Railway tracks can have various types of defects. One of these rail defects is the so-called squat. A squat is a semi-circular or V-shaped crack on the rail surface. At this location, a dark discolored and widened area appears. Squats reduce the life cycle of the rail. The current methods of dealing with these defects are associated with very high costs and effort. This study focuses on the behavior of these squats during wheel-rail contact. The wheel-rail contact situation is very complex. However, as its analysis was not the scope of the present thesis, a simplified approach has been chosen. The main focus of this thesis is the determination of the crack driving forces, the evaluation of the J-integrals and the determination of the stress intensity factors of a preexisting crack. Furthermore, the influences of different crack parameters were investigated. The most important parameters are the crack size, the crack depth, the crack position and the coefficient of friction between the crack flanks. The calculations and evaluations were largely carried out using the finite element software Abaqus®, where the loading situation due to wheel-rail contact had to be implemented in the model using additional subroutines. The results that were achieved show that larger cracks are more prone to crack growth than smaller cracks. Furthermore, the position of the force application plays a major role with regard to the crack driving forces. With the help of this calculation model, in the future further influence factors, aside from the ones mentioned aboce can be investigated.