MODELLING COMPLEX STRESS FIELDS

Do the stress measurements at your mine make sense?

Stress measurements show that at many mines, major structure influences the stress field to the extent that a simple vertical gradient will produce the wrong results. The consequences can be extreme.

BAE has shown in recent projects that once major structures and geological domains are incorporated into a mine scale inelastic model, effects such as rotation of the stress field due to structure can be reproduced.

Figure 1: Plastic strain induced in the vicinity of an open pit by caving operations for a base case and the case with the simulated geological stress-strain path

At an example mine (s. Figure 1), stress measurements suggested that the stress conditions varied significantly. The extinct volcanic pipe is the orebody, and it was believed that the geological history contributed to a low stress state inside the pipe.

This was simulated in the equilibrium steps for the model. The model results not only closely matched measurements at the mine, but the nature of the damaged pipe boundaries were also simulated directly. Figure1 shows the modelled rockmass damage at a mining step for this special stress case and a ‘standard’ stress field. The simulated stress path, with a better match to measurements produced more realistic interaction phenomena, and importantly shows an increased interaction with the pit.

For more information contact enquiries@beckarndt.com.au.