Stabilization of the subgrade formed by draining soils in the design of second tracks on railways in cold regions

During the operation of railways in the cryolithozone, in particular the Baikal-Amur Mainline, so-called thawing bowls were formed under the existing earth bed from draining soils in areas of high-temperature frozen soils. The infiltration of atmospheric precipitation into the body of the earth's surface is a key factor in its formation. Quantification of this effect is very problematic due to the uncontrolled nature of filtration processes in the body of the earth bed within the framework of traditional thermophysical calculations. The issue of precipitation filtration is particularly pressing given that the modernization of the Baikal-Amur Mainline, aimed at increasing its capacity, envisions the construction of second tracks on a common subgrade, which is primarily made of drainable coarsegrained rocky soils, in accordance with current design standards.

In this article, a hypothesis is proposed and justified by numerical modeling to solve the problem of accounting for the warming effect of atmospheric precipitation on the soils of the foundation of the roadbed. Its essence lies in the introduction of the concept of infiltration thermal conductivity, which is taken into account when determining the total coefficient of thermal conductivity of the draining soils of the earth bed in a thawed state. This approach to the description of the thermophysical picture of the draining soils of the earth bed and its base allowed us to substantiate the technological scheme proposed in the work for the phased stabilization of the frozen soil boundary at the base of the embankment during the construction of the second tracks. The process flow diagram proposed in the article eliminates the impact of the warming effect of atmospheric precipitation on the soils of the subgrade foundation. A distinctive feature of the diagram is the staged installation of waterproofing in the upper portion of both the newly constructed and existing subgrade, facilitating the restoration of the frozen state of the soil beneath the operational track.

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