Mining activities have a great impact on the health and wealth of any nation. Though technology has reduced the adverse effects to a great extent, it is still experiencing unpredictable behaviour of rocks. The physical and mechanical properties of rocks are important for design of any excavation process. Time dependence must be considered essential for the study of deformation and fracturing processes of rock material, especially for those subjected to strong compressive and tensile stresses. In this study creep test is conducted in chromite ore under uniaxial compressive stresses. Rock Behaviour is investigated as well as strength of rock. Creep behaviour of rocks has been evaluated at varying stress and temperature rate. The relationship between compressive stress and time under uniaxial compression has also been developed. Finally nonlinear creep model is used to describe the creep behaviours of rocks under uniaxial compressive strength. This non linear creep model well depicts the dependence of creep properties of the ore and its influence by temperature and stress variation.

1. Introduction

Creep refers to the time-dependent deformation of soil or rock resulting from internal rearrangement of particles in response to the application of a sustained stress difference (σ13) generally smaller than the stress difference of the soil at failure=(σ 13), where σ 1, σ 3 are the major and minor compressive principal stresses, respectively. Deformation during undrained creep results from shape distortion as the soil mobilizes a constant shearing resistance in response to the shear stresses applied upon loading or unloading. Creep models have been applied toward the solution of a variety of engineering problems, such as the closure of and loads on tunnels, chambers, and pillars in creep-sensitive materials, such as salt, shale, and fault zones.

Undrained creep behaviour is closely related to the drained creep phenomenon associated with secondary consolidation and swelling in as much as the mechanisms that cause volume change. Studies (especially on potash mine pillars) have indicated that deformation of pillars do not occur instantaneously but increase with time. Pillars, which appear stable after mining may deteriorate with time and subsequently fail due to the development of limiting vertical deformation. Pillar failure takes place at a range of vertical stresses; failure at high stresses taking place earlier than at low stresses.

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