| Landslide disaster is one of the most serious geological disasters in the world.Landslide disaster is the most widely distributed and most serious disaster in China's geological disasters,and rainfall is the main inducing factor.Anhui provinces is one of the with serious geological disasters in China.The number of geological disasters,casualties and direct economic losses occurring annually are among the top of the country.The mountainous area of Southern Anhui is the rainstorm center of Anhui Province,which is also the center of geological disaster intensive.The landslide of shallow residual soil accounts for the largest proportion of all geological disasters,and the most serious disaster.It has become one of the important factors that affect people's production and life and restrict the economic development in the mountainous area of Southern Anhui.This article is based on the Anhui Natural Science Foundation Project“Study on the mechanism of pore water pressure and sliding process of shallow landslides triggered by rainfall—The mountainous area of Southern Anhui”,taking the Fanzhangzu Landslide in the mountainous area of Southern Anhui as the research object,Using the exploration data of the slope and the laboratory data,On the basis of the saturated-unsaturated seepage theory and theory of shear strength of unsaturated soil,through numerical simulation and numerical calculation,the influence of rainfall infiltration on the stability of the slope of shallow residual soil in the southern Anhui mountainous area is studied.The main research results are as follows:1?The general situation of disaster development in mountainous area of Southern Anhui Province is statistically analyzed.Rainfall type shallow landslide is a typical disaster,and it is also the most widely distributed disaster type.In the case of a typi cal rainfall type shallow landslide,fan Zhangzu landslide,the field survey was carried out,and the soil samples were tested in the laboratory,and the basic physical and mechanical parameters were obtained.2?A model of Seep/w analysis is set up.The change of seepage field inside the slope body under different rainfall conditions is studied.?1?Under the same rainfall condition,the longer the rainfall is,the greater the pore water pressure at the shallow soil is,the greater the shift value of the groundwater level line is.The variation amplitude of the characteristic points in the slope body is larger than that of the shallow soil.?2?Under different rainfall intensity,the overall trend of pore water pressure is consistent.However,the greater the rainfall intensity is,the greater the variation of pore water pressure at the shallow soil is.The greater the rainfall intensity is,the larger the value of the groundwater level moves up.?3?In the process of rainfall infiltration,the change of the phreatic line at the toe of slope is the most obvious.The phreatic line at the toe of slope moves up and first appeared the transient saturated zone.3?A model of Slope/w analysis is set up.The change of slope stability under different rainfall conditions was studied.?1?Under the same rainfall condition,the safety coefficient of the slope gradually decreases with the increase of rainfall duration.?2?When the total amount of rainfall is the same,the greater the rainfall intensity,the faster.?3?Under natural condition,the safety factor of slope body is 1.029,and it is in under-stable.At present,there is still creep deformation in the slope.With the increase of rainfall intensity,the safety factor of the slope is reduced sharply.?4?Under different rainfall conditions,the shape of the potential slip surface of the slope is similar.The slope body is obviously influenced by the strong rainfall,and the possibility of instability and destruction in the continuous heavy rainfall weather is very great.?5?The parameter sensitivity factors of landslide body are analyzed.The friction angle is the most sensitive relatively to the slope stability,the cohesion is in the next place,the less sensitive parameter relatively to the slope stability is the soil bulk density.4?A model of Sigma/w analysis is set up.The change of the displacement field in the body of the slope under the heavy rain condition in flood season is studied.?1?With the infiltration of rainfall,the residual soil in the shallow layer of the slope has the downward and outward displacement along the slope,and the displacement to the outside of the slope is more,and there are a small amount of subsidence.The displacement of the top of slope is greater than the toe of slope.If the rainfall infiltration continues,the displacement and deformation of the residual soil in the shallow slope gradually increased,the possibility of sliding between the slope of body and the sliding bed is more likely.?2?In the natural state,the slope tends to evolve in the direction of equilibrium and stability,and the holistic instability will rarely occur.Under the conditions of rainfall infiltration,the displacement and deformation of the middle-lower part of the slope are more obvious,and the displacement is larger.There is a large amount of soil uplift,the displacement of the sliding body and the sliding bed is large,and there may be a slight slip of the slide.The displacement of the sliding bed below the upper soil of the slope is smaller and negligible.The soil slope toe slightly uplift displacement,small deformation,landslide is unlikely.5?The seepage model of infinite slope is established.On the basis of the Iverson model,the calculation expression of slope stability for shallow residual soil is derived.It can also reflect the dynamic changes of unsaturated zone saturation and soil gravity in the process of rainfall infiltration.The influence of seepage erosion on unsaturated zone saturation in slope,pore water pressure on sliding surface and safety factor of slope under different rainfall conditions is studied.?1?The pore water pressure at the sliding surface gradually increases with the rainfall infiltration,and gradually decreases with the end of rainfall.Under the same rainfall and rainfall duration,the greater the intensity of rain,the faster the water pressure in the sliding face.?2?Under the conditions of rainfall infiltration,the unsaturated zone of the slope can be saturated in a short time and is maintained in the saturated state within 30 days.T he equivalent-weight“?*”of the landslide body is approximately equal to the saturation-weight“?sat”.?3?The stability coefficient of slope decreases with rainfall infiltration,and finally stabilized at a certain value.After rainfall,the stability coefficient starts to rise,and the rate of increase is obviously smaller than the decline rate.When the total amount of rainfall is certain,the greater the rainfall intensity,the faster and the more the slope body safety coefficient is,the more it is not conducive to the stability of the slope.?4?The seepage potential erosion will affect the stability of the slope body,the more the soil fine particles lose,the more the seepage potential is,the more obvious the stability coefficient of the slope decreases.The more complete the soil particle gradation is,the weaker the seepage latent erosion is,the less the stability coefficient of the slope decreases. |
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