Grouted helical piers for use in foundation rehabilitation : centrifuge testing

Rehabilitation of building structures is a critical need facing numerous older urban areas. Many of these structures are supported on pile groups, which do not have adequate load capacity to support the demands expected after rehabilitation or superstructure replacement. Consequently, practical methods for strengthening existing foundations are of paramount concern. Recent studies have focused specifically on the use of grouted helical pier systems to strengthen pile group foundations, thereby substantiating their potential as a technique for load capacity enhancement (see companion paper by Laefer and Manke, 2006). However, these scaled studies were conducted at one-g level, resulting in soil confining stresses lower than those expected in the field. Thus, further verification through numerical modeling; full-scale experiments, or centrifuge testing is needed. This paper presents preliminary issues related to developing tools to support centrifuge testing of grouted helical pier systems. For this study, models for a 15-g centrifuge test were first explored at the one-g scale. With the small-scale model piers, a variety of grout types and pier installation methods were considered for the design and evaluation of the centrifuge tests. Based on the findings from this one-g testing, a preliminary centrifuge testing plan is presented.