Study Of The Stability Of High-speed Railway Embankment Under Wetting-drying And Dynamic Load

High-speed railway embankment is the supporting body for high-speed trains and track structures.The embankment filling soil is usually unsaturated,and directly exposed to the atmosphere.Atmospheric environment can affect the moisture,matric suction,temperature,and stress of embankment by precipitation,evaporation and other effects.With the rainfall infiltration,wetting front gradually moves downward,causing the rise of saturation and the decrease of suction.Evaporation causes the increase of suction.With seasonal wetting and drying,embankment may suffer from irrecoverable volume change,degradation of shear strength,cumulative displacement.And they can eventually lead to a general instability of embankment,which may cause a huge risk to the long-term operation of high-speed railway.1.Based on the typical section of Beijing-Shanghai high-speed railway,a moisture-heat coupled moisture migration model of the high-speed railway embankment with considering environmental effects is proposed.Based on the meteorological data of Beijing and Shanghai in 2013,the volumetric water content(VWC)response of the high-speed railway embankment is calculated to investigate the effects of climate conditions and soil types.The result shows that,the soil type and climate condition significantly affect the moisture variation of high-speed railway embankment.The influential depth of atmospheric environment on the VWC of sandy embankment is small,but the shallow embankment is affected by the atmospheric environment significantly,with a large amplitude of VWC fluctuation.The influential depths of atmospheric environment on the VWC of silty and clayey embankment are relatively deep,but the amplitude of VWC fluctuation is small at every depth.The VWC of embankment under weather condition of Beijing has a huge seasonal variation and the VWC of embankment under weather condition of Shanghai fluctuates significantly with each rainfall.2.An unsaturated cyclic triaxial test study on high-speed railway embankment filling soil was conducted to study the effects of suction level,dynamic load mode,dynamic load amplitude and wetting-drying history on the cyclic behaviour of filling soil.Results show that at low suction level,the axial cumulative plastic strain of filling soil is greater and resilient modulus of filling soil is smaller.Wetting-drying history has a great influence on cyclic behavior of the embankment with a higher wetting-drying amplitude,the filling soil has a greater axial cumulative plastic strain and a smaller resilient modulus.With the increase number of wetting and drying cycles,a softening trend of filling soil can be found.3.Using the DBLEAVES-X software,a two dimensional high-speed railway embankment soil-water coupled calculation model was built,the pore-water pressure(PWP),saturation,shear plastic strain of embankment was simulated in order to learn the stability of embankment after wetting and drying process and dynamic load.The results show that,the PWP of embankment increases significantly during rainfall.The PWP of embankment surface decreases during evaporation,while the PWP of relative deeper embankment increases slightly with the diffusion of wetting front.The plastic shear strain increases significantly with rainfall,however,it has limit increase during evaporation.Under the effect of wetting and drying,a plastic shear strain area has developed between the top and the toe of slope.It may become a potential slip surface,and decrease the stability if embankment.