Behavior of Laterally Loaded Piles in Multilayered Soils

Piles have been widely used to resist lateral loads in geotechnical engineering. In reality, piles are always embedded in layered soils; however, theoretical solutions for laterally loaded piles in multilayered soil system are limited in the literature. Based on the basic concept of the subgrade reaction theory, semianalytical solutions using the power series method were proposed to assess the behavior of a vertical pile with variable cross sections and embedded in a multilayered soil system to support lateral loads at its head. For the present method, the moduli of the lateral subgrade reaction were assumed to be of constant depth for clay soil and of linearly increasing depth for sandy soil. By considering the deflection and force continuum conditions along the pile length, a matrix form of pile response at any depth was expressed through the deflections and lateral forces at the pile head. The validity of the presented solution was verified by back-predicting behaviors of laterally loaded piles in two existing cases. Moreover, four hypothetical cases related to laterally loaded piles in uniform and layered soil systems were set up to discuss the response of the laterally loaded pile in layered soils. The comparison results indicate that the pile behavior is controlled by the subgrade soil stiffness at shallow depth (up to 3–4 times the pile diameter). It also indicates that the interlayer with a higher stiffness embedded near the ground surface, such as a sand layer presented within clay deposit, has a reduction effect on the maximum pile lateral deflection, but has a slight effect on the maximum bending moment of the pile.