特大断面连拱隧道中墙偏压机制及施工影响分析

 中墙作为连拱隧道的主要承载结构，自身的稳定性直接影响着隧道工程整体的稳定性，是连拱隧道设计和施工的重点。中墙失稳的主要力学原因是中墙受力不均而产生偏压失稳，因此，控制中墙稳定的关键是控制中墙偏压及其偏压程度。中墙偏压的出现源于隧道工程自身的地层偏压和非对称式施工产生的施工偏压，根据中墙受力状态可以确定地层偏压、施工偏压下中墙偏压的条件及偏压发生部位；利用有限元计算方法对地层偏压、施工偏压条件下不同施工工序进行计算，分析不同工序对中墙偏压的影响；根据得到的规律对施工工序进行优化分析；最后，给出双向八车道连拱隧道的工程实例。

ANALYSIS OF MECHANISM OF MID-PARTITION ECCENTRIC COMPRESSION AND CONSTRUCTION EFFECT ON SUPER-LARGE SECTION MULTI-ARCH TUNNEL

The mid-partition of a multiple-arch tunnel is very important and attracts much attention in tunnel designing and constructing as it is a main support structure of tunnel，and affects the integrated stability of tunnel engineering. The mid-partition destabilization is eccentric compression instability in which the mechanics reason is unevenly stressing，so，controlling eccentric compression of the mid-partition control is critical to the control stability of mid-partition. The geological eccentric compression of tunnel engineering and the construction eccentric compression which come from asymmetric construction are the basic cause，and according to stress state of mid-partition，the condition and the position of eccentric compression from the geological eccentric compression and the construction eccentric compression are determined. The effects of construction procedure under the geological eccentric compression and the construction eccentric compression are analyzed through the computation simulation for different construction procedures of multi-arch tunnel by the finite element method. Optimum analysis for construction scheme according to the obtained law is completed. At last，the example of the multiple-arch tunnel with eight traffic lanes is given.