Research on the tunneling methods in saturated loess

Three tunneling methods in the saturated loess for the project of water transferring from south to north of China are numerically tested and discussed with the introduced Austria software FINAL.The numercial results demonstrate:(1)Tunneling with NATM (CASE A) is possible and the 10+15 cm shotcrete immediately following the excavation is absolutely necessary ;(2)The interaction between two parallel tunneling caves with a distance of 2.5 times of tunnel diameter can be ignored ;(3)Instead of projecting concrete support to strengthen the surrounding loess of the tunnel,the traditional tunneling method(CASE B) in which the cast in site lining system is introduced to support the loess,is also possible for the local simple constructors,although the settelements of the tunnel crown reached 141 mm;(4)To reduce the tunnel settlements,another tunneling method(CASE C) with the precast lining system constructed before the tunnel excavation,is much better than CASE B with settlements of 8.5 mm, although the precast lining technics is much complex than CASE B.(5)All the feasible tunneling methods are based on the effective drainage of the water from the current level to the bottom of the tunnel.