Keywords: earthquake, seismic behaviour, landfills, landfill liner systems, liquefaction, excess pore pressures.

Seismic behaviour of landfills is a major concern especially when the landfills are located in the vicinity of densely inhabited areas. Following the Northridge earthquake of 1994 in Los Angeles, one of the main worries was the dynamic behaviour of various Waste Containment Structures storing many kinds of toxic and non-toxic chemicals. The post earthquake behaviour of these structures need to be investigated to establish their effective functionality over their full intended design life which may extend to a period of 70 to 80 years. In other words, post earthquake integrity of the landfill liners must be ensured.

This paper aims at understanding the failure mechanisms of landfill liner systems following earthquake loading with emphasis on the liquefaction scenarios. In this paper we present the analysis of experimental data from centrifuge tests where the landfill liner consisted of either a single clay layer or a clay liner-geomembrane system, overlying a liquefiable soil deposit.

In this paper we present the analysis of experimental results from a series of dynamic centrifuge tests carried out aboard the 10 m diameter beam centrifuge at the Schofield Centrifuge Centre, Cambridge. In a previous study, centrifuge tests were first carried out to look at the stability and integrity of the waste containment systems during post liquefaction period. In that study, the liquefaction was achieved by simple fluidisation of sub-strata. Following that the centrifuge model of the clay liner systems were subjected to earthquake loading and the liquefaction of the foundation soil was achieved due to the earthquake loading, as opposed to simple fluidisation in previous studies. The full data from the dynamic centrifuge tests is presented elsewhere, Madabhushi and Singh [1]. In this paper we present the analysis of the data in terms of the excess pore water pressures generated and the integrity of the landfill liner. Schofield [2] derives the dynamic scaling laws that relate the behaviour of the centrifuge models to that of the prototype. These will not be reproduced here.

1

Madabhushi, S.P.G. and Singh, S.K., Integrity of landfill liners following earthquake loading, International Symposium on Physical Modelling and Testing in Environmental Geotechnics, NECER, LCPC Centre de Nantes, Bouguenais, France, 2000.

2

Schofield, A.N., Dynamic and Earthquake geotechnical centrifuge modelling, Proceedings Recent Advances in Geotechnical Earthquake Engineering Soil dynamics and earthquake engineering, University of Missouri-Rolla, Rolla, 1981.

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