Stability of Levees over Soft Soil Improved by Deep Mixing Technology

Abstract

Stability of levees is critical to the safety of human and structures, especially at high water levels. Levees may fail due to the existence of soft soil foundations or seepage of water through the levees. Deep mixing technology has been considered one of the good alternatives to solve these problems. Studies have shown that deep mixed columns can increase the stability of highway embankments over soft soils. In those studies, however, no ponding water exists on either side of the embankment, which is not the case for levees. Experimental studies have shown that deep mixed columns under a combination of vertical and horizontal force could fail due to shear or bending or rotation. A finite difference method, incorporated in the FLAC (Fast Lagrangian Analysis of Continua) Slope software, was adopted in this study to investigate the stability of the levee with ponding water. In this study, deep mixed columns were installed in continuous wall patterns, which were modeled as 2-D deep mixed walls. Mohr-Coulomb failure criteria were used for the levee, the soft soil, and the deep mixed walls. The stability of a levee at different stages (end of construction, average service condition, and high water surge) was examined. The study clearly demonstrated that the deep mixed walls can enhance the stability of the levee by providing shear/moment resistance and hindering seepage through the levee.