Investigation Of Effects Of Excavations On Adjacent Foundations Using Finite Element Modeling

Deformations caused by excavations are important to determine because for the past decade, deeprnexcavations are becoming more common in Addis Ababa. Due to congestion of places, most ofrnthese excavations are near adjacent buildings. Numerous high rise buildings are erected and therneffect of these on the adjacent grounds which in turn on adjacent foundations have not been studiedrnvery thoroughly. The purpose of this master’s thesis is to first determine the effects of foundationrnloads at different levels on a red clay soil and to see the effect on adjacent excavations as a result ofrnvertical and horizontal displacements. Four foundation levels are used by differentiating betweenrnthe numbers of their respective building basements: no basement, one basement, two basements andrnthree basements foundation levels. For the same foundation level, the distance from the edge ofrnexcavation was also varied from 0m to 3.5m and to 7m. The variations of vertical and horizontalrndisplacements were plotted against the distance from the face of excavation. The results showedrnthat at 3.5m from the face of excavation and beyond that, the displacements decreased to arnminimum value. Similar trends are shown in the decrease of the vertical and horizontalrndisplacements for those cases with the same number of strut levels showing that the strut level willrnaffect the value of the deformation in spite of the vertical excavation level.rnThe second purpose is to determine the vertical and horizontal displacements of the ground andrnwall under different cases by changing soil, wall and excavation properties by means of parametricrnstudy. PLAXIS 3D Foundation V.1 was used as a tool to carry out all the analysis. The parametersrnare varied for three levels of excavations i.e. 4.9m, 10.35m and 15m Final excavation. The modulusrnof elasticity and the excavation depth showed prominent effect on the results. The allowablerndeformation values from EBCS 7 and other literature have been compared with the cases with thernmost critical deformation values. The result of the comparison is that those cases with low stiffnessrnmodulus values resulted with high deformation exceeding the allowable values from previousrnliteratures.rnKey words: Deformations, secant pile wall, PLAXIS, allowable values

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