灌溉诱发突发性黄土滑坡机理研究

The Mechanism Study of the Irrigation-Induced Sudden Loess Landslides

系统揭示黑方台突发性黄土滑坡物理力学机理,对滑坡防治具有重要的作用。自上世纪六十年代年黑方台常年的农业灌溉诱发了大量20~40 m厚的饱和突发性黄土滑坡。本研究在野外调查的基础上,通过分析滑坡的变形破坏特征,针对分布范围广、危害性较大的突发性黄土滑坡,利用室内GDS三轴试验和模型试验,分析研究了饱和黄土的应力应变特性及突发性黄土滑坡的力学机制。三轴试验结果表明,当围压小于300 kPa时,饱和黄土可产生完全液化,并处于流塑状态;当围压大于300 kPa时,饱和黄土仅产生部分液化,仍具有一定的抗剪强度。饱和黄土的应力—应变模式均表现为强烈的应变软化—剪缩型,并具有一定的稳态特性。模型试验表明突发性黄土滑坡的变形破坏过程可大致分为底部浸水饱和—毛细水上升—持续蠕动变形—突发性破坏4个阶段。斜坡发生突发性破坏时,孔隙水压力激增,但总应力仍大于孔隙水压力,黄土滑坡发生部分液化,饱和黄土仍具有一定的强度,为突发性黄土滑坡发生提供了应力和能量积累的力学条件。研究从有效应力原理的角度阐述了突发性黄土滑坡的力学机理,可以为滑坡的防治治理提供一定的理论依据。

The physical and mechanical mechanism of sudden loess slopes plays an important role in the prevention and control of landslides.Due to long-term excessive flood irrigation,the saturated zone with a thickness of 20~40 m has been formed at the bottom of loess slopes on the Heifangtai terrace since 1960 s.A large number of sudden loess landslides have been induced by the groundwater table rising since 1960 s.On the basis of field investigation and UAVs images,the inventory of sudden loess landslides were carried out and the deformation and distribution characteristics of loess landslides were analyzed.These landslides are widely distributed along the margin of terrace and have caused great loss of lives and properties.Then,GDS triaxial tests and model tests were designed and performed to analyze the stress-strain characteristics of saturated loess and the failure mechanism of loess landslides.The results of the triaxial tests revealed that when confining pressure was less than 300 kPa,the saturated loess at low strain could totally be liquefied and be in flow plastic state.However,when confining pressure was more than 300 kPa,the samples were partial liquefaction and still had a certain shear strength.The stress-strain mode of saturated loess was strong strain-softening way and behaved steady characteristic.From the model tests,it was found that the the deformation process of sudden loess landslide could be divided into four phases,i.e.,soakings and saturation,capillary rising,creep deformation,sudden destruction.When the loss slope was a sudden destruction,the pore water pressure increased rapidly in a period of time,but the total stress was greater than pore water pressure and was partial liquefaction,it had a certain strength.The result provided the mechanical condition for stress and energy accumulation of sudden loess landslides.From the point of principle of effective,the research expounded the mechanical mechanism of sudden loess landslide and provided a theoretical basis for prevention engineering of loess landslide.