It is known that mass blasting of ore by boreholes or mine charges under the system of forced level caving can be carried out on pre‑formed compensation chambers or without them. The latter method – single‑stage ore breaking in a confined environment – is currently used at the S. M. Kirov apatite mine, at the Zapolyarny mine of the Norilsk Combine, at the Salair mine, at the mine named after the XXII Congress of the CPSU of the Zyryanovsky Combine, and others. The breaking method affects the physical and mechanical properties of the broken ore: if in variants with compensation chambers the coefficient of initial loosening of the ore immediately after blasting the block varies from 1.3 to 1.6, then with single‑stage breaking this coefficient ranges from 1.1 to 1.3.