Deep Foundation for Playa Vista Hanger Renovation
Morris-Shea has completed the installation of permanently-cased cast-in-drilled hole (PC-CIDH) and DeWaal® Drilled Displacement Piles (DDP) at an aircraft hanger renovation jobsite in the Playa Vista, CA. To accommodate the jobsite’s restricted access and unique environmental concerns the project engineer specified PC-CIDH and DeWaal piles for the massive structure’s new foundation.
More than 1,000 DeWaal DDP piles and over 400 PC-CIDH piles were installed in critical areas of the old aircraft facility. Project phases in 2017 included the installation of deep foundations under the larger portion of the 319,000 sq ft (29,636 sq m) complex to accommodate the load capacities required for new and renovated structural development.
For the 2018 phase, the contractor’s compact Fundex CD20 drill rig was maneuvered inside the building’s interior to install 217 14-inch (355 mm) diameter PC-CIDH piles. This quiet vibration-free application was ideal for the unique urban jobsite with its surrounding technology facilities. The powerful drill rig advanced steel casings into the ground by simultaneously applying up to 20 meter tons of torque and 15 tons of crowd force.
To provide load transfer, the DeWaal DDP piles installed in earlier phases of the project incorporated a full length center reinforcing bar and partial length steel cage within the concrete, rather than a permanent casing. Similar to the PC-CIDH piles, the DeWaal DDP pile system is a vibration-free application that offers the high lateral capacities required to meet this region’s seismic concerns and to accommodate the unique soil conditions.
Design Assistance Process
Prior to commencing the project, Morris-Shea proposed to the general contractor that DeWaal Drilled Displacement Piles and permanently-cased cast-in-drilled-hole (PC-CIDH) piles be accepted for use on the project. It was agreed that these foundation systems were uniquely qualified for this project. DeWaal DDP and PC-CIDH piles provided a foundation option that met all engineering requirements while providing safety, schedule, environmental and engineering performance benefits.
The DeWaal DDP piles were primarily used where vertical and horizontal clearances were sufficient for rig access and the application of this system. PC-CIDH piles were installed where restricted access or interior height clearances were problematic for DeWaal rigs. Project considerations included the presence of contaminated soils within the building complex resulting from the site’s previous use as an airplane hangar. The primary concern was that contaminated groundwater perched atop an aquifer not be allowed to develop a mechanism to cross-contaminate or pollute a lower aquifer.
Based on the installation methodologies involved in installing DeWaal DDP and PC-CIDH piles, it was determined that their use at this site was appropriate and no significant potential existed for contamination from pile installation. Drilled displacement piles are commonly used in existing petrochemical facilities where the presence of environmentally contaminated soils and groundwater require the installation of deep foundation support without cross-contaminating deeper soils or aquifers.
Additionally, densification of soil around the DeWaal DDP pile perimeter helped to prevent groundwater from migrating along the pile, further eliminating the risks relating to cross-contamination of the aquifer.