VNII Galurgy Stock Co., St.-Petersburg, Russia:

A. G. Olovyannyi, Leading Researcher, Candidate of Engineering Sciences, agolov2009@hgepro.ru

Stressed state in a rock massif is a most important factor affecting processes around mine workings. Methods used for calculating the stresses and based on the hypotheses of resilient earth pressure or hydrostatic state do not consider the time processes developing under formation of stress field. Within the depths of engineering in a heterogeneous massif of rocks with layers with different elastic and viscous properties the lateral earth pressure irregular changes from layer to layer. In the layers of rocks with similar properties lateral earth pressure does not depend on the depth. In the clay or salt layers stress state is close to hydrostatic, due to their viscous properties and, consequently, poor permeability. Outside the zones of tectonic fractures and folds are no conditions limiting stressed state, affecting the formation of lateral earth pressure stresses in the rock massif. In the separately-block and granular massifs lateral earth pressure is determined by the properties of dry-contact friction and viscosity. In this case it is formed according to the elastic and viscous properties with a restriction on the condition of dry friction. In general, the lateral earth pressure in a rock mass is formed of two parts — the gravitational and tectonic. The gravitational part of stresses of the lateral earth pressure depends on the elastic and viscous and elastic properties of rocks and grows with depth. Tectonic component of stresses in a horizontal plane occurs due to deformation of interacting tectonic plates and is not dependent on the depth. Tectonic stresses can be calculated according to the main deformation caused by tectonic movements. Upon reaching the lateral stresses certain values in the layers of rock can occur tectonic fractures and folds, in some cases — the conditions of activation of the existing fissures. Forming of stressed state is being affected by resilient, viscous and strength properties of rocks. Relationships between stressed state forming and effect of resilient, viscous and strength properties in solid, separately blocked and loose rocks have been considered. Also the problem of tectonic stresses acting in rock massifs under the influence of tectonic plates' mutual displacement is considered. The relationships for additional stresses in a rock massif depending on tectonic plates' deformations have been obtained. Methods for evaluation of stressed state in a rock massif have been shown which differ from those adopted at present.

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