三峡库区消落带溶蚀岩体劣化指标研究

Research on the deterioration index of karst rock mass in the fluctuatingwater level zone of Three Gorges Reservoir area

三峡库区水位消落带岩体劣化松动使得部分岸坡加速朝不稳定方向演化,给溶蚀岩体岸坡带来了工程灾变效应问题。本文提出了利用高程175 m附近区域的岩体替代未受蓄水影响的岩体的"比拟法",统计分析岩体劣化情况。定义、改进和统计了岩体劣化变量Det、岩体体积节理数增量ΔJ_(v)和地质强度指标变化值ΔGSI。通过对库区10个典型溶蚀岩体的劣化程度及地质强度指标的研究,提出溶蚀岩体劣化程度的量化指标,并建立其与地质强度指标的相关关系。岩体劣化造成了地质强度指标的下降;强烈劣化时,ΔGSI≤-4.0;ΔGSI与Det满足指数函数关系,ΔGSI和ΔJ_(v)满足线性负相关。提出了岩体劣化随时间演化的三种模式,其中两种模式最终会进入加速劣化状态;岩体结构经由两条路径演变为碎裂结构。同时,讨论了岩体劣化与岸坡亚稳定阶段的关系。研究成果为系统开展三峡库区峡谷段消落带岩体劣化程度勘查、监测和风险防控提供了新的方法。

The deterioration and loosening of rock mass in the water level fluctuation zone of the Three Gorges Reservoir area accelerates the instability of the bank slope causing serious concern for its potential to trigger an engineering catastrophe effect on the karst rock bank slope.In this study,an analogy method is proposed to quantitatively analyze the deterioration of rock mass by using the rock mass near the elevation of 175 m to replace the rock mass unaffected by impounding.The rock mass deterioration variable Det,the increment of rock mass volume joint numberΔJ_(v) and the Variation of geological strength indexΔGSI is defined,improved and counted.The deterioration index of 10 typical karst rock masses in the Three Gorges Reservoir area for 12 years since the experimental impoundment of 175 m above sea level in 2008,and its influence on the geological strength index are quantitatively analyzed.Different deterioration degrees can be corresponding to different quantitative index ranges.For example,when Det≥0.05,ΔJOv≥0.65 orΔJ_(v)≥1,the deterioration degree of rock mass is categorized as serious.The deterioration of rock mass results in the decrease of GSI;when the rock mass is seriously deteriorated,ΔGSI≤-4.0;-ΔGSI and Det meet the exponential function relationship,ΔGSI andΔJ_(v) satisfies the linear negative correlation.The evolution of rock mass deterioration with time may have three development modes,two of which will eventually enter the state of accelerated deterioration,and the rock mass structure will evolve into cataclastic structure through two paths.Meanwhile,the relationship between the deterioration of rock mass and the meta-instability stage is discussed.This research provides a new method for the systematic exploration,monitoring and risk control of the deterioration degree of rock mass in the water level fluctuation zone of the Three Gorges Reservoir area.