考虑围岩冻融损伤劣化效应的隧道长期稳定性研究

Long-Term Stability of Tunnels Considering the Degradation Effects of FreezeThaw Damage to Surrounding Rock

寒区隧道围岩受到冻融损伤劣化作用会对隧道长期稳定性造成不利影响。文章以鄂西北十房高速公路通省隧道片岩为例,通过室内冻融循环及压缩试验,得到单轴抗压强度与冻融循环次数之间的关系。根据掌子面围岩现场工程地质调查结果,并基于Hoek-Brown准则,估算出考虑冻融损伤劣化效应的岩体力学参数。然后采用FLAC3D对冻融循环条件下隧道的长期稳定性进行数值分析,分别得到0次、4次、8次、12次、16次、20次冻融循环条件下隧道衬砌位移场及应力场变化特征。结果表明,冻融循环作用下,隧道衬砌的变形及主应力均出现了不同程度的增大。与不考虑冻融损伤劣化作用相比,经过20次冻融循环作用后,衬砌的变形、最大主应力、最小主应力分别增大了1.3%、5.3%、1.5%。在支护方案选择及支护结构设计时,有必要考虑长期冻融循环作用下围岩力学特性损伤劣化对隧道稳定性的影响。

The surrounding rock of tunnels in cold regions suffers from freeze-thaw damage, which has adverse effects 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 Hock- Brown 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.