Field Performance Evaluation of Jet Grout Columns for Potential Liquefaction Risk Mitigation: A Comparative Study from the 6 February 2023 Kahramanmaraş Earthquakes in İskenderun Coastal Zone

This study evaluates the effectiveness of jet-grout columns to mitigate soil liquefaction in the coastal zone of İskenderun which is one of the regions severely affected by the February 6, 2023 Kahramanmaraş earthquakes. A comparative field investigation was conducted by selecting one structure that had been improved with jet grout columns prior to the earthquake and two adjacent structures without any ground improvement. Liquefaction analyses were performed using borehole and SPT data in accordance with the Turkish Building Earthquake Code (TBDY, 2018). Before ground improvement, the liquefaction factor of safety was calculated as Fs = 0.85, indicating significant liquefaction potential. After installing 12 m deep jet-grout columns beneath the foundation, the factor of safety increased to Fs = 1.98, demonstrating that liquefaction risk was effectively eliminated. Post-earthquake field observations revealed only minimal settlement in the improved building, whereas the unimproved adjacent buildings exhibited 26.9 cm and 24.5 cm of liquefaction-induced settlement and deformation, respectively. The findings confirm that jet-grout columns substantially enhance seismic performance by reducing liquefaction-induced settlement and lateral deformation in areas characterized by high groundwater levels and loose sandy-silty layers.