Abstract：Research purposes: Now the theory on the unsaturated soil is imperfect，and the consolidation theory and settlement calculating method for the unsaturated soil are not mature because of the complexity of the unsaturated soil．The subgrade settlement becomes one of important control factors of passenger dedicated line，so it is very important to know the physical mechanics characteristics of the unsaturated soil and it is very significant to reveal the settlement characteristics of unsaturated soil subgrade for selection of more reasonable and economic treatment way for the unsaturated soil subgrade of passenger dedicated line．
Research conclusions: The saturations of unsaturated silty clay and floury soil along the Qingdao － Jinan Railway are between 46% ～ 80% ． The embankment settlement during construction period can be above 75 percent of the total settlement and about 90 percent of the total settlement after 3 to 5 months． The stress － strain curve and the strain － time curve tally with the hyperbolic model，and hyperbolic method is recommended to predict the settlement of the subgrade． It is unnecessary to treat the unsaturated soil subgrade of the ballast track of passenger dedicated line． It is necessary to conduct the treatment to the shallowness from 5 m to 8 m of the subgrade of ballastless track of passenger dedicated line． The treating depth should increase for the high filling and transition sections of the ballastless track of passenger dedicated line．
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2012, Vol. 29 
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