Performance of Two Geosynthetics-Lined Landfills in the Northridge Earthquake

Analyses of the performance of the Chiquita Canyon and Lopez Canyon landfills in the 1994 Magnitude 6.7 Northridge earthquake illustrate deficiencies in the current state-of-practice for seismic design of geosynthetic liner systems and the promise of a new state-of-the-art method for performance-based design, and suggest necessary modifications to construction quality assurance procedures for geosynthetic liner systems. Analyses of the Chiquita Canyon landfill case history using the conventional state-of-practice Newmark Analysis approach fail to predict the tears observed at the landfill following the earthquake in the side slope liner geomembrane at two different locations. However, the state-of-the-art finite difference based method does predict failure of the geomembrane at these locations if strain concentrations due to seams and scratches in the geomembrane from patches at locations where destructive samples were recovered for construction quality assurance purposes are considered. The state-of-the-art method also predicts tension strains observed in the filter geotextile for the side slope liner at the Lopez Canyon landfill following the earthquake. The analysis for the Chiquita Canyon landfill suggests that construction quality assurance guidelines for obtaining geomembrane samples for destructive testing should be developed for avoiding critical areas where geomembrane tensile strain is likely to accumulate