Investigation of the Performance of Pavement Founded on Reinforced Earth Sections Along Outer Ring Road, Nairobi

Abstract

Urbanization in Nairobi city has resulted to increase in traffic demand exerting more pressure on the existing transport infrastructure. Outer ring road which is a critical artery within the city was improved to dual carriageway to meet the surge in traffic demand. Despite the use on reinforced earth embankments, there has been observed pavement surface distresses and increased traffic volume. This raised concerns of the performance of pavement founded on reinforced earth embankments of the road in meeting the transport demands of the rapidly growing city. The primary objective of this study was to investigate the performance of pavement founded on reinforced earth sections along Outer ring road. The specific objectives were to; evaluate the impact of the existing traffic loading on the pavement, establish the structural adequacy of the pavement and evaluate the functional performance of the pavement founded on the reinforced earth sections of Outer ring road. Quantitative and qualitative methods of data collection and analysis were adopted for this study. Pavement deflection measurements were taken using Falling Weight Deflectometer (FWD), roughness and rut depth measurements using Hawkeye 2000 Pavement Surface Profiler and through visual condition survey. Classified traffic counts and axle load survey were undertaken to determine the existing traffic. It was established that pavement on reinforced earth sections exhibited lower performance compared to pavement on other sections of the road. While reinforced earth embankments are designed to provide a robust foundation to the pavement, this study concludes that they must be meticulously designed and constructed taking into consideration the local dynamics to ensure longevity and performance of the pavement. It is recommended that future similar projects incorporate detailed long term traffic projection and consideration of performance of the indigenous construction materials and methodologies. In addition, regular monitoring, evaluation and maintenance practice of road infrastructure should be established to promptly arrest any potential pavement distresses before they deteriorate into major pavement failures and increased safety hazards to the public.