CASE STUDY: MGM CASINONATIONAL HARBOR, WASHINGTON, DC DISPLACEMENT CAST-IN-PLACE PILES IN COASTAL PLAIN SOILS

摘要

Displacement Cast-in-Place (DCIP) piles are not a common deep foundation type in the Washington, DCrnMetro Area market. As a result, less regional data is available for these foundations compared to otherrnalternate deep foundation types. Displacement cast-in-place piles (DCIP) differ from traditional AugerrnCast-In-Place (ACIP) piles in that the pile annulus is formed by pushing a partially-flighted, auger bit torndepth via a large mandrel. The auger bit includes a displacing body near the bottom of the tooling.rnTherefore, little to no spoils are generated during installation and the soil around the annulus is largelyrndensified in-place due to the displacing body being slightly larger than the mandrel it is attached to.rnDue to this densification, one would expect that the theoretical DCIP capacities (compression or tension)rnwould be greater than an ACIP pile (assuming a pile of similar length and diameter). After 20 static loadrntests and the installation of over 6,000+ piles on the MGM National Harbor Casino Project, therndifferences in pile support characteristics between DCIP and ACIP piles of same size and depth wasrnsmall. The performance of both pile types depended on the density and type of soil within the bearingrnstratum. In some early cases of DCIP use, the performance exceeded expectations and appeared to bernmore in line (or better) than typical capacities obtained from driven displacement piles. Other times, therntip elevations could not be achieved or were so difficult to achieve that installation delays occurred and/orrnsignificant additional engineering effort was required to address piles short of their requirementrnembedment.rnThis paper will discuss the limitations of DCIP pile installation in dense Coastal Plain soils and willrnpresent the lessons learned during this project. The paper will also compare the DCIP pile type to bothrnconventional ACIP and driven displacement piles utilizing regional and site-specific load test andrninstallation data.