Study on Gradation Improvement of Gravel and Sand for Surface Layer of Railway Subgrade by Blending Method

Abstract

As the direct foundation of the track, the surface layer of high-speed railway subgrade bed is one of the important parts of the subgrade. Its main function is to transmit and spread the vertical load of the upper ballast bed and the vehicle dynamic load to maintain the long-term stability of the subgrade bed surface. So, the material for the surface layer of subgrade bed should have high strength, elastic modulus, wear resistance and invented filtration. The graded sand gravel, which is used as the filler for the surface layer of railway subgrade bed, has such features as high mechanical strength, high water stability, easy obtaining, convenient construction, low cost and so forth. The purpose of this study is to physically blend local sand gravel materials to solve the defect of excessive fine particle content, so that it can meet the grading requirements of the specification and design standards and also to provide a general calculation method and solution for the mix ratio design of natural sand gravel. In combination with a foreign project, the dissertation expatiated on the calculation method for improving the gradation defects of natural sand gravel by the blending method. Then, according to local conditions, the author successfully solved the gradation defects of natural sand gravel mixture with the said method and achieved good economic and social benefits.