Gwynedd Train Station

Saturday, July 13th, 2013 by Jazz Pared

Challenge

SEPTA (Southeastern Pennsylvania Transportation Authority) had settlement issues on two rail lines at a road crossing in Ambler, Pennsylvania. The 14” thick concrete slabs supporting the track had settled in areas as much as 1-7/8”. 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 2 tracks in service at all times. Slab replacement was not as 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 Quality 1st Contracting and 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 penny-sized injection holes into the concrete slab. Next, using specialized equipment, approximately 500 hundred pounds of PolyLEVEL was injected below the slab through 96 injection areas. The rail elevation was monitored continually with surveying equipment, and both the rail and slab were returned to their original position. 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, Quality 1st Contracting was able to stabilize and lift the settled concrete back to its original elevation with no concern of eventual washout. The project was completed in 8 hours over the span of two days, and the road and tracks remained open to traffic. Two hours after the track was lifted back into place, heavy loads were applied to the raised track, and 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 Quality 1st Contracting crew.