Investigation of Asphalt Pavement Failure Caused by Sub- base and Subgrade Soil Properties along Kemmisse to Dessie Road

Abstract

The studies of the present work were focused on the failures of the road which connects Kemessie and Dessie towns, Amhara Region of  Ethiopia. The main factors for the failures were subgrade soil properties and low-quality subbase. The faulty road regions were identified  and the soil samples were collected from different regions. Various testing techniques were applied namely sieve analysis, Atterberg  limits, compaction and California bearing ratio. The col- lected samples falling in AASHTO classification A-2-6 to A-7- 6, was tested in the  laboratory and found fine contents, ranging from 17.8 to 84.3%, liquid limit of 38.05 to 74.35%, plastic limit of 21.2 to 38%, plasticity index  of 16.85 to 49.25%. Furthermore, the samples were tested for Maximum Dry Density and Optimum Moisture Content. The Maximum Dry Density range was found 1.33 to 1.96 Kg/m3 and the Optimum Moisture Content range was found 12.78 to 28.6%. The California Bearing  Ratio was found in the range 3 to 50.6%. Sim- ilarly, the sub - base material was tested and found Plasticity Index in the range 6.7- 18.05  and Maximum dry density in the range 1.74- 2.25 kg/m³. The soaked specimen's California bearing ratio range was 7- 20.71%. The test re-  sults disclosed the poor standards and not maintained the standards of the Ethi- opian Road Authority. Therefore, the above factors  indicate poor road con- struction. The recommendations made in this study will be useful to the high- way engineers for effective   maintenance and for better road construction.