Experimental Study On Tangential Frost Heave Force Of Anti-Heave Pile In Seasonal Frozen Regions

In seasonal frozen regions,the frost heave often lead to the destruction of pile foundation.The aim of this thesis is to analyze the stability of tapered pile foundation which is used for antifreeze in seasonal frozen regions.The tangential frost heaving force is the direct reason for pile foundation frost heaving,however,the study of antifreeze performance of tapered pile foundation is less in our country.Therefore,the tangential frost heaving force tests of aluminum alloy and concrete pile which cone angle is a series of different angles,respectively,were conducted.At the same time,direct shear tests at low temperature were carried out to obtain the effect of freezing strength on the tangential frost heaving force.The main content and understandings are listed as follows:(1)It can be concluded from the tests results that the failure mode of pile-soil interface is plastic failure under the condition of positive temperature,while it showed brittle failure under the condition of negative temperature.It can be also seen that the freezing strength,cohesion and friction angle of pile-soil interface is increasing with the decrease of the temperature under the condition of negative temperature.Cementing property of pile-soil interface which made of aluminum alloy is less than that of concrete.(2)The temperature in the sample was verified to change as a trend of “ladder”,based on a series of indoor freeze-thaw cycle tests.There is frozen ground core phenomenon during the thawing process,and it is obvious to see the moisture migration in the sample.The frost heave of the sample is always less than the thawing settlement,and soil sample is characterized by compaction.(3)At the beginning of the freeze period,it can be seen that the tangential frost heaving force increased at first then decreased slightly due to the contraction of the soil.After that,the tangential frost heaving force increased again and reached to the peak value.At this time,the tangential frost heaving force of piles with smaller cone angle tends to be stable.But when the angle of piles reach to 7°,tangential frost heaving decreased again and the anti-heave advantage of tapered pile shows the effect.(4)The results show that the tangential frost heaving force is inversely proportional to the cone angle,that is,the bigger the cone angle is,the smaller the tangential frost heaving force.Besides,after 7°,the slope of relationship curve of tangential frost heaving force and cone angle decreased obviously with a small value of tangential frost heaving force.In conclusion,the cone angle of 7° is the best cone angle for reducing the tangential frost heaving force.(5)The tangential frost heaving force of aluminum alloy pile is less than that of concrete pile,and it can be concluded that the more smooth the surface of pile is,the lower the tangential frost heaving force.