School of Safety and Emergency Management Engineering, Taiyuan University of Technology
Postdoctoral Workstation,Huayang New Material Technology Group Co., Ltd.
Postdoctoral Workstation, Shanxi Coking Coal Group Co., Ltd.

In the research area of the CT digital coal petrography, the selection of gray threshold directly affects the accuracyof spatial structure remodeling. To allow the pores and fissures space remodeling data to more accurately represent thereal structure and improve the reliability of research on microscopic seepage of coal rock, the mapping relation between the CT digital coal rock porosity and gray threshold is established. Also, the distribution rule of gray threshold is adoptedto conduct a quantitative analysis of the development features of pore, fissure and matrix. The Bi-PTI (Biphasic PoreThreshold Inversion) model is established for the identification of pore and fissure structures. The value inversion of theoptimal gray threshold of pore and fissure based on the CT scanning data of metamorphic coal, and the comparison ofporosity obtained with the model against the mercury injection test value are conducted. On the basis of the optimal graythreshold inversion results, the spatial structure of pore and fissure is remodeled and compared with the Otsu modelthrough the parameters of spatial structure and topological structure. Research results indicate that the porosity based onthe CT digital coal petrography is in asymmetrical S-shaped distribution as the threshold value increases, with the featuresof exponential increase and logarithmic climb at different sections. The Bi-PTI model can fairly reflect the mapping relationbetween porosity and gray threshold, and represent the development features of pore, fissure and matrix. The porositycalculated through the Otsu model is as high as over 70%, the porosity calculated by the MP-Otsu model is greatly affectedby the mineral content while that calculated with the Bi-PTI model ranges from 0.40% to 16.22%, more close to themercury injection test data. The Otsu model is most likely to neglect the topological structure with partial pores and fissures.The MP-Otsu model is not effective for constructing the topology of coal samples with low mineral content, whilethe Bi-PTI model can better identify the topological features in the locations of the defect and faithfully restore the porethroat abundance and connectivity in the pore and fissure topology.

山西省基础研究计划青年资助项目(20210302124483)；山西省高等学校科技创新资助项目(2021L052)

郝晨光，郭晓阳，邓存宝，等. 基于Bi-PTI模型的CT数字煤岩孔裂隙精准识别及阈值反演[J]. 煤炭学报，2023，48(4)：1516−1526

HAO Chenguang，GUO Xiaoyang，DENG Cunbao，et al. Precise identification and threshold inversion of pores and fissures in CT digital coal rock based on Bi-PTI model[J]. Journal of China Coal Society，2023，48(4)：1516−1526