Research On Engineering Characteristics Of Aeolian Sand And Physical Improvement Subgrade Of Heavy Load Railway

A large number of high-quality fillers are needed for the construction of heavy-duty Railway Subgrade in desert area.In addition to the eolian sand resources,there is a lack of group A and B fillers.Aeolian sand is a kind of geological material with special engineering characteristics.It has poor grading,concentrated particle distribution and low cohesion.It is a group C filler with poor grading.Aeolian sand can be us ed to fill the parts below the subgrade bed,but group A or B materials are needed for the bottom layer of heavy-duty Railway subgrade bed.In this paper,based on the research background of the aeolian sand subgrade project of Menghua heavy haul rail way,from the point of view of reducing the engineering cost and making full use of the local aeolian sand resources,the aeolian sand filler is tested in the laboratory to study its physical and mechanical properties and compaction characteristics,and it is improved into group B material through physical improvement method,so as to meet the requirements of heavy haul railway for the bottom layer filler of the subgrade bed.Finally,it is applied ABAQUS finite element software establishes the analysis and calculation model of heavy-duty railway subgrade,studies the deformation law and stress distribution of the subgrade bottom layer filled by aeolian sand and improved aeolian sand,and through analyzing the influence of the improved and reinforced aeolian sand on the subgrade performance,obtains whether the reinforced aeolian sand can replace the improved aeolian sand to fill the bottom layer of subgrade bed.The specific conclusions are as follows:?1?For the analysis of Aeolian particles,the test results show that the nonuniformity coefficient Cu of three groups of aeolian sand samples is between 1.75 and 2.03,the curvature coefficient CC is between 0.97 and 1.04,and the mass of the sample with particle size greater than 0.075mm is more than 80%of the total mass of the sample.It can be concluded that aeolian sand is a group C filler with poor particle grading.?2?The results of compaction test and direct shear test show that the compaction curve of aeolian sand is inverted"s",the maximum dry density is 1.88g/cm3,and the optimum moisture content is 14.79%.When the compaction degree of aeolian sand is 0.95,under the natural moisture content?w?1%?,the internal friction angle ?₁=39.5°,and cohesion C₁=0.5 kpa;under the optimal moisture content?w=14.79%?,the internal friction angle ?₂=37.8°,and cohesion C₂=14.5kpa.?3?The physical improvement of aeolian sand is to improve the particle size distribution of the filler by adding a certain proportion of fine round gravel soil into the aeolian sand,so as to meet the requirements of the heavy haul railway for the bottom layer filler of the subgrade bed.The test uses the fine round gravel soil content of70%,60%,50%,40%and 30%,and five kinds of proportion are added into the aeolian sand filler.The test results show that the coarse particle content of each group of improved materials is more than 3 The content of particles less than 0%,0.075 mm is less than 5%,the improved materials are all group B materials,which can meet the filling requirements of the bottom layer of heavy-duty railway subgrade bed.?4?The results of numerical simulation show that the vertical displacement of the roadbed is mainly caused by the settlement of the bottom layer and the part below the roadbed.When the improved and reinforced aeolian sand is used to fill the bottom layer of the subgrade bed,the vertical displacement of the bottom layer of the subgrade bed is reduced,which effectively controls the vertical displacement of the road base,and also inhibits the horizontal displacement of the subgrade;the improved method has little change in the vertical stress distribution of the subgrade,and the reinforced method can reduce the vertical stress below the reinforcement.The effect of double-layer reinforced aeolian sand to control subgrade displacement is basically the same as that of physical improved aeolian sand.In the case of single-layer reinforcement,the change of the reinforcement position at the bottom of the subgrade bed has a certain impact on the subgrade.The closer the reinforcement material is to the bottom of the subgrade bed,the smaller the vertical displacement of the subgrade;in the case of double-layer reinforcement,the first layer of reinforcement material is to be laid on the surface of the bottom of the subgrade bed,and the second layer of reinforcement material is to be laid 1.2m from the surface of the bottom of the subgrade bed,the better the effect of controlling the subgrade displacement.