlling is treated as the most common and ultimate waste disposal method. One of the predominant causes of failures of a landﬁll cover is the large differ- ential settlements resulting due to ongoing bio-degradation of municipal solid waste (MSW) and differential settlements due to the heterogeneity of the waste in an MSW landﬁll. The impervious barriers of landﬁll covers are more likely to be subjected to more mechanical damage compared to bottom lining systems since the former is subjected to lower overburden pressure. Excessive differ- ential settlements can cause development of tension cracks in the clay barrier resulting in loss of integrity of whole cover system (Jessberger and Stone, 1991; Keck and Seitz, 2002; Dickinson and Brachman, 2006; Sharma and De, 2007; Heerten and Koerner, 2008). There are different types of impervious barriers that can be used in landﬁlls such as compacted clay barriers (CCB), geosynthetic clay liners (GCLs), geomembranes, amended soil or the combination of above. Compacted clay barriers can be considered as an economi- cally viable barrier material (Jessberger, 1994). They can be used wherever these soils are easily and economically available (Heerten and Koerner, 2008; Camp et al., 2010; Gourc et al., 2010). In modern landﬁlls, geomembranes are used in lining systems (Rowe and Sangam, 2002; Rowe et al., 2004, 2009; Rowe, 2005; Take et al., 2007; Brachman and Gudina, 2008a,b; Bouazza et al., 2008; Rowe, 2011). Geomembranes (GM) are considered to be one of the most commonly used geosynthetics in landﬁll construction and are laid above the clay barrier of cover systems. In this case, the tensile strain developed due to differential settlements will be appor- tioned by geomembrane, as geomembrane has much higher allowable elongation compared to the clay barrier material. In recent times, GCL are used in developed countries due to their * Corresponding author. Tel.: þ91 22 25767344; fax: þ91 22 25767302. E-mail addresses: divya.nair@iitb.ac.in (P.V. Divya), viswam@civil.iitb.ac.in (B.V.S. Viswanadham), gourc@ujf-grenoble.fr (J.P. Gourc). 1 Tel.: þ91 22 25764311; fax: þ91 22 25767302. 2 Tel.: þ33 687860873; fax: þ33 476825014. Contents lists available at SciVerse ScienceDirect Geotextiles and Geomembranes journal homepage: www.elsevier.com/locate/geotexmem 0266-1144/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.geotexmem.2012.06.002 Geotextiles and Geomembranes 34 (2012) 158e171