Study On Influence Of Weak Intercalation On Rock Slope Stability Under Rainfall

Landslide is one of the most important disasters affecting the development of China.Rainfall is an important external factor that causes landslides.Especially,heavy rainfall causes the slope with weak intercalation to move rapidly and destroy greatly,which causes social and economic losses and people's lives are threatened.Due to the existence of weak intercalation in the slope,the permeability of weak intercalation is high,and it is easy to soften when encountering water,so the sliding and shear capacity is reduced,which affects the stability of the slope.Therefore,it is of great significance to study the movement law of weak intercalation and slope for slope prevention and disaster assessment.In order to study the start-up law of weak intercalated landslide under rainfall conditions,this paper takes Xiashan village landslide in Huishan Town,Xinchang County,Zhejiang Province as the research object.Through field geological survey and related laboratory tests,the main characteristics of multi-stage layered basalt distribution and the basic characteristics of rock and soil physical mechanics in the landslide area are obtained.The model of landslide with weak intercalation is constructed,and the simulation test of sliding process induced by artificial rainfall is carried out.The relationship between rainfall infiltration evolution and internal stress is discussed,and the correlation between creep and rainfall is revealed.Then,based on the finite difference method,the indoor model test process is simulated.This paper analyzes the influence of different boundary conditions on the deformation and failure of landslide,studies the starting conditions and possible damage scope of landslide,and provides data support for disaster early warning and disaster assessment system.The main results of this paper are as follows:(1)The failure mode of the slope with low water saturation rate of weak interlayer is shallow block sliding failure,and the failure mode of slope with high water saturation rate of weak interlayer is multi-stage backward failure,and the failure location is at the junction of weak interlayer and slope surface.(2)Under the same rainfall intensity,the pore water pressure in the lower part and the inner part of the weak intercalation changes obviously with the change of water saturation rate,but it has no significant effect on the pore water pressure in the upper part of the weak intercalation.The response time is later when the water saturation rate is high,the pore water pressure value of the slope with low water saturation rate is relatively large,and the pore water pressure dissipation time is late.(3)In the process of rainfall,when the water saturation rate of weak interlayer is low,the earth pressure inside and below the interlayer decreases and increases gradually,while the water saturation rate increases,and the earth pressure first increases,then decreases and then increases.The earth pressure on the upper part of the weak interlayer experienced two stages: first increasing,then decreasing,and then increasing and then decreasing.The order of the values is: saturation rate 25% > saturation rate 20% >saturation rate 15%.(4)Under rainfall conditions,the order of increase of pore water pressure is as follows: the lower part of weak interlayer > the inner part > the upper part.The maximum pore water pressure in the upper part of the interlayer is 60% lower than that in the lower part.However,the pore water pressure does not change when the internal friction angle of weak interlayer is changed.(5)With the increase of the thickness of the weak interlayer,the maximum horizontal displacement of the slope is always at the intersection of the weak interlayer and the slope surface,and the maximum horizontal displacement increases by about16%.The horizontal displacement above the interlayer is negatively correlated with the cohesion of the weak interlayer,while the horizontal displacement below the interlayer is positively correlated.With the increase of dip angle of weak interlayer,the horizontal displacement above interlayer tends to increase.There is a critical angle for horizontal displacement under the interlayer: when the dip angle is 5° ? 10°,the horizontal displacement decreases with the increase of dip angle;When the inclination angle is between 10° ? 15°,the horizontal displacement increases with the increase of inclination angle.The sensitivity of the occurrence characteristics of weak intercalation to slope stability is as follows: thickness h > dip angle ? > cohesion c > internal friction angle ?.Under rainfall conditions,the order of increase of pore water pressure is as follows: the lower part of weak interlayer > the inner part > the upper part.The maximum pore water pressure in the upper part of the interlayer is 60% lower than that in the lower part.