The postconstruction settlement of compressible clayey soil can be achieved by which method?

• A. Vibroflotation
• B. Blasting
• C. Dynamic compaction
• D. Precompression by placement of temporary surcharge

Answer: (D)

The method of precompression by placement of a temporary surcharge is a widely used technique to address postconstruction settlement in compressible clayey soils. This process involves adding additional weight, typically in the form of soil, gravel, or other materials, on top of the existing ground. The temporary surcharge induces consolidation in the underlying clayey soil by increasing the vertical stress, which leads to a reduction in void ratio and an expulsion of pore water. As the excess load compresses the soil, the consolidation process occurs, allowing for significant settlement to take place prior to the construction of permanent structures. Once sufficient settlement has occurred and the soil has stabilized, the surcharge is removed, which leaves behind a more consolidated and stable ground condition for construction.

Other methods such as vibroflotation, blasting, and dynamic compaction focus on improving the soil’s density or strength in situ, but they do not specifically target the consolidation of clayey soils resulting from postconstruction settlement. While effective for certain soil conditions, they may not adequately address the long-term settlement issues associated with compressible clays. In contrast, the application of a surcharge is specifically designed to manage and mitigate settlement in such soils over time, making it the appropriate choice in this context.