Influence of accounting for solar radiation on the results of thermal engineering calculations of the railway track subgrade

Abstract

Any solution of a heat engineering problem, in particular, when designing anti-heaving measures on transport lines, requires a strict specification of temperature boundary conditions on the daylight surface. In the case of a railway track, this is the temperature of the upper layer of the ballast prism. A priori, it consists of two components – air temperature and the so-called temperature correction determined by solar radiation. In this paper, an analysis of the influence of temperature correction on the results of thermal engineering calculations is carried out – the depth of freezing and thawing of subgrade soils in cold regions. The description of full-scale experiments on the quantitative assessment of the influence of solar radiation on changes in the temperature regime of the surface of the ballast prism is given. A method is described for determining the temperature correction, which depends on such main factors as the latitude of the area, air temperature, the cloudiness index, and Albedo of the ballast. A computer program has been developed that implements the above method. The performed comparison of the calculated and experimental data of the temperature correction made it possible to conclude that the above methodology is correct for performing practical calculations of the temperature correction for solar radiation when determining the temperature regime of the surface of the ballast prism in relation to thermal engineering calculations of the subgrade of the railway track. The degree of influence of such initial parameters of the calculation method as Albedo of the ballast and the cloudiness index on the value of the temperature correction in various climatic zones is established. The “sensitivity” of the results of calculating the depths of freezing and thawing of the subgrade to a possible error in setting the temperature correction, which determines the upper boundary condition of the heat engineering problem, is revealed. The special role of taking into account the temperature correction in thermal engineering calculations in permafrost is shown.