Comparing CO2 emissions: ordinary stone vs. geosynthetic encased columns

The design engineers’ responsibility is not limited to finding a safe solution but includes considering the environmental impact of the suggested design. In many cases a soil improvement becomes necessary when constructing an embankment on soft subsoil conditions. One of the alternative soil improvement methods is installing stone columns. A more recent alternative is installing Geosynthetic Encased Columns (GEC). In this study a comparison was made on the environmental impact both methods will create. As the measure of the environmental impact, the equivalent carbon dioxide (CO2eq.) emissions was taken. For this purpose, a soft subsoil condition was considered with three different levels of weakness and three different embankment heights. In the comparison, transportation distances of geosynthetic products and granular column materials have been estimated. Since GECs can use any granular material as fill, only one hauling distance was estimated. Stone columns necessitate a more specific granular fill; hence four different hauling distances were taken into consideration. It was determined that the GEC alternative produces a much smaller CO2 footprint than the stone column alternative. Furthermore, it was seen that the advantage of GEC solution becomes more efficient in terms of reducing the CO2 emission with increasing embankment height.