Mega Project Utilizes LWA Fill Behind MSE Walls

By Bill Wolfe, Norlite LLC

In 1958, Interstate 95 opened across the southern portion of Connecticut as part of the main highway that links New York and CT LWA FillBoston. The roadway was engineered for a design speed of 60 miles per hour, with six lanes from the New York State line to East Haven, CT, and with four lanes from East Haven, CT, to the Rhode Island State line. This area of Connecticut has a large population concentration that has increased throughout the years.

Traffic along Interstate 95 in the vicinity of downtown New Haven, CT has suffered from congestion for many years. I-95 currently accommodates traffic volumes in excess of 140,000 vehicles per day in this area, more than three times the 40,000 vehicles per day in which the highway was designed. The Interstate 95 interchanges at Interstate 91 and Connecticut Route 34 suffered major backups during heavily traveled times.

In October 1989, a study was initiated to evaluate I-95 between New Haven and Branford, CT. After ten years of considering alternatives that would address transportation issues while minimizing the impact of construction on the environment and property within the project corridor, the Federal Highway Administration issued a Record of Decision which detailed the recommended alternative. The improvements would involve several contracts along the route. Included in the improvements were several interchange redesigns and the new Pearl Harbor Memorial Crossing or Q Bridge over the Quinnipiac River.

The project was named the I-95 New Haven Harbor Crossing (NHHC) Corridor Improvement Program which started construction in June of 2000. The project is a multi-modal transportation improvement program that features public transit enhancements and roadway improvements along 7.2 miles of Interstate 95, between Exit 46 (Sargent Drive) in New Haven and Exit 54 (Cedar Street) in Branford, CT.

The Connecticut Department of Transportation (CTDOT) specified expanded shale lightweight aggregate for geotechnical fill behind the mechanically stabilized earth (MSE) walls on this complex multi-year project. The in-place compacted densities, specified at 65 pounds per cubic foot or less, were half the weight of the common fills found in this area. This helped the engineers to design the roadways in the areas close to the water with poor soil conditions. The angle of internal friction was specified at a minimum of 40 degrees when measured in a triaxial compression.

The specification called for the lightweight fill to be placed in layers of a thickness of 1.5 feet to a maximum of 2.0 feet. Each layer was compacted by the use of self-propelled vibratory compaction equipment with static mass (weight) less than 6,600 pounds. The specified number of passes of the compaction equipment were a minimum of two (2) and a maximum four (4) passes. The actual lift thickness and exact number of passes were determined by the engineer and were dependent on the type of compaction equipment used.

Five different contractors under five different contracts, that utilized lightweight fill, have worked on this section of Interstate 95. Over 100,000 cubic yards of expanded shale has been supplied for the rebuilding of this highway. Completion of the project is scheduled for the end of 2018.

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