Abstract: With the rapid development of urban construction, the excavations of high-rise buildings and metro stations are becoming increasingly deeper. Consequently, the excavation will lead to a very large basal heave deformation and a very large center post upheaval, which will cause the redistribution of the internal forces in the supporting structures, and simultaneously influence the surrounding buildings and underground pipes. Through statistical analysis of the measured data of the center post upheaval in metro station excavations of Tianjin metro line 5 and line 6, the following conclusions can be derived. The maximum value of center post upheavals is approximately 1.2 times of the average value in an excavation. The average values of center post upheavals in excavations of two-level (15-18 m deep) and three-level (24-26 m deep) metro stations range from 5 to 40 mm and 30 to 55 mm, respectively. The ratios of center post upheavals to depth of excavations are less than 0.25%. The center post upheaval decreases as the embedded ratio of the diaphragm wall increase, and increases as the deformation of the diaphragm wall becomes larger. Therefore, controlling the deformation of the retaining structure would be an effective way to reduce the center post upheaval. The average value of center post upheavals in the excavations using the top-down construction method is much smaller than that using the bottom-up construction method, which ranges from 3 mm to 10 mm, equaling to 1/10-1/3 of that using the bottom-up construction method. Through fuzzy statistics, the normal center post upheaval in metro station excavations with depth of 15 to 18 m ranges from 15 mm to 25 mm.

Key words: metro station excavation, upheaval of center post, measured data, top-down construction method, fuzzy statistics