News and updates

RMC Paper 1 Download - Important Information

Friday, 30 March 2012

Dear SANIRE Member, we are apologizing for any problems being experienced during the download process, but we are experiencing very large download volumes. Be patient and try again. When successful downloading please check the following:

Install Paper 1 Material

o   Download the Installer file from the website
o   Double click of the Installer and allow it to install the information on your computer
o   When done, the Installer will create an Icon on your desktop that reads 'Rock Mechanics Theory', use this icon to open the document. You do not need to open any other files, but work through th...

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MOSHing towards zero harm

Monday, 19 March 2012

Rock related safety is a major issue. The Chamber of Mines' Mine Occupational Safety and Health (MOSH) initiative is helping to address it. Find out more by reading on.

In 2003, representatives of the South African Mining industry - employers, labour unions and government - set historic and significant milestones for health and safety, to be reached by 2013, en route to zero harm for all employees.

The Chamber of Mines realised that the milestones, let alone the targets, would not easily be met without significant effort on the part of mines. Therefore the Chamber of Mines Learning Hub was ...

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From maths and computers to rock engineering

Monday, 19 March 2012

Roger Johnson's enjoyment of his job is based on the people he works with; the diversity in terms of commodity, geographic location and mining method; and the challenges and opportunities to introduce new technology, better practice and improved solutions. Here, he shares some of his ideas and experiences with Rock Talk.

Roger Johnson (56) had more of an interest in sport, the outdoors, music and social activities than in academics in his time as a scholar as La Salle College on the West Rand, but that was no predictor of his future.

Today, he has a slew of degrees and other qualifications t...

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March will bring your first free downloadable paper

Monday, 19 March 2012

Comprehensive rock engineering learning material for the South African mining industry is almost complete – and you can download it for free. Read more about it.

The writing of comprehensive rock engineering material for the South African mining industry started in the first half of 2011. It should be completed by end of March this year. At the time of writing this article, Paper 1 was complete. It should be available for download, free of charge, on the Sanire website by the time you read this article. The other papers will be available for download as and when they are completed.

Why is t...

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Design of Merensky Reef crush pillars

Monday, 19 March 2012

saimmlogo2 The Bushveld platinum group metal deposits are two distinct, shallow-dipping stratiform tabular ore bodies which strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2300 m. The mining method is a variation of planar open stoping. Pillars are widely employed to support the open stopes. In the deeper levels, in-stope pillars are required to fail in a stable manner soon after being cut, and the residual pillar strength is used to stabilize the hangingwall. These pillars are commonly known as crush pillars. Little work has been done in the p...

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How Tuks makes positive change a constant

Monday, 19 March 2012

The University of Pretoria's Jannie Maritz asks: Are teaching and learning really making an impact? At Tuks, he thinks they are. Read on to find out why.

The University of Pretoria's department of Mining Engineering celebrated its 50th anniversary in 2011. The first mining engineering student enrolled for the degree in 1961 and subsequently graduated in 1964.

A lot has changed on and around the campus, yet one thing has stayed the same: The quality of mining engineer graduating has improved. Every year, Tuks Mining is delivering around 30 newly developed mining engineers into the industry. ...

Oct 04 2011

Tohoku was a huge shock

A combination of factors mean that the Tohoku earthquake was about the worst expected anywhere on earth. The size of the brittle tectonic plates, their thickness of around 10-40 km and the fact that they float above a much more ductile mantle limits the cumulative strain energy that may be stored in any given region before failure occurs.

Section view of Northern Japan

The problem with this earthquake was that it took everyone by surprise. Seismologists did not foresee an earthquake of much greater than M=8: This subduction zone created by the colliding Pacific and North American plates has hosted nine events of magnitude 7 or greater since 1973. None of these were above 7.8.

Had the location and strength been closer to expectations , authorities would likely have been able to take precautionary measures, especially to reduce the impact of the tsunami that hit the coastal bays and travelled several kilometres inland in some cases. The maximum wave height was reported as 39 m.

The accompanying section view of Northern Japan shows activity colour-coded to depth. It is evident that deeper earthquakes are associated with the contact along which the North American plate forces the Pacific plate into the upper mantle at a rate of 8 cm per year (source: USGS-NEIC). The colour blue corresponds to a depth range of 150-300 km.

Failure mechanism

The source region was estimated to be 300 km long and 150 km wide and the resulting permanent displacement in the slip area was 30-40 m. The failure mechanism can be described as a thrust movement (a shallow-dipping reverse fault movement).

This type of failure causes the most powerful earthquakes. Since the beginning of the past century, all six earthquakes of M≥9.0 recorded worldwide were thrust events, according to the United States Geological Survey.

Of course, it is not physical source size but the resulting peak velocity and accelerations in populated areas and the tsunami triggered by the quake that are most relevant to potential damage and injuries. A shake map of Northern Japan shows the highest ground velocities were in the region of 50 cm/s and peak accelerations reached up to 60% of gravity (around 6m/s2).

Precautions

In recent years, especially after the 1995 Kobe earthquake, Japan improved building codes and implemented new guidelines for shake-proof infrastructure. The number of seismically isolated buildings has grown rapidly since then, as can be seen from the accompanying graph.

Shake map with intensity scale

This may contain a lesson for South African rock engineers and mine seismologists: Where prediction fails, measures should be taken to keep the roof over our heads.

It is, of course, much harder to stand through a magnitude 9.0 earthquake than through a mine seismic event. By the time the wave package consisting of direct P- and S-waves, reflected and complex surface waves, generated by the quake had reached Tokyo, it lasted over six minutes. Try to imagine that: Six minutes of violent shaking at PPV levels hardly ever seen on our mines even, when close to an event (around 15 cm/s).

Tohoku (東北) literally means "East-North”. This earthquake is named after the Japanese region closest to its 70 km off-shore location.

References

M Nakashima, P Chusilp (2004): A Partial View of Japanese Post-Kobe Seismic Design and Construction Practices, Disaster Prevention Research Institute, Kyoto University, Japan.
http://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami
http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/rupturezone.php
http://www.physorg.com/news/2011-04-japan-seismologists-quake-journal.html
The US Geological Service (which made much of the above information publicly available free of charge)