Effects of Permafrost on Earthquake Resistance of Transport Facilities in the Baikal–Amur Mainline Area

Abstract

The permafrost region includes about 50% of seismic areas of Russia. One of the largest Russian railway lines, the Baikal–Amur Mainline (BAM), runs through these areas. Currently, there is much concern about the continuation of its construction in an effective manner and development of the adjacent areas that are rich in mineral resources and woods. Key characteristic factors of this region include permafrost occurring down to a depth of several hundred meters, long severe winter period, strong winds, seismic rating of up to 9 and higher. Earthquake consequences have never been considered as a natural disaster because the territory is sparsely populated. However, with anticipated populating and further development of this area in the nearest future, studying of seismic manifestation, as well as implementation of efficient solutions ensuring reliability of transport buildings and structures, will be an important national task. By reviewing geotechnical and seismic conditions in the mainline area, one of the most hazardous parts of the route can be defined, i.e., the western part where permafrost penetration is as deep as 200 m and deeper, with permafrost soil temperatures down to minus 6 °C with high ice content in the soil. This part of the mainline is characterized by rate 5–10 earthquake manifestations. In addition, mudflows, snow slips, and landslides are common in this part of the mainline. Seismic activity in this region is characterized not only by high degree of earthquake intensity, but also by frequency of earthquake manifestations. According to seismological information of researchers, in the mainline area rate 8 earthquakes can be expected to repeat in 15–20 years, rate 9 earthquakes can be expected to repeat in 60–70 years, and rate 10 earthquakes can be expected to repeat in 200–250 years. This repetition rate of earthquakes gives significant rise to the medium frequency of earthquakes in one geographic point of a seismic area, which is a parameter taken into account by seismic construction regulations. This paper discusses the issues of permafrost effects on the seismic hazard of the mainline area and includes recommendations for the need to consider these effects when designing facilities of transport infrastructure.