Development of resources via shaft sinking using the ground freezing method - Itasca Consultants GmbH (Germany)

Itasca Consultants GmbH is currently involved in planning the development of resources via shaft sinking using the ground freezing method. In the project, three shafts at different locations are investigated.
The task of Itasca Consultants GmbH is not only the simulation of the frost wall development to find the point in time at which the frost wall is stable enough to start sinking, but also to estimate the displacements that can be expected at the contour of the shaft wall and at the freezing pipes. With numerous FLAC3D models, based on the available geological information, an optimal ratio between number of freezing pipes and brine temperature is evaluated to provide the best solution for the customer. Additionally, the energy required for the ground freezing is estimated to evaluate the number of freezing machines needed. Within the models, the lithological layers are represented in order to reflect the thermal and mechanical properties of the material in the underground.
Figure 1 shows an example of a 3D model where the freezing pipes and the freezing process are well visible.

Stability of a crown pillar recovery in a gold mine - Itasca Consultores SL (Spain)

The crown pillar was left between the open-pit and the underground mine, and the current mine operator planned its exploitation by means of two vertical rooms that outcrop at the bottom of the pit.

The excavation of these rooms could potentially affect the stability of the ground at the bottom and at the pit slopes, and a 3DEC model was built to analyze that. The model explicitly includes the discontinuities of the joint sets present in the rockmass (Figure 1), and the elastic-plastic parameters of the rockmass categorized by the Disturbance Factor parameter (Figure 2).

After a number of stability calculations it seemed clear that the potentially unstable zone would be very close to the walls of the rooms (Figure 3), and that a global instability would be very unlikely. The exploitation was finally carried out by the mine operator with success (Figure 4)

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