Stability Improvement and Failure Mechanism Analysis of Calcareous Sand Slope Reinforced With Rubber Fibers

Calcareous sand is widely distributed throughout the islands and reefs of the South China Sea. Due to its high porosity and susceptibility to particle breakage, this material is prone to sliding and instability under dynamic loads, such as waves and seismic events. Developing innovative reinforcement techniques is critical for ensuring the long‐term structural integrity of offshore engineering projects. This study investigates the impact of rubber fiber reinforcement on the stability of calcareous sand slopes and aims to elucidate the underlying failure mechanisms. To this end, a two‐block sliding model was developed based on the principle of energy conservation and the upper‐bound theorem of limit analysis. This model characterizes the synergistic failure mechanism involving sliding body settlement and shear at the slope toe. Subsequently, consolidated‐drained (CD) triaxial shear tests were performed to evaluate the effects of rubber fiber content and length on the shear strength of the calcareous sand. The experimental results were then integrated into the theoretical model for sensitivity analysis. The findings reveal that the shear strength follows a nonlinear trend—increasing initially and then decreasing—as fiber content and length increase. The optimal reinforcement performance was achieved with a fiber content of 1.0%–1.5% and a length of 10–15 mm. Compared to unreinforced sand, the cohesion of the fiber‐reinforced specimens increased by up to 39.70%, while the internal friction angle increased by up to 7.97%. Theoretical calculations further demonstrate that these reinforcement conditions can elevate the slope’s stability coefficient from 1.37 to 1.50 and increase the depth of the potential sliding surface. Mechanism analysis suggests that rubber fibers form a three‐dimensional flexible anchoring network within the sand matrix, which restricts the development and propagation of shallow sliding surfaces by enhancing interparticle friction and energy dissipation.