Stone columns are a technology to improve various soil situations. Soil can be like sand, clay, silt or peat as examples. You need to watch collapse compression on peat soils, ie when wetted as says the soil collapses. Pathways for toxins can be detailed and flow into other water routes. The procedure really is displacement or replacement, the latter you core and the former you drive into the ground. Mentioned soil mixing with the clay and flow paths obstructed. One university used a 6m embankment on stone columns which resulted in a 300mm surface level settlement. I need to confirm clashes with other blogs. My initial thoughts were the stone column mostly acts as a block reinforced region, more so displacement than replacement. Know others used stone columns on rubble ground for flats, the technique uniformly altered the ground. I want to return to Blogg at a later date, initial information, need to consider failure situations.