| The railway undertakes the heavy task of transporting people and goods,and is an important support for China’s economic activities.Coarse grained soil has excellent engineering properties,so it is widely used as railway subgrade filler.The composition of coarse grained soil particles is complex,and it bears upper loads such as train dynamic load,track static load,and fill self weight.There are many factors affecting its mechanical and deformation characteristics.In recent years,extreme rainfall events have occurred frequently in China,and rainfall infiltration is bound to affect the service performance of coarse grained soil subgrade.Currently,there is insufficient depth of targeted research,and no in-depth explanation has been provided on how rainfall affects coarse grained soil subgrade.Therefore,it is necessary to explore the impact of rainfall infiltration on the deformation and particle migration characteristics of coarse grained soil fillers in order to better reveal the deformation of coarse grained soil roadbed.Therefore,this paper constructs a coarse grained soil model test system to conduct dynamic cyclic loading,static pressure,and creep tests under rainfall infiltration.The specific research contents and conclusions are as follows:（1）.To reveal the characteristics of particle migration and distribution in coarse-grained soil fillers,a model test system for particle migration in coarse-grained soil fillers was constructed.Different soil thicknesses,rainfall,and particle sizes were simulated,and 16 sets of rainfall infiltration tests were conducted.Particle analysis was conducted on the migrated samples,and the leachate was collected.It was found that the maximum migration depth of clay（particle size≤0.075）was around 500-600 mm,The maximum migration depth of quartz sand（particle size0.315-0.63 mm）is about 300-400 mm,and the migration particles will deposit at 0-100 mm to form an accumulation area.With the increase of rainfall,the lower part of the soil layer will form a second accumulation area.（2）In order to reveal the dynamic cumulative deformation characteristics of coarse grained soil filler under rainfall infiltration,a dynamic cyclic loading model test system for coarse grained soil was constructed.MTS and rainfall systems were used to simulate the effects of different loads,different rainfall intensities,and other factors.The cumulative deformation curve of coarse grained soil filler under rainfall infiltration was obtained,and the roadbed deformation caused by rainfall infiltration exceeded 100%;The change of broken particle group of coarse grained soil filler under dynamic load caused by rainfall;The permeability coefficient decreases with the increase of the breakage index Bg,and the decrease of the effective grain diameter d10is an important reason for the decrease of the permeability coefficient.（3）In order to reveal the static deformation characteristics of coarse grained soil filler,a static compression test was conducted using a coarse grained soil model test system to explore factors such as rainfall,soil layer thickness,and compaction degree P5content.The impact of particle migration on the deformation of coarse grained soil filler was expounded from the perspective of relative mass of migration,curvature coefficient Ccand non-uniformity coefficient Cu.The results show that the static compressive strain gradually increases with the increase of load,and decreases with the increase of soil thickness,compactness,and P5content;An index of particle migration and gradation loss is proposed,and a static compression model of coarse grained soil is established that considers gradation loss,load,and soil thickness.（4）Using a self-made coarse grained soil filler unit model test system,a series of two-dimensional creep tests were conducted to explore the effects of vertical stress,rainfall infiltration,and other factors on creep and particle breakage;A hyperbolic creep prediction model that can simultaneously consider rainfall infiltration,breakage index Bg,and load was established.An analysis model for creep deformation of coarse grained soil subgrade was established,and the creep deformation of subgrade under different track types was analyzed.The results show that the strain of coarse grained soil filler after creep stabilization is 0.05 to 0.101%,and it presents an attenuation type growth trend;During the creep process,particle breakage is mainly caused by large particle size particle breakage,supplemented by grinding.Rainfall infiltration causes changes in the particle size of coarse grained soil filler particles;The calculated values of the creep prediction model are in good agreement with the experimental values,and the increase in creep deformation of the roadbed caused by rainfall infiltration can reach 80%. |
