Analysis Of Embankment Slope Stability During The Construction Stage Of The Wadong Canal Subgrade Widening

With the rapid development of social economy and regional exchanges,the road traffic volume increases rapidly,more and more roads have been unable to meet the traffic demand.It is becoming more and more common to use the existing old road to widen it,In particular,the stability of the slope and the settlement of the subgrade and pavement after the widening of the high embankment have been concerned by the engineering community.In addition,The embankment near the water area under the influence of groundwater seepage,the water content in the subgrade is relatively large,and the shear strength of the embankment slope is reduced.If the soil of widen the subgrade or construction methods used in the design and construction process are not suitable,it is easy to reduce the stability of the slope,and even occur landslides.This paper is mainly based on the expansion project of motor vehicle lane along the wandong trunk canal in Hefei Changfeng county,and the slope stability analysis is conducted before and after the construction of the high embankment.This paper mainly considers the influence of groundwater,excavation form,pavement load intensity,rainfall intensity,and the shear strength of soil material,etc.,on the overall stability of embankment slope and the settlement of old and new roadbed.The main research work and results are as follows:(1)Using the finite element software MIDAS GTS NX construction stage function respectively to simulate the excavation and widen the construction process,and using shear strength reduction finite element method to analyze the stability of slope in different stages,and the finite element software ABAQUS is used to compare and contrast calculation.(2)The effects of groundwater,vehicle load and soil shear strength on slope stability and failure mode were analyzed.For the asymmetric slope of the project,the sliding surface was first appeared on the side of the high side slope before excavation,and the safety factor of the slope was greatly decreased by groundwater and vehicle load.In addition,when the internal friction angle or cohesion of soil increases,the width and depth of sliding surface increase with the cohesion of soil,but decrease with the increase of the internal friction angle of the soil.(3)The influence of different excavation depth and different excavation slope rate on the stability of slope after excavation is discussed respectively.After excavation,the excavation load has little effect on the stability of the slope.The main influence on theslope stability is the slope rate,the height of the slope and the shear strength of the soil after excavation.The higher the depth of excavation or the smaller the slope rate,the higher the safety factor under some conditions.The overall stability of the slope after excavation is improved compared with that before excavation,which is mainly because the excavation process reduces the burden on the embankment slope.In addition,it is found that the safety reduction factor of different filling depth or different new and old subgrade connection slope rate is almost equal when the roadbed is widened.It is also verified that the slope safety reduction factor of the project is mainly determined by the slope rate,height and soil shear strength after construction.It is found that the maximum settlement of the subgrade is on the side of the new widening roadbed,and the maximum settlement of subgrade increases with the increase of the area of filling.(4)It is discussed that the slope of stability after widening under different strength of vehicle load and different intensity of rainfall.The slope safety factor decreases with the increase under different strength of vehicle load.In addition,as the load intensity increases,the position of the plastic zone first appears from the slope Angle to the position near the top of the slope.The difference of the safety factor between the two conditions of the existence of groundwater and the non existence of groundwater gradually decreases with the increase of the load strength.In the analysis of rainfall,the safety of the slopes under the conditions of light rain,moderate rain,heavy rain,heavy rains,torrential rain and the rainstorm are taken into account.The slope safety reduction coefficient decreases with the increase of rainfall intensity,but the safety factor of the adjacent strength is less than 2%.(5)The different strength filling materials selected in roadbed widening have a great influence on the overall stability of the roadbed slope.The safety factor of slope increases with the increase of friction Angle or cohesion,When increasing to a certain value,the influence of the friction Angle and cohesion on the safety coefficient is no longer obvious,so it's not that the higher the intensity the better.In addition,the larger the strength difference between the old and new subgrade,the wider the range of sliding zone produced in the low-intensity subgrade region.When the strength of the broadened roadbed is low,the slip band is almost all distributed on the side of the widening roadbed,and the shape is irregular.(6)The settlement of the subgrade are influenced by the compressive modulus and poisson's ratio of the widened subgrade soil,By widening the compressionmodulus or Poisson's ratio of the subgrade soil,it is found that the maximum settlement first appears on the side of the widening subgrade,and with the increase of the load,it gradually moved to the side of the old roadbed.It is shown that the increase of the load on the slope improves the integrity of the slope to a certain extent.However,the increase of the compressive modulus and poisson's ratio of the widened roadbed has no effect on the maximum settlement position of the roadbed slope.In addition,the change of subgrade settlement with poisson's ratio is not obvious,but the overall trend is increasing.