A numerical analysis of liquefaction mitigation using stone column

Abstract

In this study, a numerical analysis is carried out for mitigation of liquefaction using stone column. The generation of excess pore pressure and also dissipation of excess pore pressure in both cases, without stone column and with stone column cases are analysed in detailed. FLAC 2D software based upon finite difference method are used here to simulate the real earthquake situation. A parametric variation was done by varying the three different stone column length with two different natural earthquake having same PGA but different time record, different dominant frequency. Loose saturated sand and medium dense saturated sand layer are considered here as liquefiable layer. A single stone column of diameter of 0.8m is installed at the centre of the liquefiable layer. Then pore pressure generation and dissipation with stone column are checked along the depth on stratified soil layer. And also, from the centre of the stone column in lateral distances various points are considered like soil-column interface, 1.5d, 3d, 4.5d (d = diameter of stone column = 0.8m) where excess pore pressure parameters are calculated. And finally comparing these results. Liquefaction potential is measure here in terms of excess pore water ratio, r u which is the ratio of excess pore water pressure to the effective stress at that depth. When r u value reached to 1, the soil is termed as liquefied. The result got from these studies when the stone column is installed in liquefiable saturated sandy layer the excesses pore pressure ratio, r u is drastically reduced up to 1.5d distances from centre of the column in either left or right side. So, the stone column is safely reduced liquefaction about a total 3d length around the stone column. And stone column having length of 10m is sufficiently mitigate moderate to high PGA earthquake.