Influence of precast microbial reinforcement on lateral responses of monopiles

• Published in: Ocean engineering 2024-09, Vol.307, p.118211, Article 118211
• Main Authors: Zhu, Tao, He, Rui, Hosseini, Seyed Mohammad Javad, He, Siyuan, Cheng, Liang, Guo, Yakun, Guo, Zhen
• Format: Article
• Language: English
• Subjects: Accumulated deformation; Cyclic loading; Lateral response; MICP; Monopiles; Stiffness
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2024.118211

Microbially Induced Calcium Carbonate Precipitation (MICP) provides an environmentally friendly solution for reinforcing large diameter monopiles for offshore wind turbines (OWTs). This study presents an investigation into the lateral responses of monopiles with precast microbial reinforcement using a low-pH one-phase method. Both static and cyclic loading tests were carried out. The results of static loading tests show that the failure mode of the bio-reinforced monopile was an overall overturn failure. The lateral bearing capacity was increased by 50% and the bending moment was reduced by about 25% with the bio-reinforcement. Further investigation was conducted on the secant stiffness, damping ratio, and accumulated deformation of the bio-reinforced monopile under various cyclic loadings. With the bio-reinforcement, the accumulated deformation under one-way cyclic loading can be reduced by 30%–60%. The influences of cyclic loading parameters and loading sequence on pile stiffness were clarified. The growth ratio of pile stiffness due to bio-reinforcement under one-way loading was between 1.65 and 2.82, and decreased with increasing load amplitude. The ratio was smaller under two-way loading. Three competing factors on pile stiffness were identified: cyclic compaction of the unreinforced sandy soil, weakening of the bio-reinforced soil and soil subsidence around the bio-reinforced soil. •Bio-reinforced soil was precast around the monopile using low-pH grouting method.•Pile lateral responses under static and cyclic loads were studied by model tests.•The pile capacity was increased by 50% and the bending moment was reduced by 25%.•The pile accumulated deformation can be reduced by 30%–60%.•Pile stiffness evolution was found to be controlled by three competing mechanism.