Uplift pressure in expansive soils

[ONENGINEER]

I have read in Das textbook that the uplift pressures acting on drilled footings is equal to (Zero Swelling Pressure) x Tangent (12 to 20). Das suggests to use the uplift pressure = Cu in the absence of Zero swelling pressure value, however, this seems very conservative. I am looking on other opinions about the value of uplift pressure that are usually practiced in Texas.
Thank you.