Stability study on swampy sloping roadbed in permafrost regions of Qinghai-Tibet railway

Stability analysis of sloping roadbed in permafrost reqions is different from due to varation of ground temperature of permafrost,and the location of freezing-thawing interface is the most important constraint of the stability of sloping roadbed.Through monitoring ground temperature at the Anduo section for three years,the variation of the ground temperature of roadbed was analyzed and the trend of variation within the next 30 years was predicted.The stability model of the present and future sloping roadbed was established,and the stability of sloping roadbed was calculated and analyzed by the improved limit equilibrium method and unbalanced thrust method.From the above research the following conclusions could be drawn: ① the permafrost temperature field was redistributed due to the filling of railway embankment;the ground temperature field was asymmetric due to the asymmetry of the direction and geometric shape of slopes and the two sides of roadbed settled differentially;② the lateral displacement of roadbed mainly occured in the soil above artificial permafrost table,and the freezing-thawing interface was the latent slide interface;③ the calculated coefficient of stability of sloping roadbed was 1.19 by the improved ultimate equilibrium method and the method in current standard(unbalanced thrust method),and it was necessary to strengthen the roadbed,such as setting thermosyphon asymmetrically,embedding slide-resistant piles downstream,widening roadbed,etc.;④ it was shown by the numerical analysis that 20 years later,the permafrost of the roadbed of Anduo test section would be completely degraded,and the coefficient of stability during the largest thawing period was the minimum in the 10th year.