Effect of organic matter in soft soils on the effectiveness of preloading for foundations

This paper examines the effect of organic matter in soil on the effectiveness of preloading soft ground to accelerate primary consolidation and mitigate creep settlements prior to foundation construction. Four organic matter contents (1·2, 4·1, 6·4 and 8·3%) and two preloading levels (25 and 50 kPa) are studied. The increase in organic matter content has a significant impact on primary and secondary consolidation, inducing an increase in the void ratio, compressibility indices and creep deformations, and a decrease in the coefficient of consolidation. The results show that the creep strain with log time changes from a linear trend for samples without preloading to an increase in the creep strain rate for samples submitted to preloading. The results of the creep tests also highlight that preloading is more effective for a higher preloading level, in the short term, and for higher organic matter content.