ABSTRACT:

The failure of the Kettleman Hills landfill slope in 1988 resulted in significant movements of the waste pile of the order of 10.5m and settlements up to 4.5m. Subsequent investigations of the failure indicated that the slide occurred along the interfaces of the multi-layered liner system underlying the waste. It was also found that due to the configuration of the liner system as well as its supporting subgrade the three-dimensional (3D) effect appeared to be significant on the waste fill stability. Physical model tests were conducted to help understanding on the slide mechanism and to provide data for verification of the unusual 3D effect. This paper presents results of 2D and 3D stability analyses of the models. The results indicate that 3D analyses correctly predicted the model failure in both pre-slide and post-slide configurations. However, due to divergent geometry of the slip surface, the 3D effect of this case appeared to be unfavorable. Conventional 2D analyses were unable to depict the unusual 3D situation and gave an overestimation on the actual stability by about 5–20%.

INTRODUCTION

The Kettleman Hills Repository is a Class I hazardous waste treatment and storage facility located in Kettleman City, California. Landfill Unit B-19 of the repository has an area of about 14.5ha, which consists of an oval shape excavated basin with 2H:1V and 3H:1V (horizontal to vertical) side slopes around the basin and nearly level ground at the center. The first stage (Phase I-A) of construction occupied the northern half of the unit, with an area of about 6ha. Since no abnormal situation was observed, including significant seismic or rainfall events, at the time of failure or in several months preceding, the slope failure was considered as a static problem. Details of the failure are referred to Seed et al. (1988).

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