Case Study: MGM Casino National Harbor, Washington, DC - Displacement Cast-In-Place Piles in Coastal Plain Soils-Paper

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The MGM National Harbor project used more than 6,000 displacement cast-in-place (DCIP) piles and conducted 20 static load tests to assess their performance in Coastal Plain soils. DCIP piles displace and densify surrounding soil during installation, potentially increasing capacity compared with conventional auger cast-in-place (ACIP) piles.<br /><br />Performance depended strongly on the bearing soil. In the western site, where piles were founded in loose to medium-dense alluvial sands, DCIP piles performed well: they supported the design load with little deflection, required substantially less embedment than initially estimated for ACIP or driven precast concrete piles, and were installed quickly.<br /><br />Conditions changed in the eastern and central areas, where dense, hard Potomac Formation soils underlay the fill. DCIP installation slowed considerably, caused rapid tool wear, and sometimes failed to reach required tip elevations. Revised installation criteria and additional engineering oversight were needed, and delays occurred. Load tests showed that DCIP pile lengths and capacities in these soils were broadly comparable to ACIP and driven piles, rather than superior. The authors suggest that limited densification in already dense soils—and possible reduction of soil strength from repeated tool rotation—may explain the similar results.<br /><br />The project also highlighted constructability concerns: DCIP rigs were large and required a thick working mat, while piles installed above cutoff elevations created concrete-removal and reinforcement-placement challenges.<br /><br />Overall, DCIP piles are effective and productive in loose to medium-dense sandy soils, but offer little capacity advantage in dense, overconsolidated Potomac soils, where installation can be difficult and slow. ACIP or driven piles may be preferable in such conditions.

Keywords

MGM National Harbor

displacement cast-in-place piles

DCIP piles

static load tests

Coastal Plain soils

alluvial sands

Potomac Formation

auger cast-in-place piles

pile capacity

pile installation performance