The method proposed in this paper may provide a new effective approach to predict and control railway settlement as well as the ground volume loss due to the metro line excavation. This paper expands/explains further the relationship of surface settlement and ground volume loss based on the theory based on the work of Peck and Mair. The superposition principal is used when calculating the surface settlement caused by twin tunnel construction. The Guangzhou metro line-9 tunneling beneath Wu-Guang high-speed railway project is analyzed based on FLAC 3D numerical modeling. The results indicate that the surface maximum settlement induced by tunneling without ground modification agrees well with Mair's theory. Three ground modification methods are examined for the twin tunnel construction and our results indicate that ground modification methods will significantly decrease the railway maximum settlement as well as ground volume loss. To ensure the safety operation of the Wu-Guang high-speed railway during and after the construction of Guangzhou metro line-9, ground modification III can limit the rail settlement within the requirement, thus is recommended.