Abstract:

The rule of the timedependent strains of the tunnels in wet subsidence loess ground is revealed by means of monitoring of the wet subsidence loess ground. A kind of 3bench construction method is developed on basis of the rule of the timedependent strains. The deformation behavior of the tunnels constructed by 3bench excavation method is summarized as follows: After top heading excavation, the tunnel stability can maintain 7 days before settlement occurs; During the excavation of the second bench, the controlled settlement of the primary reinforcement structure of the top heading is allowed, which is a stress releasing process; The settlement deformation caused by the third bench excavation is similar to that caused by the second bench excavation; When the ring is closed after invert installation, the ground tends to be stable. 3bench construction is executed under the guidance of the above deformation rule in the construction of LanzhouChongqing railway and satisfactory effects have been achieved.

Key words: wet subsidence loess, tunnel, 3 bench method, time dependent stress, rule