Raritan River Bridge Replacement

Challenge:

The Raritan River Bridge in New Jersey was originally built in 1908 and served as a swing-span bridge along the Jersey Coast Line. Due to the low profile of the bridge, the structure has experienced damage from storms, notably Hurricane Sandy in 2012, which caused a multi-day outage, interfering with traffic on the structure and in the channel. The design of the current bridge also posed risk of collision with marine vehicles traveling through the channel. In 2020, New Jersey Transit began constructing a new bridge alongside the existing one to provide a structure more suitable for extreme weather and remediating the aforementioned issues. GRL Engineers continuously provided a variety of testing services on the approach spans for the new bridge from December 2020 to December 2023.

Method:

The new foundation was comprised of various pile types, including drilled shafts, continuous flight-auger (CFA) piles, and driven piles. This required different testing methods for assessing shaft integrity, concrete quality and load capacity. For the drilled shafts, three integrity methods were utilized. Crosshole sonic logging (CSL) which transmit ultrasonic signals between access tubes was performed on 140 drilled shafts which ranged from 1.5 to 8.5 feet in diameter. The CSL is limited to concrete integrity assessment inside the reinforcement cage, therefore, Thermal Integrity Profiling (TIP) was also utilized on the drilled shafts. Thermal Wire^® cables were installed down the length of each reinforcing cage of the shaft that was tested to collect thermal data readings every 15 minutes during concrete curing. TIP testing analysis was used to assess concrete and shaft integrity across the entire shaft diameter and length. Low Strain Integrity Testing with the Pile Integrity Tester (PIT) was performed on selected shaft foundations to provide additional information for assessment of general shaft integrity. In addition, eighteen CFA piles were tested using Low Strain Integrity Testing to assess their integrity.

Large-diameter steel casings installed with a vibratory hammer were analyzed with GRLWEAP , and high strain dynamic monitoring was performed via a Pile Driving Analyzer^® (PDA) to monitor driving performance and pile stresses during installation. Dynamic pile testing was also performed on twenty-eight opened, or closed-ended pipe piles during initial drive and/or restrike in order to assess and quantify time-dependent soil strength changes to assist in the design and establishment of pile driving criteria.

Results:

The services provided by GRL Engineers were employed quickly with project schedules in mind. Utilizing multiple integrity testing methods offered a complete picture for assessing concrete quality for the drilled shafts. Low strain integrity testing results indicated no early tension reflections or issues that would need to be further assessed. Crosshole sonic logging results (Figure 1) occasionally showed potential concerns near the top of the shafts, however, this was likely due to debonding effects. Continuously measured temperature readings via Thermal Integrity Profiling cables, shown in Figure 2, offered insight and evidence of the significant temperature reductions near the top of the shaft, which was appropriately corrected during analysis. Figure 3 shows results from dynamic pile monitoring during vibratory hammer installation that was performed. Figures 4 and 5 are outputs that were generated from collected data on impact driven piles. CAPWAP analysis was performed to assess measured stresses along the pile length, soil resistance distribution, and pile capacity.