Study On The Dynamic Responses Of Loess Cutting Slope Under Low Frequency Vibrations Of Train

In the 21st century,China’s railway engineering has developed rapidly,but regional imbalances have intensified.In particular,the road network density in Northwest China is only 1.5 km/10,000 km~2.The construction of railway projects in the Northwest region is in great demand and has broad prospects.In the loess area,there are many high-lying loess slopes in the process of railway construction.The loess has the characteristics of large pores,vertical joints,water sensitivity,and collapsibility.It is easy to cause slope instability during railway operation.The variation of the slope of the loess railway under the low-frequency vibration of the train is becoming more and more prominent.This paper studies the dynamic response law of loess cutting slope under low-frequency vibration of the train and its influence on the stability of cutting slope.The work and main achievements are as follows:(1)The effects of anisotropy on the shear strength and kinetic parameters of undisturbed loess were analyzed and studied by direct shear test and dynamic triaxial test.The results show that as the angle between the horizontal and horizontal directions of the shear plane increases,the shear strength of the soil sample decreases.The effect of anisotropy on the dynamic parameters of undisturbed loess was studied by dynamic triaxial test.The experimental results show that the anisotropy of undisturbed loess has little effect on the dynamic stress-strain relationship with the change of confining pressure.When the dynamic strain is the same,the dynamic stress increases with the increase of confining pressure.However,the influence of anisotropy on the fitting parameters of the original loess backbone curve,the dynamic modulus with the strain development law and the initial dynamic modulus of the soil sample cannot be ignored.(2)Based on the ABAQUS software platform,the numerical analysis model of the track-subgrade-loess slope is established,and the dynamic response law of the cutting slope under the moving load of the train is obtained.The high slope model is a three-level large slope,and each large slope is divided into three small slopes.From the development law of the whole slope,the dynamic stress,acceleration,displacement and velocity response generated by the low-frequency vibration of the train gradually decrease along the entire slope.However,there is a significant rebound magnification trend at the top of small slopes at all levels during the attenuation process.The closer the vibration source is,the more obvious the amplification effect is.By comparing the maximum vertical dynamic stress,acceleration,displacement,and velocity response distribution curves on the key points,the amplification effect of the roller slope on the dynamic stress response is most obvious,followed by the acceleration response,and the amplification effect on the velocity and displacement response is better.Not very obvious.(3)The strength reduction method is used to analyze the stability of the cutting slope under the action of train load and no trainload.The stability safety factor and potential slip surface of the cutting slope under two working conditions are analyzed.The comparative analysis shows that train vibration will promote the instability of the slope to a certain extent.Finally,the engineering measures and suggestions for weakening the influence of train vibration on the long-term stability of the cutting slope in loess area are given in combination with the actual working conditions.