Evaluation of Airfield Pavement Subsurface Drainage Layers

Abstract: Water intrusion within a pavement structure can lead to detrimental effects such as pumping, erosion, frost heave, thaw weakening, or reduced subgrade strength. Placement of a drainage layer beneath the pavement surface is the most commonly used method to remove water from a pavement structure and is required by current military design methodology. However, multiple issues have been recently reported concerning the design and material requirements, and constructability of conventional aggregate drainage layer systems. Thus, a series of four model pavements were constructed to evaluate the performance of traditional drainage layer methods in accordance with U.S. Army Corps of Engineers subsurface drainage criteria to determine if the in-place performance justifies their required use on military airfield pavements. Evaluation procedures included the artificial introduction of rainfall onto the pavement structure for a 1-hr duration and observation of outflow. Flow and time measurements were recorded and analyzed to determine if the provided permeability of each drainage layer satisfied the current design criteria. Additionally, material porosity and storage capacity were determined and compared for each drainage layer method in accordance with U.S. Army Corps of Engineers design criteria. Results from this evaluation showed that the design criteria were not representative of the performance measured in the model pavements. Permeability rates through the drainage layers that met the aggregate gradation specifications were not within currently acceptable limits. It was concluded that the design criteria for use of drainage layers in military airfields should be reformed to better represent the performance measured in the field.

Keywords: drainage, permeability, porosity, outflow, airfield pavements