Abstract: Contract No.2 of the Shen Zhen Airport Transport Services project involved a total of three (3) lift pump stations being proposed at the east, west and south side of the "Terminal 3", respectively. The construction required 8-10 meter deep excavations. Due to the large presence of the very soft silt and clay marine deposits, the excavations were sustained utilizing a piling system consisting of drilled shafts with monotubed churning piles in between. Additionally, a layer of steel pipe internal brace with C20 shotcrete was used to further maintain the stability. These multiple measures added challenges to the construction. For safety concerns, a monitoring program was conducted during each stage of the excavation and shoring installation, as well as during each individual construction period of the overall project. The monitoring efforts were focused on the deformation of the shoring system. Results based on the monitoring data showed that such a comprehensive supporting system may be suitable for deep excavations through marine deposits that are typically featured with very soft silt and clays.

Key words: Deep excavation, Safety Monitoring, Piling, Internal Brace