A research project on the reinforcement of old railway track platforms using short soil binder columns

Abstract

The rehabilitation and construction works for the reinforcement of old railway track platforms is a complex, time-consuming and costly process that often causes significant disturbances to normal train operation (Selig & Waters, 1994). Although different reinforcement approaches have been used in the past (INNOTRACK, 2008; Indraratna et al., 2011; Li et al., 2016), from soil replacement to reinforcement with geosynthetics, only a few allow performing the treatment or applying the reinforcement with minimal hindrance to railway operation. In this context, the reinforcement the track foundation, through injection of binders, without removing the ballast layer or the track components, is of paramount importance. Although this approach is not new, it still poses challenges in terms of railway operation, construction processes and quality assurance. For example, according to Li et al. (2016), slurry injection in the track platform has been used on railways since the 80’s and with mixed results. One of the main drawbacks has been the difficulty to penetrate the slurry into the clay soils and achieve an adequate dispersion. Although reports indicate that the pressures used with this method do cause hydraulic fracture of the soil, the dispersion of slurry is somewhat poor (Karol, 1983). Soil mixing is another method with significant potential, which was studied in the EU project INNOTRACK (2008; Kouby et al., 2010) using a smaller and modified drill to create vertical soil-cement columns with diameters of up to 700 mm to a depth up to 15 m (Melentijevic et al., 2013). The RUFEX project followed up that initiative and focused on industrializing a way of reinforcing the railway platforms in the French network (Calon et al., 2011). In this paper, the authors present preliminary results of a research project - GroutRail - currently underway in Portugal.