高地应力千枚岩竖井结构受力研究分析

Research and analysis on the stress of high in-situ stress phyllite shaft structure

高地应力千枚岩竖井工程案例在国内较为少见,且目前竖井受力机理研究较少,也没有相应的设计规范,因此对其进行相应的结构受力研究分析来指导设计和施工是非常必要的。依托九绵高速某高地应力千枚岩竖井工程,借助大型有限差分数值软件FLAC3D构建工程区三维数值计算模型还原施工现场,模拟竖井施工全过程,通过分析围岩和竖井结构的位移和应力分布规律揭示高地应力软岩环境竖井受力机理。研究结果表明,与隧道相似,当竖井支护采用复合衬砌时,初期支护是主要的受力结构,二衬则作为安全储备,现有支护结构设计满足相应的强度和刚度要求。同时,受水平方向应力和竖直方向应力变化以及围岩的自承能力影响,不同深度衬砌结构受力呈现交替性变化,尽管地压随着埋深增加,但深层岩体环境下竖井结构受力不会随埋深的增加而无限增大。

The engineering cases of phyllite shaft with high ground stress are rare in China,and there are few studies on the stress mechanism of shaft at present,and there is no corresponding design specification.Therefore,it is necessary to study and analyze the corresponding structural stress to guide the design and construction.Based on a high-stress phyllite shaft project in Jiumian Expressway,this paper uses the large-scale finite difference numerical software FLAC3D to construct a three-dimensional numerical calculation model in the engineering area to restore the construction site,simulate the whole process of shaft construction,and reveal the stress mechanism of shaft in high-stress soft rock environment by analyzing the displacement and stress distribution of surrounding rock and shaft structure.The results show that,similar to the tunnel,when the shaft support adopts composite lining,the primary support is the main stress structure,and the secondary lining is used as a safety reserve.The existing support structure design meets the corresponding strength and stiffness requirements.At the same time,due to the change of horizontal and vertical stress and the self-bearing capacity of surrounding rock,the stress of lining structure at different depths changes alternately.Although the ground pressure increases with the buried depth,the stress of shaft structure in deep rock mass environment will not infinitely increase with the increase of burial depth.