CHAPTER 3: LITERATURE REVIEW ON OBSERVATION AND PREDICTION OF IMPROVED GROUND PERFORMANCE 3.1 Introduction

Over the last ten to fifteen years considerable information has been developed concerning the performance of improved ground within liquefiable soil deposits subjected to earthquakes. This information comes from physical modeling in the laboratory using centrifuge and shaking table apparatus, numerical modeling using a variety of computer codes, and field case histories. The results from physical and numerical modeling studies are particularly useful because in many cases a number of variables can be isolated for study of their impact on the improved ground behavior. In addition, several aspects of ground response are monitored in these studies, such as ground displacements, accelerations, and pore water pressure development. Information is summarized below from several key laboratory and numerical modeling studies having particular relevance to liquefaction mitigation at existing highway bridges. The focus of many of these studies is on the effect of treatment type, size, and/or location on performance. As just mentioned, numerical modeling is one of the tools used for predicting improved ground performance under earthquake loading. Over the years, a variety of numerical modeling approaches have been used for these analyses with varying success. A summary is provided of those approaches along with a brief discussion of their performance, as cited in the literature.