Research On Asymmetric Support Of Lilt Layered Rock Tunnel Excavation

The project is relied in this paper that the research on key technology of the formation mechanism,design and construction of steep obliquity and a small angle layered rock mass tunnel disaster. And the project is part of communication commission of Chongqing municipality. In connection with the common unreasonable support measures in the engineering, and based on the Yajiang tunnel engineering examples, the failure modes of the tilt layered rock mass tunnel are studied in the paper by investigation and research and numerical analysis, and the asymmetry support for the two failure modes of steep obliquity and a small angle layered rock mass is studied.The mainly conclusion is listed as following:(1)According to the occurrence condition and mechanism of the surrounding rock failure,it proposes four kinds of typical failure modes for the tunnel surrounding rock on the basis of the results of previous studies.At the same time,combined with engineering characteristics of tilt layered rock, it summarizes the corresponding failure modes according to the relationship of the chamber axis and the attitude of bed. It proposes the suitable cavern axis trend in the tunnel line selection process and the necessity of the asymmetric support combined with the classification of the failure modes.(2) Thin layer rock mass suitably uses software-specific joint model and the thin layer rock mass parameters obtain by displacement inversion analysis.Thick layer rock mass suitably uses "partition" directly creation given to different material parameters.(3) Through the analysis of the modeling, it shows significant asymmetry that antidip bending and breaking failure mode for steep obliquity and a small angle thin layered rock mass and dip side sliding and bulging failure mode for steep obliquity and a small angle thick layered rock mass.(4) In connection with the two failure modes of steep obliquity and a small angle layered rock mass,it sets a variety of conditions from the bolt length and angle in both directions,by comparative analysis it shows the parameters of the anchor has a great influence on the excation stress and displacement and is not monotonically relationship.While it exists a certain optimal range and proposes the corresponding optimization recommended value.