Application of new urban tunneling method in Baikoh tunnel excavation

This paper reports a new mountain tunneling method which yielded good results in Baikoh Tunnel construction. Since tunnels in urban areas, in many cases, are driven through soft ground with groundwater and in locations close to various utilities and structures, maintaining the structural stability of not only the tunnels but also such nearby existing structures is of utmost importance. In order to solve these problem, two methods have been developed: an auxiliary method to restrict displacements which consists of the special jet grouting for foot piles and the long steel pipe forepiling, and a boring method for groundwater drainage which does not cause adverse effects on tunnel construction. Using these methods in combination, the new mountain tunneling method is a useful means for constructing tunnels with shallow overburden in soft ground in urban areas. This method is called the new urban tunneling method. This method is cost-effective compared with other tunneling methods, especially for short urban tunnels with shallow overburden. Therefore, this method will be used in many future tunnel projects in urban areas subjects to various restrictions.