In 1964‑1965 at the mine No. 3 of Slantsy Combine the resistance of layers of the industrial oil shale stack to mechanical destruction was determined. Resistance (strength) was determined in three ways: 1) by the method of crushing with the help of the POC device (strength coefficient f); 2) by the method of cutting from the open face with the help of the DKS-3 device (strength index A); 3) by the energy indicators of the Ural‑33 cutting machine (strength index Avr)....

At Slantsy plant in 1965 an experimental cut was carried out on the upper part of the limestone “slab” layer, where there is a 0.04 m thick interlayer of clay shale with lower strength. At the total height of the cutting slot of 115‑120 mm, the destroyed part of the limestone was 75‑80 mm, and 40 mm were in the clay shale interlayer. The cutting was made by the Ural‑33 cutting machine mounted on skids above the scraper conveyor, with a bar length of 2 m and a non‑standard seven‑link chain. The useful depth of the cut was 1.7 m. The machine was operated at a reduced cutting speed (1.6 m/sec) with I‑80 cutters, whose back angle was increased from 5 to 15°.