Rigid Inclusion Supported Embankments for New Jersey Turnpike Interchange 14A: A Case Study

The New Jersey Turnpike Interchange 14A project involved the construction of embankments up to 34 ft in height to support twelve new roadways. Innovative ground improvement methods were needed to meet the significant challenges for the project which included: poor subsurface conditions, space constraints, existing/proposed utility constraints, an aggressive construction schedule, and the immense size of the project. A variety of ground improvement methods were utilized to limit settlements and ensure stability of the embankments. These methods included preloading with surcharge and prefabricated vertical drains, load balancing using lightweight fill, and rigid inclusions (RI). The proposed roadways were divided into six zones, based on location, subsurface condition, and embankment height. This paper focuses on the ground improvement performed in Zone 2, which consisted of concrete column rigid inclusions. The problematic subsurface conditions in Zone 2 consisted of up to a 25-ft thick layer of highly-compressible peat and organic soils without ground improvement. These soils were estimated to undergo up to 4 ft of primary consolidation settlement due to the proposed embankment loads. The design of the RIs was performed by a specialty ground improvement contractor (SGIC) using Plaxis 2D and 3D software. The performance of the Zone 2 concrete column rigid inclusion systems was verified and monitored by load tests and instrumentation. This paper presents details of the concrete column rigid inclusion design, construction, monitoring results, and lessons learned.