Effect of Non-Uniformity of Subgrade Soil on Asphalt Pavement Performance (A Case Study of Qena-Luxor West Desert Road)

Dr. Hassan Darwish Hassanin

The subgrade soil bearing capacity represented by its Modulus of Resilient (Mr) or California Bearing Ratio (CBR) is considered the most dependent factor in all methods of pavement design. The structural failure and the performance of the pavement are greatly related to the subgrade soil conditions. All researchers accepted that the subgrade soils under the pavements are not perfectly homogeneous because of different conditions are existing in the field including environmental, geological, water table and construction conditions. A major factor that affects the pavement performance is the non-uniformity of subgrade soil type along the road section due to the existence of various soil types in some special areas. This study was conducted based on the collected geotechnical, traffic and pavement condition data of the project of dualization of Qena – Luxor west desert road 50 km length. The road project consists of two road sections; Qena – Al Mahrosa 14 km & Al Mahrosa – Al Taref 36 km. The objective of this study is to investigate the effect of non-uniformity of subgrade soil type on the pavement performance of the constructed pavement. The investigation program included pavement surface condition and geotechnical & Laboratory investigations for the existing road bed soils. Results indicated that the performance of the pavement is greatly affected by the change of the subgrade bearing capacity due to changes in soil types. By checking the correlation between the pavement performance represented by PCI values and the subgrade bearing capacity represented by its CBR, it is found that the R² value for the predicted linear relationship is 0.6281 which does not justified due to the existence of many other factors affects the pavement performance in addition to the subgrade bearing capacity.