Published: 2023-12-21

Alternative structures of railroad subgrade protective layers

Michał Pawłowski


Structural improvement of the upper zone of railroad subgrade, designed based on local geotechnical testing, may not always prove adequate to the actual geotechnical conditions observed in field during construction. When such discrepancies occur, it is necessary to adopt and install alternative solutions. The article presents two basic protective layer structures (single- and double-layer) that increase the bearing capacity of the upper zone of railroad subgrade, as well as three most popular alternative solutions (layer of increased thickness, geogrid-reinforced layer and double-layer structure with the bottom layer consisting of hydraulically-stabilized soil). The analysis included the influence of introduction of such alternative structures on the decrease in the required minimum real values of secondary deformation modulus of subgrade observed in static plate load tests before structural improvement that would still enable one to obtain the target modulus values after installation of the chosen alternative solution. Conditions of use and applicability of the analyzed alternative structures in various geotechnical conditions are also discussed. Two analyzed structures – i.e. single layer of increased thickness and single geogrid-reinforced layer – are usable when small differences occur between the design and actual field values of secondary deformation moduli. The structure incorporating a layer of hydraulically-stabilized soil is usable in the case of considerable deficiency in secondary deformation moduli of the subgrade.


alternative structures, protective layer, railroad, railroad subgrade.

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Pawłowski, M. (2023). Alternative structures of railroad subgrade protective layers. Roads and Bridges - Drogi I Mosty, 22(4), 313–329.

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