Investigation On The Application Of Natural Fiber (Katcha) As A Weak Subgrade Soil Reinforcement Blended With Sand: In Case Of Koyefeche Project 18 Road Project

Abstract

The Performance And Quality Of Pavement Are Highly Affected By The Subgrade Property. Sometimes Subgrades Might Be Very Weak To Support The Traffic Loading, Facing Of Such A Soil Is Probable In Many Parts Of Ethiopia. The Road Project In Koyefeche Project 18 Faces Weak Subgrade Soil, Which Required External Backfill Material Resulted The Delay Of Project, Additional Cost And Reduction Of Natural Resource. Soil Reinforcement Is One Way Of Improving The Strength Of A Soil By Using Different Type Of Natural Fibers. Ethiopia Is Reach In Both Natural Fiber And Sand. However, Few Works Have Been Conducted To Investigate The Effect Of Using Natural Fibers And Sand On The Properties Of Subgrade Soil. Therefore The Main Aim Of This Thesis Is To Investigate The Effect Of Randomly Oriented Katcha Fiber And Sand On Weak Subgrade Soil Properties. Katcha Fiber Was First Treated With Kerosene And Water Absorption Test Were Conducted On Kerosene Coated And Uncoated Fiber To Determine The Fiber With Lower Water Absorption Capacity; Kerosene-Coated Katcha Fiber Gave Lower Water Absorption Than That Of Uncoated One. Therefore Kerosene-Coated Katcha Fiber And Sand Were Two Materials Utilized In This Thesis. The Katcha Fiber Was Mixed To The Clay Soil In 0.5%, 1% And 1.5% By Dry Weight Of The Soil For 20mm, 35mm And 50mm Length Of Each Percent, And 10%, 15%, And 20% Sand Was Mixed By Dry Weight Of The Soil. Gradation, Consistency, Volumetric Shrinkage, Compaction, California Bearing Ratio (Cbr), And Unconfined Compressive Strength (Ucs) Properties Are Particularly Investigated. The Analysis Results Showed That Mixing Of Sand Reduce The Percent Of Fine, Plasticity Index And Shrinkage Limit Of The Soil And Mixing Of Katcha Fiber Showed Significant Change In Compaction, Cbr And Ucs Of The Clay Soil. Test Results Indicate That The Mdd Decrease, Omc And Cbr Increases With The Increase In Fiber Length And Percent. The Increase In Cbr Value Is Substantial At 1%, 35 Mm Length Katcha Fiber. It Was Also Observed That Mixing Sand Further Decreases The Omc And Increases The Mdd And Cbr Value Of Soil, This Increment Is Considerable At 20% Sand Content. The Application Of 1% And 35mm Katcha Fiber Increased The Cbr By 189%, Ucs By 59.76%, And A Further Increase In Cbr By 240.91% And Ucs By 25.41% Was Obtained At 20% Sand Content And Introducing Sand As Layer Increased The Cbr Value By 295.45%. Thus Using Of Katcha Fiber And Sand Mixing And Sand Layer Is Found To Be An Effective Materials To Improve The Subgrade Soil Properties.