In some tunnel supporting practice, the method is sometimes Used that the higher bearing capacity of a tunnel support system is tried to obtain by the more steel arch support. In order to eliminated such unreasonable method, the cause that the steel arch frame for tunnel supporting fails and its failure form are analyzed according to the engineering examples. The failure of the steel arch frame takes placernin the weak axis plane because of its smaller lateral anti-bending rigidity. From the analysis, it is pointed that the bearing capacity of the tunnel supporting system will be made higher if the restrain to steel arch support is enhanced by the lateral connects between them to increase the anti-bending rigidity of the support in the weak axis plane. It is also shown that the method stated in the paper is effective which is simple in structure, and easy in construction. By using this method, the full use of load-bearing capacity of an arch support can be made and the best economic benefit from engineering can be come true.%针对隧道支护使用钢拱架存在的靠增加钢拱架数量提高支护系统承载力的做法,结合工程实例分析隧道支护中钢拱架失稳破坏的形式及原因—钢拱架因为侧向刚度低而发生弱轴平面内的扭曲失稳.指出采取增设钢拱架之间的适当连接,增加其相互约束,可提高钢拱架弱轴平面的抗弯刚度.这是隧道支护设计与施工中提高钢拱架支护系统承载能力的简单易行的有效方法.这样做有利于充分发挥钢拱架的承载能力,获得良好的工程经济效益.
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