By Katie Bocskor, Manager, Marketing, Presto Geosystems
Oregon State University (OSU) recently performed state-of-the-art, three-dimensional dynamic finite element modeling to analyze the reinforcing benefit of Presto Geosystems’ GEOWEB geocells in railway ballast applications. Completed in cooperation with the University of Kansas (KU), which simultaneously put in motion a testing program of geocell-reinforced ballast placed over weak subgrade.
The digital modeling results were reinforced by the laboratory tests and showed a significant decrease in settlement of the railway ballast when GEOWEB confinement was used. Using the geocell system not only decreased settlement but also reduced pressure on point-to-point aggregate load transfer contact. This resulted in less damage to ballast aggregate particles leading to less progressive deformation and longer maintenance frequencies of the entire ballast embankment. In short, more cycles mean less track downtime for maintenance.
The research results revealed several benefits in applying GEOWEB confinement for reinforcement of real ballast over weak subgrades, including:
- Significant decrease in settlement of the railway ballast. GEOWEB confinement influence reduced settlement by to up 50% under heavy freight loadings over weak subgrades.
- Decrease in subgrade interface pressure by nearly 50% for weak subgrades. The decreased pressure in subgrade results in lower subgrade settlements.
- Increase in ballast resiliency after many cycles—resulting in decreased rate of cyclic settlement.
- Decrease in lateral heave and movement of the ballast material.
- Redistribution of vertical stresses on the subgrade—resulting in higher shear strength and reduction in plastic deformation.
- For the largest loading conditions used in the analysis, the strains in the geocell were low (less than 1%) and within the elastic range for typical geosynthetic materials. The maximum tensile strains were localized at the bottom corners of the GEOWEB cells, illustrating the importance of adequately durable seams.
- Strains in the geocell ballast layer were low (less than 1%) even under heavy freight loadings over very soft subgrades. Stress concentrations were found at the seams, highlighting the importance of GEOWEB seam strength during loading condition.
A better built ballast
At Presto Geosystems, the benefits of GEOWEB confined ballast are substantiated through rigorous testing. Conventional ballast reinforcing materials (e.g., geogrids, hot-mix asphalt [HMA]) do not have the strengthening attributes that GEOWEB geocells can provide, especially in soft subgrades. Building a more stable ballast layer with less settlement, higher shear strength and less maintenance requirements is possible when built with GEOWEB geocells.
This article originally appeared on the Presto Geosystems blog, https://www.prestogeo.com/blog.