Impact involving the sealing degree of caving goaf with fine-fraction hydraulic mixtures on the ventilation parameters of longwall headings

The most common method to eliminate post-mining voids created after hard coal mining consists in natural filling them with rock rubble from the strata forming the roof the mining heading. Such rubble is characterized by free spaces that allow uncontrolled flow of air. The said flow is unfavorable due to disturbances in the distribution of airflow in the ventilation network, and it poses the risk of endogenous fire. One way to reduce such adverse phenomena is to fill the rubble with fine-fraction hydraulic mixtures, most frequently fly ash-water mixtures. The first part of the paper presents the method for determining the theoretical porosity of caving rubble. In the second part, the possibility of various degree of sealing of the numerically modelled caving rubble with a fine-fraction hydromixture was investigated in terms of assessing its impact on the ventilation parameters of a longwall working ventilated with the “Y” method. The presented numerical model was used to calculate the airflow distribution at various filling degrees of the rubble. The obtained knowledge involving the changes in the airflow distribution parameters, depending on the sealing degree of the rubble allows to define the possibility to slow down or to stop the development process of endogenous fire. In addition, it also allows to forecast the ventilation conditions of workings in the longwall area, limiting the development of other ventilation-related hazards, such as methane or climate hazards.