Causes and Effects of Poor Drainage System on the Asphalt Pavement Layer: a Case Study in Agaro to Bedele Road.

Abstract

This thesis presents results of the poor drainage system; investigate on Agaro – Bedele paved road in oromia region and proposed mitigation measures. Mitigation measures were proposed based on ERA highway drainage manuals 2002 and 2011 for Low Volume Roads. The drainage system is to prevent onsite water standing on the surface and convey the offsite storm runoff from one side of the roadway to the other. An efficient drainage system is therefore essential to allow water to flow off and away from the road as quickly as possible. In Agaro -Bedele drainage system are not properly functioning. The inadequacy of drainage system during the rainy season to pass the flood, poor quality construction, inappropriate site selection and improper alignment of some drainage structures with respect to the road alignment and disposal of solid waste into drainage structure. The objective of this study was to investigate the causes and effects of poor drainage system on the asphalt pavement of road segment in Agaro – Bedele road. The primary data are photographs that show the current drainage system conditions, site visit, field survey and questionnaires that are gathered from the engineer, residences and road users about the presentation of the drainage systems during the rainy season. The important of secondary data for this research are land cover map, topographical map, geological map, and published and unpublished material. The design peak discharge calculated and the review peak discharge calculated of the return period is not equal. From this the road around this is damaged by over flooding of the water on the road because the calculated peak discharge for the design were less than the calculated peak discharge for the review at station,18+160 ,24+200 and 42+120 the difference between them are: 48.03 , 64.859 and 42.404 values. Therefore before the culverts are constructing the design and the review data must be checked always when its design the road it must be the design peak discharge is greater than the review peak discharge to control the floods that over follow on the road. The drain suffered from low capacity, soil accumulation, absence of inlets, lack of proper maintenance and disposal of solid waste into the drain and the crossing culverts. For these problems remedies suggests that it is important to perform operations such as when its design and construct the road drainage it must be follow the drainage design manual. Maintenance and cleaning regularly the drainage structures and waste solids remove to prevent these problems. Improvement of drainage facilities through maintenance redesign and reconstruction, to improve the role of poor workmanship in the construction of drainage road. The designer and contractor should follow the minimum requirement set by ERA regarding to the drainage structure, size, length and alignments of road drainage structure so as to prevent the impact of poor drainage on the road pavement