Abstract: The completely weathered quartz monzonite soils are planned to be used as the backfill material for the railway subgrade in Beijing to Shanghai High Speed Rail project in order to reduce the construction cost. The stress-strain relationship with the number of loading cycles; the relationship between the rebound modulus and the loading cycles; the relationship between the moisture content and the failure strain are examined with the dynamic triaxial tests with minimal confining pressure to simulate the shallow embedment of these materials underneath the rail tracks. The results indicate that the higher moisture content will have a smaller failure strain. In the practical engineering application, the control of the moisture and modify the physical properties of the backfill material can result in a satisfactory engineering performance as well as cost effectiveness.
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Key words: Completely-Weathered Soils, Triaxial Tests, Moisture Contents, Critical Parameters