Abstract:
Highways play a crucial role in facilitating transportation and have a significant impact on the economic development of a country. The current condition Bahirdar –Woreta road of the road segment was subjected to heavy defects. As a result of flooding and erosion raveling was the dominant problem from Hamusit to Woreta town, which cause the pavement to lose functioning. In addition to this due to increase in traffic volume and different factors including inappropriate maintenance techniques the rates of deterioration increase rapidly. The Aim of this research was to study assessment of road failures from Bahirdar to the Woreta road segment. Road defect type, Severity level, and causes of failure are investigated. The road condition survey result indicates that most of the defect from Gombat to Woreta town has low severity with high extent of deterioration. The study focused on taking representative samples from six different failed sections of the road for both natural sub-grade soil, sub base and base coarse materials for laboratory testing the liquid limit value of the subgrade ranges from 44.3 % to 97.23 % and subbase also ranges from 21.5 % to 38.2 %. The range of the plasticity index result for sub-grade is 19.65 % to 49.45 % and the range of the plasticity index result for subbase is 4.3 % to 19.15 %. OMC sub grade from 16.9-30.5% and Sub-base material 12.5-21.5%, whereas MDD ranges sub-grade soil is from 1.28-1.84 g/cm3 and sub-base material 1.26-2.02 g/cm3. CBR values of the subgrade range from 1.51 % to 6.73 % and sub base 18.3% to 47.6 %. Based on the result of ACV and LAA all samples are below the requirements (ACV < 25 and LAA < 30).
The subgrade soil is classified as A7-6 and A-7-5.and sub base A-2-4 and A-6. The study area also suffers from poor drainage and the expansiveness of the sub grade soil varies from high to very high. Therefore, a number of factors including traffic loads, expansive subgrade, inadequate side drains, poor workmanship and the use of inferior construction materials contribute to pavement failure.
Keyword: - Highways, Road Failure, Compaction, CBR Test, Design Standards