Designing Pavement Drainage Systems: The MnDrain Software

This report outlines the development of a suite of computer codes embedded in a Microsoft Excel spreadsheet, collectively referred to as MnDrain. These codes provide a user-friendly environment in which the consequences of an edge drain design decision can be investigated. Edge drains consist of pipes that run along the length of a road to remove moisture from the granular base of the road system. The pipes are placed in a high permeability gravel trench below the shoulder/road surface. The rate at which moisture is removed will depend on the geometry and materials used in the base and the soil type in the sub-grade. A full copy of the MnDrain code, including all source programs and an on-line manual, can be downloaded on visiting http://www.ce.umn.edu/~voller/voller_research/task5/mndrainrequest.html. The main attributes of the MnDrain system are: a relevant easy to use graphical interface, meaningful drainage design scenarios, flexible assignment of materials properties, an easy to maintain database for unsaturated properties, and a state of the art saturated/unsaturated numerical solution engine. The code is freeware that can be readily reconfigured for alternative and novel applications. As it stands the MnDrain code is a solid initial framework from which further developments can be made. In this project the operation of MnDrain was purposely constrained to work with simple geometries (the scenarios) to establish a system that could be used by a field engineer with only a limited knowledge of soil physics and numerical modeling. MnDrain, however, does not need to be constrained in this way. Because MnDrain offers free access to all source codes, it can be reconfigured to deal with a large array of pavement drainage issues. To take advantage of this feature, further investigation is recommended.