EFFECT OF TYPE AND WIDTH OF SHOULDER ON STRUCTURAL CAPACITY OF FLEXIBLE PAVEMENT

Abstract

The highway shoulder is a very important cross-section element of roadway having influence on safety and efficiency of vehicle operation. Well designed and properly maintained shoulders contribute to the structural capacity and performance of flexible pavements as they provide lateral support to the layers of road pavement, and thereby prevent shear failure of pavement edges. Shoulders are vital for single and two lane roads. According to available data, 15 percent length of National Highway (NH) and 80% length of State Highway (SH) are still single lane carrying 35-40% of total road traffic. In present investigation, an attempt has been made to observe the effect of different type and different width of shoulders on structural capacity of two layer flexible pavements. For that purpose laboratory tests such as triaxial tests were conducted on WBM material with aggregates with size limited to 25 mm. Plate load tests were conducted on these pavements using 30 cm diameter plate. The test results indicate that lateral confinement provided by 0.6 m wide shoulders is of the order of 0.29 kg/cm2 for earthen shoulder, 1.67 kg/cm2 for brick on edge shoulder and 2.79 kg/cm2 for gravel shoulder. It is found that the life of the pavement gets increased by 45-50% by provision of brick on edge and by 58-60% by gravel shoulders. The economic analysis shows that the construction cost of a pavement with brick on edge is about 59% more and that of pavement with gravel shoulders is 52% more than that of a pavement with earthen shoulders. However, the direct and indirect benefits derived from shoulder can easily offset this increase in the cost of the pavement