Soil-binder columns for the rehabilitation of railway track platforms

Abstract

Railway track reinforcement using soil-binder columns without removing track structure can be an efficient method to rehabilitate old lines. This work presents results of a study on a reinforcing method of old railway track platforms with poor bearing conditions. It consists in drilling through the ballast layer and in-jecting binders into the soil to form short columns in the track subgrade. Experimental injection testing has been successful in demonstrating the feasibility of the method, in that it was possible to inject the grout below the ballast layer and to create soil-binder columns with diameters ranging from 30 to 60 cm, depending on the injection parameters, for the different tested soils. The results of the numerical modelling of tested reinforce-ment configurations suggest that the columns provide a reduction of the deviator stress at the top of the plat-form in untreated soil areas between the columns. Therefore, the approach helps to mitigate typical and unde-sirable phenomena of old railway platforms such as progressive shear failure and excessive accumulation of plastic deformation at the ballast-platform interface. To validate the method even further, cyclic loading tests on true scale physical models are currently underway to study the resilient and permanent deformation of rail-way tracks with poor bearing conditions, submitted to the reinforcement method