| With the acceleration of the process of modernization in the west,the construction of the project will be large-scale "dig deep and fill" due to the adverse topography and geological conditions,and the number of man-made slopes will increase day by day.Coupled with the current global warming,extreme weather is deteriorating all over the country,all kinds of slope instability problems are common,causing huge casualties and economic losses.Through the study of predecessors continue the analysis of rainfall infiltration and slope instability is closely related to rainfall infiltration caused not only directly reduce the shear strength of rock and soil,and the dynamic change of unsaturated zone and groundwater level in the slope,the slope hydrodynamic and hydrostatic pressure changed,the slope toward the stable development.Therefore,it is of important theoretical and practical significance to analyze the slope saturated unsaturated seepage field under rainfall infiltration and the deformation and stability of slope under the influence of saturated unsaturated seepage.In view of the high embankment slope,in order to study the influence of rainfall on the stability of the rainfall infiltration in the saturated and unsaturated seepage theory,the rainfall infiltration seepage field characteristics of Panzhihua Airport 12# landslide are carried out under the condition of numerical calculations and theoretical analysis,obtained in different rainfall conditions,the change law of seepage field.On this basis,numerical method is used to study the stability of the landslide.The main achievements of this paper are as follows:1.The basic engineering geological conditions,hydrogeological conditions and landslide deformation characteristics of 12# landslide in Panzhihua airport have been found out,and the instability and failure mechanism of landslide has been summarized and analyzed.2.Numerical simulation was used to calculate and analyze the variation of the seepage flow field in the rainy season before 12# landslide and in different rainfall forms,and the change law of groundwater level under different rainfall conditions was obtained.(1)Under natural rainfall conditions,the rainfall levels also increase continuously due to the increase of rainfall infiltration during the rainy season.When the rainfall is the maximum,the water table increases accordingly.If the rainfall continues,the groundwater level will remain higher and the rock and soil will be saturated for a long time,which is very unfavorable to the stability of the slope.(2)The rainfall types of short duration and small rainfall have little effect on the change of groundwater level because of their small total rainfall and the effect of excretion and evaporation.But if the rainfall intensity is long enough to make the total rainfall reach a certain size,the rainfall pattern with small rainfall intensity can also raise the water table to a certain extent.On the contrary,when the rainfall intensity is large,because the infiltration is rapid and the infiltration amount is large,the groundwater level changes greatly with rainfall and takes place earlier.(3)When the total rainfall amount is the same,the influence degree of different rainfall duration on the slope is different,in which the short duration of heavy rainfall is longer than the weak rainfall,and the duration of rainfall is more significant to the slope groundwater.(4)The groundwater level gradually rises with the continuous rainfall;after the rainfall,the upper layer rainfall continues to seep in,and the surrounding groundwater collects so that the water table does not fall and rise until it is stable.This rule can better explain the characteristics of the instability and failure of the rainfall type slope,and have certain guiding significance for the water treatment of the slope.(5)When the rainfall intensity is constant,the total rainfall increases with the increase of rainfall duration,and the groundwater table increases gradually.For intermittent rainfall,because the ground water level has begun to decrease during the next rainfall,the same rainfall intensity is the same,the continuous rainfall is more intermittent and the groundwater level is higher under the total rainfall time.3.The deformation characteristics of 12# landslide under various rainfall conditions are analyzed by numerical simulation method,and the deformation law of the slope under the rainfall infiltration condition is obtained.(1)With the increase of rainfall infiltration in rainy season,the amount of settlement deformation is more and more big.When the groundwater level increases obviously,the amount of deformation increases,but the increase is not the biggest.Because of the continuous maintenance of high water level,the influence of saturated water softening effect on rock and soil mass is obviously reduced,the settlement deformation amount reaches maximum value,and the slope failure is lagged.(2)When the rainfall duration is the same,the overall deformation of the slope increases with the increase of rainfall.Because with the increase of rainfall intensity,rainfall infiltration quantity,underground water level gradually increased,unsaturated zone shrinking,the trailing edge of saturated soil is more and more,resulting in decreased strength parameters,deformation increases,the slope stability coefficient decreased.(3)When the rain stopped,the groundwater level is still rising because of the hysteresis.The saturated soil area is still expanding,and the settlement is increasing.After a period of time,although the groundwater level has dropped down,the subsidence of the soil decreases slowly due to the water storage and softening effect of the soil,which is still larger than the initial value.(4)With the increase of rainfall time,the increment of shear strain increases gradually,and the potential slip zone(surface)of continuous coalescence is formed gradually.The same time interval of rainfall relative to continuous rainfall,while the underground water level is relatively low,but the soil in the constant dynamic change of groundwater level,basically saturated,produces a softening effect,if every time interval of rainfall is short and rainfall intensity are more prone to failure. |
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