One-dimensional consolidation behavior of cement-treated organic soil

Abstract

This paper addresses the effects of cement treatment on the one-dimensional (1D) consolidation behavior of a highly organic soil (LOI ∼ 40%–60%, where LOI is the loss on ignition), based on 1D constant rate of strain and incremental loading tests. The effects of Portland cement addition are evaluated for dosages ranging from 8% to 100% by dry mass of soil, corresponding to values of the cement factor of 24 and 296 kg of cement per cubic metre of untreated soil, within the range used in deep mixing practice. Additional parameters investigated are the impact of curing surcharge and duration. The most evident effect of the treatment is the development of a cementation-induced preconsolidation stress: the greater the cement dosage, the greater the preconsolidation stress and the greater the vertical effective stress that can be sustained at any void ratio. The results also provide a consistent picture of the effects of cement treatment on stiffness, hydraulic conductivity, coefficient of consolidation, and creep. Comparison to data obtained for the untreated soil demonstrates the “stable” nature of the structure generated as a result of treatment. The consolidation results are complemented by pH measurements, extraction tests, elemental analyses, and Fourier transform infra-red (FTIR) spectroscopy analyses, which provide insight into the interaction between soil organic matter and cement.