Railway track stability depends not only on the subgrade sustainability, but also on the quality of ballast itself. Ballast bearing capacity depends on limit stress state of ballast layer and subgrade, characterized by limit stress in ballast under sleeper. Ballast bearing capacity in terms of rolling stock vibrational dynamic impact is evaluated using limit equilibrium theory. This theory incorporates inertial forces, generated in soil media by vibrational dynamic impact. Inertial forces depend on vibrational accelerations of soil particles. This paper presents the results of railway ballast field tests. Tests were aimed to study vibrational acceleration (VA) of ballast particles in terms of train traffic with heavy axle loads. Tests were held at Russian Railway Research Institute experimental track. A set of RA 021 accelerometers were put into ballast layer at two levels: 10 and 55 cm below the sleeper. The test results are vibrational acceleration distribution in ballast layer and experimental relationships of vertical and horizontal vibrational accelerations damping in terms of train operation with axle load up to 294 kN. Increasing of rolling stock axlу loads leads to rise of vibrational dynamic impact on railway track. Axle load growth from 225 to 294 kN provides increased vibrational acceleration under the sleeper. Maximal values of vertical vibrational accelerations are registered at the underrail section. Maximal values of horizontal VA are registered at the section near the center line. Stated test results provide references for calculation of ballast and subballast bearing capacity.

ballast, vibrational acceleration, vertical stress, heavy axle load