الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 85 |  |  |
| | | from | 85 | | |
Abstract
Gravels roads represent a significant percentage of the road network. Improving the mechanical properties of gravel roads has been much researched using many approaches, which include soil reinforcement using geosynthetics. Geosynthetics include geotextiles, geogrids, and geocomposites. The main advantage of using geosynthetics arises from the ability of geosynthetics to provide tensile reinforcement through frictional interaction with base course materials. Geogrids are preferred in gravel roads reinforcement due to their high ability to resist erosion, high shear strength, high tensile strength and durability. The lateral restraint is considered the primary function of geogrid reinforcement; it develops mainly through the shear interaction of the base course layer and geogrid layer placed within or at the bottom of the base aggregate layer. In addition, the bearing failure model of subgrade may change from a punching failure without reinforcement to a general failure with ideal reinforcement The objective of this report is to identify the geosynthetics properties governing the design of geosynthetic-reinforced gravel roads. The report includes a review of geosynthetics types, reinforcement mechanisms, studying the reinforcement design methods and cost benefit of using geosynthetics in reinforcement. Several approaches for designing gravel roads using geogrids were reviewed, including Barenberg design method, Steward design method, Giroud and Noiray approach, and Giroud and Han method. Giroud and Han method was found to be the most comprehensive approach since it considers many design factors such as the type of the geosynthetic, the aperture stability modulus of the geogrid, the modulus of the base course, and the modulus of the subgrade in addition to the traffic volume, the wheel load, the tire pressure. Based on Giroud and Han design method and case study considered, it was concluded that the use of geogrid for reinforcement of weak subgrade soil for gravel road construction can reduce the required thickness of the aggregate base layer by up to 47%, resulting in significant economic benefits.