Influence of Dry-Wet Cycles on Uniaxial Compression Behavior of Basalt Fiber-Reinforced Loess Facilitated by 3D-DIC Technique

Cyclic dry-wet actions severely impair the stability of bridge, highway and building foundations in the Loess Plateau and fiber reinforcement provides an available countermeasure. By means of 3D-DIC technique, the uniaxial compression tests were carried out on the basalt fiber-reinforced loess with different fiber contents (i.e., 0.0wt% 0.3wt%, 0.6wt%, 0.8wt%, and 1.0wt%) after different dry-wet cycles (0, 1, 2, 5, 10), with the morphology of microstructure analyzed by SEM tests. Results show that the uniaxial compressive strength (UCS) of fiber-reinforced loess declines with the increase of dry-wet cycles, but the decay rate decreases gradually, and increases first and then decreases with fiber content. At the optimum fiber content of 0.6%, the UCS damage after 10 dry-wet cycles is minimal at 48.62%, which is much lower than that of 62.19% for unreinforced loess. The failure strain exhibits consistent changes with UCS, implying its close relationship to the compressive resistance. The fiber addition transformed the failure pattern of loess, with brittle failure observed in unreinforced loess and plastic failure after reinforcement. The surface deformation of reinforced loess becomes more uniform and shows higher plasticity at the optimum fiber content. The failure of reinforced loess transforms from bulging to fracture failure after dry-wet cycles, and the maximum of the strain field overall increases. Scanning electron microscopy (SEM) images imply the pronounced influence on loess microstructure and the reinforced loess deteriorates mainly at the fiber-soil interface. Insignificant weathering on reinforced loess was observed compared to that of unreinforced in that the fiber network inhibits soil deformation during loading. Fiber reinforcement can effectively improve the strength and plasticity of loess and weaken the deterioration of dry-wet cycles.