Study On Mechanism Of Shallow Loess Landslides Induced By Surface Water

The loess is loose,and contains numerous large pores and vertical joints inside,which provides channels for the rapid infiltration of water.In order to effectively reduce the impact of landslides triggered by rainfall and irrigation on social and economic,it is of great realistic significance to carry out the laboratory experimental study on two kinds of landslides.The shallow loess landslides in Jingyang region were selected as the research object,and indoor physical experiments were carried out in this paper,aiming to study the effects of different rainfall pattern,different slope structure under the condition of rainfall and different slope gradient under the condition of irrigation on the deformation and failure process of loess slope.Five groups of indoor physical model experiments were designed and conducted in this paper,including loess slope with continuous heavy rainfall,loess slope containing a vertical joint with continuous heavy rainfall,loess slope with intermittent heavy rainfall,and slopes of 45 degrees slope of 60 degrees with drip irrigation,respectively.And three kinds of sensors including volume moisture sensors,matric suction sensors and pore water pressure sensors were buried to record the internal changes in each loess slope.Based on the experimental process and results,and combined with the numerical results of SLOPE/W and SEEP/W modules in Geo-studio,the following results are obtained as follows:(1)In this paper,the changes of readout of three kinds of sensors in the irrigation and heavy rainfall experiments were analyzed,meanwhile,the change law and the relationship between the readout were also summarized.And what's more,the wetting front,pore water pressure,and the position of the slip surface in the experimental results were used to verify that in the numerical results.Finally,the relationship between slope safety factor and elapsed time were analyzed as well.(2)According to the change of the wetting front in the experiments,the infiltration law of the loess slope was acquired.That the sequence of seepage velocity from large to small is:toe of slope,trailing edge of the slope and middle slope in the experiments of loess slope with continuous heavy rainfall and loess slope with intermittent heavy rainfall.While based on the experiment of loess slope containing a vertical joint with continuous heavy rainfall,the order of infiltration rate is:the joint,toe of slope,trailing edge of the slope and middle slope.It can be also known that the order of seepage rate in the irrigation experiments is:Irrigation point,toe of slope,trailing edge of the slope and middle slope.(3)Based on the process and results of experiments,the deformation and destruction law of the loess slope was summed up.In the irrigation experiments,the smaller the slope gradient is,the larger the depth of the sliding surface is,the bigger the irrigation amount needed,the greater the increasing amplitude of the pore water pressure required,and the further the sliding distance is.At the same time,in the heavy rainfall experiments,it is concluded that,the deeper the sliding surface is,the greater the increased range of pore water pressure is and the longer time required for the landslide initiation,with the condition of no pre-formed joint in the loess slope.In addition,according to the different rainfall required in the rainfall experiments,it is considered that the effects of slope structure on slope stability is greater than that of rainfall pattern.(4)From the deformation and failure process of the slopes,the author obtained the deformation and failure modes.In which the failure mode of loess slope with continuous heavy rainfall is:?The original slope;? Erosion of water at the slope shoulder;? Erosion of water at the toe of the slope;?Formation and growth of fracture in the trailing edge of the slope;? Sliding failure of the slope.While failure mode of loess slopes containing a vertical joint with continuous heavy rainfall is quite different as it is:? The original slope;? Erosion of water on shoulder of slope;? Erosion of water on toe of slope;? Growth of joint in the trailing edge of the slope;? Sliding failure of the slope.(5)The deformation and failure mechanism of the Loess Slope under the conditions of rainfall and irrigation are well uncovered by experimental results,that is,in the early stage of the experiments,the matric suction of the loess decreased gradually and maintained stable in the end,therefore the strength reduced,with the continuous increases of volume moisture.In the later stage,the upper loess of the slope reached the saturation stage,slope deformation appeared and result in the formation and growth of the fracture or the expansion of the joint,excess pore water pressure generated by the slope deformation and poor drainage of the loess decreased the effective stress and the strength of the loess,and as a result,the strength declined and reached the minimum,and when it was less than the critical value,the potential slip surface was formed and the landslide occurred.