Clay mineral content has an important influence on the mechanical behaviour of tailings, and this mechanical behaviour significantly affects the stability of tailings dams. X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests were carried out on tailings from three different regions. The chemical and mineral composition of the tailings are analyzed. The strength and failure deformation of the tailings were studied by laboratory triaxial compression tests. The effect of clay content on the behaviour of tailings was investigated. The microfabric of tailings sample was examined with the scanning electron microscope (SEM) and nitrogen adsorption tests. The results show that the confining pressure corresponding to the samples exhibiting strain hardening increases with the increase of the content of clay minerals. The cohesion of tailings increases linearly, and the specific surface area decreases as the content of clay minerals increases. Nitrogen adsorption test results reveal from a microscopic point of view that changes in pore structure are associated with the content of clay minerals. The higher the content of clay minerals is, the higher the proportion of micropores is (aggregated interior). Macroscopically, the overall porosity decreases and the size of the pores increases with clay content, which will directly affect the mechanical properties of tailings.
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