Index Properties Of Typical Tropical Residual Soils Of Adama Town

Abstract

Residual Tropical Soils Can Have Characteristics That Are Quite Distinctively Different From Those Of Transported Soils, I.E., The Conventional Concept Of Soil Mechanics Is Not Applicable To Many Residual Soils As It Consists Of Relict Of Parent Rocks And Weathered Mineral Matter That Break Down And Become Progressively Finer Under Continuous Manipulation. In Practice, Since The Determination Of All The Engineering Properties Of Soils Is Expensive, Often Index Properties Are Simpler And Cheaper To Characterize Engineering Properties Of A Given Soil. In This Study Typical Index Properties Of Residual Soils Have Been Studied In Detail As Per Literature Recommendations Considering The Case Study Of Adama Science & Technology University, Research Park Project Area. The Specimens Were Tested At Different Sample Preparation Conditions Prior To Conducting The Laboratory Test And Consequently Resulted In Different End Values. The Index Properties Studied Includes; Particle Size Analysis, Atterberg Limits, Free Swell Index And Specific Gravity In Which Samples Were Conditioned For Three Different Test Temperatures (At Received Moisture, Air-Dried And Oven Dried At A Temperature Of 105oc).Moisture Content Determination Using Oven Temperature Of L05??C And Air Dry Conditions Were Also Carried Out On The Soil Samples To Investigate Presence Of Loosely Bound Water Of Hydration. It Was Found That The Soil Samples Contain Considerable Amount Of Water Of Hydration Or Structural Water Which Leads To Irreversible Changes On Drying. Sample Manipulation Is Also Found To Change The Results Of The Atterberg Limit Values By Affecting The Bond Between Soil Structures. From The Soil Classification, Almost All Soils Are Clayey Sands With The Highest Probability Of Changing To A Coarse Graded Fraction Over 2.5m Depths. The Laboratory Results Of The Atterberg Limit Values For The Soil Has To Necessarily Be Simulated With The Field Conditions With Respect To Wetting And Drying Prior To The Test. The Free Swell Test Result Shows That The Soil Under Investigation Has Relatively Low Degree Of Expansion (<50%), Whereas The In-Situ Specific Gravity Of The Soil Under Investigation Is Between 2.33 To 2.98.Therefore, The Appropriate Test Procedures For Tropical Soils Are Strongly Recommended For Research And Practical Engineering Application Where Such Soils Are Likely To Exist.