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金沙江某水电站引水洞出口边坡为千枚岩类软岩边坡,其地质条件复杂、结构面发育。由于边坡特殊的岩体结构及其重要性,其稳定发展趋势便成为工程技术人员关心的主要问题。本文在地质调查的基础上,分析了边坡岩体结构特征,建立边坡地质模型,并采用3D-FLAC模拟边坡-洞室组合开挖后的应力、变形分布特征及破坏区范围。结果表明,洞室开挖主要影响6倍洞径范围内围岩应力分布状态,对边坡整体稳定性影响不大;但边坡开挖会使得坡面产生不同程度的受拉区域,对边坡稳定性影响较大。另外,在此基础上选取典型的边坡进行稳定性分析,分析表明,天然状态下,边坡开挖后局部岩体稳定性较差,存在块体失稳的可能,但整体稳定性较好;暴雨、地震条件下,边坡稳定性较差,边坡顶部岩土体有沿结晶灰岩与千枚岩的地层分界面发生失稳的可能。
The outlet side of the diversion tunnel of a Jinsha River hydropower station is a soft rock slope of phyllite type. Its geological conditions are complex and its structural surface is developed. Due to the special rock mass slope structure and its importance, its stable development trend has become a major concern of engineering and technical personnel. Based on the geological survey, this paper analyzes the structural features of slope rock mass, establishes the slope geological model, and uses 3D-FLAC to simulate the stress and deformation distribution and the scope of failure zone after the slope-cave combination excavation. The results show that the excavation of the cavern mainly affects the stress distribution of the surrounding rock within the range of 6 times of the hole diameter, and has little effect on the overall stability of the slope. However, the excavation of the slope will cause different degrees of tension zone on the slope, Slope stability is more influential. In addition, based on this, the typical slope is selected for stability analysis. The analysis shows that under natural conditions, the stability of local rock mass after slope excavation is poor with the possibility of block instability, but the overall stability is better Under the condition of heavy rain and earthquake, the slope stability is poor. The rock mass at the top of the slope is likely to instability along the stratigraphic interface of crystalline limestone and phyllite.