Investigation of Instantaneous Shear Failure in Pavement Subgrade Subjected to Superheavy Load Vehicle

Abstract

The movement of superheavy loads (SHLs) on the US highways is an increasingly common, economic necessity for many important industries, such as chemical, oil, electrical, and defense. They often require specialized trailers and components that are assembled to suit the SHL vehicle’s characteristics. The SHL vehicles are often oversized and exceed legal gross vehicle weight, axle, and tire load limits. The overlapping stress distributions in pavement layers under such high tire loads can render a critical condition of instantaneous ultimate (global) shear failure, especially in the subgrade pavement layer. In this paper, a methodology to examine the risk of instantaneous shear failure in a flexible pavement subjected to an SHL vehicle movement is presented. To this end, Meyerhof’s general bearing capacity equation is employed since it is a well-established and validated foundation design procedure under static or slow-rate loading conditions. The proposed ultimate failure analysis that considers the influence of pavement layers with distinct stiffness and strength properties, focuses on the failure of subgrade layer as it is generally the weakest layer in a pavement structure. The distributed vertical stress induced by an SHL vehicle on top of the subgrade layer is compared to the bearing capacity of the subgrade layer. In order to demonstrate the developed methodology, the analysis steps and the associated results for an SHL vehicle configuration permitted by the Louisiana Department of Transportation and Development (LaDOTD) are presented.