Measurement and modeling of water content distribution during spontaneous imbibition in coal

The flow process of water in hydraulic measures includes the processes of seepage and spontaneous imbibition. The process of seepage can displace free gas. However, the displacement capacity of free gas decays very fast. The process of spontaneous imbibition can replace the adsorbed gas. The water content distribution in coal during spontaneous imbibition is closely related to the gas distribution. If the water content distribution is uneven, a gas disaster is very easy to happen. However, it is difficult to measure water distribution in real time and dynamically. To obtain the model of water content distribution in the coal samples during spontaneous imbibition, the water content distribution model without considering the gravity factor is established by introducing the Boltzmann variable. The diffusion coefficient in the water content distribution model is an exponential form. To determine the parameters in the model, the method of assignment, convergence trend, and spontaneous imbibition experiments are conducted. The saturated volume water content decreases with increasing pressing load. The calculation result of water adsorption rate in unit area increases with increasing pressing load at a certain time. The experimental value of water content distribution is consistent with the theoretical value by the water content distribution model. This model can also be used to calculate the water content distribution for other porous media as long as the change law of water absorption quality with time is known.