A probabilistic approach to assess slope stability of roadway shoulders under superheavy traffic operations

Abstract

Non-conventional Super Heavy Load (SHL) units generally transport heavy loads weighing significantly higher than conventional trucks. Movements of such SHL trailer units with overweight tires and non-generic axle assemblies are detrimental to the structural integrity of sloped roadway shoulders. This research proposes an approach to realistically evaluate stability of roadway shoulders under subjected to SHL units. The developed methodology upgrades conventional Limit Equilibrium Method to a probabilistic approach to consider uncertainties attributed to orthogonal stiffness characteristics of aggregate materials in pavement structures. The proposed novel approach is also capable of assessing complex traffic loads imparted under SHLs. To achieve these objectives, the researchers first developed a field-testing scheme to obtain prominent features associated with the SHL trailer units and their loading configurations, as well as pavement material and road shoulder characteristics for ten overweight corridors in Texas. The field-derived information was then used as inputs in a series of 3D finite element model to characterize SHL-induced forces. Monte-Carlo methods was also deployed to establish a distribution of shear strength factors, within the bounds of laboratory-derived data for base and subbase layers as well as subgrade soils. Eventually, the resisting forces were contrasted with mobilizing forces along failure surfaces to assess stability of pavement shoulders. Results underscored the importance of tire load magnitude, shoulder slope inclination, surface treatment, and moisture management mechanisms in stability studies of roadway shoulders under demanding stress paths in overweight routes. The permutations pertaining to extreme weather events such as flooding, heavy rainfall, and prolonged inundation events also showed the detrimental effect of SHL operations on the stability of sloped shoulders. The proposed approach and synthesized results for Texas SHL corridors provided in this research facilitate realistic evaluation of the potential failure risk of sloped shoulders under SHL operations, considering non-typical nature of SHLs, environmental factors, and unique features of roadway shoulders in such regions.