pile design in expansive soils

[ONENGINEER]

Could someone be kind to let me know design methodologies for calculating the pile length in expansive soils. I understand this is a function of the position of line of zero swelling pressure and uplift pressure on the pile perimeter. However, I do not know how to calculate/estimate these two parameters. I have referred to Das textbook but the values are much higher than what the engineers use locally. What other practical references are available for use by design engineers? Thank you.