Precompression for Improving Foundation Soils

The precompression of weak and compressible subsoils, with or without vertical sand drains to accelerate consolidation, to increase their strength and to decrease postconstruction settlements to tolerable amounts is discussed with reference to uses and to design procedures. Precompression is an effective means for eliminating, in advance of construction of structures or roads, primary consolidation and a portion of secondary compression that would otherwise occur. The amount of secondary compression that is avoided by precompression can be estimated reasonably well, and the surcharge fill can be designed to reduce the remaining secondary compression settlements to tolerable amounts. Design procedures to minimize secondary compression effects are presented.