为改善上部支护结构受力条件而设置在隧道底部的反向拱形结构，是隧道结构的主要组成部分之一。通俗解释为向上仰的拱。
The loading ratio is 40% and 60% respectively for the initial supports and secondary linings. The stress of the secondary lining is pressure stress,which is the largest on the upper arch loin and is smaller on the inverted arch.
在标准断面地铁隧道中左、右线墙脚位置初期支护与围岩之间接触压力较大,表明这两位置承受了大部分垂直压力;初期支护与二次衬砌承受的荷载比例为40%和60%;二次衬砌混凝土基本受压,拱腰及以上位置应力较大,仰拱处应力较小。
参考来源 - 黄土地区浅埋暗挖地铁隧道衬砌受力分析·2,447,543篇论文数据，部分数据来源于NoteExpress
研究结果表明：既有隧道仰拱迎爆侧附近应力最大；
The study results indicate that the stress on the inverts toward the bla. sting side is the largest ;
结果表明：突水位置发生在仰拱或墙脚位置时，对衬砌结构的受力影响显著；
The results show that mechanical behavior of lining structure change evidently when suddenly effluent water happen at inverted arch or foot of wall.
最后提出了最佳的黄土仰拱一次性开挖长度，并应用于黄土连拱隧道的施工。
According to the final results of analysis, a reasonable excavation length of inverted arch in one step was put forward and applied to the construction of multi-arch tunnel in loess.
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