Performance of Geogrid Reinforced Recycled Ballast under Dynamic Loading

摘要

Railroad ballast consists of open graded crushed stone used to support railroad track andprovide lateral stability. It provides drainable support for the track base and distributes the loadto the weaker subgrade below. The issue of ballast performance has become more acute withincreased traffic and heavier traffic.Over time ballast degrades and loses strength. Fouling of ballast is one cause of degradedperformance and has been a major issue of railway engineering. Fouling can be caused by breakdown of ballast itself or intrusion of fines from below or from the environment. Fouling materialcan be removed by undercutting and the remaining ballast can be recycled back on to the rightof-way. It is possible to install a geogrid reinforcement layer in the ballast during anundercutting action.In this experimental study a full-scale railroad section five feet in length was constructedwith and without geogrid reinforcement of recycled ballast. The track was dynamically loadedup to approximately 35 psi tie bearing pressure. The reinforced test section with geogrid placed7 inches below the tie performed better than the unreinforced test section with regard tosettlement and fouling of ballast. Settlement of the reinforced test section between the ties andgeogrid was substantially less than the settlement of the same portion of the unreinforced testsection. The percentage of rock dust and small diameter particles generated by ballastbreakdown beneath the ties was observed to be less for the reinforced test section than for theunreinforced test section.