Study on the Shear Performance of Plastic Rubber–Concrete Impermeable Walls for Rock‐Bound Embankments

Shear damage at the base of seepage control walls in rock‐bound embankments presents a critical challenge in flood defense engineering. This study examines the shear behavior of plastic rubber concrete by varying rubber powder dosage (0–30 kg/m 3 ), water–binder ratio (0.6–0.8), and rubber particle size (40–80 mesh). Direct shear tests on Φ 150 × 150 mm specimens show that increasing the rubber dosage from 0 to 30 kg/m 3 nearly doubles the friction coefficient (0.4824 → 0.9634) while reducing cohesion (1.1829 MPa →0.7509 MPa). Lowering the water–binder ratio effectively offsets this cohesion loss; at W/B = 0.6, cohesion increases by up to 37.8%, and the friction coefficient reaches 1.8366. Particle‐size analysis indicates that 60‐mesh rubber provides the best balance, raising cohesion to 1.85 MPa and more than doubling friction relative to the control. Mechanism tests (ring‐shrinkage and SEM) reveal that rubber introduces compliant interfacial zones that redistribute stress, delay cracking, and enhance post‐peak shear resistance. The optimized mix (30 kg/m 3 , 60 mesh, W/B = 0.6) was successfully applied in a Yellow River cutoff wall and met all design requirements, with 2 years of monitoring confirming stable mechanical and hydraulic performance. This study provides practical insights and empirical evidence for the application of rubberized plastic concrete in seepage control structures, promoting sustainable use of waste rubber in civil infrastructure.