Journal of Cold Regions Engineering

This paper presents a case history study of a tunnel in the cold plateau region of China. It describes the permafrost distribution of the mountain in which the tunnel is located and the observed air and surrounding rock temperatures in and outside the tunnel. By comparing these measured temperatures, it is found that the effect of the thermal insulation doors, installed at both ends of the tunnel, raises the air temperature in the tunnel higher than the antisnow shelter installed at both ends of the tunnel. The thermal insulation doors are thought to be better than the antisnow shelters in preventing the tunnel from being damaged by frost action.

On the basis of the results of small-scale and medium-scale indentation tests and full-scale measurements of ice forces, a methodology to estimate crushing ice forces is presented. The main point to note is that the effective pressure depends on the relative indentation speed, which in turn depends on the speed of a moving ice floe and the compliance of a structure. An increase in indentation speed leads to a change in failure mode from ductile to brittle, resulting in decreased effective pressure, and vice versa. The ice forces also depend on the temperature of the ice, because its strength and brittleness increase with decreasing temperature. The two codes for bridge piers and offshore structures are valid for brittle crushing of ice at high indentation speeds, and the recommended design effective pressure from these two codes is the same for wide structures (or large contact area) but differs for narrow structures (or small contact area).

Heat convection in ballast mass in railway embankments is a problem of heat convection in porous media. In order to calculate the temperature distribution of the Qing-Tibet railway embankment from the governing equations used to study forced convection for incompressible fluids porous media, detailed finite-element formulas for heat convection in porous media are derived using Galerkin’s method. The temperature distributions on central lines of the traditional railway embankment, the ripped-rock embankment, and the ripped-rock revetment embankment that were constructed on July 15, 2002 have been analyzed and compared on July 15, October 15 in the 24th year after construction, and January 15 in the 25th year after construction under the climatic and geological conditions on the Qing-Tibet Railway. The calculated results indicate that the traditional railway embankment will raise the permafrost temperature under the embankment base and make the permafrost embankment thermally unstable. The ripped-rock embankment and the ripped-rock revetment embankment will reduce the permafrost temperature under the embankment base in cold regions, therefore maintaining the thermal stability of permafrost. However, the ripped-rock embankment needs more rock mass while the ripped-rock revetment embankment need less rock mass, and its construction cost is lower than that of the former. Therefore, it is highly recommended that the ripped-rock revetment embankment be used for the Qing-Tibet railway embankment structure in high temperature permafrost regions so that the permafrost embankment can be protected as much as possible.