The entry gate facility at New York National Guard’s Camp Smith training site in Cortlandt Manor, New York, required modernization to meet anti-terror design requirements and minimize facility downtime during periods of flooding. The project required installation of up to five feet of grade raise fill, construction of a new support building, and had a fast-track schedule to meet the Army’s new anti-terror regulations.
Matrix New World, the project geotechnical engineer, discovered in their site investigation that the site was underlain by a highly compressible layer of organic silt and Peat soils varying in thickness from 1 to 18 feet.
Placement of up to 5 feet of new grade raise fill would cause excessive total and differential settlements using traditional soft-soil foundation solutions. Matrix New World Engineering developed recommendations for employing a surcharge program, deep foundations, or ground improvement system to manage the differential settlement for the structure and site features.
Using Matrix New World’s report, Arold Construction reviewed the various options: Surcharge Option – Was a low-cost option but would take too long to implement and did not address the secondary settlement due to decay and secondary consolidation of the organic layer.
Deep Foundation Option – Was an expensive option due to the cost of the piles and would require a structural concrete slab for the pavement section but would control the short and long-term settlement.
Ground Improvement Option – Was a lower cost option than the Deep Foundation, allowed for use of flexible pavements and would control the short and long-term settlement.
Arold Construction consulted with GeoStructures to develop a ground improvement solution and ultimately chose Geopier Rigid Inclusions as the preferred ground improvement solution.
Geopier Rigid Inclusions
■ Controlled Settlement of the soft organic soils;
■ Saved Money by allowing for design and construction of conventional shallow foundations and slab on grade; and
■ Allowed for Conventional Construction of cost-effective flexible pavements to be used by supporting the sitewide fill.
Arold Construction managed the project and made ground improvement construction easier by providing several construction benches which minimized overburden drilling which saved money. Rigid Inclusions were installed at various elevations using a unique installation method where the top of the Rigid Inclusion was installed with ungrouted aggregate and the bottom portion in the organic and Peat layers was grouted. Coupled with a geogrid load transfer platform installed by Arold, these hybrid rigid inclusions provided settlement compatibility between the rigid ground improvement elements and the flexible pavement and site features.