Effect of groundwater and associated drainage on a roadside stabilisation method integrating a gabion-faced geogrid-reinforced retaining wall and embedded laterally loaded piles

A distinctive slope stabilisation method that integrates two well-developed slope stabilisation methods is investigated in this study. This slope stabilisation method combines embedded piles with geogrid-reinforced retaining walls which have flexible gabion basket wall facing. To study the effect of this integrated slope stabilisation method on the stability of the slope under the negative impacts of groundwater, the strength reduction finite element method with steady seepage analysis is adopted. By defining several different locations of the water table, the influence of the groundwater on the slope stability has been studied. The numerical results indicate that the highest water table reduces the stability of the slope up to 28.8%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$28.8\%$$\end{document} and causes the loss of matric suction to approximately 34.3%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$34.3\%$$\end{document}. Moreover, to mitigate the negative impact from groundwater on the slope stability, a typical retaining wall drainage based on the Australian Standards has been utilised and analysed. The results from the comparison among slope configurations with and without the drainage indicate that the drainage system can reduce the negative impacts of the groundwater and preserve the matric suction effectively. As a distinctive slope stabilisation method, the contribution from embedded piles to the stability of geogrid-reinforced retaining walls under the negative effect of groundwater has been demonstrated. In addition, the effect of groundwater and typical retaining wall drainage on the behaviour of slope and the performance of geogrids and piles has also been investigated.