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Long-Term Stability of Tunnels Considering the Degradation Effects of FreezeThaw Damage to Surrounding Rock
(1 School of Resource and Civil Engineering, Wuhan Institute of Technology, Wuhan 430073; 2 Faculty of Engineering, China University of Geosciences, Wuhan 430074)
Abstract The surrounding rock of tunnels in cold regions suffers from freeze-thaw damage, which has adverse ef? fects on the long-term stability of the tunnels. Based on the Tongsheng Tunnel of the Shiyan-Fangxian Expressway in the north of Hubei province, the relationship between the uniaxial compressive strength and the freeze-thaw cycle times of schist is obtained by an indoor freeze-thaw cycle test and uniaxial compression tests. Mechanical parameters of the rock mass are estimated considering the deterioration effects of freeze-thaw damage based on the HoekBrown criterion in light of the field geological survey of the rock surrounding the work face. FLAC3D was used to perform a numerical analysis on the long-term stability of tunnels under the conditions of freeze-thaw cycles, and the characteristics of the displacement field and stress field variations of the tunnel under freeze-thaw cycles times of 0, 4, 8, 12, 16 and 20 were obtained. The results show that tunnel lining deformation and principal stress both increase to different degrees under the effects of the freeze-thaw cycle. Compared with the situation, which doesn′t consider the effect of freeze-thaw deterioration damage, the deformation, maximum principal stress and minimum principal stress of the lining increase 1.3%, 5.3% and 1.5%, respectively, after 20 freeze-thaw cycles. Thus, it is necessary to consider the influence of degradation of the mechanical properties of surrounding rock on tunnel stability under the long-term effects of freeze-thaw cycles regarding support program selection and design for the support structure.
Abstract：
The surrounding rock of tunnels in cold regions suffers from freeze-thaw damage, which has adverse ef? fects on the long-term stability of the tunnels. Based on the Tongsheng Tunnel of the Shiyan-Fangxian Expressway in the north of Hubei province, the relationship between the uniaxial compressive strength and the freeze-thaw cycle times of schist is obtained by an indoor freeze-thaw cycle test and uniaxial compression tests. Mechanical parameters of the rock mass are estimated considering the deterioration effects of freeze-thaw damage based on the HoekBrown criterion in light of the field geological survey of the rock surrounding the work face. FLAC3D was used to perform a numerical analysis on the long-term stability of tunnels under the conditions of freeze-thaw cycles, and the characteristics of the displacement field and stress field variations of the tunnel under freeze-thaw cycles times of 0, 4, 8, 12, 16 and 20 were obtained. The results show that tunnel lining deformation and principal stress both increase to different degrees under the effects of the freeze-thaw cycle. Compared with the situation, which doesn′t consider the effect of freeze-thaw deterioration damage, the deformation, maximum principal stress and minimum principal stress of the lining increase 1.3%, 5.3% and 1.5%, respectively, after 20 freeze-thaw cycles. Thus, it is necessary to consider the influence of degradation of the mechanical properties of surrounding rock on tunnel stability under the long-term effects of freeze-thaw cycles regarding support program selection and design for the support structure.
.Long-Term Stability of Tunnels Considering the Degradation Effects of FreezeThaw Damage to Surrounding Rock[J] MODERN TUNNELLING TECHNOLOGY, 2017,V54(2): 68-72
2017, Vol. 54 