Abstract:

Due to the effect of ground stress, problems such as deformation, collapse and accident may occur after tunnel excavation, and secondary enlarging excavation may be needed in extreme cases. In the paper, the deformation allowance, advance reinforcement, weak blasting, comprehensive information method, support measures and key construction points for large crosssection tunnels in soft rocks are summarized and studied on basis of typical work cases, so as to guarantee the construction safety of soft rock tunnels and to avoid secondary enlarging excavation. The study shows that: 1) In the determination of the deformation allowance, the maximum ground stress and the physical properties of different soft rocks should be taken into full consideration. 2) Large crosssection excavation can be carried out after effective advance reinforcement of the top heading. 3) The deformation can be brought under effective control by optimizing the supporting parameters on basic of ground stress and deformation properties.

Key words: tunnel, soft surrounding rock, ground stress, deformation control, special support