基于高陡交填界面软弱带影响下黄土填方边坡失稳模式研究

INSTABILITY MODELLING OF LOESS FILL SLOPE WITH INFLUENCE OF WEAK ZONE OF HIGH AND STEEP FILLING INTERFACE

近年来,我国黄土高原地区为了扩大土地可利用资源,开展了大范围的填沟造地、平山造城等工程建设。针对高陡原始坡-填方坡交填界面可能存在的灾变隐患开展了室内物理模型试验,发现黄土填方边坡在连续强降雨下会沿高陡交填界面发生整体滑移失稳。进一步通过有限元数值模拟对交填界面处无软弱带、不同软弱带厚度与弱化系数等工况进行了对比分析,证明了交填界面通过该处滋生的相对软弱带对填方边坡的稳定性产生影响,软弱带的不断发展在降低填方边坡稳定性系数的同时也改变了潜在最危险滑面的位置。设定的弱化系数对稳定性系数的影响可划分为3个阶段:无影响阶段、等速陡降控制阶段、等速缓降控制阶段;其中定义的“关键弱化系数”是对边坡稳定性开始产生影响的临界弱化系数,在实际工程中应采取相应措施来避免软弱带弱化系数降到其“关键弱化系数”之下。降雨诱发基于高陡交填界面软弱带影响下黄土填方边坡的失稳模式可归纳为:坡表侵蚀并形成冲沟→坡脚多级局部滑塌、交填界面软弱带逐步发展→土体沿交填界面滑移下错及坡脚剪出→剪切裂缝贯通、填方体整体滑移失稳。研究成果可为修筑在陡坡上的黄土填方边坡防灾减灾工作提供理论支撑。

In recent years,in order to expand the available land resources in the Loess Plateau area,people have carried out a wide range of engineering construction,such as gully filling and land building and city building.This paper aimed at the potential disaster hazard of the interface between high and steep original slope and filling slope and carried out the indoor physical model test.The results show that under continuous heavy rainfall,the loess slope would slip and lose stability along the high and steep filling interface.This paper further used finite element numerical simulation software and carried out a comparative analysis on working conditions including no weak zone,different weak zone thickness and weakening coefficient at the filling interface.It is found that the continuous development of soft zone reduces the stability coefficient of the filling slope and changes the position of the most dangerous sliding surface.The influence of the set weakening coefficient on the stability coefficient can be divided into three stages:no influence stage,equal speed steep descent control stage,equal speed slow descent control stage.This paper further defined the“key weakening factor”.It is the critical weakening factor and has an initial impact on the stability of the slope.Measures in actual engineering should be taken to prevent the weakening factor of the weak zone from falling below its“key weakening factor”.Under the influence of the weak zone of the high-steep intersection interface,the rainfall-induced instability mode of loess fill slopes can be summarized as:at first slope surface erosion and formation of gullies are developed,the multi-level local collapse of slope foot are present,then weak zone of cross-fill interface is gradually developed.The soil slips down along the interfill interface and the slope foot is sheared out shear cracks are penetrated and the fill slope is completely lost stable.The research results can provide theoretical support for the disaster prevention and mitigation work of loess-filled slopes built on steep slopes.