| Landslide disaster occurs frequently in Yunnan mountainous area,especially in the concentrated rainfall area.Dashaba landslide,located in Sinanjiang Town Mojiang County of Yunnan Province,is a valley slope on the left bank of Amojiang,there is a large number of residents on the landslide,and highway of 218 line across the landslide.It is found that the deformation of the front and the trailing edge of the landslide is obvious,threatening the safety and property of the 160 residents on the landslide and the traffic safety of the provincial highway of 218 line.At present,there are few studies about the influence of rainstorm and small reservoir discharge on landslide stability.Therefore,to carry out the rainstorm and flood influence on the stability of landslide dam sand has a vital significance.This thesis uses Dashaba landslide as the object of study,through field investigations,we have identified the boundaries,shape and scale of the characteristics,structural characteristics and deformation characteristics of the landslide,and evolution and deformation mechanism of deformation and failure mode of landslide has been analyzed.Fiel test and soil test were used in analysis of landslide.,by using the limit equilibrium method,The rainstorm and flood influence on Dashaba landslide seepage field and stability has been studied.Main conclusion and cognition as follows:1.Mojiang county,where the landslide is located,is a tectonic erosion of Zhongshan landform and a subtropical semi humid monsoon climate zone with heavy rainfall,which the average annual rainfall is 1338 mm.The west side of the landslide has Amojiang river with the average annual precipitation of 1100 ~ 2500 mm,and the range of water level fluctuation is about 517~530m,and the maximum fluctuation amplitude is about 13 m.2.Dashaba landslide slope features: trailing edge slope averages about 30.4 degrees,the central front slope averages about 18.2 degrees.The plane of the landslide is approximately irregular ellipse,the horizontal projection axis of the landslide is about 240 m and the long axis is about 490 m,the horizontal projection area is 9.65×104m2,the thickness is about 19 m,and the volume of the sliding body is about 183×104m3.3.The landslide is mainly composed of the Quaternary sediments,which mainly is crushed silty clay,and the sliding zone is mainly composed of silty clay.At present,the landslide in the front of the formation of local collapse,the central deformation is not obvious andthe development of the edge of the landslide occurs tensile cracks.4.Field experiments were carried out to obtain severe parameters.In the field of borehole water injection test,the permeability coefficient is calculated.The results show that the landslide is mainly medium permeable.5.Indoor permeability test and indoor direct shear test were carried out.The results of laboratory permeability test and borehole water injection test are compared and analyzed.The results show that the permeability test results are small,and the results of borehole water injection test are closer to reality.Through the direct shear test,the soil physical and mechanical parameters of landslide,and the representative profile for parameter inversion,then the soil physical and mechanical parameters of slip have been determined.6.Combined with the meteorological and hydrological data of Amojiang River Basin,the river swells and a rainstorm after heavy rain flood affecting to Dashaba landslide seepage field is simulated and analyzed,the results show:(1)The seepage field characteristics of the landslide are similar in the same way,and the difference is mainly in the superficial range.The influence of the sudden rise of the water level on the landslide is limited to the superficial range.The seepage is mainly concentrated below the groundwater level,and the direction is parallel to the direction of the groundwater flow.(2)Under the sudden rise of the stormwater level,as the water level rises more and more,the seepage field near the front of the landslide becomes more complicated,and the river is near the front of the landslide The groundwater is deflected in the slope.(3)The higher the water level of the stormy river,the longer the duration,the greater the deflection direction of the seepage direction,the wider the range of the flow,50 years in the case of the flow to the flow area of 30 m.7.According to the stability of natural and seismic conditions of Dashaaba landslide,it is concluded that the landslide is in steady state under natural conditions,and the whole landslide is in a stable and stable state under earthquake conditions.8.(1)The stability of the three sections shows a different variation rule due to the combined effect of the sudden rise of the water level.In the 50 years,the stability coefficient of the I-I 'profile increased from 1.93 to 1.99,and the front part of the profile II-II' Its stability coefficient fluctuates around 1.222,and the amplitude is not large;the section III-III 'gradually decreases,but the amplitude is small.(2)After the storm discharge,the stability of the landslide occurred in different degrees,and then the stability coefficient increased and stabilized with the time.The stability coefficient of section I-I 'decreased from 1.966 to 1.894 after 24 hours of rainwater discharge,and then the stability recovered and stabilized at 1.97,and the stability coefficient of section II-II' was decreased from 1.224 To 1.216,and section III-III 'from 1.293 to 1.291.(3)The results of the local stability analysis of the landslide after the storm discharge show that the most dangerous potential sub-slippers are located near the leading edge of the landslide,and the stability of the landslide is larger.The stability coefficient of I-I 'section decreased rapidly from 2.066 to 1.028 and then slowly increased to 1.056;the local stability of II-II' section decreased from 1.120 to 1.029,then slowly rose to 1.034.(4)The size of the potential loss near the leading edge of the landslide is different in different working conditions,such as the potential instability in the vicinity of the leading edge I-I ',the largest in the 20 years,II-II 'is the largest in 10 years. |
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