Failure Mechanism and Design Criterion for Low-Volume Roads Subgrade Widening

Abstract

During the past decade, a large number of low-volume roads have been rebuilt in China to accommodate a sharp increase in traffic volume. An in situ investigation of highway reconstruction found cracking, a pattern typical of deterioration in pavements related to subgrade widening. The cracking is caused by the development of differential deformations between the widened subgrade and the existing subgrade. On the basis of finite element analysis and full-scale simulation laboratory tests, characteristics of subgrade differential deformation and its impact on pavement performance were studied. For typical asphalt pavements with a semirigid base course, three kinds of cracking modes related to subgrade widening were noted: shear cracking, bottom-up cracking under wheel loads, and top-down cracking induced by subgrade differential deformations. Finally, on the basis of the sensitivity of pavement cracking to change in horizontal slope, a design criterion for pavement subgrade widening was proposed.