Abstract: This paper presents a case history of an investigation into the responses of the surrounding ground to the deep excavation of a metro station of Metro line 9 in the karst strata of Guangzhou, China. The metro station is 259.7 m long by 18.7 m wide by 15.81 m deep. The construction site mainly consists of two typical strata of the karst strata and sand layer. The karst strata, with poor mechanical properties and low self-stability, is a geological formation shaped by the dissolution of the carbon limestone. The thickness of sand layer is 0 15 m, which is of high hydraulic conductivity. During the field test, lateral deflections of the diaphragm wall and ground surface settlements were monitored. The test results show that the maximum lateral displacement of diaphragm wall is 12 mm and the maximum ground surface settlement is 10.1 mm. The monitoring results indicate that during construction there is minimal impact on the surroundings. Such field monitoring may allow for the formation of a database to guide the future engineering practices.

Key words: karst strata, deep excavation, lateral deflections, ground surface settlements