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 (ε_a,p). For all the untreated and LS-treated specimens, the rate of increase in ε_a,p increases with the increasing cyclic stress ratio (CSR). A critical value of CSR exists for a given LS content (i.e. CSR_CR), 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 = 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 = 2%. When the LS > 2%, there is no additional advantage, implying that 2% LS treatment is an optimum for this soil.