Maryland Grade Crossing
Railway Grade Crossing Repair–Polyurethane Grouting, Baltimore, Maryland
Light rail, suburban highway
Settlement and pumping/deflection of double crossing near major international airport required speed restrictions for light rail trains connecting metro area to the airport. The roadway was a primary access route to multiple offsite parking facilities for the airport, as well. Mud jacking had been proposed to repair the crossing, however it was going to require four separate work periods, with no rail or automobile traffic for 18 hours each. This presented a significant potential disruption to the rail schedule.
Previous work using mud jacking to correct similar problems throughout the system had required backhoes and heavy excavating equipment to hold the grout injection pipes in place during work. Because of the equipment’s size and vertical reach, the overhead catenary system had to be shut down during work. This was incredibly disruptive to rail operations, particularly when combined with the need for 18 hours of cure time with no traffic.
Both sides of the double track crossing were affected, and settlement was up to 3 inches out of line. Both of the precast crossings were constructed of Premier panels.
The goal of the operator was to avoid having to de-energize the overhead catenary system, and to avoid having to single track through the crossing during work periods or material curing time.
High density polyurethane grouting to stabilize and lift the affected precast grade crossing panels. This was the first time that polyurethane grouting had been proposed to correct settlement and instability of a crossing for this rail operator. The proposed work was predicted to take fewer than 6 hours start to finish, and to allow for immediate reuse by both rail and automobile traffic. Due to the relatively light loading associated with the rail line, a high density polyurethane foam with a bearing capacity 5 times that of the underlying soil was chosen for the repair.
CJGeo lifted and stabilized 33 panels in fewer than four hours. According to a track foreman who had been on previous jobs where mud jacking was used, when we finished all of the work, “they [the mud jacking company] would still be drilling those big holes they use.” This grade crossing repair was completed on budget, on schedule, and with much less disruption than associated with mud jacking.