Semi-homogeneous model of coal based on 3D reconstruction of CT images and its seepage-deformation characteristics

To study the effect of isolated pores on gas seepage and coal deformation, computed tomography (CT) scanning was used to analyse the porosity and fractal characteristics of isolated pores. A geometric model of coal was then established using 3D reconstruction. Finally, a seepage-stress semi-homogeneous coupling model was established by considering the adsorption and desorption of gas. The significant difference between this model and the existing models is that the non-homogeneity of isolated pores is considered. The results show that the porosity of the isolated pores is 5.73%, accounting for 58.41% of the total pores, and the diameter is concentrated in the range of 0-10 mu m. The average fractal dimension of the connected pores (1.25) is smaller than that of the isolated pores (1.35), indicating that isolated pores have a more complex structure. The gas seepage velocity is negatively correlated with the isolated pore porosity, and it varies strongly at each point of the model, with a maximum and minimum of 5.08 m/s and 1.45 x 10(-4) m/s, respectively. The inhomogeneous distribution of isolated pores led to a differential deformation of the model. The total displacement of the slices varies from 13,550 mu m to 14,300 mu m and decreases with increasing isolated pore porosity and fractal dimension. Both low fractal dimension and low isolated pore porosity increase the deformation.

Automated summary

This study investigated the effect of isolated pores on gas seepage and coal deformation. The porosity and fractal characteristics of isolated pores were analyzed using computed tomography scanning, and a geometric model of coal was established. A seepage-stress semi-homogeneous coupling model was developed that considered the adsorption and desorption of gas. The results showed that the isolated pores had a more complex structure and influenced the deformation of the model.