采用ANSYS软件讨论无衬砌黄土隧洞安全系数

Exploring the Safety Factors of Unlined Loess Tunnel by ANSYS

通过分析黄土隧洞的破坏机理,借鉴有限元强度折减法的思想,在黄土隧洞稳定性分析中提出剪切安全系数与拉裂安全系数的概念。通过不断折减土体的抗剪强度参数,使黄土隧洞围岩塑性区不断扩展,直至塑性应变或位移发生突变时,即表明隧洞发生剪切破坏,此时的折减系数即为剪切安全系数。通过不断折减土体的抗拉强度参数,使黄土隧洞内临空面处(不包括底部临空面)围岩出现第一个单元拉裂破坏时,即表明隧洞发生拉裂破坏,此时的折减系数即为拉裂安全系数。为了保证黄土隧洞的整体安全性,在隧洞设计中必须给出上述两种不同的设计安全系数值。

Through analyzing the failure mechanism of loess tunnel, applying the idea of strength reduction finite element method, the definition of shear safety factor and tensile safety factor can be got during the stability analysis of loess tunnel. With the c - tamp reduction, the plastic zones of rock mass keep expanding. When the value of the nodal displacement or plastic strain has a big jump compared with that before failure, this means that the loess tunnel rea- ches shear failure, the reduction factor is just the shear safety factor. With the tensile reduction, loess tunnel reaches tensile failure when the first element of rock mass around loess tunnel free face fails in tension except for the bottom free face. The reduction factor is just the tensile safety factor. In order to ensure the safety of loess tunnel, two kinds of safety factors should be calculated when it is designed.