Modelling fracturing,disturbed and interaction zones around fully confined detonating charges

In order to gain better insights into the complex mechanisms at play under fully confined blasting conditions in mining applications, several models were constructed and analysed using the hybrid stress blasting model (HSBM). A disturbed zone or microdamage criterion was proposed and used in the modelling analysis. It combined a lattice bond contact tensile failure criteria and a simple peak particle velocity based approach. Estimates were made of the extent of fracturing, disturbed and interaction zones from fully confined blastholes spaced at distances of up to 18 m, simultaneously initiated with primers positioned every 8 m. Continuous interaction was evident along the explosive column at spacings of <15 m. When blastholes were spaced at 18 m, the attenuation of the stress wave showed only partial or limited interaction along the column. With regards to the influence of in situ stress magnitudes in the range of 500–1500 m, modelling results appeared to capture the impact of stress intensity on the final extension of the macrofracturing zone. At depths of 1200 m and above, the degree of continuous interaction was diminished at the level of the initiating primers. For the simulated geotechnical conditions, the orientation of radial fractures with respect to the principal stress direction is more evident at anisotropy ratios greater than two. However, the extent and shape of the disturbed zone does not appear to be influenced by anisotropy, which showed a deficiency in the implementation of in situ stresses in the current modelling framework and further work is being conducted to address this limitation.