| Ulanqab City is one of the league cities prone to sudden geological disasters in Inner Mongolia.The area is located in the middle and eastern north edge of the Tianshan-Yinshan zonal structural belt.Since the Cenozoic,the eruption of basaltic magma accompanied by crustal movement has caused a large amount of basic magma to overflow the surface,a large area of basalt covering layer was formed to cover the upper part of the old clay layer(mudstone)of ancient landform like mound and gentle mound in Jining District and other places.Because the basalt overburden is porous,vertical joints and fissures are extremely developed,and the surface water seeps,the lower mudstone is softened with rich water to form a weak open sliding surface,which constitutes an active landslide condition.The safety and stability research and analysis of influencing factors on basalt-mudstone slopes reveal the mechanism and evolution process of basalt-mudstone landslides,and provide a theoretical basis for the prevention and treatment of basalt mudstone slopes.It is a requirement for infrastructure engineering in Inner Mongolia.In this paper,basalt-mudstone slope in Jining District of Inner Mongolia is taken as the research object,and the safety and stability of basalt-mudstone slope is analyzed by using laboratory tests combined with the finite element software ABAQUS.The main content of the study and the consequence of the article are as follows.1.The liquid limit,plastic limit,specific gravity,particle analysis and other physical properties of mudstone are tested,and the basic physical properties of the underlying mudstone are obtained: plastic limit is 21.8%,liquid limit is 43.9%,plasticity index is 22.1,specific gravity is 2.78,particle size Mainly distributed between 7.91-8.64?m.2.According to the triaxial test of mudstone with different water content under different confining pressure conditions,the law of weakening of mudstone strength when encountering water is studied.The strength indicators of mudstone were obtained under different conditions of water content,and it was found that with an increase in water content,the shear stress required to destroy a mudstone sample at the same holding pressure gradually decreases;with an addition to the limit pressure,the shear stress of the argillite samples under the same conditions of water content gradually improves;the relationship between the cohesive force c value and the moisture content shows an exponential decline,and when the moisture content decreases,the internal friction angle ?decreases,showing a linear decrease relationship.3.The ABAQUS finite element program is used to analyze the stability of basalt-mudstone slopes with different water content in mudstones,different slopes of the mudstone structural surface and surface structural shapes based on the strength reduction method.The results show that as the water content in mudstones increases,the stability margin of the basalt-mudstone slope will decrease;Convex mudstone structural surfaces have the lowest safety and slope stability compared to straight and concave structural surfaces;reducing the slope of the structural surface of mudstones below the slope can increase the safety factor of the basalt-mudstone slope;the water content of mudstone has the greatest impact on the safety and stability of basalt-mudstone slopes.4.The soil-water characteristic curve test of mudstone found that the matrix suction of mudstone decreases with the increase of volumetric water content,and the relationship between mudstone saturation and matrix suction is obtained,which provides parameters for the slope rainfall model.5.According to unsaturated soil seepage theory and seepage-stress coupling mechanism,to study the characteristics of seepage slope due to rainfall conditions.The results showed that during rainfall,because the basalt and mudstone structural surface has a certain slope,the rainwater seeps down along the structural surface,Thus,saturation,pore water pressure and flow velocity of the toe region vary widely.Due to the reduction of the matrix suction at the slope foot,the effective stress reduces,and plastic strain appears first,and gradually extends upward along the mudstone structural surface from the slope foot.Finally,the plastic zone is penetrated and the slope is damaged,which causes the edge The slope is unstable.In addition,Rainfall duration increased from 0h 72 h,the factor of safety decreases.After 72 hours of rainfall,under five different rainfall intensity conditions of 5mm/h,10mm/h,15mm/h,20mm/h,and 25mm/h,the slope safety factor decreased by 17%,34%,44%,,47%,and 55% respectively,reduced to 1.66,1.33,1.13,1.06,0.9.There is a negative correlation between rainfall intensity and slope safety factor. |
PDF Full Text Request