Experimental Research On Seasonal Subgrade Freezing Damage In Gobi Region

The gobi seasonal frozen soil area,which distributes in the south of Mongolia, Xinjiang and Inner Mongolia.The natural environment is formidable.It's blazing hot in summer,the surface temperature increases up to a 60℃.It's severely cold in winter, the surface temperature declines to -30℃,the subgrade soil layer's distributing is fine grained soil.In this condition,the surface of road easily engenders temperature stress crack,and the subgrade soil will cause freezing damage in the freezing and thawing process.This article based on the tests of subgrade soil taken from Mongolia regional road development project Choir-Sainshand-Zamiin Uud highway of package B1,and combines the highway freezing damage inquisition in Inner Mongolia and Mongolia Gobi area.This article analyses and summarizes the present condition and mechanism of the seasonal subgrade freezing damage in Gobi area.The seasonal subgrade freezing damage in Gobi area takes the form of frost expansion,thaw,plasm formed from strength reduction of subgrade in a long period cycle of freezing and thawing process.The influencing factor of freezing damage includes the soil quality,temperature and water.The lower soil content in Gobi desert area can easily endanger the freezing damage.This cut off the vaporation path of asphalt concrete road surface and result in the transference of moisture of subgrade.The test data from Mongolia region highway development project Choir-Sainshand-Zamiin Uud on package B1 shows that the strength of sand soil is better than clay,which tend to choose subgrade soil field on the follow linear,and obtaining the corresponding roadbed strength-index parameter.Aiming at the frozen soil test of Mongolia regional road development project Choir-Sainshand-Zamiin Uud on Km29+180-Km30+166 of package B1,the article carries up roadbed mechanics of frozen soil property test research,and Obtaining occurrence trend and strength change trend with the temperature reduction in the different soil quality. To Establishing hydro-thermal coupling mathematic model of the frozen soil roadbed.Applying finite difference software FLAC to simulate temperature field and stress field of the test segment.Verifying the stability of the subgrade in the segment after the freezing and thawing process.