Experiment Study on the Relationship between the Height of Capping Layer and the Porosity of Broken Rocks

Abstract

The gas seepage characteristics of four kinds of broken rocks of different gradations and the relationship between the capping height and the porosity were studied by means of the simulation experiment and the theoretical analysis. The results show that the air flow in the capping layer composed of broken rocks is in the non-Darcy state which can be described as Forchheimer equation and Ergun equation. Moreover, on the basis of the experimental data, the relational expressions between the permeability, the non-Darcy β factor and the porosity were determined. Through the numerical fitting, the equation of the minimum capping height and the porosity was ultimately derived, which provided the basis and the reference for the determination of capping height and the air leakage control of mine.