Performance of stone columns in organic soil: insights from large-scale field load tests

The use of stone columns to improve the strength and deformational behaviour of soft clay and loose sand is not uncommon and use of it for treating organic soils remains challenging. This study investigates the efficacy of stone columns in soils with high organic content (≈40%) through large-scale field load tests. The tests were performed on stone columns with a diameter (d) of 900 mm and spacings of 2.2, 1.8, and 1.6 m. The thickness of organic soils (t) ranged from 1.50 to 8.50 m. Performance was assessed based on load–displacement response, and improvement in bearing capacity, where the loading was applied using hydraulic tank. The load–displacement response shows that stone columns improved ground experienced significant settlement when t/d >4.45, making them unsuitable. In contrast, settlements remained within permissible limit and stabilised when t/d <2.22, demonstrating their suitability. This study provides valuable insights into the limitations and suitability of stone columns in organic soils.