WATERPROOFING OF MINE WORKING JUNCTIONS IN A WATER-BEARING ROCK MASS

Abstract

Junctions of mine workings are among the most expensive components of underground structures in coal mines, and their operational reliability is largely determined by the condition of the concrete lining under the influence of mine waters. The paper examines the mechanisms of concrete corrosion resulting from contact with groundwater of various chemical compositions typical of the Donetsk coal basin, concidering changes in hydrochemical conditions with depth. The main types of chemical attack on cement matrix are analyzed, including sulfate, carbonate, and acid corrosion, as well as the effects of mineralization, hardness, and pH of mine waters on the strength characteristics of concrete. Experimental studies were carried out on cubic concrete specimens of strength class B3.5, which were subjected to immersion in fresh water and mine water of varying degrees of aggressiveness for periods ranging from several days to 45 days. It was established that with contact durations of up to 45 days, chemical corrosion of concrete is practically negligible, and the reduction in strength and load-bearing capacity is mainly caused by the adsorption-induced strength reduction associated with increased moisture content. It is shown that an increase in concrete moisture content from 5 to 56.7% leads to an average decrease in strength indicators of about 31%, while the qualitative nature of the deformation diagrams remains unchanged. Based on the results obtained, practical recommendations are substantiated for accounting for estimating the operational strength of concrete linings under short-term and long-term flooding conditions. In addition, effective methods are proposed for protecting mine workings junctions from aggressive mine waters, including surface and volumetric hydrophobization and the formation of protective shells.