三峡库区碳酸岩岸坡消落带岩体劣化特性

Rock Mass Deterioration in the Hydro-Fluctuation Belt of Carbonate Riverside in the Three Gorges Reservoir of the Yangtze River,China

岸坡消落带是库水位升降形成的干湿交替作用区域。与岸坡其他地段相比,岸坡消落带水岩作用强烈,不断改造库岸的形貌特征,影响岸坡的整体或局部稳定性。消落带岩体劣化研究在劣化特征、劣化分类,以及劣化评价方法、指标研究方面存在不足。本文以三峡库区秭归和巴东干(支)流碳酸岩岸坡消落带岩体为研究对象,采取调(勘)查与试验、“比拟法”等综合分析方法,对碳酸岩消落区岩体劣化特征、过程及机制进行了系统研究,得到以下结论。(1)基于岸坡消落区岩体劣化的宏观效应,可划分为4种劣化类型;库水和地下水联动作用影响消落区岩体劣化的范围,沿深度方向呈现逐渐减弱的趋势,根据岩体劣化程度,可划分为3个区。(2)岩体各类结构面劣化最为严重,尤其是裂隙结构面,控制着岩体劣化的主要特征和类型。(3)库水作用方式和水的溶蚀性强弱影响岩体劣化的进展和演化发展模式。(4)根据库水与岸坡地下水联动程度,结合工程应用,提出了碳酸岩岸坡消落带岩体劣化的评价指标和评价方法。研究成果对消落带岩体劣化评价及岸坡稳定性演化评价具有一定的参考意义。

Hydro-fluctuation belt is a distinct area with alternating dry-wet action formed by ceaseless shifting of rise and fall of reservoir water table.Compared with other parts on a shore slope,strong water-rock interaction develops on a hydro-fluctuation belt,consequently altering geomorphology of the shore slope,even undermining its stability to some extent.Although great efforts were made to investigate the roles of hydro-fluctuation belt in riverside stability,there were still insufficient knowledge of rock mass deterioration characteristics,degradation classification and assessment,and deterioration indicators.In this study,it investigated carbonate rock masses suffered erosion from hydro-fluctuation effect in the reach of Zhigui and Badong of the Three Gorges reservoir of the Yangtze River,China.Field survey,indoor experiments,analogy method,etc.were used to reveal the characteristics,process and mechanism of rock mass deterioration.(1)Based on the macroscopic erosion effect to rock mass in the hydro-fluctuation belt of shore slope,it could categorize four levels of deteriorations.Joint water-rock interaction inflicted by reservoir water and groundwater controlled degradable extents of carbonate rock mass,but it weakened gradually along the depth direction;therefore,rock mass could be divided into three zones in terms of the property variation.(2)The most serious deterioration took place along various discontinuity planes in rock mass,among which fracture planes played crucial roles in governing primary deterioration characteristics and types of rock mass.(3)Erosion behaviors of reservoir water associated with erodibility jointly affected deterioration phases of rock mass as well as development pattern.(4)Based on interaction levels between reservoir water and groundwater in riversides,this study introduced deterioration indicators and a proper approach to evaluating of carbonate rock mass deterioration in hydro-fluctuation belt,and justified by engineering applications.The research has reference significance for evaluation of rock mass deterioration in hydro-fluctuation belt.