Bridge Approach Slab Stabilization
From Commercial - Infrastructure
URETEK Deep Injection (UDI) is the rapid, economical solution for repair and maintenance of the bridges that keep our nation moving. For stabilization of bridge abutments, bridge entrance and exit ramps, and transitions, UDI offers almost immediate results. For the state highway departments that are tasked with maintaining more than 600,000 bridges in the United States, UDI restores those critical assets to a stable, safe, and level condition above stabilized soils in much less time and for dramatically less money than full-reconstruction methods.
Common Causes of Bridge Foundation Issues
Both natural and man-made causes can lead to weak soils beneath bridge abutments and approach / departure ramps. The original soil composition may have included loosely-packed materials that were not packed well before construction, or nearby drilling or excavation may have resulted in compromised soil quality. Regardless of the cause, weak soils generally result in subsidence, which often leads to the formation of voids beneath the surface in base and subbase soils. Left unchecked, subsidence can have a negative impact on bridge abutments and entrance and departure ramps. Symptoms of weak soils include foundation settlement, cracks in slabs, dips and heaves, a rough ride when entering or departing the bridge, and evidence of soil subsidence in proximity to the bridge.
Settled Bridge Approach and Departure Slabs Endanger Drivers
For drivers, early settlement at a bridge approach might manifest itself as a pronounced “bump” upon entering the bridge. A song might skip or maybe a little coffee gets spilled. But as the settlement progresses, serious safety issues are presented for drivers, many of whom are completely unprepared for the adrenaline rush that accompanies the temporary loss of control upon entrance onto or exit off of a seriously settled bridge abutment. Bridges like these present a serious safety issue, and the only ones who don’t mind are probably the owners of the local front-end alignment shop.
The severity of the elevation difference between the bridge approach and the deck determines the degree of danger present for drivers. From a transportation department’s point of view, bridge settlement issues can be the face of larger public perception challenges, with citizens pointing to dangerous bridge ramps as an indication of overall department effectiveness. In some cases, faulty bridge approach and departure ramps have resulted in costly litigation that have seriously compromised already-tight budgets.
The solution to bridge settlement problems, therefore, must always seek to reduce the size of the “bump” at approach and departure ramps, and it must do this in an economical manner that provides enough flexibility to address a wide variety of site-specific variables.
Providing a Safe Transition Between Road and Bridge
Simply stated, the approach slab provides a transition between the roadway pavement system and the bridge. In this capacity, the approach slab acts as an intermediate bridge to span the portion of embankment directly behind the bridge abutment, which was excavated during construction of the abutment. It is understood that this area is traditionally difficult to compact during construction and is therefore prone to settlement.
The approach slab bridges the gap between the rigid abutment and the undisturbed embankment beyond the area excavated during construction. Even on new construction projects, it is typical for there to be some settlement below the bridge ramp, even with diligent compaction. In these cases, just like in older bridge installations, the pavement end of the approach slab may settle, creating an uneven transition onto the bridge.
Important Bridge Integrity Consequences
While driver safety is always of paramount importance, the structural integrity of the bridge is also a major consideration for highway officials. Left uncorrected, settled approach and departure slabs cause undue impact upon the bridge, especially from trucks.
Over time, these impacts can have catastrophic effects on longitudinal members, imparting stresses for which they were not designed, and significantly weakening them. In these cases, the causes of a momentary catastrophic bridge failure can be traced back to years of improper stress loading on the bridge.
Therefore, it is easy to understand that smooth bridge approaches deliver much more than just driver comfort and safety.
Bridge Maintenance with URETEK Deep Injection (UDI)
When bridge approach and departure slab settlement has become a priority for state highway officials, URETEK offers proven solutions. As mentioned above, loose, poorly compacted foundation soils, or erosion from water penetration can result in a rough ride when approaching or leaving bridges. Furthermore, the bridge structure itself is also placed under stress from the impact loading experienced when cars and trucks pound on and off the bridge.
Fortunately, loose, poorly compacted foundation soils are our specialty. URETEK has extensive experience with this type of work and a long list of completed projects, many of which will likely match the particular circumstances you face with bridge settlement in your area. Our experience will assure you that we have the specific solution you need to restore the smooth flow of traffic onto and off of your bridge.
Local DOT’s Rely on UDI to Keep Traffic Moving
Beginning in 1989, with the introduction of URETEK Deep Injection® (UDI), our trusted pavement preservation method has been relied upon by state DOT officials all across the country. In every climate, they depend on UDI to stabilize soils, fill voids, and most importantly, maintain smooth and level bridge approach and departure slabs.
UDI involves the injection of structural polymer into base and subgrade soils to increase their load bearing capacity. This is achieved by injecting the polymer through small holes drilled directly through the pavement structure to depths determined by site-specific analysis. URETEK’s proprietary high-density polyurethane foam (HDPF) polymer material flows easily into voids and weak zones within the soil mass below. Then, through a controlled chemical reaction, the expanding polymer compacts surrounding soils, increasing their load bearing capacity. The composite material quickly cures into a strong, dimensionally stable, environmentally inert, non-toxic, and water-resistant geo-material that provides years of reliable service.
Trusted Vendor for Bridge Maintenance Programs
Since 1988, URETEK has been a trusted, reliable partner for DOT officials and Prime Contractors intent on maintaining critical pavement systems. With increasing traffic loads across the country, the need for reliability and trust has never been more important than it is today. With its rapid response and crew scheduling that takes advantage of overnight and off-peak hours, URETEK is the vendor most prepared to complete bridge approach and departure slab maintenance tasks without severely impacting traffic.
When we arrive, our crews get right to work on a site-specific repair or maintenance solution that quickly mitigates weak soil issues and extends the reliable working life of important bridges. Best of all, our zero-excavation solution means the work is completed in days, not weeks or months. When the job involves stabilizing base and subbase soils and restoring critical pavement systems to their optimal functional state, nobody does it better, or faster, than URETEK.
The UDI Advantage
- Fast – UDI requires no excavation, and projects can often be completed in hours or days. Traditional repair methods often involve excavation, and the time required for project completion can be weeks.
- Effective – URETEK’s 486 Star® polymer material has been used to successfully complete over 100,000 projects nationwide. The lightweight, expansive geo-polymer material not only realigns concrete pavement but also addresses the problem at the source – weak soil composition – giving customers a long-lasting solution.
- Economical – The repair process is priced consistently below alternative repair methods, and implementing repairs now significantly reduces further repair costs down the road.
- Minimally Disruptive – Unlike other repair methods, UDI is minimally disruptive and requires no excavation.
- Durable – URETEK’s 486 Star® polymer is specially formulated for stability and strength, even in the harshest environments. Our polymer is hydro-insensitive, and UDI is warranted against loss of dimensional stability or deterioration.
- Safe – Liability risk is greatly reduced with UDI due to an inherently safer working environment without deep excavation or heavy equipment. The process and material are eco-friendly and meet today’s high environmental standards.
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