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**.