Heavy-haul asphalt (HMA) underlayment trackbeds: Pressures/deflections/materials properties measurements

During the past twenty years the use of hot mix asphalt (HMA) as a sub-ballast layer within the track structure has steadily increased until it is becoming standard practice in many areas of the United States. This asphalt-bound impermeable layer, typically 125 to 200 mm thick, forms a superior “hardpan”...