Matlock (1970) proposed p-y curve model for soft clay under both static and cyclic loading conditions. The following figures show the relationship of the ratio between soil resistance (P) and ultimate soil resistance (Pu) with the ratio between lateral deflection (Y) and the deflection occurring at 50% of the ultimate resistance (Y50).

The ultimate soil resistance (Pu) is calculated with the following equations:

The reference displacement (Y50) is calculated by the equation below:

where E50 is the strain at one-half the maximum stress for an undrained tri-axial compression test. If no direct laboratory data is available, the following recommended values of are adopted for clays based on the undrained shear strength value:

The input dialog for Matlock soft clay p-y curve model in the PileLAT program is shown in the figure below.

The following figure shows the typical p-y curve of Matlock soft clay model from the PileLAT program's PYAnyTool.