Effects of surfactant treatment on the strength of frozen overburden soil samples from coal deposits in the cryolithic zone

The harsh climatic conditions of the cryolithic zone with its long winter period and presence of permafrost soils significantly slow down all technological processes in surface mining. The resistance of frozen rocks at coal mines to digging with mining equipment can be reduced by their preliminary softening with the use of surfactants. The paper discusses the softening effect of aqueous surfactant solutions on samples of frozen overburden rocks. The authors demonstrate that treatment of rocks with solutions of optimal composition and concentration decreases their strength, which makes it possible to enhance the efficiency of In-Pit Crushing and Conveying Systems based on the rotary mechanical shovel in combination with a conveyor as well as the use of continuous miners. Experimental data are presented on the strength properties of artificially made samples of overburden rocks from the Kangalassky coal deposit saturated with surfactant solutions of different concentrations. The authors point out that the highest decrease in the samples strength is achieved when using aqueous solution of aluminum chloride. The results of experiments carried out to establish the effects of distilled water (H2O) and NaCl solutions of different concentrations on the strength properties of fine-grained sandstones from the Elga coal deposit are presented, which confirm that at the temperature of -10°С the maximum reduction of up to 55% is achieved in the strength of the samples, and when the temperature decreases from -10°С to -20°С a slight increase is observed in the sample strength. The authors suggest that the use of surfactants will reduce the strength of the frozen overburden soils, thus making it possible to apply a blast-free mining technology.