Optimization of Retaining Wall Types for Deep Excavation of Addis Ababa Clay Soil
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Date
2020-05
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Addis Ababa University
Abstract
Construction of retaining wall type for deep excavation is always anticipated in urban areas especially in Addis Ababa where construction is highly growing due to the limited availability of land. The most common type of retaining wall for deep excavation in the city is contiguous bored pile wall. This retaining method may not be effective in terms of various parameters like soil type, embedment depth, size of the wall and construction cost. Thus other alternative retaining systems should be considered and analyzed to select a best option. The results presented in this paper are for specific types of retaining structures. i.e. diaphragm and contiguous bored piles. Actual site selected for this study was around commercial college of Addis Ababa University, Addis Ababa.
In this research, diaphragm wall and contiguous bored pile have been considered for the analysis. by employing the finite element software Plaxis 2D. The primary goal of this thesis was to study the effects of the two walls for deep excavation in terms of wall deflections and cost incurred. The effects of wall stiffness, embedment depth and no of Anchors have been investigated for that purpose in detail.
The Finite element results shows for both DW and CBP, an increase in stiffness (size of the wall), decrease deformation.BS 8002 recommends, the wall displacement is to be limited to 0.5% of the wall height. Because of this those wall sections above 600mm fulfill the requirement. Similarly, when increasing the embedment depth, the deformation increase, However, it is only to some extent because of wall friction deformation decrease when embedment depth increases. Since the adjacent structure in the research area is road, embedment depth require is at a shallow depth of 7m is enough.
Based on comparison of cost incurred, Diaphragm wall require minimum cost for installation than contiguous bored pile walls. Finally, based on the results of this Research the optimized wall type for the selected site is Diaphragm wall with thickness of 600mm with embedment depth of 7m.
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Optimization, Retaining Walls, Embedment depth