ANALYSIS AND PREDICTION OF TEMPERATURE AND STABILITY OF SWAMPY AND SLOPE ROADBED IN PERMAFROST REGIONS OF QINGHAI-TIBET RAILWAY

Stability of slope roadbed in the permafrost regions of Qinghai-Tibet railway is a potential threat to the railway long-term operation. Assessment of stability of the current and future slope roadbed can guide the roadbed project to correctly design and construction, thus ensuring to operate the railway safely. Changes of ground temperature of permafrost make the analysis of the slope roadbed stability different from others. The location of the freezing-thawing interface is an all-important constraint of the stability of the slope roadbed. Through monitoring the ground temperature at the Anduo section for three years, the changes of the roadbed ground temperature are analyzed and the change trend of the ground temperature in the next 50 years is predicted. The stability model of the present and future slope roadbed is established and the stability of the slope roadbed is calculated and analyzed. Through these investigations, conclusions can be made as follows: (1)filling the railway embankment makes the permafrost temperature field redistribute; the asymmetry of the slope direction and the geometric asymmetry make the ground temperature field asymmetric; (2)based on the location of the freezing-thawing interface and the ground temperature characteristics of the active layer, the frozen roadbed can be divided into four different times, namely, the severe winter period (January-February), the spring and summer melting active period (March-August), the largest thawing depth period (September-October) and the refreezing active period (November-December); (3)the numerical analysis results show that 20 years later, the permafrost of the Anduo test section roadbed will completely degrade, and the stability coefficient in the largest thawing depth period is the minimum in the forecast 10th year.