Abstract:

The mined tunnel of EndingHuoqiying section of line 10 of Beijing Metro crosses underneath 2 existing cable tunnels. The features of the convergence of the primary support of the mined Metro tunnel located in sandcobble ground are studied by means of dynamic simulation of the construction of the mined tunnel and comparison between the measured convergence and the simulation results. The study results show that： 1）The maximum ground surface settlement is 646 mm, the maximum convergence of the primary support of the Metro tunnel obtained by numerical simulation is 710 mm, and the maximum convergence measured is 6.77 mm. The deformation of the primary support of the Metro tunnel is controlled within a safe and rational range; 2) The technical countermeasures adopted, i.e., reducing the spacing of the steel ribs and performing fullface grouting, have good effect in improving the stability of the primary support and surrounding rock of the Metro tunnel; 3)The right tunnel tube that is excavated first causes serious damage to the surrounding environment, while the left tunnel tube that is excavated later causes less damage to the surrounding environment; 4)Technical countermeasures, such as primary support with higher strength and fullface grouting, should be designed for the tunnel tube that is excavated first.

Key words: tunneling under shallow cover, numerical simulation, tunneling underneath existing cable tunnel, primary support convergence, cable tunnel