INFLUENCE OF STRESS-PATH ON THE STRESS-STRAIN RELATIONS OF JOINTED ROCKS

摘要

The actual stress path at a point in a rock mass near an underground excavation is complex. It is generally not in accordance with the loading path applied in a triaxial compression test (σ_3 = const.), the standard loading path used to determine the stress-strain relationship in laboratory tests. In most cases, a loading path of fixed mean principal stress ((σ_1+σ_3)/2 = σ_m = const.) would be a better approximation of the stress path encountered in-situ near an underground excavation. In the present study, the effect of stress path on the stress-strain relationship of jointed rocks is studied using Distinct Element Method code UDEC. The simulation results demonstrate that the non-linearity in the stress-strain curve is stronger under a loading path of fixed mean principal stress than with a fixed confining stress, which is in agreement with laboratory and in-situ test results. It is recommended that for stability analyses of underground excavations, the constitutive relations of jointed rock mass be obtained from tests conducted in a constant mean principal stress loading condition.