Discussion about Analysis Method for Particle Composition of Coarse-Grained Soil and its Compaction Test

摘要

It is found that the coefficient of uniformity of coarse grained soil is very large, while its coefficient of curvature is relatively small by analyzing the filler from Gobi Desert area in Xinjiang Province which is used in the second double-line of Lanzhou-Xinjiang high-speed Railway. According to the current standard in China, the coarse grained soil is poorly graded since the coefficient of curvature is too small, which, however, may not necessarily cause poor grading for coarse grained soil. The limitation and inapplicability of the current standards on grading are figured out based on the analysis of particle composition of coarse grained soil, and a new method dividing the coarse grained soil into the coarse and fine part to value the grading is proposed in the paper. The coarse and fine fillers are distinctly segregated from each other in the conventional compaction test. In order to ascertain the optimum moisture content and maximum dry density, it is suggested in this paper to run a compaction test only on the fine grain fraction in the soil to measure its optimum moisture content and its porosity, and use the conversion method to control the density of the subgrade.