A new Method to Determine the Desired Minimum Railway Embankment Dimensions

Abstract

The dimensions of a railway embankment have a significant impact on the investment costs of a railway track. Due to the cold climate and the consequent harmful effects of seasonal frost in northern regions, embankments are typically constructed of relatively thick structural layers. The embankments have also traditionally had fairly steep slopes and narrow widths in order to cut construction costs. Introduction of higher allowable axle loads and traffic speeds is, however, exposing the embankment structures to a continuously increasing intensity of repeated loading which respectively increases the rate of permanent deformations taking place in the embankment structure. The problem described above has been studied at the Laboratory of Earth and Foundation Structures of Tampere University of Technology. The study is divided into four main parts: monitoring of full-scale test embankment sections located in the southwestern part of Finland, loading of laboratory scale instrumented test embankments, FEM-modeling and evaluation of the long-term deformation behaviour of an actual railway track line based on laser scanner measurements. This paper focusses on introducing the new method for determining the required embankment dimensions and describing a case study of the first practical application of the new method in Finland. In addition, the paper briefly discusses the most significant findings of the project, but a detailed analysis of the test results is presented elsewhere. The new method for assessing the required minimum embankment width is based on the amount of recoverable vertical displacement of the railway track measured from sleepers under a moving train load. So far, the new method has been tested in a renovation project between the cities of Tampere and Kokemäki where the suggested limit values have been observed to be realistic.