What technique is used to densify cohesive soils by placing additional weight on surface?

The technique used to densify cohesive soils by placing additional weight on the surface is surcharging. Surcharging involves the temporary placement of a load on top of the soil to increase the effective stress within it, thereby promoting consolidation and reducing the volume of voids over time. This approach is particularly effective for cohesive soils, which are prone to settlement and deformation. By applying a surcharge, the pore water pressure is reduced, causing the soil particles to rearrange and achieve a denser state.

In contrast, compaction refers to the mechanical process of increasing soil density by reducing air voids through mechanical means, such as tamping or vibrating, which is typically done during construction rather than by placing weight. Excavation is the removal of soil or rock from a site, which does not contribute to densification. Grading involves leveling or shaping the land surface, which can have an impact on drainage and surface contours but does not specifically aim to increase soil density through added weight.