A Study On Dynamic Wetting Characteristics Of Heavy Load Railway Subgrade Soil

In order to improve the ability of railway transportation,our country is vigorously developing the capacity expansion and reconstruction of heavy haul railway.But after the scene investigation found that in some existing heavy haul railway,the coupling effect of natural rainfall and train dynamic load will produce large deformation of subgrade,caused a lot of water diseases of subgrade such as mud pumping,embankment collapse,uneven settlement of roadbed,these problems seriously hindered the development of China's railway construction revamping.Therefore,studying the dynamic humidification characteristics of heavy haul railway subgrade soil under the coupling action of immersion and cyclic load is very important for analyzing the disease mechanism and predicting the deformation of roadbed effectively.This study is under the support of National Natural Science Fund “Research on mechanism and adaptability of subgrade dynamic slaking deformation of existing line that running big axle load train”,the test of dynamic wetting under water immersion is carried out with the combination of the GDS three triaxial instrument and self developed martensitic bottle with constant head,the dynamic triaxial instrument applies cyclic loading,and real-time replenishment of martensitic bottle,which simulates the actual state of the subgrade under the coupling of rain and train dynamic load.Considering that the actual subgrade will undergo a complicated immersion process,the influence of the immersion process on the dynamic wetting characteristics of subgrade soil is also studied.In order to effectively predict the deformation of Subgrade under the coupling of water immersion and cyclic loading,a dynamic humidification model considering the coupling effect of wetting and cyclic loading is established on the basis of the modified Iwan series model and the test.The main work and research results of the article are as follows:(1)Field investigation is carried out on many disease sections,understand the condition of the disease and take back the soil sample.The basic physical property test for the returned soil samples is carried out,and the properties and basic physical parameters of the soil samples are determined,and the main causes of subgrade disease are analyzed.(2)The GDS dynamic triaxial instrument is improved so that it can be soaked at the same time when cyclic loading is applied.The dynamic wetting test under the effect of water immersion is carried out by the improved test instrument,the variation of strain,water immersion,hysteretic curve,damping ratio,dynamic elastic modulus and backbone curve of soil during dynamic humidification is studied.It is found that the strain increases with the increase of the strain stress amplitude,the difference of strain increment after the stability of the dynamic stress amplitude at all levels is about 0.3%,and the amount of water decreases with the increase of dynamic stress amplitude,the hysteresis loop will move to the right side and slope reduction due to strain accumulation and strain softening,and the dynamic elastic modulus and damping ratio will basically decrease with the increase of vibration number.For a larger transmission line with larger axle load,the larger dynamic stress will be borne for the larger axle load.At the same time,with the action of water immersion,the roadbed will cause greater deformation and risk of damage.(3)The dynamic wetting test of soil under different soaking process was set up in three kinds of immersion process,the variation of strain,hysteresis curve,softening index,dynamic elastic modulus and damping ratio of subgrade soil under different water immersion process is studied.The results show that soaking process has a significant effect on the strain,hysteresis and softening index of the soil,and the dynamic elastic modulus and damping ratio decrease as a whole,and there will be fluctuations in the local area.The subgrade will experience complex deformation after experiencing different soaking process,especially before and after expansion and expansion.The deformation of the roadbed will be greatly improved,so we must pay enough attention to it.(4)Based on the modified Iwan series model,a dynamic humidification model considering the coupling effect of water immersion and cyclic loading is established,Fortran language is used to compiling the calculation program,and the test results are simulated and the goodness of fit is good,this model can better predict the dynamic humidification deformation of soil under long-term cyclic loading..