Regression models of irregular vertical displacement of a roadway cross section caused by frost heaving

Subgrade clay is subjected to frost heaving under the effect of cold air and adequate soil moisture. The existing prediction models for frost heaving have a number of drawbacks: they are complicated for practical use and unable to evaluate irregular vertical displacements. Winter monitoring of 14 road sections was performed to evaluate irregular vertical displacement of pavement surface cross section under the action of frost heaving. The obtained data on vertical displacement of points were processed using mathematical statistics methods, and predictive regression models were built for vertical displacement of pavement during winter season. Stable relations were defined between displacement of points on the broken line (center-line of a road) and the factors including air-freezing index, thermal resistance of pavement, impact of subsurface water on frost heave, the pressure of pavement on the subgrade surface. Adequacy of the built models was checked using the results of displacement of points on the pavement surface within test sections. The first check concerned comparison of the values of modeling of the average displacement of points on the broken line caused by frost heaving, where mean absolute error was up to 20 %. For the case of close occurrence of subsurface water, the model prediction of the average displacement of points on the broken line showed significant difference from the actually recorded values. The second check concerned the displacement of points on the pavement in relation to displacement of points on the broken line, with the mean absolute value of up to 13 %.