Hydro-mechanical behaviour of straw fiber-reinforced cemented dredged sediment at high water content

Purpose: Straw fiber (SF) is a natural and environmentally friendly material, which has great potential in improving the hydro-mechanical behavior of cemented dredge sediment. However, the treatment mechanisms and optimum application dosage of SF in cemented sediment at high water content are unclear. This study investigates the effect of SF on the shear strength and permeability of cemented sediment at high water content (3 times the liquid limit). Methods: Various SF contents (0%, 0.3%, 0.5%, 1%, 3%, 5%, 8% and 12% by mass) and curing ages (3, 7, 14, 28, 60, 90, 180 days) were considered to improve cemented dredged sediment. The effectiveness of the improvement was evaluated through unconfined compression and permeability tests. Results: The test results show that there is an optimum SF content of 0.5%, below which the unconfined compression strength (q_u) of SF-reinforced cemented sediment (SFCS) increased with SF content. Beyond this point, q_u decreased with SF content. The brittleness index (I_b), which indicates the ductility behavior, increased with SF content across the entire SF range (0–12%). When SF addition was relatively low (< 0.5%), pore filling and bridge effects increased the interface force between SF and sediment particles, resulting in positive effects on the improvement of SFCS strength. However, when SF content exceeded 0.5%, the higher organic matter from SF could suppress pozzolanic reaction, leading to weaker cemented bonding between sediment particles and hence lower sediment strength. Conclusion: This study suggests that 0.5% SF should be applied in cemented dredged sediment at high water content to optimize its strength.