Landslide distribution and sliding mode control along the Anninghe fault zone at the eastern edge of the Tibetan Plateau

Tibetan Plateau is known as the roof of the world. Due to the continuous uplift of the Tibetan Plateau, many active fault zones are present. These active fault zones such as the Anninghe fault zone have a significant influence on the formation of special geomorphology and the distribution of geological hazards at the eastern edge of the Tibetan Plateau. The Anninghe fault zone is a key part of the Y-shaped fault pattern in the Sichuan-Yunnan block of China. In this paper, high-resolution topographic data, multitemporal remote sensing images, numerical calculations, seismic records, and comprehensive field investigations were employed to study the landslide distribution along the active part of the Anninghe. The influence of active faults on the lithology, rock mass structures and slope stress fields were also studied. The results show that the faults within the Anninghe fault zone have damaged the structure and integrity of the slope rock mass, reduced the mechanical strength of the rock mass and controlled the slope failure modes. The faults have also controlled the stress field, the distribution of the plastic strain zone and the maximum shear strain zone of the slope, thus have promoted the formation and evolution of landslides. We find that the studied landslides are linearly distributed along the Anninghe fault zone, and more than 80% of these landslides are within 2-3 km of the fault rupture zone. Moreover, the Anninghe fault zone provides abundant substance for landslides or debris flows. This paper presents four types of sliding mode control of the Anninghe fault zone, e.g., constituting the whole landslide body, controlling the lateral boundary of the landslide, controlling the crown of the landslide, and constituting the toe of the landslide. The results presented merit close attention as a valuable reference source for local infrastructure planning and engineering projects.     

The sedimentary characteristics and formation mechanism of shell ridges along the southwest coast of Bohai Bay

The present paper studies the sedimentary characteristics and mechanism of the shell ridges on the southwestern coast of Bohai Bay, which are the largest and have the highest shell (or shell fragment) content in the world. These shell ridges are composed of two sedimentary subfacies: the ridge subfacies and the ridge infill subfacies with different inner textures and sedimentary structures. The ridge subfacies primarily consists of fresh shells and/or shell fragments with parallel beddings and high-angle oblique beddings. The ridge infill subfacies consists of finer shell fragments and silty sand with parallel beddings oblique to land. The evolution of the shell ridge is controlled by the accumulation of substantial shell material,the relative slow erosion of shoreline, storm waves, winds and the shift of river routes. Wind tunnel tests indicate that the critical movement velocity of shell is lower than that of quartz sand of the same grain size. Deltaic progradation alternates with shell ridge growth. While the Yellow River empties into the sea through this area, accompanied by deltaic progradating, the shell material is scarce, which is unfavorable to the growth of the shell ridge. Conversely, erosion occurs along an abandoned delta coast where a shell ridge may develop, e.g. the shell ridge on the southwest of Bohai Bay.     

断陷盆地顺向断坡油气优势运移通道及聚油模式——以渤海湾盆地沾化凹陷孤北斜坡为例

为明确断陷盆地顺向断坡隐蔽油气藏形成的主控因素和运聚规律,以渤海湾盆地沾化凹陷孤北斜坡为例,采用构造地质学、岩相学与地球化学结合的方法,探讨优势运移通道及聚油模式。结果表明:研究区顺向断坡油气聚集表现为"综合控运"模式,其中断裂和砂体占主导,是油气成藏的关键控制因素。断裂对油气进行垂向输导,汇聚型断裂相对发散型断裂具有明显的控运优势,在汇聚型断裂带上油气包裹体更发育,均一化温度分布范围更广。砂体是油气侧向输导的关键,与不整合构造搭配为油气侧向调整提供优势运移通道。在该聚油模式的控制下,顺向断坡带油气空间分布规律强,主要沿汇聚型断裂与输导型砂体耦合分布,地形上表现为沿"断鼻"分布。顺向断坡带是断陷盆地普遍发育的构造单元,该结果可为同类研究提供参考。     

滨里海盆地东缘中石炭统台内滩分布预测及甄别: 以北特鲁瓦斜坡区为例

滨里海盆地东缘中石炭统KT-Ⅱ油组广泛发育开阔台地相的台内滩,台地内沉积环境开阔且稳定,地势平坦,台内滩往往呈孤立状漂浮在台地内的微地貌高地,故其分布规律难以预测。钻探实践表明,台内滩相是后期发生建设性成岩改造作用的基础,亦是形成优质储层的主控因素,对其分布进行预测至关重要。为了提高滩体预测准确率,立足于区域沉积演化分析,并逐步开展三维地震属性分析及高分辨率反演,充分结合地震资料的预测性和地质认识的规律性,通过总结相带地质规律对地震储层预测进行补充和甄别,做到地质和地球物理认识上的统一。研究结果表明,地震属性趋势控制下的统计学反演可以较准确地刻画小层级别的薄层滩体空间分布特征。结合沉积规律对预测滩体进行了筛选和分类,其中一类滩体7个,二类滩体4个,三类滩体3个,一类、二类滩体已有钻井证实,符合沉积规律,三类滩体与地质认识相悖,予以筛除。研究成果建立了该区隐蔽型滩体预测的完整技术体系,而且已见到实效,目前针对一类滩体的钻探成功率高达100%。      

音频大地电磁法对深部隐伏构造的识别与应用:以贵州省松桃县李家湾锰矿为例

面对国家级整装勘查区——贵州铜仁松桃锰矿整装勘查区深部找矿难度加大的现状,特别是隐伏构造的识别对于第二空间(500~2 000m深度)找矿至关重要的问题,鉴于当前锰矿床后期保存条件的研究需要,利用音频大地电磁法对深部隐伏构造的识别很有必要。以区内岩石物性特征为基础,结合“大塘坡式”锰矿地质模型,建立了初步的正演模型,比较了正演TE、TM两支理论正演曲线,TM模式视电阻率响应较TE模式纵向分辨率强;对比了两支曲线在断层上下盘的响应特征。贵州省松桃县李家湾锰矿实测数据的不同反演结果表明:以一维Occam-TE反演作为初始模型的二维NLCG-TE反演能较好地反映真实的电断面结构。通过剖面电性结构特征分析,为查明“大塘坡式”锰矿深部构造格架及其对含锰岩系的破坏程度提供了地球物理依据,为进一步“攻深找盲”工程部署提供参考。      

降雨与开挖作用下黄土滑坡失稳过程分析:以关中地区长武县杨厂村老庙滑坡为例

降雨入渗和人工开挖是诱发黄土滑坡的重要因素,为了研究在这2种诱因作用下关中地区黄土滑坡失稳过程及其对稳定性的影响,以陕西省长武县杨厂村老庙滑坡为研究对象,通过现场调查、地质测绘和钻孔勘探,查明了该滑坡变形特征,定性分析了滑坡变形演变过程;基于滑坡变形前15 d内日降雨量实测值,采用有限元软件,对坡脚开挖后连续降雨作用下滑坡形成过程进行了仿真模拟;基于强度折减法对该滑坡稳定性变化规律进行了研究。结果表明：(1)关中地区特殊的地层结构是滑坡变形的内因,降雨是最主要的诱发因素;(2)滑坡失稳演化过程表现为：坡体处于蠕滑状态,坡脚开挖后,坡体前缘失稳,牵引中后缘坡体向下错动而产生张拉裂缝,在降雨作用下,雨水沿裂缝渗入坡体深部,滑坡中部岩土体浸水后抗剪强度降低,从而导致黄土层与红黏土层接触面饱水形成贯通滑带,诱发深层滑坡;(3)滑坡开挖后较初始状态,稳定性系数降幅为0.102,此后受连续降雨影响,稳定性系数在前10 d以平均0.010/d的速率缓慢下降,第10～13 d以0.034/d的速率快速下降至最低,第13 d以后开始回升。研究结果可以为该类滑坡防治提供有效依据。     

广东沿海牡蛎体Cu含量水平及其时空变化趋势

为了解广东沿海 Cu含量水平的时空变化趋势 ,1989～ 1997年实施“南海贻贝观察”对广东沿海 12个地点进行了连续监测。实测数据和有关历史资料综合分析结果显示 ,广东沿海牡蛎体 Cu含量(湿重 )范围为 2 .70～ 352 mg· kg-1,平均值为 94 .1mg·kg-1,总超标率达 35.1% ;局部海区属重污染水平。牡蛎体 Cu含量的空间分布特点呈珠江口海区 >粤西海区 >粤东海区格局 ;Spearman顺位相关分析结果表明 ,1989～ 1997年间 ,广东沿海牡蛎体 Cu含量年际间无明显的趋势性变化。     

The starting mechanism and movement process of the coseismic rockslide: A case study of the Laoyingyan rockslide induced by the “5.12” Wenchuan earthquake

The"5.12"Wenchuan earthquake in 2008 triggered a large number of co-seismic landslides.The rear boundary or cracks of co-seismic landslide are generally located at the steep free surface of thin or thick mountains.Dynamic process of this kind of landslides could be divided into two parts:the seismic dynamic response of the slope and the movement process of rock mass.Taking the Laoyingyan rockslide as an example,the amplification effect was studied by single-degree-of-freedom system analysis method.Besides,the dynamic process of landslide under seismic loading was simulated by the finite difference method(FDM)and discrete element method(DEM).The amplification coefficient of the rockslide to seismic wave is 1.25.The results show that the critical sliding surface of the Laoyingyan rockslide was formed at the 23 th seconds under the action of seismic wave.At the same time,tension failure occurred at the rear edge of the sliding mass and shear failure occurred at the front edge.The maximum displacement was 0.81 m and the initial velocity was 2.78 m/s.During the initiation process of the rockslide,the rock mass firstly broke down along the joints which are along the dip of the rock stratum,and then collapsed bodily along the secondary structural planes.In the process of movement,the maximum velocity of rock mass was 38.24 m/s.After that,the rock mass underwent multiple collisions,including contact,deceleration to 0 and speed recovery after rebound.Finally,due to the constant loss of energy,the rocks stopped and accumulated loosely at the foot of the slope.The longest distance of movement was about 494 m.Besides,the smaller the damping ratio,the farther the rock mass moved.Compared with the results without considering the amplification factor,the movement distance of landslide by considering the amplification factor was more accurate.The study of the Laoyingyan rockslide is helpful to strengthen our field identification of potential co-seismic rockslides.At the same time,understanding its movement and accumulation process can help us better predict the hazard scope of the co-seismic rockslides,and provide a reference for the design of treatment projects.