Installation behavior and uplift performance of multi helix helical piles in marine soft soil

Helical piles are increasingly used in offshore and nearshore foundations, where installation effects play a critical role in their performance. This study employed Coupled Eulerian-Lagrangian (CEL) numerical simulations to model helical pile installation in marine soft soil sites under varying advancement ratios (AR) and soil strengths. The analysis focused on installation torque, penetration resistance, energy consumption, stress distribution, plastic strain, and soil disturbance. The immediate post-installation uplift response was further evaluated to elucidate the combined effects of AR and undrained shear strength (su). Results showed that, as AR increased from 0.50 to 2.00, the installation torque at the final penetration depth decreased by approximately 42%, while the penetration resistance increased by approximately 105% and the cumulative installation energy decreased by approximately 87%. AR = 1 provided the most favorable installation coordination and the highest short-term uplift capacity of 360.1 kN. Increasing undrained shear strength from 26 to 76 kPa increased the uplift capacity from 71.9 to 424.3 kN. The post-installation disturbance was primarily concentrated near the pile shaft, helix plates, and pile tip. This study offered a short-term undrained limitation of helical pile installation in marine soft soil sites and supported optimized engineering design.