Investigation Of Collapsible Soil Of Adama-Asella Asphalt Road In The Case Of Dodota Area

Abstract

Collapsible Soils Are Characterized By Relatively Low Density And Cohesion, Appreciable Strength And Stiffness In The Dry State, But Are Susceptible To Significant Deformations As A Result Of Wetting. The Collapsible Soil Sample Was Collected From Adama To Asalla Asphalt Road Of The Case Dodota Area. The Objective Of This Research Was To Investigate The Engineering Behavior Of Collapsible Soil Of The Area With A Field And Laboratory Tests. The Test Result Shows That The Soils Have Very Low In-Situ Densities, Mainly Consist Of Sands And Silts And Low Plasticity. The Shear Strength Of All Sample Were Observed As Below 50 Kn/M2. The Aashto Classification Is An A-4 Material (Silty Soil) Which Is Fair To Poor Rating In Terms Of General Rating As Sub-Grade Material. The Clay Fraction Was Ranges From 19.44%, To 20.73%.. The Moisture Content Was Ranges From Was 17.35%, To 17.45%. The Plastic Limit Was 29.68 To 30.66. The Plasticity Index Ranges 8.95% To 9.62%. The Maximum Dry Density Of Sample Ranges From 1.513g/Cc To 1.558g/Cc And The Optimum Moisture Content Varies From 24.98% To 27.40%. The Soil Sample Is Silty Sand With Substantial Amount Of Clay And Is Not Suitable For Sub-Grade Material. The Structure Of The Soil Has Meta Stable Texture As The Bonds Between The Grains Breakdown When The Soil Is Wet. Hence, The Collapse Process Represents A Rearrangement Of Soil Particles Into A Denser State Of Packing; Also The Soil Has An Open, Partially Unstable And Unsaturated Fabric.