Study on preventing frost heave methods for highway foundation in seasonal frozen area

In order to resolve the frost-heave problem of highway foundation,firstly,the author discussed the law to frost heave of highway roadbed and gave an analysis on its influencing factors,such as soil,water and temperature.Meanwhile,sand clay and silt are given a classification according to frost heave ratio.Secondly,the roadbed frozen damage shows to frost heave and froze boiling based on the frost heave law and its influencing factors.In addition,taking some highway as an example and some principle suggestion was given through the theory on providing frostbite methods for highway foundation frost heave in seasonal frozen area.Specially,an effective method,STYROFOAM extruded polystyrene foam was introduced.

Discussion on applying an analytical method to optimize the anti-freeze design parameters for underground water pipelines in seasonally frozen areas

Adopting the quasi-three-dimensional （Quasi-3D） numerical method to optimize the anti-freeze design parameters of an underground pipeline usually involves heavy numerical calculations. Here, the fitting formulae between the safe con-veyance distance （SCD） of a water pipeline and six influencing factors are established based on the lowest water temper-ature （LWT） along the pipeline axis direction. With reference to the current widely used anti-freeze design approaches for underground pipelines in seasonally frozen areas, this paper first analyzes the feasibility of applying the maximum frozen penetration （MFP） instead of the mean annual ground surface temperature （MAGST） and soil water content （SWC） to calculate the SCD. The results show that the SCD depends on the buried depth if the MFP is fixed and the variation of the MAGST and SWC combination does not significantly change the SCD. A comprehensive formula for the SCD is estab-lished based on the relationships between the SCD and several primary influencing factors and the interaction among them. This formula involves five easy-to-access parameters： the MFP, buried depth, pipeline diameter, flow velocity, and inlet water temperature. A comparison between the analytical method and the numerical results based on the Quasi-3D method indicates that the two methods are in good agreement overall. The analytic method can be used to optimize the anti-freeze design parameters of underground water pipelines in seasonally frozen areas under the condition of a 1.5 safety coefficient.

Simulating and validating the effects of slope frost heaving on canal bed saturated soil using coupled heat-moisture-deformation model

The lining canals in seasonal frozen soil areas can be severely damaged by frost heaving.The freezing and thawing contributes to the continual change of the temperature field and moisture field beneath lining canal,which will seriously affect the safe operation of the canal.In order to study the frost heaving damage mechanism of lining canal and to solve the associated engineering problems,the permafrost body was regarded as an elastomer,and a three-field,coupled,partial differential equation describing the temperature,moisture and deformation fields for a saturated two-dimensional canal bed was derived and established based on the Harlan model.The coupling equations were discretized using the finite element method in space and the finite difference method in time.The parameters were simplified appropriately based on compliance with the actual conditions and were simulated using finite element software.The results of a sample simulation showed that the simulated results and test results were basically consistent with variation laws,which proved the correctness of the numerical simulation theory and solution methods and the reliability of the calculation.The model can simulate the water,heat and deformation issues in the side slope of saturated canal bed soil in a seasonally frozen area and forecast freezing damage in the canals.