Impact of environmental site location and groundwater table depth on thickness of flexible airfield pavements

This comprehensive sensitivity study of a newly developed computer code at Arizona State University incorporates the influence of environmental site factors and the groundwater table depth on flexible airfield pavement design and performance. The newly developed code, called ZAPRAM, is a mechanistically based pavement model based on limiting strain criteria. The completed study used the newly revised U.S. Army Corps of Engineers failure criteria for subgrade shear deformation. The experimental factorial conducted comprised three aircraft types, three levels of as-compacted (optimum) subgrade condition, two levels of design aircraft passes, and an environmental combination of six groundwater table depths and five environmentally different city locations. The methodology used in this study applied the same analytical method to achieve real-time environmental effects on unbound layer modulus as the new AASHTO Mechanistic-Empirical Pavement Design Guide. The results of this effort showed for the first time the quantitative impact of the significant effects of climatic conditions at the design site, coupled with the importance of the depth of the groundwater table, on the predicted design thicknesses. Significant cost savings appear to be quite reasonable by using the principles of unsaturated soil mechanics in the new airfield pavement design procedure in ZAPRAM.