البحث — المستودع الرقمي العراقي

المستخلص: Road transport is Iraq's primary mode of transportation; although other types of pavement have been used, flexible paving is the most common in most Iraqi governorates. In general, the design life of flexible paving layers for Iraqi roads is not met; structural and functional failures appear early, resulting in significant yearly maintenance costs. The most prevalent failures are fatigue and rutting, which various reasons may cause. One of these reasons is the inaccuracy in design resulting from using empirical design techniques, in addition to the mistakes due to the complications of the manual calculations of these traditional methods; another reason could be the imprecise estimation methods of the resilient modulus of the pavement layers due to a lack of necessary equipment.
This study presents a feasible methodology for analyzing flexible pavement structures by the Finite Element Method (FEM) implemented using EverStressFE, which is (3D-Finite Element) software tailored for flexible pavement structures. The EverStressFE results were compared with the Kenlayer software for the Burmister multi-layer theory. Both software packages were utilized to perform 152 simulations for various pavement models. The statistical quality of the convergence degree between the two software's outputs was evaluated. Levene's and t-tests were used to compare the means and variances of tensile and compressive strains.
A Dynamic Cone Penetrometer (DCP) tester was fabricated to provide a tool for investigating the characteristics of the implemented pavement layers. The fabrication process complied with the American Society for Testing and Materials (ASTM) standards. Before calculating distress models for Al-Mujama'at Road, one of Najaf's roads used as a case study, the correlation equation between DCP and the California Bearing Ratio (CBR) was established using lab tests.
The coefficient of determination (R2) for the DCP and CBR correlation equation was found to be 0.97, indicating that the DCP can be used as an alternative to the CBR test. As for the comparison study, EverstressFE is more convenient and straightforward than traditional design methods; it facilitates comparing pavement components, and its results are similar to Burmister's multi-layer theory. For Al-Mujama'at Road analysis, Single Axle Dual Tires load caused a fatigue damage factor of 13.9E-07 and a rutting damage factor of 9.86E-07, indicating that the pavement lifespan is shorter by 29% due to fatigue damage compared to pavement life concerning rutting deformation. In other words, there is no good pavement component utilization for balancing the pavement life of distress models, which prompted an investigation into the sensitivity of these models to each of the pavement properties, which concluded that the thickness of the subbase layer and the elasticity modulus of the subgrade are the key components that control the balance point between fatigue and rutting in pavement life considerations.

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