强震作用下堆积体边坡动力响应机理及稳定性评价方法研究

A large number of large-scale landslides were induced under Wenchuan earthquake and the talus slopes had a considerable proportion. It is imperative to research on dynamic failure mechanism of the talus slopes. Research results will provide theoretical basis for landslide prevention and forecast and early warning. Firstly, field researches and information collection will be started on the talus slopes in the Wenchuan earthquake zone. Dynamic response laws will be achieved about the talus slopes under Wenchuan earthquake. Secondly, conceptual models of the talus slopes will be build. Physical and numerical simulation experiments will be carried out. Dynamic response universal laws will be summarized about the talus slopes under strong earthquakes. Thirdly, dynamic failure mechanism of the talus slopes will be researched systematically, based on research results of in-situ monitoring and physical and numerical simulation experiments. Failure controlling factors and mechanical mechanism will be acquired of the talus slopes. Thus failure criterion and permanent displacement calculation methods will be set up of the talus slopes. At last, multi-particle limit equilibrium theory will established based on single-particle limit equilibrium theory. Multi-particle limit equilibrium theory will checked by engineering prototypes and conceptual models. Research results will verify existed concepts and produce quantitative evidences. Existed stability methods of the slops will be put forward.

汶川地震诱发了大量大规模滑坡，其中松散堆积体滑坡占有相当的比例，对堆积体边坡的动力失稳机理开展研究，可为滑坡防治和滑坡预警预报提供理论依据。本项研究拟在汶川地震震区堆积体边坡现场调研和监测资料收集的基础上，对堆积体边坡在汶川地震作用下的动力响应规律进行总结。然后建立堆积体边坡的概念模型，开展振动台物理模拟试验和数值模拟试验，研究强震作用下堆积体边坡动力响应的普遍规律。基于现场监测、概念模型试验和数值模拟试验的成果，对强震作用下堆积体边坡的动力失稳机理进行系统研究，明确堆积体边坡的动力失稳主控因素和动力失稳力学机制，建立堆积体边坡的动力失稳判据和永久位移的计算方法。最后，基于极限平衡理论建立多质点极限平衡理论，并应用工程原型和概念模型予以验证。研究成果有望验证已有概念认识，并提供定量依据，推进现有边坡动力稳定性评价方法的发展。

堆积体在我国西南地区分布广泛，在地震作用下极易滑坡。2008年汶川地震诱发了众多滑坡，与重力作用形成的滑坡失稳机理迥异。针对强震区堆积体开展深入研究，有利于修正和加深对强震作用下堆积体变形破坏机理的认识。.本项目以强震作用下堆积体边坡的动力响应规律、动力失稳机理及动力稳定性评价为研究内容，在现场调研和原位监测成果分析基础上，建立地质概念模型，开展了室内振动台试验和数值模拟研究，明确了强震作用下堆积体的动力响应规律和动力失稳机理；改进了边坡动力稳定性评价的水平条分法，并提出了双向条分法。.在汶川地震中，强震区未发生大型堆积体滑坡，但堆积体均发生了变形甚至于局部破坏，其主控因素为汶川地震主震；堆积体地表变形量级为dm级、基覆界面位错量级为cm级，震后位移矢量方向大多指向SE向；堆积体存在水平向、铅垂向放大效应，在坡表陡峻部位达到最大值，PGA与地震动特性、地层岩性、地形地貌、库水位等因素相关；地震作用时，滑面处孔隙水压存在激增现象。.在地震作用下，堆积体首先在P波作用下竖向振动，随后在S波作用下水平向振动，后缘产生拉张裂缝；随地震力持续作用，后缘坡体向前推移，与基覆界面发生相对位错，前缘逐步形成剪出口；在竖向和水平地震力耦合作用下，后缘拉张裂缝不断拓深，滑面贯通，岩土体逐次前移，前缘隆起，坡体在剪断前缘锁固段后失稳破坏。.基于极限平衡理论，借用底部剪力法描述不同高程的地震力，采用水平条分法，推导了边坡的动力稳定性评价公式。为解决折线形滑面和地震力沿高程的放大效应，提出了双向条分法，推导了滑体的整体平衡方程，据此可参照常用的极限平衡方法进行边坡动力稳定性评价。