Abstract: With the urban development, the metro alignment selections have encountered an increasing difficulty in avoiding building and other structures and well as facilities on the ground. The chance of the metro tunnels under crossing the existing building structures are increasingly higher. At the same time, associated tunnel construction problems have to be dealt with. This paper presents a case history of the construction of the metro tunnel under crossing the existing expressway. This project is located between the Antuoshan Station and Nongling Station for the second bid package of the proposed Shenzhen Metro No. 7 Line. The subsurface conditions along the tunnel alignment is complicated with soft overburden soil underlying with the hard rock mass. The tunnel excavation supporting techniques considered the characteristics of the mining excavation method as well as the current code regarding the tunnel undercrossing existing structures. The safe operation of the existing Guangzhou-Shenzhen Expressway is ensured by using the surrounding rock mass grouting and deformation control technique.

Key words: Metro Tunnel, Under Crossing Projects, Expressway, Construction Technique, Supporting Measures