大型红层缓倾岩层滑坡形成机制——以川北断渠滑坡为例  

Formation mechanism of large-scale red bed gently inclined strata landslide:Taking Duanqu landslide in north Sichuan as an example

作　　者：唐然 任穗川[1] 范宣梅 许强[2] TANG Ran;REN Suichuan;FAN Xuanmei;Xu qiang(School of Architecture and Civil Engineering,Chengdu University,Chengdu 610106,China;State key laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都大学建筑与土木工程学院,成都610106 [2]地质灾害防治与地质环境保护国家重点实验室(成都理工大学),成都610059

出　　处：《成都理工大学学报（自然科学版）》2024年第4期673-686,共14页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家自然科学基金项目(42293353)。

摘　　要：大型缓倾岩层滑坡在红层地区广泛分布,由于滑前迹象不明显,很难做到早期防范。为了探索此类滑坡的风险斜坡判识和早期识别,以四川北部南江县断渠滑坡为例,从孕灾地层沉积相和岩性组合特征、区域地质构造演化和层间剪切带发育特征等角度,分析了该滑坡的形成机制。该滑坡体积约为1153×10^(4)m^(3),主滑方向总体向南(170°),为一特大型缓倾岩层古滑坡。滑坡发育于侏罗系中统沙溪庙组上段和沙溪庙组下段交界部位,是岩性和岩相的转换面。沉积相的组合特征决定了斜坡上硬下软的坡体结构。滑坡位于四川盆地北缘新华向斜北西翼,受到了多期地质构造作用,米仓山南缘前陆盆地盖层底部楔入冲断构造模式产生了上部地层原地掀斜效应,增加了层间机械破碎作用,并且软硬2个系列地层交界处应力更易集中,在孕灾地层上下厚度约80 m范围内共计发育了数10条层间剪切带。在地下水大量参与下,破碎程度高且原岩含大量黏土矿物的层间剪切带被逐渐泥化,为滑坡下滑提供了力学条件。Large-scale slow dip landslides are widely distributed in the red bed area,and it is difficult to prevent them early because the signs before sliding are not apparent.In order to study the potential risk of such landslides slope identification and early warning,the formation mechanism of the Duanqu landslide in northern Sichuan basin is analyzed in this study,with a focus on several key aspects including the sedimentary facies and lithological combination characteristics of the disaster-prone strata,the regional geological tectonic evolution,and the basic features of interlayer shear zones in bed rock around the landslide.The volume of the landslide is approximately 1153×10^(4)m^(3),with an main sliding direction of 170°.Duanqu landslide is a large-scale,thick-layer,gently inclined strata ancient landslide.The disaster-prone strata of the landslide are situated at the junction of the Middle Jurassic Upper Shaximiao Formation and Lower Shaximiao Formation,marking a lithological and lithofacies transition zone.The combination characteristics of sedimentary facies determine the slope's structure of hard on top and soft on the bottom.The Duanqu landslide is located on the northern margin of the Sichuan Basin,on the northwestern wing of the Xinhua syncline,and has been subjected to multiple phases of geological tectonic activity.The wedge thrust tectonic mode at the base of the foreland basin cover on the southern margin of the Micang Mountain has induced an in situ tilting effect on the upper layers,resulting in the regional occurrence of shallow monoclinal red beds.This deformation pattern is more prone to generate layer disturbances distributed throughout the entire layer along the stratigraphic tilting range,thereby increasing interlayer mechanical fragmentation to some extent,and the junction between the soft and hard strata is more prone to stress concentration,which make dozens of interlayer shear zones distributed surrounding the disaster-breeding strata within the thickness range about 80 meters.With signif

关 键 词：缓倾岩层滑坡 断渠滑坡 沉积相 构造模式 形成机制 

分 类 号：P642.22[天文地球—工程地质学]