Experimental study on monotonic and cyclic lateral behavior enhancing mechanism of semi-rigid pile under different foundation reinforced methods in clay

Monopiles are the most commonly utilized foundation type for offshore wind turbines. Due to continuous growth in the capacity of offshore structures, increasing the diameter of piles is a relatively simple but costly method. How to improve the bearing capacity of monopile foundations without increasing the pile diameter is the research purpose of this paper. A series of laboratory model tests of laterally loaded monopiles in clay were carried out considering different foundation reinforcement methods (i.e., annular point post-grouting, distrib-uted post-grouting and jet-grouting) to investigate the lateral monotonic and cyclic response of unreinforced and reinforced piles. As a result, the three foundation reinforcement methods improve the lateral capacity of piles, among which jet-grouting-reinforced piles have the greatest improvement. After the monotonic test is completed, an excavation test is carried out. It is determined that the cement slurry injected by the annular point post -grouting reinforcement mainly diffuses in the clay by splitting, while the reinforcement body formed by the distributed post-grouting and jet-grouting more evenly covers the outer surface of the pile, and the effect of improving the lateral capacity is improved. The accumulated displacement calculation formulas of different reinforced piles are obtained. The accumulation coefficient of distributed post-grouting and jet-grouting rein-forced piles is small, which means that they can more effectively reduce the cumulative displacement of the pile.