Behaviour of lignosulfonate-treated soil under cyclic loading

In this paper, the effectiveness of an environmentally-friendly stabilising agent for soil, lignosulfonate (LS), is examined through a series of cyclic triaxial tests. The deformation characteristics of the contents of LS-treated sandy silt when subjected to undrained cyclic triaxial loading are investigated at different confining pressures and cyclic stress levels. Test results indicate that under a given confining pressure and cyclic deviator stress, the rate of increase in axial strain is controlled by the addition of LS, which results in a smaller value of plastic axial strain (εa,p). For all the untreated and LS-treated specimens, the rate of increase in εa,p increases with the increasing cyclic stress ratio (CSR). A critical value of CSR exists for a given LS content (i.e. CSRCR), below which the specimens could remain stable irrespective of the number of load cycles. The longevity of treated specimens is improved significantly, especially for the specimens with LS equals 2% by weight. As the treated specimens are subjected to a high level of cyclic stress, the excess pore pressure shows a decreasing trend with the increasing number of cycles, but then increases again rapidly when the failure becomes imminent. Compared with the untreated soil, the resilient modulus increases significantly as a result of LS treatment, especially for LS equals 2%. When the LS is greater than 2%, there is no additional advantage, implying that 2% LS treatment is an optimum for this soil.