Assessment of influence of short-period geodynamic movements on stress-strain behavior of rock mass

Abstract

Geodynamic diagnostics of rock mass is critical in terms of safe arrangement and operation of subsoil use objects. The modern geodynamic movements are one of the factors that govern the stress-strain behavior of rocks. The experimental research accomplished in the recent decades show that geodynamic movements are the wide-spread phenomena of complex time-and-space distribution. It is conditionally assumed to distinguish between the trend movements of the same direction and velocity over the period of observations and the cyclic short-period movements with cycle duration from a few minutes to a few hours. The cyclic short-period geodynamic movements can exert direct or indirect impact on subsoil use objects. The cyclic nature is governed by many natural factors. The influence of one or another factor on the stress-strain behavior of rock mass is yet unstudied unambiguously to date. However, it is evident that strains governed by the cyclicity of movements should be taken into account in geodynamic diagnostics. The implemented studies of short-period movements on testing grounds by continuous monitoring using GNSS methods for many hours at spacing from two hundred meters to two kilometers revealed that directions of displacement of check points frequently exceeded accuracy of their determination. During the experiments, a procedure was developed to determine parameters of strain tensor in rock mass based on the prevailing direction and amplitude of short-period movements. The amplitude of short-period movement is a difference between the minimal and maximal values of displacements in a set of discrete measurements within continuous observation session. The obtained field of strains was compared with the values calculated by the data on the trend geodynamic movements for 6 years with the same check points in the same pattern. The correlation is found between the orientations of principal axes of strain tensors calculated by the data on the trend and shortperiod movements. The developed procedure makes it possible to take into account the shortperiod cyclicity of the modern geodynamic movements, and the found correlation between the orientation of strain tensor of the trend and cyclic movement enable express estimation of changes in the stress-strain behavior of rocks.