Influences Of Culvert On The Thermal Stability Of Roadbed With Thermal Pile In Permafrost Region

Stability of roadbed is the core of road construction technique research in the permafrost regions of plateau. The soil body temperature influences the stability of roadbed in permafrost regions in the aspects of intensity, transfiguration, growth and melt of frozen soil and so on. Thermal stability of roadbed must be evaluated when the stability of roadbed in the permafrost regions is evaluated. On the basis of understanding the characteristics of variation and trend of development of climate in the permafrost region of Beilu river of Qinghai-Tibet Plateau, this dissertation studies the characteristics of variation and trend of development of ground temperature of general landfill roadbed and thermal probes roadbed in the permafrost regions under the background of studying the temperature variation. This research also involves studying the influence of culvert on the thermal probes roadbed thermal stability. The main research works are as follow:1. The concept of roadbed thermal stability was expatiated and the important significance of studying the influence of culvert on roadbed thermal stability was discussed.2. 3-D numerical value calculation model of the frozen roadbed thermal field was built and influence of thermal probes on frozen roadbed stability was studied and finite element method was adopted to predict and compare the thermal field of general and thermal probes roadbed by rising 2.6°C in the coming 50 years, difference of the negative and positive slope of roadbed was considered in studying and the measured data of ground temperature with the scene was the foundation and numerical simulation was adopted. The results show that the thermal difference of the negative and positive slope can cause asymmetry of soil layer temperature field under roadbed, which will arouse uneven transverse deformation of roadbed. Under the condition of air temperature going-up, the general roadbed may come into being melting more to sink deformation in the coming 50 years and couldn't guarantee the long-term stability of roadbed. The thermal probes roadbed has the effect of cooling down on self s own initiative. The thawing depth of thermal probes is smaller than that of general roadbed and the difference of negative and positive slope reduced obviously. All of these explained that the thermal probes structure roadbed can counteract the influence of climate being changed into warm and guarantee the stability of the roadbed.3. Seepage theory and thermal transmission theory were adopted to set up finite element equations of coupled action of frozen culvert temperature field and seepage field under the condition of taking into the infiltration of seeper of the front culvert. The temperature fields of general and thermal probes roadbed were calculated when taking into seepage under the condition of passing water by culvert in warm seasons. Influences of seepage on the culvert roadbed temperature field and culvert on the thermal stability of roadbed were discussed. The results show that the action of seepage can deepen the season melting depth of culvert roadbed soil, which will cause adverse influences to culvert as well as thermal stability of general roadbed. But the stability of culvert and roadbed will be guaranteed for the roadbed by adding the thermal probes due to the refrigeration effect of thermal probes can counteract the adverse influence of culvert on the roadbed thermal stability.