关键词: 小净距隧道, 大断面隧道, 施工特性, 净距优化, 屈服接近度

Abstract: The closely spaced tunnels with large cross － section have large excavation span，low flat rates and significant effect of two holes. The mechanical behavior and stress mechanism of closely spaced tunnels with large cross-section are more complicated than those of normal tunnels in construction. Based on the engineering project of Chaoyangsi tunnel which underpasses the Yu-Ling expressway，the deformation characteristics of supporting structure and the rock surrounding tunnel are obtained. Then the concept of close proximity to yielding degree is adopted to make an evaluation of the mechanical characteristics in supporting structure and the rock surrounding tunnel. Finally，the changing rule of the closely spaced tunnels with large cross-section during excavating is discussed. The research results show that the reasonable distance between two tunnels should be 1D ～ 1. 2D. Their deformation and mechanical characteristics of the surrounding rock in the naked tunnels are obtained by the strength reduction method. These calculated results are in accordance with the foregoing results. So a new reasonable distance of the closely spaced tunnels with large cross-section is proposed. The research findings would provide some references for the design and construction of similar tunnels.

Key words: closely spaced tunnel, tunnel with large cross-section, construction characteristics, distance optimization; close proximity to yielding degree