Ellipse Modules

The AASHTO HS-20 Standard uses a 32,000 lbs axle as the design load (two axles at 25,000 lbs each at depths greater than 38”). To conservatively model the R-Tank’s performance under these types of traffic loads, several steps are taken and additional factors considered:

• The axle load is distributed to two sets of dual wheels, each10” x 20” at 80 psi
• The tire contact area is transferred down through the cover layers at a conservative 1:2 angle (33%) to determine theArea of Applied Load on the top of the R-Tank
• An impact factor is added to account for the movement ofthe load
• Weight of cover material in a saturated condition is added(130 lbs/cf

With these factors in place, the HS-20 load can be modeled and the resulting safety factor determined. The table on page 2 shows how the R-Tank performs at various depths of cover, and it suggests which module should be used. Since most projects are designed for HS-20 loads in parking lots, this table is ideal for most installations.

If you are designing for HS-25 loads, or if you are considering applications with multiple HS-20 loads regularly travelling in multiple parallel lanes (for example, active roadways or shipping terminals), tables for these specific circumstances are available.

Modeling product performance using engineering equations to ensure a successful project is important. But what really matters is product performance in the field. That’s why we’ve done real-world testing with third party agencies who have installed the R-Tank and subjected it to brutal testing. One test involved installing 18” ofsand cover over a standard R-Tank unit (the R-TankSD should havebeen used at this depth) without geogrid, and driving a 31 ton dump truck over the system. Even in these harsh conditions, the R-Tank has supported the loads, passing every field test that’s been done.

Your project REQUIRES a proven system. With thousands of installations around the world, R-Tank has proven itself again and again as one of the strongest systems available for underground detention/retention. Specify R-Tank and you can be confident your system will support the traffic loads above. Call ACF today to discuss your project’s requirements.