OPTIMIZATION ANALYSIS OF EXCAVATION SEQUENCE OF A DEEP FOUNDATION PIT IN MUDDY SOFT SOIL

A deep foundation pit in Nanjing is located on the lower bank of the Yangtze River. The site is a typical binary structure with widely distributed muddy silty soil, high pressure water level, and complex geological conditions of the foundation pit. The foundation pit is adjacent to a high-rise building. The excavation scope involves thick muddy silty soil, and the supporting structure is all buried in the muddy silty soil. The excavation sequence of the foundation pit is directly related to the safety of the foundation pit and surrounding buildings. Based on the condition of the deepest part of the foundation pit, the excavation sequence of the foundation pit is divided into 3 methods:I first excavation of the main tunnel and then excavation of the ramp; Ⅱ first excavation of the ramps and then excavation of the main tunnel; Ⅲ parallel excavation of the main tunnel and the ramp, using FLAC^3D simulation software to analyse the deformation of the supporting of foundation pit and surrounding buildings under three excavation methods. And know that when first excavation of the main tunnel and then excavation of the ramp or first excavation of the ramps and then excavation of the main tunnel, the deformation and impacts on surrounding buildings and the supporting of foundation pit is minimal. This study provides experience for the excavation and design of deep and large foundation pits in deep muddy silty soil.