Comprehensive analysis of deep foundation pits for underground space in Guangzhou

The cut-cast piles with interior support,prestressed anchor and soil nail were combined to form the optimized comprehensive retaining structure.Owing to large difference of foundation pit depth in different zones,neighbouring metro line No.1 and No.2,existing wind wells and underground lane,etc.,the monitoring project was prepared in detail to make construction of foundation pits be informationized,thus the full data were obtained.Based on the analysis of the above data,several laws were summarized.It was shown that the measured active soil pressures were smaller than the theoretical values and diminished with time,the measured pore water pressure decreased with the time and increased with the depth of soil,the combinative effects of cap girder and supporting structure were obvious which diminished the displacement of foundation pits,and the measured axial force of the anchor and interior steel beam were far less than the design force,indicating that the design safety factor of the foundation pit was too large to be economical.