BRIDGES / TUNNELS INJECTION CASE STUDY
Project: Bay Parkway Bridge Rehabilitation Project
Location: New York, New York
Owner: State of New York
NYC Dept. of Transportation
The New York Dept. of Transportation Bureau of Bridges is responsible for the building and maintenance of bridges in the State of New York. Many of these bridges were constructed and waterproofed at the beginning of the twentieth century utilizing the “state of the art” technology at that time. However, today these same bridges have begun to exhibit signs of leakage and deterioration. One of the reasons for the deterioration is directly related to the defective and / or missing waterproofing seal in the are of the concrete arches covered by soil and pavement topping.
If today’s “state of the art” practice of keeping and sustaining the life span of our bridges through corrosion protection of reinforcement and concrete rehabilitations is to be maintained, it must also include the function of sealing the areas covered by soil and pavement.
Currently, the NYCDOT has done the following to waterproof these structures:
- Pavement Demolition
- Boring and cutting through the existing soil above
- Construction and placement of new waterproofing membranes
- Replacement and reconstruction of the soil and pavement
This type of rehabilitation is cost intensive, interruptive to mercantilism and not practical in case of a superstructure or for bridges in major traffic areas.
Thus, the project was brought to the attention of Jean’s Waterproofing, Inc. (JWI) by R. J. Watson, a supplier of bridge repair materials who have successfully complete several jobs which required injecting though the concrete structure to create an impermeable waterproofing barrier via pressure injection in either a bridge of tunnel structure.
In April of 1998 a meeting was held at the New York City Dept. of Transportation office in Manhattan where the injection materials and waterproofing technology were introduced. Following several subsequent meetings where material samples were mixed and job site inspections were conducted, approval for a “test” bridge was obtained by the city.
The main objective of this procedure was to create am impermeable waterproofing barrier on top of the concrete arch and between the back-filled soil by using an acrylate-ester resin injected through a two-component pressure pump from underneath the structure.
The manufacture supplied the engineering and injection port pattern along with on-site supervision, while the actual injection work was performed by JWI. A Method Statement was submitted to the NYCDOT and the drilling of four separate arches with a total of 1,400 injection portholes was commenced.
The four separate arches consisted of two (2) local tracks – E-1, E-2 Manhattan and Coney Island Local Tracks and E-3 and E-4 Manhattan and Coney Island Express Tracks under the Bay Parkway Bridge. To create a waterproofing barrier between the concrete arch structure and the compacted soil, the manufacturer and JWI utilized a rehabilitation technique, which consists of injection from underneath the arch with the use of a low viscosity, acrylate injection resin, injection ports, and a two component pressure pump.
The acrylate-ester is a specially formulated injection resin, which is specifically designed to seal soil covered areas. Due to its low viscosity and low resistance to flow, a homogenous gel membrane is created at the concrete and soil interface void areas. Also, in the case of dynamic vibrations inherent to bridge structures, the consistency of the waterproofing barrier will be guaranteed by the swelling and self-healing properties of the injection material.
While no test borings were done prior to injection, a formula was utilized by the manufacturer to determine the quantity of injection resin required along with spacing of the injection ports across the the crown of the arch. Drilling of the injection holes took over three months and required overhead drilling through the concrete to intersect the soil on top of the arch by at least 1 inch in depth. Specialized drill bits were required as the thickness of the concrete varied from the sides to the crown of the arch. A systematic timed injection tool one month’s time. Approval and clearance to finish the last arch was obtained and the entire project was complete and remains dry.
These concrete arch barrel type bridges over tracks and station areas are prevalent throughout New York and over 200 of these bridges require rehabilitation for future serviceability. Following the success of this “test” bridge, new specifications are being developed for future bid work.