Assessment Of Cause Of Road Pavement Failure Along Teji-Tulu Bolo Road

Abstract

A Road Pavement Is A Structure Of Superimposed Layers Of Selected And Processed Materials That Are Placed On The Basement Soil Or Subgrade. Pavement Deterioration Process Starts Directly After Opening The Road To Traffic. This Process Starts Very Slowly So That It May Not Be Noticeable, And Over Time It Accelerates At Faster Rates. Teji-Tulu Bolo Road Is One Of The Roads Which Failed Before Reaching Serving Time And This Research Aimed At Assessing The Causes Of Pavement Failure Along This Road. To Achieve The Objectives Of The Research The Sampling Technique That Was Used Is The Nonprobability Purposive Sampling Method. The Idea Is To Collect Soil Samples At Different Locations Of The Road With The Worst Failure Rates. Accordingly, 17 Sample Locations/Stations Of Test Pits That Represent The Type Of Failures Observed Along The Road Section Were Selected. And The Sampling Of The Soil Was Accompanied With Field Density Tests For Each Subsurface Layer. To Determine The Causes Of Failures The Laboratory Tests Such As Grading Analysis, Atterberg Limits Test, Soil Compaction, Cbr Tests And Moisture Content Determination Were Performed. To Check If The Road Failure Was Associated With Traffic Or Not The Traffic Count (Aadt) From 2014-2022 G.C Was Obtained And Compared With The Design Aadt. From The Comparison Of Field And Lab Results With Era, 2013 Standard Technical Specification And Method Of Measurement, Most Of The Test Results Didn?�?T Complied With The Requirement. The Difference Between The Nmc And Omc For The Subgrade Ranges Between 13.6 And 2.69 Percent And Swell Of Sub Base Range From 0.55%-1.2% Which Shows Expansive Sub Base Material. From The Gradation Test Done On Base Course The Material Was Finer At Some Spots And Courser At Other Spots Than Era Requirements. And Also The Base Material Shows Cbr Of Ranges From 80%-185% And Swell Between 0.4 % And 0.85% Which Are An Indication Of Presence Of Expansive Soil In Base Course Crushed Stone. Additionally The Soil Exist Under The Road Structure Was Black Cotton Soil And Didn?�?T Replaced To Required Depth Through Full Stretch Of This Segment. From The Secondary Data Obtained From Era The Existing Traffic Was Higher Than The Design Traffic The Road Is Capable To Carry. The Study Has Recommended To Reconstruct The Road With Provision Of Extra Depth, Adopting Mitigation Measure For Existing Expansive Soil, Solving Drainage Issues And By Reusing The Material.