Study On Tangential Frost Heave Force And Anti-frost Jacking Effect Of The Cone Piles In Cold Regions

The phenomenon of pile foundation frost jacking damage is a common engineering problem in severe cold area.Aiming at a new type of anti-frost jacking cone pile,through the laboratory test combined with theoretical analysis,the anti-frost jacking property of the cone pile compared with ordinary pile and its calculation method of tangential frost heave force are studied.On the basis of determining the physical parameters of the test soil material,a special anti-frost jacking property test device was adopted,and the pile with the cone angle of 9° was used as the main test object,and the pile with the cone angle of 0° was used as the comparison object.Comparative tests of freezing performance under test soil quality,water content and pile material conditions were carried out.According to the test results,the relationship between the anti-frost jacking performance of the pile and the above variables was obtained.Based on this,a prediction formula for the reduction of the 9°cone pile tangential frost heave force reduction effect is proposed,which can provide theoretical guidance for the design and construction of 9° cone piles.The main research contents and results are as follows:(1)During the process of pile frost jacking test,the temperature curve of the soil around the pile shows a simple harmonic motion with time,and there is a frozen core phenomenon inside the soil during the melting stage.The water in soil around the pile is vertically uneven distribution of water under the action of water migration after the freeze-thaw cycle.The frost heave and thawing settlement deformation of the soil increases with the increase of fine grained soil content and water content in the freeze-thaw cycle,which has a significant impact on the frost jacking property of the pile.(2)Under different experimental conditions,the development history of frost jacking force of 0° pile with time can be divided into three stages: rapid growth,slow growth and basic stability.The 0° pile frost jacking force increases with the increase of fine grained soil content,water content and surface roughness of the pile,and decreases with the number of freeze-thaw cycle.(3)The 9° cone pile has a reducing effect on the frost jacking force.Under different conditions,the 9° pile freezing pull force is far less than 0° pile,and in general,the frost jacking force is 0.Under the condition of silt clay,the initial frost jacking water content of 9° aluminum alloy pile is 16%,and the initial water content of 9° cement mortar pile is 15%.When the test conditions satisfy the initial frost jacking conditions of the 9° pile,the variation law of the 9° pile frost jacking force with the water content,surface roughness of the pile and the number of freeze-thaw cycles is similar to that of the 0° pile,but the value of the frost jacking force is only 25%~30% of the 0° pile.(4)When the test conditions satisfy the 9° pile initial frost jacking conditions,the tangential frost heave force reduction effect of 9°pile is almost not affected by the number of freeze-thaw cycle and the moisture content of the soil,and decreases with the increase of the surface roughness of the pile.(5)When the test conditions do not meet the initial frost jacking conditions of the 9° pile,the 9° pile tangential frost heave force reduction effect is 100%.When the test conditions satisfy the 9° pile initial frost jacking conditions,the tangential frost heave force reduction effect of 9° aluminum alloy pile is 84%,and the 9° cement mortar pile tangential frost heave force reduction effect is 81%.According to the 9° pile tangential frost heave force reduction effect and the 0° pile tangential frost heave force which can be checked in the code,the tangential frost heave force and frost jacking force of the 9° pile can be calculated,which can provide a theoretical basis for the design and construction of 9° pile.