Permafrost railroads of Eastern Siberia and the Russian far east: types and causes of contemporary deformations

Based on long-standing field observations carried out by the authors, along with a comprehensive analysis of archival materials, including those dating from the last century, the types and causes of contemporary deformations affecting the main railroad lines of the Russian permafrost zone are characterized. The peculiarities of each deformation type are demonstrated using a specific example. According to the observational data, the contemporary rate of permafrost degradation at the roadbed base of the railroads of Eastern Siberia and the Russian Far East, which were constructed over 40 years ago, is around 1–2 cm/year. However, the rate of roadbed settlement exceeds the thawing rate of permafrost soils in its base by several times. Thus, thermal (due to permafrost degradation) settlement of the roadbed gives way to plastic and suffusion settlement types. Plastic roadbed settlement is associated with the transition of thawed soils to a fluid-plastic state. Under the influence of the dynamic load of train traffic, such soils are then squeezed out from under the roadbed. Suffusion settlements, which are characterized by their sudden activation, are caused by the removal of the fine fraction from the body and base of the embankment by water flows. Along with the increased air temperatures and higher annual precipitation observed in recent decades on the territory of Russia, deformations of the roadbed associated with seismic effects are becoming more widespread. Railroad facilities and track sections with taliks in the base, as well as those characterized by water-saturated sandy soils, are the most vulnerable during earthquakes. Observations of roadbed sections with water-saturated sands in the base show that, following an earthquake, embankment deformations continue over extended periods of time. The results of the conducted studies demonstrate the likelihood of serious climate-change-related problems arising in the Russian railroad sector if current principles of infrastructural maintenance and technical standards for preserving the infrastructure of railroads with an operational life of several decades remain at the same level.