Comparing the alternative supply methods to meet the expansion in energy demand, coal-fired thermal power plants stand out with the advantage that rich reserves are suitable for cost-effective production. Longwall mining is a method that is widely used in our country, in line with the trend in the world, that enables the economical and sustainable production of underground coal resources with mechanized equipment. Estimation of stress distribution and concentration zones in the excavation face and roof is critically important in terms of determining the appropriate hydraulic support properties in production by longwall mining. Advancing the wide excavation face along the mining direction causes in-situ stress distribution in the rock mass to change and the stresses associated with the excavation to intensify. This may trigger potential instability events. This study investigates the relationship of stresses developed on pillars due to longwall production with pillar dimensions and field loadings in a typical underground coal mine using numerical simulations. Parametric analysis was performed on three-dimensional models using Distinct Element Method. The simulation outputs characterize the performance of alternative pillar designs under different field loading conditions, in terms of stress distribution and concentration zones that will develop due to production.