Undrained cyclic behaviors of fiber-reinforced calcareous sand under multidirectional simple shear stress path

A series of monotonic and multidirectional cyclic simple shear tests were performed on reconstituted fiber-reinforced calcareous sand specimens prepared by the dry deposition method, at a relative density of approximately 50%, considering the effects of fiber contents and cyclic stress levels. The peak shear strength, the linkage between monotonic and cyclic behaviors, liquefaction resistance, and pore pressure responses of calcareous sand with and without fiber reinforcement were analyzed. The results indicate that both unreinforced and fiber-reinforced calcareous sand exhibit limited flow instability behavior and the peak shear strength increases with the increase in fiber content under monotonic loading. The inclusion of fibers and increasing fiber contents can improve the liquefaction resistance of calcareous sand under cyclic loading. A linear relationship was found between the normalized liquefaction resistance of reinforced sand and the number of cycles for triggering liquefaction, and the prediction of liquefaction resistance of fiber-reinforced calcareous sand with various fiber contents can be conveniently achieved according to the linear relationship. The pore pressure prediction model considering the effect of fiber contents was proposed, which was capable of effectively simulating the pore pressure generation of fiber-reinforced calcareous sand.