Abstract: The subsurface condition of a municipal engineering project consists of thick soft cohesive soil of the first terrace of Yangtze River. Both the deep excavation and the soil improvements are required for the project. A high construction cost and extended construction period were expected if the soil improvement and the deep excavation supporting system were designed and constructed separately. Using the grid formed soilcement mixing columns as the soil improvement and the strengthening of the passive zone of the excavation supporting zone has the advantages in both cost and the construction schedule.

Key words: Grid Formed Soil-Cement Mixing Columns, Soil Improvement, Strengthening of the Passive Zone of the Deep Excavation Supporting System