Performance of geogrid reinforced ballast under dynamic loading.

Railroad ballast consists of open graded crushed stone used as a bed for railroad track to provide stability. Over time, ballast degrades and loses its strength. Fouling of ballast with fines has been a major issue of railway engineering. In this experimental study, a full-scale railroad section 5 ft in length was constructed with and without geogrid reinforcement. A full-scale trapezoidal cross-section of a railroad was built. The subgrade was covered with 2 ft of ballast 9 ft wide at the top and sloped down on both sides on a 2:1 slope. The track panel ties were embedded in the ballast to a depth of 7 in. The reinforced test section that had geogrid placed 7 in. below the tie performed better than the unreinforced test section in regards to settlement and fouling of ballast. Settlement of the reinforced test section between the ties and geogrid was reduced by 37 to 65 percent compared with the settlement of the same portion of the unreinforced test section. The percentage of rock dust and small diameter particles generated by ballast breakdown beneath the ties was less for the reinforced test section than for the unreinforced test section.