Effect of geogrid on railroad ballast particle movement

Abstract Individual ballast particle movement significantly affects ballast performance. In order to improve ballast performance, geogrids are widely used to create interlocking of ballast particles to reduce particle movement. To better quantify the effect of geogrid on particle movement, two types of ballast box tests were conducted in this study: one without geogrid as a control and the other one with a layer of multiaxial geogrid placed at 25 cm below the top of the ballast. The ballast box represents a half section of a railroad track structure consisting of a ballast layer, two crossties, and a rail (I-beam). A wireless device – “SmartRock” was embedded underneath the rail seat and the edge of a tie in the ballast layer to monitor particle translation and rotation under cyclic loading. The results indicate that (1) horizontal translation and rotation are important modes of movement for ballast particles under cyclic loading; (2) particle translational movement and rotation were higher beneath the edge of the tie than those beneath the rail seat; (3) the particle movement, such as translation and rotation, were significantly reduced with an inclusion of the geogrid under 500 load cycles. This investigation also demonstrates that the SmartRock is capable of recording and visualizing real-time particle movement including translation and rotation and, hence, can be used as a fundamental research and monitoring tool in railroad.