一概述拱轴线的选择主要须看工程的目的而定,单从力学观点而言最好的拱轴线当然是和拱的压力曲线相重合,对于超静定拱则使其拱轴线尽可能地接近压力曲线,但这样作往往使施工复杂化,因之有时采用圆拱,惟其受力情况却不够理想。故应综合考虑受力和施工条件,不宜偏废。铁路隧道衬砌及拱架主要承受恒载土压力,目前采用多心圆组成的拱轴,使之较为接近抛物线,而在施工上仍不失为圆拱体系。由于一般书籍中尚未对这种 An overview of the choice of arch axis mainly depends on the purpose of the project. From a mechanistic point of view, the best arch axis of course coincides with the pressure curve of the arch, and the arch axis is as close as possible to the statically indeterminate arch Pressure curves, however, tend to complicate construction, which sometimes results in circular arches, but their forces are less than ideal. It should be combined stress and construction conditions, should not be partial waste. The lining of railway tunnels and arch frames are mainly subjected to earth pressure under constant load. At present, the arch axis composed of multiple concentric circles is used to make it closer to the parabola while the arch construction remains a dome-shaped system. As the general book has not been on this