Research On Frost Heaving Characteristics And Evaluation System Of The Subgrade Soil In Seasonal Frozen Region

Seasonal frost heave is always an important problem of northern area highway construction. However, research about frost heave mainly concentrated in the permafrost in our country. The study of seasonal frozen soil remains to be further. With the increasing of highway mileage, highway early built followed into the maintenance period and the testing and maintenance were promoted to an unprecedented importance.In order to study the feature of the subgrade soil frost heave in the frozen area and evaluate the frost heave condition, the paper selected three different levels road in season frozen area of Heilongjiang province, carried on the field investigation and observation to the actual frost heave condition, collected subgrade filling for closed frost heave test, carried on regression analysis of single factor and multiple factors to the result of experiment, established multi-factor frost heave rate prediction model applying the SPSS statistical analysis software basing on the test result, classified the frost heave characteristics of the clay and sandy soil, established the subgrade frost heaving status evaluation system according to the survey and related standards and applied in actual operation. The results show that degree of impact on the frost heave rate is that moisture content is the maximum, compaction degree is the second, freezing temperature is minimal. The initial moisture content of frost heave of silty clay is0.89times the plastic limit, the critical moisture content of frost heave is0.97times the plastic limit. The initial moisture content of frost heave of the low liquid limit clay is0.89times the plastic limit, the critical moisture content of frost heave is0.97times the plastic limit. The initial moisture content of frost heave of sand soil is0.89times the plastic limit, the critical moisture content of frost heave is0.97times the plastic limit. The classifying result of the clay can solve the problem that frost heave evaluation of clay was unsafe in the specification. The classifying result of sandy soil can evaluate the frost heave characteristics of medium sand soil, gravel coarse sand and gravel soil, which content of pink clay is more than fifteen percent. The subgrade frost heaving status evaluation index system is suitable for evaluation of different grading road subgrade frost heaving conditions, which considered influencing factors of frost heaving. Research results have certain significance for prevention and control of frost damage and the evaluation of the frost heave condition of subgrade in seasonal frozen region.