【摘要】 龙蟠为拟建虎跳峡水电站的比选坝址之一,其右岸斜坡发育大规模的松动变形岩体。结合最新钻孔、平硐等工程地质勘察和CSAMT法物探资料,在分析区域地质环境效应和剖析斜坡岩体变形特征的基础上,否定了该斜坡为“古滑坡”的定论,并基于其特殊的斜坡地质结构和特殊的地质孕育环境提出了斜坡岩体变形的地质力学机制:断裂活动的构造挤压作用造成了近岸岩体的深层破碎;区域构造应力场的转化使岩体呈先压后拉的受力效应,地壳抬升、河流下切使深部岩体卸荷–拉裂和斜坡后部反倾的软硬相间地层发生了弯曲–蠕变和局部倾倒变形;以坡脚深厚覆盖层压缩和塑性变形为主因,斜坡后期主要表现为岩体的局部错滑、扩容等自适应性结构调整和追踪顺坡向结构面的累进性破坏变形,但尚未形成贯通性剪切变形带。龙蟠斜坡的地质结构和变形模式在虎跳峡工程区具有代表性,因此,该结论不仅为虎跳峡电站龙蟠坝址抉择提供了理论依据,也为分析库区斜坡成因演化和评价其稳定性奠定了基础。更多还原

【Abstract】 Tiger Leaping Gorge hydropower station is a large project to be build on Jinsha River in southwest China.Longpan is one of the comparative dam addresses,but large-scale deviant rock mass was discovered on the right bank slope,where an old landslide once happened,so that Longpan dam was given up.In the latest studies,based on systematic field survey,especially through CSAMT exploration and comprehensive analyses of deformation characters of the rocks,it was proven not to be an old landslide but a deforming slope.The geologic structure of Longpan slope is very specific,and the dip direction of the stratums is opposite to slope.The sandstone stratums and slate stratums intercross alternately,and deep-seated stratums are dominate sandstone rock which are thick and hard,with large inclination angle.But the top of the slope stratums are with thin and small inclination,and the hard and soft rock-formations intercross mutually.Lake sediments at the foot of the slope account for the particular geologic structures.The results show the geomechanical deformation patterns are as follows:(1) the activities of the fractures induce deeply fragmentized phenomenon;(2) lithosphere raising,valley cutting downwards and transforming of the regional tectonic stress-field cause unloading rebound and cracking of lower rock mass;and(3) the main deformation pattern of top stratum was bend-creeping.By reason of the compressibility and plastic flowing of lake sediment and superficial stratum at the foot of the slope,rock mass is adjusting to the structure by the way of stagger-sliding and lateral expanding locally,but there is no weak zone of penetrating the slope.The mode can be named Longpan-pattern,which is universal in Tiger Leaping Gorge Reach in Jinsha River,and it is significant to choose the dam address and analyze the stability of reservoir banks.更多还原