For LPILE, when you want to ignore say the top 5 ft of soil do you input that into the soil properties or just start the first soil level at a lower depth?
To make the model more accurate, I often include the frost-susceptible layer with the actual unit weight but negligible lateral resistance (k and phi values near zero), so that the overburden pressure on the deeper layers is accounted for. Ignoring it completely is conservative, though.
Rod Smith, P.E., The artist formerly known as HotRod10
As BridgeSmith mentioned, ignoring X feet is typically due to frost. If bottom of pile cap/grade beam is below the frost depth, then you shouldn’t need to ignore soil resistance for the first 5’ of pile. Just confirm that with the geotechnical engineer who provided that recommendation.
