Study On Engineering Geological Characteristics And Stability Of Huangjiawan Landslide

The landslide studied in this paper is located at the Huangjiawan slope,Xiaoshi village,Jingyuan Town,Jiangyou.The basic characteristics of this landslide and its current deformation status as well as the associated influence factors were figured out based on the summary of the regional geological data of the landslide area.The deformation characteristics and stability state of Huangjiawan landslide under natural condition,rainfall condition?soils were saturated under this condition?,and seismic conditions?peak ground acceleration was 0.15g?were studied by transfer coefficient method and three-dimensional numerical simulation.The main conclusions can be drawn as follows:?1?The mass of the Huangjiawan landslide is mainly composited of soil,which slides along the interface between overburden generated in Quaternary and bedrock.The bedrock is mainly consisted of gray dolomite(D₃^tn),and the overburden is composed of Quaternary alluvium silty clay(Q₄^al)and Quaternary colluvial deposit gravelly soil(Q₄^col+dl).This landslide is a typical deposit landslide with a simple spatial binary structure.The deformation characteristics of the landslide at current stage are obvious,and many evidences indicate that the landslide is under global deformation.So it is a potential unstable slope.?2?The stability of the landslide is affected both by internal and external factors.Lithologic structure and surface state are internal factors,while earthquake and rainfall are external factors which are the main factors affecting the stability of landslide.If the landslide was initiated under the condition of rainfall or earthquake,the tributaries of the Qing Jiang River would be blocked forming a barrier lake,which wolud threaten the safety of the villagers in Xiaoshi village and Jingyuan town which are located at upstream and downstream of the river,respectively.?3?The results of landslide stability calculated by transfer coefficient method under different conditions showed that:1)under natural condition,the stability coefficient is 1.18,and the remaining sliding force is zero,so the landslide is in stable state;2)under rainfall condition,the stability coefficient is 0.98,and the remaining sliding force is 1132kN/m,so the landslide is unstable;and 3)under seismic condition,the stability coefficient is 1.04,and the remaining sliding force is 63kN/m,so the landslide is in unstable state.Under the conditions of rainfall or earthquake,the status of landslide changes from stable to unstable,and landslide is prone to failure.?4?FLAC^3D5.0 software was used to calculate the established three-dimensional landslide model in this paper.Based on the results of displacement and stress,combining with maximum shear strain increment,plastic zone distribution and safety factor,the deformation characteristics and stability of landslide under different conditions were discussed further.The results show that the landslide is stable under natural condition,unstable under rainfall condition,and understable under seismic condition.Comparing the deformation characteristics and stability evaluation results of this landslide under different conditions,the effect of rainfall on the stability of Huangjiawan landslide is relatively larger than earthquake.Both rainfall and earthquake will cause deformation and failure of landslides,especially when the overburden materials are saturated.Moreover,in unstable state,failure first occurs in the front of the landslide,triggering the sliding deformation in the rear of the landslide consequently,which shows the characteristics of retrogressive landslides.?5?Considering the climatic and environmental conditions as well as engineering geological characteristics of the landslide area,large-scale instability and failure of the landslide under the conditions of rainfall and earthquake is potential to occur,which will cause serious damage,so the author suggests that Huangjiawan landslide should be treated as soon as possible.This paper recommends two kinds of management schemes,and determines the optimal plan after comparison.?6?In this paper,the conclusions drawed by numerical simulation analysis on the stability of landslide under different conditions through flac^3D5.0 software show that,the calculated deformation characteristics of landslide under unstable condition are consistent with the actual deformation characteristics,and the stability results are consistent with those obtained by the transfer coefficient method.Therefore,the conclusions of this paper can reflect the deformation characteristics and stability state of Huangjiawan landslide under different conditions accurately.Besides,the conclusion can also reflect the general rule of displacement deformation and stability changes of retrogressive landslides under unstable condition.