Abstract:

The untimely primary support closure and overlarge of advancing distance are often encountered during soft rock tunnel excavation by bench method. As a result, onetime bench excavation method (with inverted arch) is proposed for some tunnels on Menghua heavy haul railway; the construction flowcharts of threebench method (with inverted arch) and twobench method (with inverted arch) are introduced; the construction parameters such as bench height and bench length are put forward by comprehensively analyzing the structural mechanism, deformation response, construction convenience and arrangement of equipments; the construction organization, technical key points and applicable effect of the onetime excavation method of bench and inverted arch in Duanjiaping Tunnel and Zhongtiaoshan Tunnel are presented. Finally, the construction characteristics of the abovementioned technology are summarized, and the technology is prospectively popularized.

Key words: soft rock tunnel, bench method, onetime excavation, inverted arch, bench height, bench length