Van Nuys Maintenance
At the Van Nuys train station in Van Nuys, CA, the maintenance crews were having to deal with a ballast that was continually settling and having to be refilled and regraded. In typical situations, refilling and regrading a ballast would only have to happen every couple of years, but the Van Nuys track was having to be regraded every 4 to 5 months. After multiple regradings in a year, the maintenance company determined that something more was afoot and contacted EagleLIFT to look into their soils.
There are a variety of transportation-related applications polyurethane can be used for.
- Rail Ballast Stabilization
- Bridge Approach and Departure Leveling
- Roadway Lifting
- Void Filling
- Inflow and Infiltration Mitigation
- Runway Lifting and Leveling
When EagleLIFT got onsite, they conducted Dynamic Cone Penetrometer (DCP) tests at every 10' on center to test the soil's stability and find the competent soil. The test results were that 320' of track needed stabilization, with blow counts in the center being less than 1 per 10 cm.
Many issues can lead to loss of support soils underneath a rail structure, such as settlement, soil loss into sewer infrastructure, sinkholes, or geological events. In these instances, the only way to have long-term repair is to address the soil issues. What EagleLIFT proposed was to use its EL-077 polyurethane to densify and restore the soils' load-bearing capacity at depth.
The injection plan comprised of addressing the soils based on their blow counts and injecting at a depth range of 5’-35', with shallower depths at the points furthest from the weakest zones and deeper zones where the soils were the most compromised.
"The plan was to address the soils based on need," states Cliff Frazao, COO of EagleLIFT. "The soils were in terrible shape, and the additional weight of more ballast on top of the continued train traffic was causing the soils to degrade continuously."
Frazao continued, "We determined that an injection pattern that deepened based on soil conditions would ensure the problem source, thought to be an abandoned culvert, would be effectively addressed. The injection pattern would allow the soils to gain a significant increase in densification and load-bearing capacity without the need for excavation or interruption to the Van Nuys Station's operations."
The project began by drilling the 5/8" metal rods to the target injection locations and depths. The injection pattern was every 4' on center and every 5' up to the respective target depth. For instance, if the target depth were at 10', the injections would be at 5' and 10', or if the target were 35', the injection depths would be 5’,10', 15', 20', 25', 30', and 35' respectively.
After the installation of the injection rods, injections took place using 3-man injection teams conducting simultaneous injections. The injections would occur at adjacent injection points at the same depth at the same time to maximize the polyurethane coverage. The polyurethane, once injected, initially travels into the treatment zone in a liquid form. After approximately 15-25 seconds, the polyurethane reacts and expands throughout the voids and loose soil. After about 5 minutes, the polyurethane cures to 90% capacity leaving a highly dense polyurethane and soil matrix.
The EagleLIFT crews worked in tandem with flaggers and the railroad maintenance team. EagleLIFT was able to abandon the track when a train approached, ensuring the train could continue on schedule without interruption. After the train's departure, EagleLIFT would continue injections. The project's injections took approximately one week, without excavation, no interruptions to train traffic, and with a delighted customer.