Foundation subsidence due to trenching of diaphragm walls and deep braced excavations in alluvium soils

This paper presents a case history in Giza, Egypt in which the settlements of existing structures founded on shallow and deep foundations surrounding a deep excavation retained by strutted diaphragm walls were monitored. The presented case history comprised inclusive settlement monitoring during the different stages of construction including diaphragm wall trenching and the stages of excavation to the foundation level. The measured settlements were back-analyzed using two and three dimensional numerical models to evaluate the different deformation patterns associated with wall and pit excavation stages. The analyses showed that foundation settlements, during the different stages of deep excavations including the diaphragm wall trenching, are substantially influenced by the foundation type and depth and its relation to the depth of excavation.