Understanding the reinforcement mechanism of the polymeric liner using numerical models is key to measuring its performance for field applications. In this study, numerical models are developed for the coal and the polymer liner, and then, they are validated with the results obtained from the earlier experiments. In the next stage, a field-size coal pillar in an underground mine was simulated to evaluate the liner performance as surface support. In this study, two different scenarios were simulated. In the first case, an unsupported coal pillar was considered, and in the subsequent models, a mine pillar reinforced with polymeric liner was simulated for different thicknesses of liner material, viz. 5 and 10 mm. The results obtained from the numerical simulations are assessed in terms of the major and minor principal stresses and the equivalent plastic strain to evaluate the effectiveness of the liner thickness on the post-yield behaviour of the coal pillar. It was observed that tensile stress was concentrated at the pillar’s corner, which is in the polymeric liner. The extent of damage observed by equivalent plastic strain was nearly 2 m inside the pillar. The magnitude of maximum damage for an unlined pillar is 0.81, and with a 5 mm thickness of liner, the magnitude is reduced by 16% to 0.68. For a 10 mm liner thickness, this reduction was nearly 28% as compared to the unlined coal pillar.