坡底饱和型黄土滑坡离心模拟试验

Study on the failure mode of a bottom-saturated loess slope by conducting a centrifuge test

黄土极具结构性和水敏性,人类活动及自然因素作用下的水致地质灾害备受关注,其中坡底饱和型黄土边坡极易失稳破坏并造成危害。基于离心模拟手段,采用未扰动原状黄土制作模型,自主设计模型后缘渗水装置,模拟坡底饱和型黄土边坡的失稳过程;通过模型顶部视频监测、侧面粒子图像测速(particle image velocimetry,简称PIV)分析、底部孔隙水压力及土压的联合监测手段,分析其失稳破坏特征,并结合现场滑坡演化特征进行验证对比。主要得出以下结论:加速度达80g时,模型底部饱和,前缘出现滑移、后缘发生塌陷及内部湿陷,呈多元破坏形式;模型侧面位移表现为滑移前的表层张拉变形、底部湿陷变形及后缘塌陷前的顶部沉降变形;模型底部高孔隙水压力区分布于大面积滑移和塌陷区域下方,表征了坡底高水位对破坏的影响及底部水渗流的不均匀性;模型滑移破坏与现场滑坡具相同演化进程:坡底饱和-张拉裂缝-后退式小型滑移-水位抬升-后退式大型滑移。研究成果可为原状黄土的模型试验研究思路及原位滑坡的多元破坏机制研究提供借鉴。

Loess is highly structured and water sensitive.Water-induced geohazards due to human activities and natural factors are of great concern,especially the loess slope with a saturated base.The failure process of a bottom-saturated loess slope was reappeared in this research based on a centrifuge test using the intact loess model.Monitored by the video,the PIV technique and the pore water pressure and soil pressure,the failure mode of the loess slope was analyzed.The main conclusions are as follows.The bottom of the model is thoroughly saturated when the acceleration is increased to 80g and there exists multiple failure forms on the slope model including sliding failure,collapse failure and internal subsidence failure.The PIV results indicate that the fractures on the surface of the model occur before the sliding failure and the collapse failure.The sliding failure and collapse failure both occur on the high pore-water pressure area though the pore-water pressure distribution is nonuniform at the bottom of the model.The sliding failure process in the model is the same as that of the field landslide following the process of base saturation,tensile fractures occurring,small backward sliding,water level increasing and large backward sliding.The results can provide reference for the model test study on undisturbed loess and the multi-failure mechanism of in-situ landslide especially in the long term irrigated loess areas.