ISSN 1003-8035 CN 11-2852/P

    西藏雅鲁藏布江缝合带震裂山体发育特征、孕灾条件与研究进展

    Characteristics, hazard conditions, and research progress of shattered mountains in the Yarlung Zangbo Suture Belt, Tibet, China

    • 摘要: 雅鲁藏布江缝合带震裂山体是由印度-欧亚板块碰撞运动和近期强震活动作用叠加而形成,具有岩性结构混杂、构造作用强烈、松动变形明显等特点,极端力学条件下容易失稳成灾,是边疆城镇和工程建设运营的重大地质安全挑战之一。文章基于实地调研和地质勘查工作,深入分析了雅鲁藏布江缝合带震裂山体发育特征,并从岩性组合、构造活动以及岩体结构等3个方面总结了其孕灾地质条件,从板块缝合带岩体工程地质性质、震裂山体结构特征、山体地震动力响应规律、山体强震失稳破坏机制、研究方法等5个方面梳理了相关最新研究成果。主要研究结果为:(1)雅江缝合带震裂山体受控于墨脱活动断裂系,遭受了1950年察隅8.6级大地震作用,山体结构发生了明显松动,形成了多处大型变形区,在强烈扰动下容易发生大规模失稳滑动;(2)雅江缝合带震裂山体具有特殊的易灾地质结构,孕灾条件主要受控于特殊的岩性组合、强烈的构造活动和松散的岩体结构;(3)目前亟待建立雅江缝合带震裂山体精细地质力学模型,分析构造混杂岩岩体震裂损伤破坏机制,阐释强震作用下的缝合带跨断层震裂山体动力响应和失稳机理。文章最后建议选取墨脱巴登则山体为重点研究案例,系统开展雅鲁藏布江缝合带震裂山体失稳机理研究,为青藏高原特大地质灾害防灾减灾提供相应科学依据。

       

      Abstract: Shattered mountains in the Yarlung Zangbo Suture Belt, Tibet, were formed by the collision movement of Indo-Eurasian plates superimposed with recent strong seismic activities. They are characterized by complex lithologic structures, strong tectonic actions, and significant deformation, which are beneficial to failure under certain extreme mechanical conditions. Thus, the shattered mountain problem becomes one of the major geological safety challenges in the construction and operation of the border towns and major engineering projects. Based on field investigation and geological explorations, this paper deeply analyzed the characteristics of the shattered mountains in the Yarlung Zangbo Suture Belt. Hazard conditions were summarized from three aspects: lithological combination, tectonic activities, and rock mass structure. Moreover, this paper overviewed the latest research results, including engineering geological properties of rock masses in suture zones, structural characteristics of the shattered mountains, seismic dynamic responses of mountain slopes, mountain failure mechanism induced by strong earthquakes, and relative research methods. Main conclusions include: 1) The shattered mountains in the Yarlung Zangbo Suture Belt are controlled by the Motuo active fault system and were subjected to the Great Chayu M 8.6 earthquake in 1950; the mountain structures were loosened, and the rock masses were deformed, which were prone to large-scale instability under intense disturbance. 2) The scattered mountains in the Yarlung Zangbo Suture Belt have special disaster-prone geological structures, and the favorable conditions are mainly governed by the particular lithological combination, strong tectonic activity, and loose rock mass structure. 3) At present, it is urgent to establish a detailed geomechanical model of the shattered mountains in the Yarlung Zangbo Suture Belt, to analyze the damage and failure mechanism of the tectonic mélange rock masses, and to explain the dynamic response and instability mechanism of the shattered mountains in the suture zone under strong earthquakes. In the end, it is suggested to choose Badengze Mountain in Motuo county as the key study case to systematically analyze the failure mechanism of the shattered mountains in the Yarlung Zangbo Suture Belt, which would support the prevention and reduction of major geological disasters on the Qinghai-Tibet Plateau.

       

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