Study on explosion in different cross-sectional shape charge cavity in tensile stress field

Abstract

Purpose. To study nature and patterns of main cracks development in a solid medium during an explosion of explosive charge in charge cavity with longitudinal symmetrical incision and various cross-sectional shapes Methodology. Experimental methods were used to study process dynamics, nature and direction of cracks development during the explosion of explosive charge of various shapes and their transformation into a clear optical image under the influence of a focused laser beam through an optical system – the method of caustics. Study on stress field changes under the combined effect of static and dynamic loading on fracture medium by polarisation-optical method. Based on correlation analysis methods, study results are analysed. Findings. It is experimentally proved that changing angle from 0 to 45° between longitudinal cut and plane jointly affected by tensile stresses and explosion action promotes opening of main cracks both parallel and perpendicular to cut direction. Dependences of propagation of main cracks caused by an explosion in model under different loading conditions are constructed. Calculations of stress intensity coefficients in medium under explosion and tensile stresses were performed. Originality. Improved research methodology for establishing the mechanism of explosive loading of solid media by explosion of explosive charge of different cross-sectional shapes is proposed. Physical mechanism of main cracks formation and propagation in blast cavity under action of explosive charge of different shapes under different conditions of dynamic loading is revealed. Dimensions of symmetrical longitudinal incision and spatial location of crack along direction of tensile stresses are substantiated. Also, an idea of using a directed explosion to form a protective strip in the rock mass was further developed. Practical value. The research results received can be necessary for developing new technical solutions to provide additional protective measures in the field of environmental and seismic safety of protected civil and industrial facilities during blasting operations in quarries and mines.