Ballast is an important part of railroad infrastructure. It is used as a support base for bearing the track load and facilitating drainage of water from the track. Unfavorable ballast performances (e.g., ballast fouling, loss of lateral confinement) can contribute to damage and deterioration of rail structures such as the rail, tie and fastening components. Therefore, accurate and timely monitoring of ballast condition is critical for rail safety operation and effective maintenance. This paper presents a series of ballast box tests to investigate the ballast particle movement pattern inside railway ballast under different ballast, loading, moisture and shoulder confinement conditions. Eight wireless devices, SmartRocks, were embedded in different locations in the ballast box to monitor individual ballast particle movements. The results indicate that (1) load magnitude and frequency have apparent effect on ballast particle movements. (2) The difference of particle movements in fouled ballast under dry versus wet condition is more dramatic than the difference in clean ballast. (3) Lack of shoulder confinement would cause failure of interaction between the shoulder ballast with tie and surrounded particles, which could generate more space for ballast particles away from the shoulder translation and rolling above other particles. (4) This study also demonstrates that SmartRock is capable of recording the particle translational accelerations and particle angular rotations information under different ballast and load conditions.