EFFECT OF TEMPERATURE ON STRESS STATE OF MINE EXCAVATIONS IN PERMAFROST ZONE

ABSTRACT

The choice of support design for mine excavations driven beyond the influence zone of stoping in the conditions of permafrost is governed by the service life of the excavations, geomechanical behavior of surrounding rock mass and by working temperature range of ventilation. The research findings on influence exerted by temperature on stress state of rock mass around a single tunnel are presented. Based on solution of quasistatic thermo-elastic problems, the mechanisms of change in the stresses and displacements at the tunnel boundary depending on the service life and temperature of ventilation of the tunnel are determined. For the specific mineral deposit, it is shown that in a tunnel driven in rock mass with the initial temperature of -1.5°С at a depth of 350 m, with the ventilation temperature of 20°С during 3 years, the vertical convergence is comparable with the elastic displacement caused by the tunnel drivage. The approach is proposed for determining rock mass stability category based on the estimated displacements at the boundaries of a single tunnel with regard to thawing of adjacent rock mass. The obtained results are meant for the use in development of standards and procedures for selecting and validating support designs for mine excavations in permafrost zone.

Keywords: permafrost zone, mine excavation, support, temperature, displacements, stresses