الفهرس | Only 14 pages are availabe for public view |
Abstract The issue of movements of insitu walls has become more important over the past decades with.new technologies being introduced, and increased concern about litigation over possible damages to adjacent facilities. This research presents information about the construction of subway stations using the cut - and - cover techniques employing reinforced concrete diaphragm walls constructed in the ground by means of a process of trenching with the aid of a fluid support (bentonite). This study intends to update and clarify previously available data for controlling ground movements with minor effects on the adjacent existing structures. The analysis of the diaphragm wall is conducted through two domains: First In the early stage, the bentonite suspension has the ability to form a membrane of low permeability at the soil - liquid interface, allows development of the fuU hydrostatic pressure of the fluid against the sides of the trench, Second The braced wall is a powerful, specific soil - structure interaction problem of embeded reinforced concrete wall on deformable soil media This research proposes a numerical modelling for analysis of diaphragm walls during the different construction stages. Several analyses have been made to improve undestanding of the conditions and mechanisms governing the stability of slurry - filled trenches. The associated variations in the surrounding soil stress field and deformations during wall construction and subway excavation are investigated, the progress of construction portrayed The numerical techniques, such as the finite element method are quite useful to carry out such analysis. A computer program was upgraded using the Fortran language. Eight- node isoparametric finite elements were used to simulate the soil continuum and the diaphragm wall, the nonlinear stress- strain behaviour of the soil employing modified Duncan model (1984) utilized. Spring type interface elements were introduced to model the soil - diaphragm wall contact surface. This thesis illustrates a comparative study between results of the nonlinear finite element analysis and the field measurements which had been compiled during construction of the Greater Cairo Underground Metro, Lines 1 and 2. Also, results of the analysis were compared with the predicted values from the commonly used empirical design rules of such walls. The study has concentrated exclusively on the numerical modelling of slurry trench wall by simulating two operations as one stage and multi - stage: I. The progressive excavation of relatively narrow trench in the ground and the slurry is introduced simultaneously. On completion, the trench is filled with slurry. 2. The slurry is displaced from the bottom upwards by the continuity of the supply of concrete. Finally. the trench is filled with concrete. |