Current railway rehabilitation methods are ineffective in solving the problem of soft, variable subgrades. The proposed cast-inplace minipile support system "stiffens" the subgrade and offers an inexpensive, versatile alternative to the costly, conventional use of thickened ballast sections, grouting, and geotextiles. As proposed, miniature piles will be constructed of self-cementing material, possibly a Type C fly ash at varying depths and spacing intervals. Varying depth allows for variation in soils and loading conditions; varying spacing removes "bumps" at crossings and bridges by providing for gradual changes in lateral gradation. The piles are proposed to be installed in connecting pairs, thus keeping ties over the pile caps as trackage "walks." Phase I research includes: (a) The testing and installation of minipiles on a pilot track section; (b) A physical modeling program to evaluate element interactions; (c) Testing and evaluation of Type C fly ash mix designs with and without admixtures, as well as installation procedures; and (d) Estimated cost-benefit ratios. The foreseeable result is continuous, computerized site evaluation, design selection, and pile-installation by track-operational machinery.The potential commercial application as described by the awardee: Research will lead to: a product and service for the railroad industry to solve problems in soft and variable subgrades.
