Effect of Non-uniform Soil Subgrade on Critical Stresses in Concrete Pavement

Rigid pavements are directly supported on foundation soil/sub-base, and hence, it is necessary to prepare uniform subgrade. The calculation of critical stresses given by various guidelines like PCA (1984) and IRC 58 (2015) are based on the assumption of uniform subgrade below the pavement slab. However, practically uniform compaction is hard to achieve in newly constructed roads as compared to old existing roads. Many times, widening of roads is done after few years, and it leads to non-uniformity in stiffness along width. Moreover, stiffness of the soil foundation shows variation along the length of the pavement. Recent guidelines do not suggest any solution for non-uniform stiffness of foundation. The study has been carried out by performing finite element (FE) analysis of slab with non-uniform soil stiffness. Portable falling weight deflectometer is used to study the variation of soil stiffness along the width and length of road. Realistic concrete slab is modeled and performed analysis for axle load, temperature load, and combined effect of axel and temperature to obtain critical stress. Stiffness of the spring is varied along the length as well as the width, and static load response is observed in several FE models. The paper compares various panel results with variation in subgrade stiffness.