In geotechnical civil engineering, the p-y method is a method of analyzing the ability of deep foundations to resist loads applied in the lateral direction. This method uses the finite difference method and p-y graphs to find a solution. P-y graphs are graphs which relate the force applied to soil to the lateral deflection of the soil. In essence, non-linear springs are attached to the foundation in place of the soil. The springs can be represented by the following equation:
where k is the non-linear spring stiffness defined by the p-y curve, y is the deflection of the spring, and p is the force applied to the spring.
The p-y curves vary depending on soil type.
The available geotechnical engineering programs for p-y method include FB-MultiPier, PileLAT 2014, LPile, PyPile.