River Dike Slope Stability Analysis Under Seepage And Earthquake Load Effect (Case Study On Amibera District, Middle Awash River)

Abstract

Flood Dike Is An Earthen Structure Which Is Constructed Along The River To Protect The Surrounding Area From The Overrun Of Flood Water. Poor Planning, Design And Faulty Construction Of The Dike Structure, Internal And External Soil Erosions Due To Water Impoundment On The Upstream Dike Slope Face Are The Major Problem That Have Put Endanger The Stability Of The Dike. The Study Was Conducted On Amibera District, Afar Regional State On The Newly Constructed Flood Defense Dike With The Objective Of Analyzing A Steady State Seepage And Slope Stability By Considering 7m MWL On The Upstream Slope Face And Seismic Load On The Structure Stability. Also Sugarcane Bagasse Ash Mixing With Soil Sample One And Slope Parameters Are Taken To Study There Effects On Seepage And Slope Stability. A Finite Element Method Through A Computer Program Named SEEP/W And SLOPE/W Which Is Based On A Limit Equilibrium Approach Were Used To Determine The Amount Of Seepage Through The Dike Body And Its Stability Respectively. A Total Of Three Soil Samples Were Collected From Different Dike Sections And Index (Atterberg Limit, Grain Size, Specific Gravity) And Strength Property (Compaction, Direct Shear, Permeability) Are Determined In The Laboratory. The Result Obtained From SEEP/W Software Showed That The Total Flow Rate Of 3.31*10?????? M??/Sec, 1.89*10?????? M??/Sec And 8.36*10?????? M??/Sec Are Obtained From SS-1, SS-2 And SS-3 Respectively. To Verify The Accuracy Of The Analysis, The Results Were Compared With Hand Calculations Using Flow Net Method. It Showed A Good Close To The SEEP/W Computed Flux. For All Case The Hydraulic Exit Gradient Was Less Than The Critical Gradient. It Showed The Dike Sections Are Safe Against Piping Failure. From Slope Stability Analyses Result Observed That The Dike Safety Was Not Endangered During Seepage And Seismic Load Effect For Field Dike Geometry Section. The Result From Bagasse-Ash Mixing With SS-1 Showed A Significant Increment Stability Factor Of Safety Were Observed By Adding Bagasse Ash Content 4% By Weight. Further Increment Reduces The Stability Factor Of Safety And Increases The Total Flow Rate. Hence, From This Investigation Using Sugarcane Bagasse Ash Mix With Proper Ratio On Slope Stability Can Increases The Stability Factor Of Safety.