The Influence of Freeze-Thaw Cycles on Unconfined Compressive Strength of Lignin Fiber-Reinforced Loess

Abstract

In the seasonal permafrost region with loess distribution, the influence of freeze-thaw cycles on the engineering performance of reinforced loess must be paid attention to. Many studies have shown that the use of fiber materials can improve the engineering performance of soil and its ability to resist freeze-thaw cycles. At the same time, as eco-environmental protection has become the focus, which has been paid more and more attention to, it has become a trend to find new environmentally friendly improved materials that can replace traditional chemical additives. The purpose of this paper uses new environmental-friendly improved materials to reinforce the engineering performance of loess, improve the ability of loess to resist freeze-thaw cycles, and reduce the negative impact on the ecological environment. To reinforce the engineering performance of loess and improve its ability to resist freeze-thaw cycles, lignin fiber is used as a reinforcing material. Through a series of laboratory tests, the unconfined compressive strength (UCS) of lignin fiber-reinforced loess under different freeze-thaw cycles was studied. The effects of lignin fiber content and freeze-thaw cycles on the strength and deformation modulus of loess were analyzed. Combined with the microstructure features, the change mechanism of lignin fiber-reinforced loess strength under freeze-thaw cycles was discussed. The results show that lignin fiber can improve the UCS of loess under freeze-thaw cycles, but the strengthening effect no longer increases with the increase of fiber content. When the fiber content is less than 1%, the UCS growth rate of loess is the fastest under freeze-thaw cycles. And the UCS of loess with 1% fiber content is the most stable under freeze-thaw cycles. The freeze-thaw cycles increase the deformation modulus of loess with 1% fiber content, and its ability to resist deformation is obviously better than loess with 1.5%, 2% and 3% fiber content. The fiber content over 1% will weaken the strengthening effect of lignin fiber-reinforced loess, and the optimum fiber content of lignin fiber-reinforced loess under freeze-thaw cycles is 1%.