A methodology for road cutting design guidelines based on field observations

Abstract

Road networks in low and lower-middle income countries (LIC/LMICs) are rapidly expanding to enhance social and economic growth. The construction of a new road often requires cuttings to be made, especially in hilly topography. In LIC/LMICs, many practitioners rely on guidelines to design roadside cuttings, however, some of these guidelines lack accuracy as they are not developed using rigorous stability analysis methods. Stability charts offer a more reliable alternative to some guidelines; however, these are difficult to use in the field. To overcome this gap, we present a new methodology to develop rigorous and user-friendly guidelines for the preliminary design of roadside cuttings. The guidelines are developed using failure criteria commonly employed by practitioners (i.e. Generalised-Hoek-Brown for rock and Mohr-Coulomb for soil) and a rigorous Limit Equilibrium Method, Morgenstern-Price, for stability analyses. In addition, we consider upslope geometric boundary conditions and slope seepage. The guidelines are designed to be user-friendly by including categories with accessible descriptions to characterise the slope material and geometry that can be selected by a practitioner in the field. Then the methodology is showcased by producing new guidelines for the design of road cuttings in Nepal and Ethiopia. We believe the systematic use of guidelines developed following the novel methodology here illustrated will reduce design error, and thus lead to road cuttings of increased life span.