Load–deflection analysis of laterally loaded piles in unsaturated soils

The lateral response of piles is governed by the soil–pile interaction in the shallower layer of surrounding soil, which may be above the water level and thus is unsaturated. There is no comprehensive analytical model for the soil–pile interaction under lateral loads considering both linear and nonlinear behaviors in unsaturated soils. In this study, an analytical solution is proposed to simulate the linear and nonlinear load–displacement variations for laterally loaded piles supported by unsaturated soils. Analytical formulations are developed to determine the stiffness per unit pile length considering the influence of soil suction on the soil modulus of elasticity. Since the current p – y curves available in the literature are unable to adequately address the unsaturated soil reaction to piles, analytical p – y relations for three types of soil are developed regarding the soil suction parameter. In order to expand the scope of application of presented method, the developed solution is extended to step-tapered piles and to piles subjected to simultaneous horizontal and vertical loads. The developed solutions are validated with the results obtained from laterally loaded pile tests reported in the literature. Parametric studies evaluated the effects of pile length and cross-section configuration and applied vertical load on the pile lateral response under various soil unsaturation conditions. The results revealed that the stiffness of the pile–soil system and its load-deformation behavior are improved significantly as the soil suction pressure increases. Furthermore, the lateral pile displacement in unsaturated soil decreases as the pile length and diameter of the upper pile portion increase, and by considering the applied vertical load. Considering the positive effect of soil suction on reducing the lateral response of piles in unsaturated soil (in arid areas) in design may help shorten the pile length or reduce its diameter while achieving a desired force–deflection demand.