Accuracy analysis of 2D numerical methods of deep‑seated failure analysis in embankments on stone column reinforced ground

摘要

Global instability analysis using two dimensional (2D) numerical methods are based on the conversion of a real-world situation into the simplified two-dimensional plain-strain condition. These methods are simpler compared to the complex three dimensional (3D) numerical methods of analysis, hence they are more commonly used. These methods are indirect and approximate and the existing 2D methods viz. the column wall (CW) and equivalent area (EA) methods give different values of factor of safety (FOS) for a single embankment. This study is aimed at analysing the accuracy of the existing 2D methods of analysis compared to the three dimensional (3D) numerical environment. To achieve this, stability analysis of embankments on stone column reinforced soil was carried out using the existing 2D numerical methods of analysis. The results of the 2D analysis were then compared with the values obtained from the 3D numerical method. The embankments were analysed by varying various material and geometrical parameters viz. S/D ratio, the cohesion of soil, friction angle of stone column infill, friction angle of embankment fill, the height of embankment and slope of the embankment. The detailed parametric analysis was carried out using 2D and 3D numerical methods to generalise the performance of the existing 2D numerical methods. Finite element programme PLAXIS2D and PLAXIS3D were used to carry the 2D and 3D analysis, respectively. The results show that the CW method underestimates the FOS values whereas the EA method overestimates the FOS values compared to the 3D numerical analysis. Since the 3D numerical method is more accurate, conversion factors of 1.033 for the CW method and 0.929 for the EA method are proposed to get more accurate FOS values. Two regression equations were also proposed for conversion of FOS values obtained by the 2D numerical methods into the values of equivalent 3D numerical analysis. It is concluded that among the two methods of 2D analysis, the estimation of FOS values using the CW method is more accurate and conservative than the EA method.