Clark Engineers was engaged by the owner of an upscale property on a lake. The bulkhead was bowed outward 2.5 ft in 97 ft shown in the left photo. The lot was built up with about 8 ft-5 in of fill. The bulkhead was 22ft-6in away from the house. Soil slipping on the slope is clearly shown in the right photo.
The original bulkhead design revealed that it was grossly under designed for this site with 8-5in feet of fill and 4.5 feet minimum embedment for the bulkhead piles.
A geotechnical investigation was done, and it was found that the slope was failing under general instability where the entire soil mass was rotating along a slip plane.
Insert GS shot here from MCAD sheet by jmc/rlw
Two options were provided for repair.
1) Install 2 ft diameter cantilever soldier piers
2) Install cantilever helical piles with 18in diameter steel pipes filled with concrete grout
In both cases the new piles are installed behind the original bulkhead.