雅砻江中游某滑坡群形成条件及工程影响分析

Formation Condition and Project Influence of Landslide Group in the Middle Reach of Yalong River

某大型水电站位于雅砻江中游,在调查期间发现短短30 km河段内发育10个特大型-巨型古滑坡体,滑坡体规模巨大,方量4 000×104~12 000×104m3不等,沿江长度达数千米,最大深度达200 m以上,且70%发育于河流右岸,滑坡群对拟建的工程影响巨大且不可回避。通过因素分析获知：滑坡群在此处的发育有其必然性,其与河谷形态、陡峻的深切峡谷地貌、软硬相间的岩层结构、分区性前波大断裂的切割等因素密切相关,其形成机制可归纳为滑移-拉裂型、滑移-弯曲型（溃屈）、弯曲-拉裂型（倾倒）3大类。最后结合滑坡的稳定性和拟选坝址位置对工程影响进行评价,得出如下结论：工程区滑坡数量众多,与坝址相间分布,在上、中、下坝址间选择上坝址对工程安全性最为有利,尤其是避开了下游有复活迹象的3个特大型滑坡,最后提出相应工程建议,可对工程建设起一定参考。

The investigated large hydropower station is located in the middle reach of Yalong River.During the investigation,it is found that there are 10 extra-large and huge ancient landslides developed in a short river section of 30 km.Survey shows that the landslide group has enormous and unavoidable impact on the proposed project with huge landslide volume of 4 000×104 m3 to 12 000 ×104 m3 and a total length of several kilometers along the river,as well as a maximum depth of over 200 m,and 70% of the landslide developing at the right bank.In this paper,factor analysis shows that the development of landslide group is inevitable as it is closely related to factors such as the valley shape,steep canyon geomorphology,alternatively distributed soft and hard rock layers,and the cutting of partitioned reverse fracture.The formation mechanism can be concluded into 3 categories,namely sliding-tension fracturing,sliding-bending（buckling）,and bending-tension fracture（collapse）.Finally,based on the assessment of landslide stability and the influence of dam location on the project,the following conclusion is obtained： as the landslides and dam sites are interspersed,the upstream dam site is the best choice for engineering safety as it can avoid three huge landslides which have signs of reactivation.Corresponding project proposal is also put forward.