Abstract: The construction of Guangdong-Hong Kong-Macao Greater Bay Area is a major national development strategy of China. Shenzhen is a core city in the Greater Bay area. The karst in Shenzhen typically is found in Longgang and Pingshan districts. It has brought great challenges and threats to the underground exploitation and ground construction safety for the city. In this paper, borehole data are first collected from karst geotechnical investigation projects in Shenzhen and from the relevant literature. Based on the data, the spatial features of the karst in Shenzhen are statistically characterized considering strata and rock type, rock stratum depth and burial type, main corrosive indices of the groundwater, depth of the karst caves, thickness of the cave ceiling, cave height, fillings, karst line ratio, karst borehole ratio, and ground karst growth density. Results showed that the karst in Shenzhen is typically buried shallowly, but largely varies as of the spatial features. Statistically, on average the karst cave is about 20 m in depth, 2.5 m to   4 m in height, and mainly half filled with silty clays. On average the karst is about 15% for line ratio, 40% for borehole ratio, and over 300 caves per km² for the ground karst growth density. Overall, over 90% of the sites are ranked as high in karst development. It is also found that the above karst parameters follow lognormal as well as Weibull distributions. The ceiling thickness tends to be smaller as the rock depth increases for limestone stratum, whereas these two factors are statistically uncorrelated at a significance level of 0.05 for marble stratum. The cave height appears to be statistically independent or positively weakly correlated to rock depth, ceiling thickness, underground corrosive indices, and groundwater table. The findings from this paper provide valuable priori information to risk assessment on karst hazards in Shenzhen. 

Key words: karst geology, Shenzhen, spatial distribution characteristics, statistical analysis