Centrifuge model tests on the response characteristics of pile–bank slope systems in different clay sites

Pile-supported wharves are widely applied in port development over coastal soft soils, while deformation of the subgrade induced by external loading may exert adverse effects on pile foundations. Based on the engineering prototype of a representative pile-supported wharf at Tianjin Port, this study investigates the influence of different soil properties on bank slope deformation and the response characteristics of pile-supported wharves under yard loads through centrifuge model tests. The scaled test model, incorporating the clay stratum, pile foundations, and superstructure, was carefully designed and fabricated with a geometric scale ratio of 1∶80. Two sets of centrifuge model tests were conducted on clay strata with distinct properties. According to the prototype site conditions, Malaysian kaolin was selected for preparing the upper clay layer, while a sand layer was placed at the bottom of the model box. For preparation of the clay stratum, preloading consolidation was first carried out under 1g conditions using a staged loading method in a large consolidometer. After achieving a clay stratum with relatively uniform strength, final consolidation was completed under hypergravity acceleration. Hollow aluminum tubes were adopted to simulate pile foundations, following the equivalence principle of similar flexural stiffness. The pile foundations, pile caps, and upper panel were assembled and connected by bolts to form the pile-supported wharf structure. The yard load was applied using a hydraulic actuator in displacement-controlled mode, with a displacement increment of 1.00 mm per stage. This study primarily focuses on a comparative analysis of bank slope soil deformation, superstructure displacement, lateral earth pressure behind piles, and bending moment distribution within pile foundations. In addition, the mechanisms governing pile–soil interaction were examined. The results indicate that soil deformation induced by yard loads acts on embedded pile foundations, leading to significant horizontal displacement of the wharf superstructure. The variation in the strength of the clay stratum affects the horizontal displacement of the wharf superstructure. Compared with clay stratum A, i.e. the higher-strength clay stratum, the maximum horizontal displacement of the rear platform increases by 18.9% under the conditions of clay stratum B. Significant compression-induced separation occurs between the pile foundations and the soil near the slope surface in the lower-strength clay stratum. In clay stratum A, both the peak magnitude and the influence depth of lateral earth pressure adjacent to the yard are significantly greater. The lateral earth pressure in clay stratum B decreases to below 10 kPa at a depth of 240 mm from the pile top. The bending moment response of pile foundations adjacent to the yard exhibits an S-shaped distribution pattern along the depth. Notably, the peak bending moment in the second row of piles shows a significant reduction compared with the front-row piles. As the distance from the yard increases, the elevation of the peak bending moment shifts progressively downward. Furthermore, as the strength of the clay stratum decreases, the peak pile bending moment exhibits a significant increasing trend. For instance, compared with clay stratum A, the peak bending moment response of the P1 pile foundation increases by 29.5% in clay stratum B under the 8 mm surcharge-induced displacement condition. In summary, based on the results of centrifuge model tests, the response characteristics of the soil–wharf structural system under deformation of different clay strata are presented, and a comprehensive analysis is conducted on wharf and bank slope deformation, lateral earth pressure, and internal force responses of pile foundations. These findings provide technical support for the design of pile-supported wharves. Future research may extend centrifuge model tests to multi-factor coupling by incorporating dynamic loads such as ship impacts and wave forces, and by integrating field monitoring data to further improve the safety assessment system for pile-supported wharves.