There are many types of lenses in tailings ponds that have important influences on stability. Lens types of more than 150 tailings dams were analyzed in China's severely cold regions, cold regions, hot summers and cold winters (the civil building thermal design code (GB50176-2016)). The mechanism of lens formation is discussed in this paper. Triaxial tests of tailings were carried out with fine mud tailing lenses, notched lenses, ice lenses and soft plastic soil lenses. Moreover, a three-dimensional triaxial test model with a flexible boundary is constructed to study the influence of different lenses on the mechanical properties of the tailings. The lens can change the failure mode of the tailings. These faults can change the dilatancy failure of tailings to failure along the lens-tailings interface. With increasing confining pressure, the ability of the lens to weaken the strength of the tailings increases. At 500 kPa, the strengths of the samples with fine mud tailing lenses, notched lenses, ice lenses and soft plastic soil lenses are 95.28%, 88.79%, 76.99% and 5.49%, respectively, of those of the sample without lenses. In addition to soft plastic soil lenses, other lenses provide space to accommodate the deformation of tailings, thereby reducing the bulk strain of tailings. The conclusions of this study can provide theoretical support for studying the failure mode of tailings dams under the influence of lenses and improving the local stability of tailings ponds.

A universal testing machine and a 50 mm split Hopkinson pressure bar (SHPB) were used to conduct salt erosion and freeze -thaw (F -T) cycle coupling tests on cement soil specimens with 0.5% polyvinyl alcohol (PVA) fiber and without fiber in order to study the effects of salt solution and F -T cycles on the dynamic and static mechanical properties of cement soil. In four distinct solution settings (clear water, 9 g/L sodium sulphate solution, 9 g/L sodium chloride solution, and 9 g/L sodium sulphate and sodium chloride mixed solution). After F -T cycles, the cement soil specimens underwent the unconfined compressive strength (UCS) test, SHPB test, and SEM test. The findings indicate that as the number of F -T cycles increases, the dynamic and static mechanical properties of cement soil specimens decrease, and the rate of decline is rapid followed by slow. After five F -T cycles, the combined solution ' s unconfined compressive strength dropped to 15.91% (without fiber) and 29.41% (with fiber), respectively. After five F -T cycles, the dynamic compressive strength in sodium sulphate solution fell by 95.17% (without fiber) and 93.86% (with fiber). Fibers help to some degree by preventing salt erosion and F -T cycles. With more F -T cycles, the absorbed energy declines exponentially, and the order of the solutions ' effects on the absorbed energy is: mixed sodium chloride and sodium sulphate solution > sodium chloride solution > sodium sulphate solution > clear water.