Evaluation method of permeability performance and similarity of raw coal based on NMR coal model materials

Physical model experiments are an important research method to reveal the mechanism of coal rock dynamic disasters, and the preparation of coal like physical model materials is the key to laying similar coal seams. For dynamic disasters such as coal and gas outbursts, water inrush, etc. caused by fluid solid coupling and temperature loss, simulating the permeability performance of materials is the key to the experiment. To reasonably evaluate the similarity between simulated material permeability and raw coal, a method of using Pearson correlation coefficient between material pore structure and permeability during loading and unloading process for similarity evaluation was proposed, and coal like materials were configured for experimental verification. The results showed that: Correlation coefficient P can effectively reflect the similarity of the permeability performance between raw coal and coal like materials during the loading and unloading process. The minimum correlation coefficients P for the porosity, permeability, and compressibility coefficient (C_P) of the two coal samples were 0.624, 0.913, and 0.888, respectively. The permeability performance remained strongly similar or extremely similar in overall changes. During the loading and unloading process, the porosity and permeability of both coal samples are negatively correlated with confining pressure, and the permeability is highly sensitive to stress. C_P of the two coal samples is negatively correlated with confining pressure, and C_P value during unloading is higher than that during loading. The research results provide a basis for evaluating the similarity of permeability performance of coal like physical model materials, and have guiding significance for conducting physical model experimental research.