Permeable Design Pro
As the demand for permeable pavement increases, designers rely on design tools like Permeable Design Pro to develop structural and hydrologic solutions for permeable interlocking concrete pavements (PICP). The program integrates two areas of civil engineering that typically are separated in training and practice; pavement design and hydrology. Since permeable pavements are designed to infiltrate water into the soil subgrade, they experience greater exposure to saturated soils than conventional pavements. The weakened condition must be considered in designing the base thickness especially when the pavement supports vehicular traffic.
The worst case design situation is when the soil subgrade is saturated for several days over PICP subject to vehicular traffic loads. Permeable Design Pro software allows the user to design for this critical condition by simulating weakened, saturated soils. This helps reduce the risk of rutting from traffic by calculating a thicker subbase layer. The thickness calculations for the subbase layer thickness are based on the AASHTO flexible pavement design method.
Since most slow draining soils that maintain a saturated state are clays, the user can input the soil gradation (sampled from the site), and input this into the software program. The program models soil infiltration (at saturation) and forecasts the number of hours or days required to drain that soil given a rainstorm depth. If the soil drainage is very slow, the user can introduce perforated drain pipes and the program recalculates the time required to completely drain the soil of water, thereby limiting the number or hours the soil is saturated, and rutting risk. This powerful and handy feature is unique to Permeable Design Pro software. It is especially handy since most permeable pavement projects are built on slow-draining, clay soils.
Permeable Design Pro software has many other design features for PICP designs for parking lots and low-speed roads. The features can save designers time and money while greatly reducing risks and providing clients with a cost-effective PICP solution. To learn more about the software, a webinar introducing Permeable Design Pro hosted by the Interlocking Concrete Pavement Institute is scheduled for Tuesday, March 12, 2013 at 1:00 p.m. EST. Visit www.icpi.org/webinar2013mar to register. Participants receive a copy of the software program.