Numerical Modeling of Laterally Loaded Pile Groups in Soft Clay Improved by Jet Grouting

Abstract

Pile foundations are often subjected to high lateral loads (for example, wind, water, and/or earthquake loading) when they are used to support superstructures, such as buildings, bridges, and offshore platforms. Piles are commonly installed in a group for such applications. Pile groups in weak soil (e.g. soft clay and loose sand) may be susceptible to lateral failure due to inadequate lateral soil resistance. Structural retrofit has been widely used to increase the lateral resistance of piles in weak soil by adding additional piles. In comparison with the structural approach, jet grouting has been proven as a cost-effective approach to increase the lateral resistance by improving the properties of the surrounding soil. A series of field tests reported in the literature evaluated the effects of jet grouting on the lateral resistance of a pile group in soft clay and showed that jet grouting significantly increased the lateral resistance of piles and reduced the cost as compared with adding piles. To simulate the reported field tests, a numerical analysis was conducted in this study, in which a finite difference method incorporated in FLAC 3D software was employed to simulate laterally loaded pile groups in soft clay before and after jet grouting. This paper discusses the selection of soil parameters and compares the numerical results with the experimental data. The comparison showed that the numerical method reasonably simulated the lateral load-displacement responses of the pile group in the soft clay before and after jet grouting; however, the computed bending moment from the numerical method was different from that of the measured in the middle pile of the front row.