Traditional ballasted tracks have been used intensively around the world with ballast as the main material for tracks. Ballast has a significant contribution to the track alignment, stability and sustainability. After service, ballast deforms and degrades. Periodic ballast maintenance is needed which is a time and cost expensive activity. Understanding the mechanical behaviour of railroad ballast leads to better design and efficient maintenance. From the literature, there are two main approaches used to understand the mechanical behaviour of railroad ballast; large scale experimental and modelling. This paper aims to review the state of the art of literature on the modelling approaches used to understand ballast mechanical behaviour. It discusses the key findings from each modelling approach in understanding ballast mechanical behavior. It presents the main concerns and limitations of each modelling approach from different perspectives related to ballast modelling. It summarizes the limitations, gaps and gaps’ developments of the researches used to understand ballast behaviour via modelling approach.

The use of railway transportation systems has been increased throughout the years. The conventional ballasted tracks have been used widely in many countries around the world. Ballast material is the basic element of ballasted tracks. Ballast degrades and deforms after service. Therefore, periodical ballast maintenance is needed which is a cost and time expensive activity. Understanding ballast mechanical behavior leads to better design and efficient maintenance. From the literature, experimental approach is used to understand the mechanical behavior of railroad ballast. Traditional experimental tests provide inaccurate results due to the large ballast particle size with relative to sample size. Researchers used large scale triaxial and box tests extensively to understand the mechanical behavior of railroad ballast. The target of this paper is to present a concise review of the extensive literature presented on the mechanical behavior of railroad ballast using large scale triaxial and box testing. It discusses the various aspects of large-scale equipment such as apparatus' setup , size, material and shape, simulated load condition and test purpose. It presents the key findings of the large-scale triaxial and box tests in understanding ballast mechanical behavior.

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The use of railway transportation systems has been increased throughout the years. Conventional ballasted tracks have been widely used in many countries around the world. Ballast material is the basic element in ballasted track, it degrades and deforms after service. Therefore, periodical ballast maintenance is required which is a cost and time expensive activity. Understanding of ballast behavior leads to efficient design and maintenance. From the literature, Discrete Element Method is used extensively to understand the behavior of railroad ballast through box test. However, most researches in the literature simulate the train loading as a pure continuous sinusoid unlike the actual loading induced by the trains. This paper aims to show the influence of simulated loading of moving train on the dynamic behavior of railroad ballast using box test via DEM. The paper utilizes the theory of Beam on Elastic Foundation to simulate a more realistic loading on railroad ballast. The results from the simulated train load are compared with those from a sinusoidal load. The results show a difference up to 6.89% between simulated train and sinusoidal loading.