International competence a strength for Itasca - shaft project
How can one excavate stable shafts in difficult rock conditions at large depths? Itasca Consultants AB was tasked to seek the answer to this question and has used worldwide experience and knowledge! To excavate long shafts using raise boring in difficult rock conditions is challenging. Mining companies ask themselves how others deal with this issue. Itasca was given the assignment to solve this problem for Boliden!
– It is quite rare that companies present when projects with long shafts fail, and it is thus not easy to learn from other's mistakes, says Catrin Edelbro. She goes on to say that she and Jonny Sjöberg decided to look outside of Sweden and seek assistance from those best qualified!
– Itasca has the advantage that we have a worldwide presence. We seeked assistance from our competent collegues in Minneapolis and Sudbury. They have practical knowledge of the problems and collected data and information from their respective areas. I myself turned to Australia, where there is a long tradition of doing long shafts in difficult ground conditions. They also shared data from failed cases, says Catrin, and states that even though it is sensitive to tell about things gone wrong, one can learn a lot from this.
– The case studies that we have from Canada can be applied to Swedish conditions, as the rock is fairly similar. For the Australien cases, we have to "translate" some of their experiences (from much poorer ground) to Swedish conditions. We have found many cases where one reinforces the shafts in a different way than what is normally done in Sweden today, says Catrin, and states that she has learned a lot through this international cooperation.
Itasca is now on its way to find a solution to increase shaft stability during and after raise boring, even in the most difficult rock conditions.
– This shows how important it is for us in Sweden to keep an open mind, and how "little Luleå" becomes international, thanks to our international presence.

Distinct-Element Modelling of a Tunnel - Excavation Test with PFC2D

GRL has called on Itasca Consultants S.A.S. to develop a parametrized PFC2D model to simulate laboratory experiments of tunnel excavation. A two-dimensional plane-stress tunnel experiment was developed in a laboratory: the circular hole representing the tunnel is created with by means of an inflated vinyl air bag, whereas the soil consists of laid aluminum bars with two kinds of diameters. Tunnel excavation is then mimicked by performing stepwise reduction of the inflation pressure. Displacement of the material is monitored as the applied pressure is reduced at the end of each excavation step.

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