• A DEM-MBD multiscale framework accurately simulates track-seabed interactions across flat, slope, and ditch terrains.
• Traction performance is rate-dependent: higher speeds increase peak traction but worsen slip instability on complex terrain.
• Optimal speed thresholds are 0.7 m/s for flat terrain and ≤0.5 m/s for slopes and ditches to ensure stability.
• Grouser design optimization: involute grousers reduce slip by 35–40% on slopes, while triangular grousers improve ditch-crossing performance by 30–35%.