Lateral Pile Analysis: Episode 4 – Geotechnical Design Parameters

One of the most telling parts of any geotechnical report is the section where the design parameters are selected. This is where you can see whether the engineer truly understands the ground and the design problem.

Most learning resources focus on:

• The theory

• The software

• The final outputs

But the real engineering work happens between these steps:
selecting and justifying the input parameters.

This requires judgment, not memorization.
It requires understanding what controls the behavior of the system. 

In practice, we spend more time on a few key parameters because they have the greatest influence, for example:

• The friction angle for cohesionless soils

• The undrained shear strength for cohesive soils

You only gain confidence in these values when you understand the theory behind them and when you perform your own sensitivity checks. When you do that analysis yourself  (not just read it in a report) the relationship between the soil behavior and the design response becomes something you can feel. And once you reach that point, no one can replicate your understanding, because it is built through reasoning, not copying.

In my courses, I always make sure to cover:

• The theory

• The software workflow

• The outputs

• And the reasoning that links them

That is the part that turns a model into engineering, and engineering into confidence.

The slide below is from Chapter 8 of the Lateral Pile Analysis course, where we focus specifically on how to select parameters for sands, clays, and rock, and why each parameter matters.

If there is one skill that elevates a geotechnical engineer, it is understanding which parameters matter and why.