Urban modular grade crossing repair–Cumberland, New Jersey
Heavy haul freight (silica mine), urban main road by short line
32 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail, and caused tripping hazards at the adjacent pedestrian sidewalk. The grading in the area was relatively good, however the adjacent ballast was fouled, which caused water to accumulate under the crossing panels and wash out the sandy subbase material. The crossing had been replaced recently. Due to the urban, primarily passenger automobile traffic, there was little deflection of the crossing panels from highway traffic. However, there were up to four inches of deflection from rail traffic loading.
The deflection from rail traffic loading caused the top edges of adjacent panels to be in compression with each other. This caused extensive spalling of the surface, which affected two of the panels. While not a functional problem for panel integrity, the spalled areas were within the sidewalk portion of the crossings, and therefore posed tripping hazards.
The repair had to allow immediate vehicular traffic to facilitate a single lane closure. The repair also had to allow for immediate resumption of rail traffic. The crossing served a sand mine, so repair was designed around high service loads for heavy haul rail traffic.
Due to scheduling constraints of the railroad, the repair method had to tolerate the potential for rail traffic during the repair.
High density polyurethane polyurethane grouting to stabilize and lift the affected modular grade crossing panels.
Supplemental anchor bolting was also used to ensure longterm integrity of the repair.
Epoxy-augmented patching of the spalled areas to restore a smooth walkway for pedestrians.
CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day. Asphalt patching was done concurrently with polyurethane injection. The entire repair was completed in less than two hours. The roadway and rail opened up immediately after the repair. Traffic control was done to accommodate pedestrians and roadway traffic.
Two trains passed through the crossing over the panels being repaired during the repair. This did not affect the integrity of the repair.
25,000 square feet of industrial floor at a military facility settled up to 4 inches and was affected by sub-slab voids. The affected area also included 250 track feet of embedded rail, which was set in an independent, thickened slab section. The building had been used for warehousing, but was being transitioned to light manufacturing/maintenance.
Plans called for an 4” thick overlay slab being installed, with a vapor barrier, over the existing floor. Geotechnical investigation work determined there were extensive voids below the floor throughout the area affected by settlement.
The proposed repair method had to provide adequate bearing capacity for manufacturing, and ensure complete void filling and stabilization.
Polyurethane grouting to fill voids under the floor to stabilize against future settlement. Additionally, in areas which had settled, polyurethane grouting was proposed for correcting settlement.
Due to extensive compressive soil layers below the floor, polyurethane grouting was proposed as an alternative to the specified cementitious grout. The specified grout had an in-place density exceeding 115 pounds per cubic foot. The proposed polyurethane grout had a constrained density of 5.5PCF, yet a bearing capacity exceeding 12KSF.
CJGeo mobilized three polyurethane grouting crews to the facility, with a combined pumping capacity exceeding 5,000 pounds per hour. Nearly 2,000 dime-size injection holes were drilled through the slab, and 5,000 cubic feet of polyurethane grout was installed under the floor & section of embedded rail. Void filling was confirmed by visual inspection (material showing at adjacent drilled holes to injection locations), and slab lift.
In areas which had not settled, 1/8 inches of lift was used as the benchmark change in elevation to confirm complete void filling. Areas which had settled, including the embedded rail sections, were lifted up to 3 inches above the original elevations.