The causes of railway roadbed deformations on permafrost soils

Currently, the problem of forecasting and maintaining the geotechnical condition of railway infrastructure facilities caused by the activity of destructive cryogenic processes in saline alluvial, marine and lagoon-marine sediments is one of the key aspects of improving the reliability and safe operation of railway infrastructure. Continuous monitoring of the railway roadbed state helps to preliminarily assess the technical condition of the roadbed and identify problem areas by external signs. The paper highlights an instrumental survey using thermal chains and ground-penetrating radar equipment which is carried out in local places most susceptible to deformations and exposure to hazardous geological processes. The obtained results of instrumental surveys help to assess changes in geocryological conditions and the state of foundation soils in the study area. The compilation of numerical models of temperature regimes of foundation soils and roadbed based on climatic data is carried out in the Borey 3D software. According to the results, an increase in the temperature regime is observed in the period from 2015 to 2023 not only in the active layer of the object, but also in the zone of zero temperature fluctuations permafrost soils from 0.5 to 1.5 degrees. During thawing, the foundation soils are compressed under the weight of the railway roadbed, thereby forming flooded low-lying areas along the embankment base. Due to the flooding of the slope parts of the embankment, water saturation of the soils of the roadbed body occurs causing cryogenic processes in the structure and foundation of the road. In most cases, the accumulated water along the slopes of roads is in a thawed and frozen state all year round. Thus, the construction of linear railway embankments on permafrost soils of the West Siberian Plate is an expensive experiment, due to the fact that the feasibility of preserving the foundation soils and adjacent territory in a permafrost state is highly questionable.