What roles do geology and geotechnics play in our underground waste disposal plants? Two K+S employees explain what is so fascinating about their work.
Dr. Stefan Höntzsch is a Senior Geologist at K+S and his passion for his profession shows: ‘As a geologist in potash and rock salt mines, I am a traveller between two worlds. Every day I deal with strata that are more than 250 million years old up-close and in 3-D! We work at depths of up to 1500 metres, see unique sediments and depositional textures that exist in only a few places in the world.’
K+S’s underground waste disposal plants have multiple geological and technical safeguards. In fact, the geological barriers are particularly special, explains Dr. Stefan Höntzsch. ‘These thick protective layers safeguard the opposing storage sites from the effects of water. Over and under the potash seams, we have a minimum of 50 metres of salt everywhere. Often the strata are up to 300 metres thick. In other words, it’s like a 70 to 80 storey building! What’s unique is that layers of clay and claystone more than 30 metres thick follow above. These are our groundwater stoppers. ‘
The Geotechnical Engineer
Here Stefan Höntzsch’s colleague, Dr. Jan-Peter Schleinig, enters the scene. Based on the statements of the geologists on the composition of the salt deposits, the geotechnical engineers calculate the structural stability of the mine layout, ‘because we need to verify this far in to the future as required by the landfill ordinance’.
‘The special thing about salt is its flowability, due to which the deposited waste is tightly surrounded by something resembling a thick, very tough honey. This occurs so slowly that the salt moves without cracking. And this means our barriers stay intact. The demonstration of long-term safety rests on this principle. ‘
Dr. Jan-Peter Schleinig explains how such verification comes about: ‘we formulate the task of verification and commission external specialist engineers whose assessments must be contained in the proposal. We are only allowed to dispose when the safe containment of the waste in the cavities has been confirmed.
‘It starts,’ says Dr. Schleinig, ‘with geology, mining situation and waste chemistry followed by information on the multi-barrier system. Then the geotechnical evidence in which we figure out the current condition using a model and then the geomechanical behaviour of the waste disposal area is forecast. And finally, there is the assessment of potential geological factors which might be come into play, such as volcanism.’
Contact with nature is also something that has fascinated the geotechnical engineer for almost 20 years at K+S: ‘Assessing the short and long-term geomechanical effects of mining as well as their subsequent use for the long-term safe transfer of waste is an incredibly exciting job. Our calculations are the foundation for safe, sustainable mining and for the environmentally-friendly disposal of waste. For this reason, it is a really important task.’
More to follow …
This section is an ongoing series with more “Insights” to come.