基于强度折减与刚度退化小净距隧道围岩稳定性研究

摘要

运用刚度退化的基本原理和方法，将泊松比ν和弹性模量E进行调整，提出变刚度隧道围岩强度折减法。以某小净距隧道为例，在只调整ν或E、同时调整ν和E、保持ν和E不变4种情况下，探讨了刚度退化对小净距隧道围岩稳定性的影响。结果表明：ν对隧道拱顶下沉、拱底沉降、最大主应力的影响要强于E；隧道两拱脚向内位移随折减系数的增大而增大，内侧拱脚向内位移比外侧拱脚的要大，且在刚度调整时拱脚位移要比保持刚度不变时大；等效塑性应变随折减系数的增大而增大，刚度调整导致等效塑性应变区减小，考虑刚度退化推迟了中夹岩柱塑性区贯通；将变刚度隧道围岩强度折减法应用于小净距隧道工程围岩稳定性评价，可依据安全系数的大小来评判设计的合理性，为支护参数及施工技术的选用提供参考。%Based on the basic principle and method of stiffness degradation, the Poisson's ratio ( v) and elastic modulus ( E) were adjusted, and a strength reduction method of surrounding rock in tunnel with variable stiffness was proposed.Taking a certain neighborhood tunnel as example, the influence of stiffness degradation on stability of surrounding rock in neighborhood tunnel was discussed under four conditions, such as only adjusting v or E, ad-justing v and E at the same time, and keeping the v and E constant.The results showed that the v has stronger in-fluence on arch settlement, dome settlement, and the maximum principal stress than E.The higher of the reduction factor, the inwards displacement of tunnel arch springing is greater.The displacement of inside arch springing is bigger than that of outside arch springing, and the displacement under the condition of stiffness adjustment is grea-ter than that keeping stiffness constant.The equivalent plastic strain increases with the growth of reduction factor. The stiffness adjustment leads to the decrease of equivalent plastic strain zone.Considering the stiffness degrada-tion, the transfixion of interval pillar plastic zone is delayed.When the strength reduction method of surrounding rock in tunnel with variable stiffness is used to stability evaluation of surrounding rock in neighborhood tunnel, the rationality of design can be judged according to the size of safety factor, so as to provide references for the selection of support parameters and construction technology.