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|Title||Study of the CBR Requirements of Subgrade for Roads Design in the Gaza Strip|
This research was proposed based on the practical experience of the researcher as a design engineer in the Special Environment Health Program (SEHP) at UNRWA Gaza, in the field of road design and specifications. It was found that the specifications recommended for the minimum CBR (California Bearing ratio) value used in the preparation of the sub-grade layer for roads in most national and international institutions in the Gaza Strip, Such as UNRWA, PECDAR, Gaza and other Municipalities and Consultancy offices, are not suitable. These specifications require a relatively high value of CBR (15%) for the natural soil below the sub-grade layer. This also requires that the top layer (in most cases) should be replaced or improved regardless of the road class or the expected ESALs during the design period. This is expected to cause an increase of cost, time, human and material resources. This is particularly true for low category roads as well residential and local roads. Determination of the minimum CBR value corresponding to each category of roads was one of the main objectives of this thesis in addition to road classification according to the ESALs. Special attention was given to residential and local roads which form the highest percentage of the area of roads. This is expected to lead to more adequate and economical design. In this frame, the research methodology included in the practical part; traffic counts, soil tests, theoretical analysis and cost analysis. The theoretical part included the applications of the basic design equation of AASHTO Modified Method, the application of total structural number equation and finding the most suitable replaced depth for sub-grade. Based on the analysis of the traffic count results and the applications of the above mentioned equations, tables of the roads classification and the minimum CBR values corresponding to the load categories were determined. In addition, design tables and charts were prepared under the condition that all parameters are constant except CBR and the total design equivalent single axle load (TDESAL) values.
|Publisher||the islamic university|
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