Abstract:

Tunneling in boulder strata may face great risks due to the difficulty in detection and treatment of boulders,i.e. ground hollow and ground subsidence. Therefore, it is worthwhile exploring ground subsidence pattern and associated mechanism when boulder encountering. By integrating the methodology for simulating irregularly shaped particles into PFC2D, the discrete element model of tunneling in boulder strata is established; and then parametric analysis is performed. The analytical results show that: (1) The location of ground subsidence can be estimated according to the position of boulder. (2) Inappropriately tunneling would induce ground collapse, especially when boulder diameter or buried depth of tunnel is beyond critical value. (3) In case of same particle size, tunnelinginduced ground displacement is hardly affected by shapes of boulders.

Key words: tunnel, shield tunneling, boulder, ground surface subsidence, discrete elements, disaster mechanism