Supervised by Dr. Sami Hijjawi Prepared by Hamza Saifan Abdul-Rahman Easa
Civil Engineering Department Soil Improvement and Design of Pavement For Sanour – Maythaloon Street – Jenin Supervised by Dr. Sami Hijjawi Prepared by Hamza Saifan Abdul-Rahman Easa 2010– 2011
Types of Pavement Typical stress distribution under a rigid and a flexible pavement.
Flexible Pavement • Asphalt concrete Surface • Basecourse layer • Subbase layer (Rock Fill) • Subgrade
Study Area • Sanour –Maythaloon Street .
Pavement Distresses Description 1. Longitudinal Cracking • Cracks parallel to the pavement's centerline or lay down direction, • usually a type of fatigue cracking.
Pavement Distresses Description 2. Alligator Cracking • Series of interconnected cracks caused by fatigue failure of the Pavement surface under repeated traffic loading.
Pavement Distresses Description 3. Raveling • The progressive disintegration of an Pavement layer from the surface downward as a result of • the dislodgement of aggregate • particles.
1. Lime Stabilization • Lime stabilization involves the use of burned lime products, quicklime, hydrated lime (oxides and hydroxides, respectively) and Codel. • Lime is a strong alkaline base which reacts chemically with clays, causing a base exchange Calcium ions displace sodium and hydrogen cations and combine with available silica and alumina in the soil to form complex silicates and aluminates .
1. Lime Stabilization • The principal changes to a soil stabilized with lime include: reduction in plasticity index (PI) and volume change; increase in optimum moisture content, permitting compaction under wetter conditions and allowing the soils to dry out more rapidly; increase in strength and stability through a cementing action; and resistance to water absorption and capillary rise.
2. Cement Stabilization • Portland cement is one of the older materials used for stabilization. The cement hardens the soil material and structural strength . • Soil cement is a mixture of Portland cement, water and soil compacted to a high density. When cured, the soil cement mixture becomes a hard, rigid base material.
2. Cement Stabilization • Soil cement is used as a base course, a subbase course and a subgrade treatment for flexible and rigid pavements. Almost all types of soils can be used for cement stabilization except highly organic soils and heavy clay soils. • Four fundamental factors control the construction of soil cement : moisture content, curing duration, compaction, and cement content.
3. SubgradeReplacement • A common approach taken where soft subgrade soils are encountered is to remove and replace the in situ soils with stronger, usually granular, materials. • This method can be practical and economical where soft deposits are shallow and are located above groundwater levels.
4. Geosynthetics • Geosynthetics have been found to provide significant improvement in pavement construction and performance. • Geotextiles placed at the subgrade increase stability and improve performance of pavement constructed on high fines subgrade soils.
4. Geosynthetics • Without using geosynthetics, these tensile stresses will cause tension cracks to develop within the bottom of the base course. • Due to dynamic traffic loads these cracks allow fines from the subgrade to migrate upward into the base course layer while base course aggregate simultaneously migrates downward into the subgrade.
PAVEMENT DESIGN USING AASHTO METHOD 1- Determine the type of treatment: Reconstruction 2- Collect Traffic Data 5 - Determine thicknesses of pavement layers 3- Determine Average Annual Daily Traffic AADT 4- Calculate Equivalent Single Axial load ‘ESAL’
PAVEMENT DESIGN USING AASHTO METHOD Flexible Pavement Design with 10 Years Design Period
PAVEMENT DESIGN USING AASHTO METHOD Thicknesses
Total Cost = 701,400 $ • PAVEMENT DESIGN USING AASHTO METHOD Costs
PAVEMENT DESIGN USING AASHTO METHOD Flexible Pavement Design with 20 Years Design Period
PAVEMENT DESIGN USING AASHTO METHOD Thicknesses
Total Cost = 764,400 $ • PAVEMENT DESIGN USING AASHTO METHOD Costs
Conclusions and Recommendations • The subgrade layer consists mostly of silty clay materials with classification of A-7. The high plasticity of the encountered silty clays indicates a high possibility of soil volume change. This could be the sole explanation of the pavement condition. • Due to weak and swelling soil of subgrade layer , it is recommended to use soil improvement which is soil replacement with Rock Fill layer to reduce the effect of subgrade moisture content on the road layers .
Conclusions and Recommendations • It has been noticed that the difference in cost between two scenarios is too small so it is recommended to use 20 year Design period than 10 year Design period . • Visual inspection of the pavement surface reveals the existence of several types of distresses (longitudinal cracks, alligator cracks, …etc.) . • Upon to visual examination and record of distresses , it is recommended to reconstruct the pavement and its layers after removing the existing one .