INVESTIGATION ON THE CAUSES OF PAVEMENT FAILURE ALONG DAMATURU-GASHUA HIGHWAY

Pavement failure remains a major challenge affecting highway performance in Nigeria, particularly in regions characterized by weak soils, inadequate drainage, and increasing traffic loads. This study investigated the causes of pavement failure along the Damaturu–Gashua highway in Yobe State, northeastern Nigeria, with emphasis on the geotechnical properties of the subgrade and subbase materials. A reconnaissance survey was conducted to identify failed pavement sections, after which representative soil samples were collected from the right-hand side (RHS) and left-hand side (LHS) of the roadway. Laboratory tests including sieve analysis, Atterberg limits, Standard Proctor compaction, and unsoaked California Bearing Ratio (CBR) tests were carried out to determine the engineering characteristics of the soils. Sieve analysis results revealed that the soils are predominantly sandy with poor gradation and limited fines, indicating weak load distribution capability. Atterberg limits showed very low plasticity values, suggesting minimal binding strength and susceptibility to strength loss when exposed to moisture. Compaction test results indicated relatively low maximum dry density and high optimum moisture content, reflecting poor compaction efficiency and reduced soil strength under wet conditions. The CBR values obtained were significantly below the recommended minimum of 10%, particularly for the RHS subbase material, confirming extremely weak load-bearing capacity. These geotechnical deficiencies explain the observed pavement distresses such as cracking, rutting, potholes, and surface deformation along the study highway. The study concludes that pavement failure along the Damaturu–Gashua highway is primarily caused by weak and poorly compacted subbase materials, especially on the RHS, compounded by moisture infiltration, heavy traffic loading, environmental effects, and inadequate construction quality control. The study recommends material stabilization or replacement, improved drainage provision, strict quality control during construction, and routine maintenance to enhance pavement durability and service life.