Geomechanical conditions of vein gold deposits in permafrost zone

Abstract

Developing the vein deposits in the permafrost zone results in specific geomechanical conditions. The paper describes the main results of studies of the geomechanical conditions of 8 vein deposits located in the permafrost zone for 2000-2020. In the process of research, zoning of the temperature conditions in mines has been carried out. The research has established the position of the permafrost zones, the natural transition zones of frozen rocks to thawed rocks, the zones of seasonal ventilation thawing and technogenic thawing. The authors have made the qualitative assessment of the degree of stability of the mine workings and pillars, taking into account the temperature conditions. It is proposed, when evaluating the stability of structural elements of geotechnologies, to adjust the strength properties of rocks using a differentiated coefficient of structural weakening. The paper has presented the results of field measurements of the initial stress-deformed state at various temperature conditions. The general regularities of the distribution of initial stresses are established: hydrostatic stresses act in frozen rocks, and increased gravitational-tectonic stresses act in natural and technogenic thawed rocks. The authors have proposed to use the obtained results as boundary conditions for the calculation of geotechnological parameters in the design and initial development of vein gold deposits of the permafrost zone. The authors have proposed the measures to improve the safety of mining operations in permafrost: thermal insulation of mine walls, use of electric transport, regulation of ventilation.