By Jack Parker*
If I were an airframe designer and I recognized a couple of fatal flaws in the design of Boeing’s new Dreamliner I would not rest until I had done my utmost to prevent a disaster, regardless of the odds, the opposition and the name-calling. That’s what engineers are supposed to do -- to apply the science responsibly.
With the Eagle mine plan I have sixty-some years of mining and geological engineering experience to apply, specializing in stability problems. Here we go.
THE CROWN PILLAR, THE LID OF THE MINE, AS DESIGNED, IS NOT STABLE. INSTEAD IT IS ALMOST CERTAIN TO BE UNSTABLE. I will list the reasons in case somebody wishes to dispute that assertion.
1. The basic data put into the design formulas were fudged, intentionally manipulated to ensure passage of permits. When corrected and entered into those formulas the safety factors become lower than 1.0 -- which indicates that the crown pillar will probably collapse. Nobody has denied the fudging.
2. The diamond drill cores show significant zones of poor rock. They were deliberately omitted from the pillar design process. Nobody denies that either. The fudged numbers and core descriptions were supplied to all designers and reviewers, including MDEQ; and not one of them insisted on independent data. In engineering work that constitutes a misdemeanor.
3. The quoted design thickness, 87.5 meters, includes some of that poor rock, some of it the fractured and weathered rock near surface. To include that as an asset instead of a burden is ridiculous.
4. The crown was assumed to be of peridotite, one of the strongest rocks. In reality the cores show that a large proportion would be of the weaker sedimentary and ore-bearing rocks. That is undeniable.
5. I, personally, have no use for computer modeling in mine design because the input is what we used to call "garbage." You cannot assign rock properties as measured in the lab, on small cores, to a huge mass of millions of tons of widely variable rock in which the mine would be constructed. It is not possible to select a suite of small samples which will be representative. Try it next time you look at an extensive roadcut or a quarry! You will almost certainly select the best rock. You will not select any poor rock.
6. Computer modeling is normally tempered by "case histories" -- what happened when similar designs were used in similar conditions. For reasons not made public, but suspect -- the DEQ told their hired expert, David Sainsbury, to delete case histories from his report on the Application for Permits.
Sainsbury described the 87.5 meter thick crown as SUBSTANTIAL, not STABLE. Blake misquoted him. So did the KEMC (Kennecott Eagle Minerals Company) attorney in a tête-à-tête with Ms. (Judge) Manderfield. I heard it. Ms. Manderfield followed his lead.
7. One of the deletions was the Athens iron mine, near Negaunee. The "crown pillar" was 1800 ft thick, in jaspilite -- an extremely strong rock in lab tests -- and it collapsed overnight. The geologic structure is not unlike that at the Eagle site. That leads to the next -- an overwhelming observation.
8. NOBODY, not even a judge, can assert that a crown pillar will be stable, NOBODY, without knowing the stressfield in the rockmass. Horizontal compressive stresses are necessary to hold up a normal rockmass, with its many structural defects. If the stressfield is low compressive or, worse yet, tensile, then collapse is to be expected -- as at the Athens mine.
In at least three places in the literature we have indications of locally tensile stress. At the White Pine mine Parker measured and wrote about it. On the Yellow Dog Plains Bill Cannon (USGS) and Jim Trow (LSGI) recognized that the geological structure (primarily the long, straight, subvertical, E-W intrusive dikes) indicate that the stressfield is tensile, oriented N-S. That was our interpretation too.
Ignoring that information would probably be fatal. Stresses could and should have been measured in the rockmass in a week or so, at a cost of a few thousand dollars. Kennecott failed to do that. They guessed.
9. Neither of the DEQ experts, Sainsbury and Blake, showed facts or figures to indicate that the crown pillar would be stable.
10. To summarize: There is no credible evidence to support Ms. Manderfield’s conclusion that the 87.5 m crown pillar would be stable. All supporting statements are conjecture, based on dubious data and faulty reasoning. The conclusion was incorrect. The "Motion to Stay" should have been approved.**
I can only assume that she was misinformed by advisors.
These points have been brought to the attention of all concerned but have been ignored, with some blustering -- but not even a critical investigation. It is almost too late -- but not too late, to reconsider.
Please do that.
Jack Parker, Mining Engineer, Toivola MI 49965*
* Mining expert Jack Parker, semi-retired mining engineer/geologist, is well respected for his practical experience in more than 500 mines around the world. Parker -- who has degrees in mining engineering, geological engineering and geology from Michigan Technological University -- specializes in practical rock mechanics.
Parker recently published two reports on the Eagle Mine, pointing out reasons why it is likely to collapse if mined as planned in Kennecott's mining permit. To read about
them see our illustrated Dec.6, 2010 article, "Mining expert Jack Parker says Eagle Mine likely to collapse."
** See "Groups ask Judge to halt mine blasting at Eagle Rock."
(Judge Manderfield denied this "Motion to Stay" last week. See the Sept. 15, 2011, Mining Journal article.