الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
According to the Egyptian Ministry of Transport, in the last 4 years more than 4,500 kilometers of newly constructed roads were accomplished. Similarly, over 5,000 kilometers of development of the existing road network are under construction in this time period. This study provides an overview of previous work and a review of work related to soil strength which affects directly on the design and the performance of flexible pavement and tries to find out if there is a relation between soil strength and chemical composition of soil. For the purpose of investigating the effect of poor subgrade soil on the design of the road and studying its bearing capacity which will surely affect the design of the subbase, base, and surface layers, different types of soil were collected from four sectors of Alexandria and Beheira to examine this effect. Sieve analysis, Atterberg’s limits (liquid limit and plastic limit), and California Bearing Ratio (CBR) tests were performed for the purpose of investigating the type and classification of the four samples. from the results of the previously mentioned tests, the soil was classified using the AASHTO classification method and flexible pavement. Comparison was done by designing the flexible pavement for the studied samples using the AASHTO design methods. Chemical analysis was also performed on the different four samples. The outcomes of the laboratory tests and the design of the flexible pavement for the four samples confirmed that sample (1) and sample (2) are the strongest soil and good as a subgrade, while sample (3) and sample (4) are poor soils. The chemical analysis also reveals that there is a relation between soil strength and chemical composition, while the poor subgrade has the highest percentage of loss on ignition, total and dissolved Sulphates, (CaO) and (MgO) and the lowest content of silica. This study recommends that the soil improvement methods should be taken into consideration when it comes to construct a pavement on poor or weak soil and further studies may be conducted to confirm the relation between chemical composition and soil strength.