Abstract:

In order to avoid the occurrence of slabs and bedding collapse of the surrounding rock wedge of tunnel in slate, analysis of long section of bedding collapse of Banshan Tunnel with primary support is carried out; the mechanical properties and deformation characteristics of slate are studied; and the engineering characteristics of surrounding rock of the tunnel in slate and the geological structure type prone to collapse are summarized in terms of tunnel construction. The results show that: the traction increasing and continuous developing induced long section of bedding collapse occurs after instability of local weak points of surrounding rock and lining under the comprehensive influences of excavation blasting vibration, groundwater infiltration, gravity and large crosssection excavation induced free face when the angles between bedding structure rock or joint occurrence and tunnel are small and the tunnel crosses long unfavorable structural plane generated by intercuting between multigroup joints and form. Finally, an analysis method for the influence of the bedding structure, the joints and unfavorable structural plane of the tunnel excavation on the stability of surrounding rock is proposed. The measures to prevent the instability of the surrounding rock and the optimization of the support structure are put forward.

Key words: tunnel in slate, collapse, stability of surrounding rock, primary support