EFFECTIVENESS OF NEAR SURFACE GROUND IMPROVEMENT AROUND PILED-RAFT FOUNDATION IN WEAK SOIL BASED ON ANALYTICAL DESIGN AND FINITE ELEMENT MODELING.

Taller wind turbines are preferred to access high and steady wind at a higher altitude to increase the efficiency of a wind turbine, but they require an extensive foundation, particularly when subsurface soil has poor engineering properties. One of the solutions to this problem is to improve the engineering properties of the poor near-surface ground to gain a net economic advantage for foundation construction. In this study, the effectiveness of the ground improvement around piled-raft foundation in weak soil is investigated using analytical and three-dimensional finite element (FE) methods. Five different ground improvement depths from 2.0 m to 3.6 m and radii from 6 to 15 m were considered to develop a relationship between the geometry of ground improvement, the performance of the foundation, and the cost of the foundation. The analytical analysis shows that the pile length required to meet the safety and serviceability requirements decreased from 48.4 m in the unimproved soil to 9.85 m in the 3.6 m improved soil, resulting in a 33.5% cost reduction. The cost-benefit for various depths of ground improvement shows a nonlinear variation, indicating that the most economical depth of ground improvement is within the range considered in this study. The finite element modeling was conducted using ABAQUS with frictional contacts at the soil-pile and raft-pile interfaces to capture the load transfer accurately. The ABAQUS results were much lower than the analytical results for the linear elastic and elastoplastic constitutive models. [ABSTRACT FROM AUTHOR]