Microstructure Characterization of Bubbles in Gassy Soil Based on the Fractal Theory

The microscopic characterization of isolated bubbles in gassy soil plays an important role in the macroscopic physical properties of sediments and is a key factor in the study of geological hazards in gas-bearing strata. Based on the box-counting method and the pore fractal features in porous media, a fractal model of bubble microstructure parameters in gassy soil under different gas contents and vertical load conditions is established by using an industrial X-ray CT scanning system. The results show that the fractal dimension of bubbles in the sample is correlated with the volume fraction of bubbles, and it is also restricted by the vertical load. The three-dimensional fractal dimension of the sample is about 1 larger than the average two-dimensional fractal dimension of all the slices from the same sample. The uniform porous media fractal model is used to test the equivalent diameter, and the results show that the variation of the measured pore diameter ratio is jointly restricted by the volume fraction and the vertical load. In addition, the measured self-similarity interval of the bubble area distribution is tested by the porous media fractal capillary bundle model, and the fitting curve of measured pore area ratio in a small loading range is obtained in this paper.