Design of underground mine voids filling operations in difficult flow conditions of fly ash – water mixtures

Abstract

Abstract. Filling the underground voids created during mining extraction of minerals plays a crucial role in different phases of mining operations. A common practice in Polish coal mines is filling the cavings resulted from coal extraction in longwalls for various safety and technical purposes. Moreover, liquidation of redundant underground workings and decommissioning of mines also require filling of large volumes of voids. As the obsolete mining systems with hydraulic backfill have been entirely replaced by longwalls with caving, a need arose for flexible and easily available method for filing of voids. Nowadays, the most frequently applied are mixtures of fly ash and water, which are able to meet a wide range of requirements of specific applications. These objectives may be achieved by the selection of the type of fly ash and adjustment of concentration of solid in mixture in the respect to geometrical parameters of the transport pipeline. These correlations have been demonstrated on the example of measurements conducted on a laboratory pipeline loop for a wide range of fly ashwater mixtures and flow conditions. Measurement results revealed a complex relationship between rheological properties of mixtures and geometrical parameters of pipelines, which strongly influence the distance at which a mixture may be delivered.

Utilization of Carbon Dioxide and Fluidized Bed Fly Ash in Post-Industrial Land Remediation

“…Furthermore, although the use of untreated fly ash from conventional boilers in the handling of voids resulting from the mining of minerals and rocks is recognized in the literature, it is focused mainly on the flow properties of filling mixtures in pipeline transport and site-specific or modelled filling effects [ 37 , 38 , 39 , 40 ]. Some works involve more extensive studies of the chemical, hydraulic and mechanical properties of backfilling mixtures prepared with the addition of only a limited amount of conventional fly ash [ 40 , 41 , 42 , 43 , 44 , 45 ], or the use of unconventional materials or treated waste materials, like temperature-treated coal refuse as a component of blends with conventional fly ash in backfilling mixtures [ 43 ], limestone aggregate with conventional fly ash and low pozzolanic cement [ 46 ], or waste glass granulated blast furnace slag and fumed silica [ 47 ]. Most of the research is devoted to the cemented paste backfill composed usually of coal gangue, binders (e.g., Portland cement), slag and conventional fly ash [ 42 ].…”