CURRENT RAILWAYS REHABILITATION METHODS IGNORE THE PROBLEM OF SOFT, VARIABLE SUBGRADES.

CURRENT RAILWAYS REHABILITATION METHODS IGNORE THE PROBLEM OF SOFT, VARIABLE SUBGRADES. THE PROPOSED CAST-IN-PLACE 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 CONCRETE PILES WILL BE CONSTRUCTED OFSELF-CEMENTING 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 GHRADATION. THE PILES ARE PROPOSED TO BE INSTALLED IN CONNECTION 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 PROCEDUCES; AND (D) ESTIMATED COST-BENEFIT RATIOS. THE FORESEEABLE RESULT IS CONTINUOUS, COMPUTERIZED SITE EVALUATION, DESIGN SELECTION, AND PILE-INSTALLATION BY TRACK-OPERATIONAL MACHINERY.