Abstract: Taking the red sandstone deep excavation at Dongfanghong square subway station in Lanzhou city as the research object, the displacement of the retaining piles and the ground settlement around the foundation pit during the excavation of the foundation pit are monitored on site, and the measured results are analyzed. Using the MIDAS GTS numerical simulation software, three-dimensional models for deep excavation support and seepage analysis were established respectively, and the displacement of the deep foundation pit during the excavation process was calculated. The results show that the horizontal displacement of the pile increases first and then decreases with the depth of the pile body emplacement, and the overall shape is “)”. The settlement of the surface of the pit is basically stable after the completion of the excavation. The maximum displacement occurs before the setting of the third reinforced concrete cross braces, and the displacement has an obvious spatial effect.The trend of displacement change of the two simulation is basically the same, but the displacement result of the numerical analysis considering the seepage effect is o larger. The numerical analysis result of the seepage shows: the seepage effect caused by the imbalance of pore water pressure reaches the maximum after the excavation of the foundation pit is completed.

Key words: red sandstone deep foundation pit, supporting system, monitoring, displacement, simulation