Enhancing Pore-Water Drainage in Coastal Soft Soils: Enzymatic Degradation and Hydraulic Performance of Straw-PLA Vertical Drains

Abstract

Prefabricated vertical drains are critical for accelerating pore-water pressure dissipation and consolidating water-saturated soft soils in coastal and riverine environments. Straw drainage boards, composed of agricultural straw and polylactic acid (PLA), offer an alternative to traditional plastic drains, mitigating potential water pollution and microplastic accumulation in sensitive aquatic ecosystems. However, their slow natural biodegradability can impact long-term hydraulic performance and post-construction settlement. This study investigates the enzymatic degradation characteristics of straw–PLA drainage boards to optimize their hydraulic behavior and degradation in simulated water-saturated soft soils. We explored the effects of various bio-enzymes, specifically cellulase and alkaline protease, on the structural integrity and hydraulic properties of the drainage boards. Our results demonstrate that both enzymes significantly alter the water flow capacity of the boards, indicating accelerated degradation. Furthermore, a synergistic effect was observed when cellulase and alkaline protease were applied concurrently, leading to more pronounced degradation. The findings suggest that enzyme-enhanced degradation offers a promising strategy to optimize the hydraulic performance of drainage boards, facilitating more effective pore-water pressure dissipation and rapid soil consolidation in offshore and coastal engineering projects.