Effects of Soil Unloading and Grouting on the Horizontal Response of Monopiles

Horizontally loaded monopiles have been widely applied in the foundations of cross-sea bridges and offshore wind turbines. The soil unloading effect induced by borehole excavation significantly impairs the bearing capacity of nongrouted monopiles, whereas pile-side postgrouting can effectively alleviate this impairment. In this study, a modified p–y model incorporating the coupling of soil unloading and pile-side postgrouting is established. Indoor model pile tests and numerical simulations under horizontal loading were conducted. The modified p–y model was validated by integrating the experimental data of this study, numerical simulation results, and results from other scholars. A series of parameters affecting the horizontal bearing characteristics of monopiles were analyzed using the modified p–y hyperbolic model. The analysis results indicate that under the same soil unloading conditions and horizontal displacement, the horizontal resistance of the surrounding soil decreases with increasing pile length-to-diameter ratio and grouting pressure and increases with increasing soil internal friction angle. When the soil unloading ratio is <0.5, the weakening effect of soil unloading on the horizontal bearing capacity of the pile must be noted.