A parametric investigation study by numerical analysis on the contribution of jet grout columns for liquefaction mitigation

As dynamic motion source earthquakes release energy propagating outward and result in many hazards including soil liquefaction phenomenon. Actually, liquefaction is primary concern for fully saturated, cohesionless soil. Therefore, various ground treatment methods are used in order to improve soil against liquefaction. As a soil improvement method, jet grout columns which are also known as high modulus columns are commonly preferred as a liquefaction mitigator. However, jet grout columns have become general engineering practice in terms of liquefaction mitigation although their effectiveness has not been validated thoroughly by both case and numerical analyses. Besides, only total stress analysis that does not take excess pore water pressure into account widely form numerical studies. Thus, in this study, role of jet grout columns as a precaution are investigated parametrically with intensive numerical analyses scheme. Numerical analyses performed using FLAC3D software in this study stand on three-dimensional, non-linear Finn Model and finite difference-based effective stress analyses. With the help of numerical analyses, two cases, namely, liquefiable soil and this type of soil involving jet grout columns are assessed for liquefaction. In that analyses, different dynamic motion inputs involving different peak acceleration values are used to evaluate contribution of jet grout columns against liquefaction. Also, effects of jet grout column spacing, stiffness of jet grout column and depth of consideration are investigated. Effectiveness of jet grout columns is mainly assessed with respect to pore pressure ratio. In addition, free field results obtained from this type of evaluation is compared with total stress approach. As the concluding remark, jet grout columns can prevent liquefaction by decreasing pore pressure ratio. Their effectiveness increases with decrease of stiffness and spacing while peak acceleration value of dynamic motion input does not have significant role on their contribution.