The Causes of Typical Subgrade Problems in Railway Track beds and Mitigation Methods: A Review

Abstract

Subgrade plays an important role in maintaining satisfactory performance of railway track under repeated traffic loads. In the past, the role of subgrade as the foundation of the tracks, the typical problems affecting it, the causes and corrective measures were not recognized adequately. This study aims at identifying the problems, causes, effects and the remedial measures to correct them. The scope of this study was limited to water-induced railway    subgrade problems. Water may cause frost heave, thaw softening, ballast mud pumping, ballast pockets and weakening of the load bearing capacity of a track, resulting in unplanned track maintenance, imposition of speed restrictions, delay, safety issues and damage to third party property. To address these problems, the systematic literature review (SLR) methodology was used in this study, to review some selected published research articles on railway track subgrade problems, causes and solutions. The study found that the typical railway subgrade problems were mainly caused by the presence of excessive moisture content generated from surface water due to rain dew or snow, moisture sucked up by       capillary action resulting in increase of moisture in the subgrade or embankment,  seepage water from adjacent area, and lack of adequate drainage. The paper concludes with recommendations that drainage should be provided for railway tracks to reduce the rate of subgrade failures and to improve railway track subgrade functionality, and that good soils, preferably a well-graded material of high-internal friction having high-cohesion without any characteristic of detrimental shrinkage should be used for subgrade.