Dec 2014, AutoPIPE V8i 09.06.01.10
I have been doing a hand calc verification of the American lifeline s alliance (ALA) soil calculator, and cannot validate AutoPIPEs results, specifically for the Qu term (vertical up) for sand.
The equations should be Qu = Nqv * Density * H * D, where Nqv = (phi * H) / (44 * D) I ran a coarse parameter study with many cases, and got proportionality for phi and density (which is good) and weirdly proportional to H/D. With my second parameter study, just looking at H/D, it looks like there is an additive term that I can't identify. what is causing the difference?
There are 2 calculation differences identified from your had calculation in AutoPIPE.
1. Value of Nqv should be taken as less than Nq value:
2. Please note that gamma*H*D is meant to calculate the weight of soil on top of pipe. AutoPIPE calculates the weight of soil on top of pipe + considering the weight effects on sides of pipe as well. Thereby calculating weight of soil more accurately than found in the code:
AutoPIPE calculates Qu as
Note: cohesion of soil c = 0.
Model Soil Properties with Soil Calculator