Gwynedd Train Station - Ambler, PA

Monday, May 12th, 2014 by Laura Crary

Challenge

SEPTA (Southeastern Pennsylvania Transportation Authority) had settlement issues on two rail lines at a road crossing in Ambler, Pennsylvania. The 14 inch thick concrete slabs supporting the track had settled in areas as much as 1-7/8 inches. For passenger trains, safely navigating this area of the tracks required a 40 mile per hour reduction in speed. SEPTA’s main concern was for the safety of their passengers, as continued settlement could lead to derailment. Additionally, minimizing the disruption to train schedules during repairs would require keeping one of the two tracks in service at all times. Slab replacement was not an option due to the expense, time and disruption it would cause to both street traffic and SEPTA trains. Previous attempts to lift settled rail slabs with mudjacking were not precise and were prone to washouts over time.

Solution

SEPTA chose Foundation Supportworks® of New Jersey and the PolyLEVEL™ Polyurethane Injection System to resolve the problem. PolyLEVEL™ is a two-part urethane that, when combined, expands into a waterproof, rigid foam that is used to fill voids, stabilize slabs, and lift concrete. The installation of PolyLEVEL™ began by drilling 5/8 inch injection holes into the concrete slab. Next, using specialized equipment, approximately 500 pounds of PolyLEVEL™ was injected below the slab through 96 injection ports. The rail elevation was monitored continuously with surveying equipment, and both the rail and slab were returned to their original elevation. With a compressive strength of 100 psi (pounds per square inch), PolyLEVEL™ provides the necessary strength to support extremely heavy loads. With the use of the PolyLEVEL™ system, Foundation Supportworks® of New Jersey was able to stabilize and lift the settled concrete and rails back to their original elevations with no concern of eventual washout. The project was completed in eight hours over the span of two days, and the road and tracks remained open to traffic. Two hours after the track was lifted, it was proof rolled with a large road-rail dump truck fully loaded with track ballast (rock). No movement was observed visually or with surveying equipment. SEPTA was extremely pleased with the results as well as the efficiency and professionalism of the Foundation Supportworks® of New Jersey crew.

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