考虑卸荷损伤的柱状节理岩体开挖特性研究

Excavation characteristic analysis of columnar jointed rock mass considering unloading damage

通过建立柱状节理岩体径向应力比与力学劣化系数的数学关系,获取柱状节理岩体卸荷损伤效应的定量表达式。结合FLAC^(3D)提出一种考虑卸荷损伤的柱状节理岩体开挖分析方法,实现岩体单元的力学参数在开挖过程中随实际应力状态得到动态调整。在此基础上开展柱状节理岩体试验洞的开挖特性分析。结果表明,考虑卸荷损伤的计算数据与实测数据基本吻合,试验洞围岩的位移、体积应变增量和塑性区均随开挖断面的逐步增加而增大,且呈边墙最大,底板次之,拱顶最小的分布规律。最后采用体积应变增量大于0.10%和塑性区作为岩体松弛的综合判别指标,其分析结果与钻孔声波测试数据相一致。

The quantitative expressions of unloading damage effect of columnar jointed rock mass are obtained via establishing a mathematical relationship between radial stress ratio and mechanical damage factor of columnar jointed rock mass. Then com- bined with FLAC3D , a new calculation method for excavation of columnar jointed rock mass is proposed, which takes unloading damage into account. By the proposed method, mechanical parameters of each element are dynamically adjusted according to its stress state in the process of excavation calculation. On this basis, the excavation characteristics of the experimental tunnel in co- lumnar jointed rock mass are analyzed. The calculation shows that the results that take into account of unloading damage match the measured data well. The displacement, volume strain increment and plastic zone of the experimental tunnel are gradually increasing with the increase of excavation section, presenting a distribution law that these variables are maximum at sidewall, medium at floor, and minimum at vault. Finally, volume strain increment larger than 0. 10% and plastic zone are both taken as discriminant index of relaxation of the columnar joints rock mass, and the corresponding analysis results are verified by the borehole acoustic test data.