降雨及地震作用对岷江上游干暖河谷区大型冰川(水)堆积物复活变形的贡献度研究

In the dry-warm and less rainfall valley and strong earthquake zone of the upper Minjiang River, there are many large-scale glacial (glaciofluvial) deposit slopes that have occurred obvious revived deformation, forming a certain type of landslide that is called "revived landslides". The preliminary research results thought that these phenomena were caused by rainfall and earthquake action, and the rainfall influence was greater than earthquake. But the respective contribution of rainfall and earthquake action is lack of effective contrast and supports of the system testing, and evaluation results of the impact of earthquake intensity gained from current standard deviated quiet large from actual value, also with the actual mesoscopic structure change and macroscopic features reflect of deposit is not well understood. So, this project firstly studies the basic mesoscopic structure and the characteristics of the deposit, and then combined with the typical rainfall patterns and earthquake action, through the contrast test about the mesoscopic structure evolution and the mechanics and deformation response, determines the respective extent of rainfall and earthquake action on the stability of slopes and their change law, as well as the two relations and possible critical transition point of impact. Meanwhile, the research tries to ascertain the corresponding relationship between the dynamic strength parameter and the seismic acceleration of the deposit, and suggests proper earthquake acceleration and dynamic strength values. Finally, combined with typical examples, the research, using the large-scale centrifuge testing or vibrating table and three-dimensional numerical simulation analysis method, will validates the rainfall and earthquake action to the contribution of the revived deformation. The result will provide strong supports for further understanding the mesoscopic structure, the properties, and the stability analysis method of the deposits, and so on.

岷江上游分布的众多大型冰川(水)堆积体斜坡，地处干暖少雨的河谷区和强震地带，目前已发生明显复活变形形成滑坡。前期初步研究认为由降雨和地震作用引起，且降雨影响更大，但对二者作用的贡献度还缺乏系统试验支撑和有效对比，且对地震烈度影响的评价还与实际偏差较大，对堆积体细观结构特征变化和宏观特性反映的认识还不深入。为此，本项目拟首先对该类堆积体的基本细观结构及特性进行研究，然后结合典型降雨模式及地震作用，对其细观结构特征演变及力学和变形特性反应进行对比试验，确定降雨和地震各自对斜坡稳定性的作用程度和变化规律，以及二者关系与影响可能的临界转换点。同时，研究切合实际的堆积体动强度参数与地震加速度变化的关系，提出地震加速度和动强度建议值。最后，结合典型实例，采用离心机/振动台和三维数值模拟分析方法，验证分析降雨和地震对斜坡复活变形的贡献度。成果将为深入认识该类堆积体细观结构与特性及稳定性分析方法等提支撑。

岷江上游分布大量大型冰川(水)堆积体斜坡，受复杂地质与气象环境影响，呈现出明显复活变形迹象，部分变形区进一步发展形成滑坡。前期研究认为地震、降雨是诱发这类斜坡发生复活变形的主要影响因素，但二者的影响程度和贡献度大小未明确。本课题采用多种研究手段对其影响开展对比分析研究，取得成果和认识如下：.（1）结合研究区典型冰川(水)堆积体特征详细调查，采用电镜扫描等技术，查明了堆积体的粒组组构特征，发现了堆积体的粒度和矿物成分随高程变化规律，揭示了该类典型堆积体宏观沉积演化和结构特征。.（2）结合室内和现场力学试验，深入研究了冰川(水)堆积体的力学特性，获得了不同含水率、砾粒含量、动荷载等条件下粉质粘土、角砾土的动、静力学强度参数，总结了堆积体的力学性质与不同影响因素之间的特征关系；同时，结合水化学分析、电镜扫描等试验，获得了堆积体在降雨、动荷载作用过程中结构损伤模式和力学衰减机理。.（3）结合汶川-马尔康高速公路建设工程，采用综合遥感技术、现场变形监测、数值模拟等手段，探究了降雨及地震作用下典型冰川(水)堆积体斜坡变形特征、复活机理、破坏过程和失稳模式，发展了非饱和土边坡水力-力学耦合强度计算与模型系统，提出了地震/动荷载作用下斜坡稳定性理论与位移计算模型，完善了降雨及地震作用下堆积体斜坡稳定性评价方法。.（4）地震/动荷载、降雨均会导致冰川(水)堆积体强度衰减，但其劣化效应有着显著差异性。地震/动荷载是该类型堆积体斜坡发生复活变形的主控因素，而降雨则是其复活变形持续发展的长期作用因素，降雨强度、降雨持时、降雨频率控制着复活变形的程度及发展趋势。.（5）课题研究揭示了地震及降雨作用下岷江上游冰川(水)堆积体滑坡的孕灾环境、成灾模式和灾变机理。成果为岷江上游地区人居环境改善、工程建设开发及科学减灾防灾提供了基础科学依据和有益思路借鉴，丰富了西南地区地质灾害防治与地质环境保护理论与实践。