Aggregation and dehydration of excavated soft clay and use for subgrade engineering–Part 1: A laboratory study

Abstract

The reuse of the excavated soil for subgrade construction, as an alternative to the traditional excavated soil management approach, has demonstrated great potential for engineering application. However, its application is currently hindered by the poor engineering properties of soft soils and the pretreatment process. In this paper, an improved technique employing aggregation and dehydration for rapid stabilization of excavated soft clay was proposed. By wet mixing with stabilizers, excavated soft clay was transformed into separated aggregates with the larger surface areas exposed to air. During turning preservation, aggregates were further stabilized and dehydrated as a result of the combined hydration and enhanced evaporation effect. The performance of the produced stabilized-soil aggregates was explored by performing a series of laboratory tests and it was demonstrated that by enhancing the evaporation effect, moisture content of excavated soft clay decreased by over 20 % in 4 days. Through the aggregation effect, the soft clay tended to be silty in the plasticity chart and experienced an increase in optimal moisture content and a decrease in maximum dry density. Unconfined compressive strength and Californian bearing ratio tests showed that compacted aggregates exhibited reliable strength and water stability because of the enhanced cementitious and pozzolanic reactivity, which was capable for various sections of the subgrade with different classifications. Meanwhile, the performance of compacted aggregates was found to be dominated by the stabilizer content and the characteristics of the raw soil, which indicates that it would be preferred to distinguish the stabilizer dosage and the excavated soft clay to counter different requirements for engineering application. And a draft, dry and thermostatic environment for turning preservation is highly recommended for the purpose of improving the efficiency of excavated soil management.