Around our office, I've heard these phrases used occasionally. 'Standard of care' is used when determining the appropriate work scope for evaluating a site and providing recommendations. 'Industry accepted practices' is used when making recommendations, assessing construction conditions, and...
I suspect that the heavier section is due to the lessened passive resistance (very soft clay vs silty sand) on the embedded portion of the sheet piling, resulting in larger deflections and bending moments. That's been my (very limited) experience when analyzing sheet piling in soft clays with...