Experimental investigations on granular column improvement in saturated ground subjected to repeated shaking events and its performance assessment in liquefaction and reliquefaction mitigation

Soil liquefaction significantly contributes to inducing catastrophic damage to the infrastructures. Different ground improvement methods were used widely to improve the seismic resistance of liquefiable deposits to mitigate liquefaction. Use of granular column technique is a popular and well-recognized improvement technique due to its drainage, shear reinforcement, and densification characteristics. However, studies relating to seismic resistance of stone column-reinforced ground against multiple shaking events were limited. Recent seismic events also have shown the possibility of liquefaction and reliquefaction due to multiple seismic events. Considering this, the performance assessment of the granular column technique in liquefiable soil under repeated shaking events is addressed in this study. The possibility of re-using construction and demolition waste concrete aggregates as an alternative to natural aggregates is also attempted to propose sustainability in ground improvement. For experimental testing, a saturated ground having 40% density was prepared and subjected to sequential incremental acceleration loading conditions, i.e., 0.1 g, 0.2 g, 0.3 g, and 0.4 g at 5 Hz loading frequency for 40 s shaking duration using a 1 g Uni-axial shake table. The efficiency of selected ground improvement was evaluated and compared with untreated ground. The experimental results showed that ground reinforced with granular columns performs better up to 0.2 g shaking events in minimizing pore water pressure and settlement. Possibility of column clogging, and inadequate area replacement ratio (5%) affects the performance of column during repeated shaking. Also, irrespective of improvement in in-situ ground density; continuous generation of pore water pressure due to absence of drainage posing reliquefaction potential in untreated ground under repeated shaking events.