Abstract: The urban traffic congestion is becoming more and more serious, and the rail transit has become an important development trend to relieve the pressure of the urban traffic. In recent years, a series of shallow buried continuous karst rock cavities have been encountered in the urban subway construction in southern Jiangsu Province. Based on the summarizing of a large amount of geological exploration data, it is found that there are four types of shallow buried continuous karst rock cavities. Combined with the development characteristics of the continuous karst rock cavities and the buried depth range of the subway shielded tunnel in southern Jiangsu Province, the mechanical characteristics of the tunnel excavation and the karst rock cavity stability are analyzed by the numerical simulation method. It is found that with the excavation of the tunnel, the displacement of the vault and the arch bottom of the tunnel increases obviously, and the slope of the displacement curve gradually becomes steep, which indicates that the displacement release rate will increase by the excavation of the karst rock cavities. The deformation caused by the development of the continuous karst rock cavity at the bottom of the tunnel is far greater than that caused by the development of the karst rock cavity at the top of the tunnel; the deformation is the largest when the type IV continuous karst rock cavity is developed at the bottom of the tunnel; when the karst rock cavity is developed at the top of the tunnel, the influence of type III continuous karst rock cavity on the deformation of the tunnel and surrounding rock mass is the greatest; when the karst rock cavity is located at the bottom of the tunnel, the maximum value of the maximum principal stress appears in the tunnel shoulder and waist, which is an asymmetric distribution; when the karst rock cavity is located at the bottom of the tunnel, the maximum value of the principal stress appears at the top of the tunnel, and the stress is concentrated and distributed symmetrically. At the same time, the targeted mitigation measures are proposed for the four types of continuous karst rock cavities in southern Jiangsu Province. The research results can provide the necessary technical support for the tunnel construction in the shallow buried continuous karst rock cavity area, and have a direct significance for the scientific and the quantitative design and the construction of the tunnel.

Key words: Southern Jiangsu Province, Shallow Buried Continuous Karst Rock Cavities, Subway Tunnels, Surrounding Rock Mass Stability, Mechanical Response, Numerical Simulation