隧道初支与二衬间接触压力统计分析

复合式衬砌一般由初期支护和二次衬砌共同组成,二者相互作用关系是隧道工程中的研究热点,本文通过对43座隧道79个监测断面初支与二衬接触压力的统计分析,探讨了接触压力的总体分布特征及其与围岩等级、隧道埋深、跨度等因素的关系,研究了二衬荷载分担比在洞周的分布规律,讨论了接触压力随时间的变化规律及其空间分布特征。结果表明:初支与二衬接触压力值分布在10~200 kPa之间;接触压力及其离散程度随隧道埋深增大而增大,Ⅴ级围岩增大趋势比Ⅳ级围岩更明显;二衬荷载分担比集中在0~20%范围内;接触压力有明显的时间效应,随时间的变化表现为快速增长至峰值之后减小,进而缓慢增大趋于稳定,稳定所需时间在二衬浇筑后30 d左右;接触压力空间分布规律为拱顶→拱肩→拱腰→拱墙增大,拱墙→拱脚→拱底减小。研究结论可为隧道结构受力分析与优化提供参考。

Statistical Analysis of the Contact Pressure between the Primary Support and the Secondary Lining of Tunnel

The composite lining widely used in tunnel and underground engineering is generally composed of the primary support and the secondary lining, and the interaction between them is a research hotspot. Since it is very important and difficult to determine the contact pressure and the load sharing ratio between the primary support and the secondary lining, the statistical analysis of contact pressure between the primary support and the secondary lining obtained from 79 monitoring sections of 43 railway, highway and metro tunnels in China were carried out to investigate the overall distribution characteristics of contact pressure between the primary support and the secondary lining of tunnels and its relationship with surrounding rock grade, tunnel buried depth and the tunnel span etc. The distribution relationship of the load-sharing ratio of the secondary lining at various locations around the tunnel was studied. The change patterns of contact pressure with time and the spatial distribution characteristics were discussed. The results indicated that the contact pressure between the primary support and the secondary lining was basically distributed between 10 kPa and 200 kPa; the contact pressure between the primary support and the secondary lining and its dispersion increased with the increase of the tunnel depth, and the increasing trend of grade Ⅴ surrounding rock was more obvious than that of grade Ⅳ surrounding rock; the load sharing ratio of the secondary lining was within the range of 0~20%; the obvious time effect showed that with the change of time, it first increased rapidly to the peak value, then decreased rapidly, then increased slowly, and finally tended to be stable gradually. The time required for stability is generally about 30 days after the secondary lining concrete is poured; the spatial distribution rule of contact pressure is arch crown → arch shoulder → arch waist → arch wall increases gradually, arch wall → arch foot → invert arch decreases gradually. The research and the conclusions can provide a reference for the stress analysis and design optimization of tunnel structures.