A numerical model was developed to analyze the effectiveness of active and passive secondary support systems on the stability of a retreating longwall tailgate opening. The range of loading conditions that any tailgate can be subjected to was identified to form the basis of numerical modeling. The tailgate entry was considered as a part of roof-pillar-floor system, whose behavior is controlled largely by the structural integrity of each member. Numerical modeling was then conducted on tailgate openings to determine roof, floor, and rib responses, including failure modes to a variety of loading conditions for wood cribs and roof trusses employed as active and passive means of secondary support. Trends were developed from numerical modeling to determine optimum load capacity and paints of application for reducing the potential for entry failure. / Master of Science