Abstract: An increasing number of deep foundation pit project in complex conditions has emerged with the comprehensive transformation of old urban area in the process of urbanization. Deep foundation pit projects with single sup-port could not easily meet the requirements of usage and economic benefit simultaneously, which, however, can be effectively addressed by composite support. In this research, a foundation pit project encountering existing power tunnel, air-raid shelter and old pile foundation in Zhengzhou city was taken as a case study of composite support form. Through analysis on geographical environment, engineering geological conditions, construction condition, and construction safety, a composite support plan integrating pile anchor and soil nailing structure is adopted. Monitoring results show that the composite support plan could well solve the problems posed by complex environment.

Key words: pile-anchor, soil-nailing, complex environment, composite support, monitoring and analysis