Case Study on Design and Construction of a Urban Subway Tunnel in Karst Regions

The running tunnel section between Yanan Road Station and Zhongshan Road Station of the Guiyang Metro Line 1 is located in the Yunyan District of Guiyang Province, China. In this bid section, construction encountered numerous challenges: karst caves wholly or partially filled, fractured rock masses, substantial water inflow, many adjacent buildings, large numbers of municipal pipelines and under crossings of rivers all added to the construction risk and the complicated geological environment. Excavated by a roadheader using the bench method, it is a representative and successful construction project which provides not only a systematic approach for suitable design in karst regions but also appropriate support techniques. This paper is going to analyze the design of this urban subway tunnel section’s main structure based on Chinese national specifications and other successful projects’ experiences. Furthermore, comparison of different design methods in different countries and analysis of effective support techniques in karst areas will also be summarized.