乌蒙山区重大地质灾害的地层构造制约及其风险防控建议

    Stratigraphic and structural constraints on catastrophic geohazards in Wumeng Mountain area and risk prevention and control recommendations

    • 摘要: 【研究目的】乌蒙山区地处云贵高原腹地,地形地貌复杂,构造改造强烈,是地质灾害高易发区,近年来发生在飞仙关组及其同期异相的夜郎组(以下统称飞仙关组)中的多起地质灾害造成了巨大人员伤亡及财产损失。飞仙关组区域岩相差异和精细地层结构控制下的孕灾地质本底条件如何制约重大地质灾害频繁发生有待深入研究。【研究方法】论文以乌蒙山区3起典型重大地质灾害为研究对象,通过灾害现场调查、剖面实测、实验测试、层序地层对比分析等手段,结合岩相古地理编图,研究飞仙关组发育特征及其对区域重大地质灾害控灾规律。【研究结果】乌蒙山区飞仙关组主要发育于海陆过渡环境,陆源碎屑与海相碳酸盐岩的混合沉积奠定了飞仙关组碎裂状地层的物质基础,区域碳酸盐岩和碎屑岩互层及飞仙关组砂泥岩互层等多尺度软硬地层组合组成了独有的易灾地质结构,多期次碳酸盐岩和碎屑岩互层序列控制下的飞仙关组二段—三段是致灾的重点层段,隔档式褶皱宽缓向斜与紧闭背斜转换位置高陡的“靴状”地貌是地质灾害易发的重点部位,构造改造下飞仙关组广泛发育的垂直节理裂隙、滑脱变形、错动破碎变形及层间溶蚀等岩体碎裂化结构是区域地质灾害孕育的关键易灾地质结构。【结论】乌蒙山区地质灾害调查下一步应重点关注飞仙关组二段—三段分布区、“靴状”地貌区及飞仙关组中含碳酸盐岩夹层的顺向斜坡区,研究可为乌蒙山区飞仙关组重大地质灾害隐患的精准识别与防范提供科学指导。

       

      Abstract: Objective Wumeng Mountain is located in the hinterland of the Yunnan-Guizhou Plateau, with complex topography and strong tectonic activity. The widely distributed Feixianguan Formation and its contemporaneous heterogeneous Yelang formation(hereinafter referred to as the Feixianguan Formation) in the area is an important target layer for geohazards. How the geological background conditions under the control of lithofacies and stratigraphic structure of Feixianguan Formation contribute to the frequent occurrences of catastrophic geohazards remains to be further studied. Methods This paper took three typical catastrophic geohazards as the research objects. The development characteristics of the Feixianguan Formation and its geohazards control law on catastrophic geohazards are studied by means of on-site investigation, profile measurement, experimental testing, comparative analysis of sequence stratigraphy, combined with lithofacies paleogeographic mapping. Results The results show that the Feixianguan Formation in Wumeng Mountain area mainly developed in a transitional environment between land and sea. The mixed sedimentation of terrestrial debris and marine carbonate rocks laid the material foundation for geohazards; Multi-scale combination of soft and hard strata, including Formation- Section- Lithological layer, is a key disaster control structure,and the 2nd and 3th members of the Feixianguan Formation are the key disaster causing layers for catastrophic geohazards under the control of the third-order sequence stratigraphic structure; The high and steep "boot shaped" terrain in the wide and gentle syncline belt is a favorable terrain condition for disaster development. Fractured structures are widely developed in the Feixianguan Formation,such as vertical joint fissures, slip deformation, staggered crushing deformation, interlayer dissolution,which are important disaster-prone geological structures. Conclusions It is concluded that the next step of geohazard investigation in Wumeng Mountain should focus on the distribution area of the 2nd and 3th members of the Feixianguan Formation with the "boot-shaped" terrain, and the dip slope area with carbonate interlayers. This study will provide scientific guidance for the accurate identification and prevention of potential geohazards in the Feixianguan Formation of the Wumeng Mountain area.

       

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