Construction of Twin Large Cross-section Mined Tunnels Adjacent to Existing Metro Line

It has great construction difficulties and great construction risks to build a twin-tube large cross-section mined tunnel underneath the existing Metro station.Furthermore,in such cases both the existing Metro structure and the Metro operation have strict requirements on the deformation control.Therefore,the success of the tunnel construction depends on the proper construction technology and proper assistant construction methods adopted during construction.The central mined section of a Metro station,which takes the form of a twin-tube tunnel,is built underneath an existing Metro station.During construction,full-face deep-hole pre-grouting is conducted for the purpose of advance reinforcement,the existing Metro works are monitored to perform information-aided construction and proper construction sequence is adopted,which guarantees safe and rapid construction.The project case can provide reference for similar works in the future.