| The gently inclined accumulation landslide is widely distributed in southwestern China and is a special type of landslide.The overall slope of the sliding surface is relatively small.It is difficult to predict the landslide accurately by traditional limit equilibrium theory.It has a serious impact on engineering construction,transportation and pipeline transportation.Therefore,the study of landslides with gently inclined accumulation is of great significance for disaster prevention and mitigation.This paper takes the Yingtaogou landslide as an example,systematically analyzes the instability mechanism of landslides with slowly inclined accumulative bodies by using a combination of various research methods including "on-site monitoring-indoor test-numerical analysis-model test",which reveals the effect of rainfall The parameter weakening characteristics,seepage characteristics,stability and the progressive deformation and failure process of the slope with gently inclined accumulation body.The main research contents and results are as follows:(1)The in-situ monitoring of Yingtaogou landslide,combined with the rainfall data of Longquanyi District,analyzed the deformation characteristics of Yingtaogou slope.The study found that the slope of the slowly inclined accumulation body has the characteristics of creep,and the greater the rainfall,the faster the slope creep rate;the slip surface of the slope of the slowly inclined accumulation body tends to appear near the interface of the base and its creep deformation characteristics It is consistent with the sliding characteristics of the traction landslide.(2)By setting samples with different water content and conducting a direct shear test,the parameter weakening effect of the interface between the soil and the ground cover of the slope slope of Yingtaogou was analyzed.The results show that: with the increase of water content,the cohesion of the soil and the "internal friction angle" of the interface of the foundation show an exponentially decreasing law;the friction angle of the soil and the "cohesion" of the interface of the foundation show a linear decrease of law;when the slope contains water When the rate is lower than 24%,the shear resistance of the slip zone soil body is greater than the shear resistance of the base cover interface.The sliding surface is mainly distributed along the base cover interface;when the slope body moisture content is higher than 27%,the slip zone soil body The shear resistance is smaller than the shear resistance of the structural surface,and the slip zone is distributed along the weak zone of the soil.(3)Based on the actual rainfall data of Longquanyi District,setting different rainfall intermittent working conditions,a numerical simulation was carried out on the Yingtaogou landslide,and the characteristics of the slope seepage field,groundwater level and safety factor were analyzed.The calculation results show that the stability of the slope body in the non-rainy season is significantly affected by intermittent rainfall,and the stability recovery ability of the slope body after the rain stop is weak;under the same rainfall in the rainy season,the longer the intermittent cycle,the more unstable the slope body;The first rainfall has a significant effect on the weakening of the slope body;rainfall infiltration is easy to store on the bedrock surface of the gently inclined slope body,forming a transient groundwater level and slope seepage field.The infiltration water mainly plays a role in weakening the parameters.The slope safety factor has little effect;as the slope water level rises,the sensitivity of the slope safety factor to rainfall is gradually weakened;rainfall tends to accumulate at the gentle slope,forming a local high pore water pressure area,which enhances the slope body storage Water capacity;the stability coefficient of the slow dip landslide has small fluctuation range,and creep slip easily occurs under the action of intermittent rainfall.(4)Through model tests,the mechanism of deformation and failure of the gently inclined slope body under intermittent rainfall is analyzed.The model test results show that: The deformation characteristics of the slope body under the effect of early rainfall are that the front edge slips and subsidence,the middle part slips,and the rear edge subsidence occurs,slope body cracks are generated,and the front edge cracks expand significantly,In the later period of rainfall,the slope foot area first sliding,and then the sliding was transferred to the trailing edge in order to cause progressive sliding failure;Rainfall infiltration is easy to store on the bedrock surface,forming transient groundwater level,high pore water pressure area and slope seepage field,the soil near the bedrock face is saturated with water for a long time,has a high degree of softening,and has a significant weakening in shear strength,which leads to slopes that are prone to landslide along the soil layer at the base interface;Slope sliding tends to occur during the intermittent period,the triggering characteristic is that the water in the transient saturation area of the slope body and the accumulated water on the slope surface continue to infiltrate after rain,causing the rise of the groundwater level to lag behind the rainfall,causing buoyancy in the slope,permeability and pore water pressure increase,the effective stress in the slope body decreases,and landslides are induced. |
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