Failure mechanism and lateral bearing capacity of monopile-friction wheel hybrid foundations in soft-over-stiff soil deposit

Experimental and numerical studies are carried out to explore the lateral load and moment resistance capacities of the monopile-friction wheel hybrid foundation in soft-over-stiff soil deposit. Model tests are firstly conducted to preliminarily investigate the soil failure mechanism of hybrid foundation under lateral eccentric load (lateral loading at a certain height above the seabed), which is followed by full model tests conducted to investigate the lateral load and moment resistance behaviors of the monopile-friction wheel hybrid foundation under static horizontal loading in soft-over-stiff soil deposit. A numerical model is then generated and validated with the laboratory testing results. Parametric study is performed to quantify the lateral bearing capacity of hybrid foundation in clay-over-sand soil deposits. Both the experimental tests and numerical simulations show that compared to conventional monopiles the hybrid system can provide a higher lateral bearing capacity and a larger lateral stiffness. The bearing capacity is found to be mainly influenced by the diameter of wheel D-w, undrained shear strength of clay s(u), loading eccentricity e and clay layer thickness T-c. Finally, empirical design formulae are proposed to estimate the lateral bearing capacity of the monopile-friction wheel hybrid foundation system under static horizontal loading in soft-over-stiff soil deposit.