Abstract: In deep excavation engineering,the assistant retaining struts are usually designed to reduce the diaphragm displacement and ground settlement in soft clay.In improved soil layers,an average soil strength is usually used for the analysis.A deep excavation case in Taipei area was studied.By using the two-dimensional finite element code PLAXIS,a numerical analysis was carried out.Compared with the field data,the characteristics of the improved ground under the deep excavation were evaluated.