USING DYNAMIC PHOTOELASTICITY TO EVALUATE THE INFLUENCE OF PARTING PLANES ON STRESS WAVES INTERACTING WITH STOPES

Dynamic photoelasticity is used as a means for visualizing the complex interaction process between elastic waves and geometrical discontinuities. The photoelastic experiments are back-analysed by the dynamic finite difference program WAVE, and the code is assessed in terms of its accuracy and modelling capabilities. Three model geometries are investigated : (i) a stope situated within a homogeneous medium ; (ii) a stope surrounded by softened material, the interface between the softened and bulk material being bonded and (iii) a stope situated within softened material, with a non-cohesive material interface. Prominent waves resulting from the diffraction, refraction and reflection of incident waves, as well as normalized dynamic stress intensification factors at the stope face, stope back area and along the hanging-wall skin are analysed in this study. The parting planes are found to reflect a portion of the incident energy and thus shield the stope. However, a non-cohesive parting plane traps energy within the hanging-wall beam, and any shielding benefits are negated. WAVE has been proven to model accurately the diffraction, refraction and reflection of stress waves in a homogeneous medium and the interaction with cohesive and non-cohesive interfaces separating two material types.