Frost heave control of fine round gravel fillings in deepseasonal frozen regions

Fine round gravel soil is widely employed in the subgrade of high speed railways in cold regions to prevent frost heavingand thawing. The lower the fines content in fine round gravel soil, the smaller the quantities of frost heaving and thawing,but compaction difficulty increases. This study is to obtain the optimum fines content and limited frost heaving andthawing. The fine round gravel soil filling (FRGSF) used in the Harbin-Qiqihaer Passenger Dedicated Line is taken as thestudy object. Influence of fines content on optimum water content, maximum dry density and frost heaving properties ofFRGSF were studied by means of compaction and frost heaving tests. Results show that the maximum dry density of theFRGSF increases first and then decreases with an increase of fines content, namely there is an optimum fines content foreasy compaction. The method of surface-vibratory instrument is fit for coarse-grained soils, and wet state ofcoarse-grained soil is in favor of compaction. Considering the relationship of fines content with maximum dry density andthe frost heaving ratio of FRGSF, the fines content should be limited to within the range of 9%-10%, so that the frostheaving ratio is less than 1%, and the FRGSF is easily compacted. Water supply is proved to be an important factor influencingthe amount of frost heaving of FRGSF. We also conclude that in the field, it is imperative to control waterproofingand drainage measures.