Steel pipe piles
The proposed construction involves construction of five (5) buildings ranging in footprint from about 5,225 ft2 to 11,825 ft2 and associated utilities which include storm, water and gas. The subsurface conditions consist of varying thickness of uncontrolled fill over discontinuous soft and compressible organic deposits over deep varved clay with intervening sand layers at some locations.
The thickness of the varved clay stratum varies from about 50 feet in thickness to over 80 ft. in thickness and is underlain by till and/or shale/siltstone bedrock. Based on the uncontrolled nature and large thickness of the uncontrolled fill, the need to raise grades and the estimated large settlements that could be mostly differential, it was recommended that pile foundations be used to support all structures. Two (2) piles were evaluated which are closed-end 7 5/8 in. and 9 5/8 in. steel pipe piles.
The limit on the factored structural load per pile and other criteria were provided. As differential settlements were expected to be significant, all utilities were specified to be pile supported. As the utility enters the structure it was recommended to be hung from the pile supported slab using straps that are protected from corrosion. It was noted that as the fill settles, the utilities will be subjected to downdrag forces in addition to the weight of the overburden above the pipe and the weight of the pipe.