Increased effectiveness of mining can be achieved in several ways one of which is the decreasing of rock resistance to drilling. The effect of low temperatures (-16C) on physical and mechanical rock properties was studied in the Leningrad Mining Institute by determining temporary resistance to compression of the granite, diabase, granite-gneiss, and sandstone samples subjected to 25 freezing-thawing cycles, heating to 400C and cooling in moist sand; during this procedure the sample temperature was changed up to 50 times, passing through zero. The results indicated that the temporary compressive strength of the rocks was in some cases lowered to 43%. Experimental investigation of compressive strength variation during heating and cooling (to - 180C) of sandstones, gabbro, graphite, and marble was conducted in the IGD laboratory.
