Groundworks February 2008 HCItasca eNewsletter

I am pleased to have this opportunity to greet you at the start of a new year and say, in my first address in this space, how privileged and excited I am to lead HCItasca into the future. I also would like to thank John Markham, our new CFO, for his many years of outstanding leadership. For more information about changes in HCItasca leadership, see HCItasca World below. Best wishes to friends and clients for a prosperous and productive 2008.

– Loren Lorig, Chief Executive Officer

Development of New Analysis Tools for Open Pit Design (Itasca S.A.)

The design of open pits normally involves several scales of analysis (bench, interramp, overall) where different acceptability criteria apply. There is no unique methodology to perform the bench/berm design process; several approaches are proposed. The methodology that Itasca uses is based on statistical analysis of the interaction between the structural sets identified in the wall to be designed and the application of a catchment criterion to decide the appropriate bench geometry.

With encouragement from the mining industry to improve the efficiency of these calculations, Itasca S.A. has developed an automated, faster, more reliable calculation process. As a result, the codes SWISA (for wedge failures) and PFISA (for planar failures) have been created.

The codes perform a statistical analysis of the volumes of unstable wedges formed by the joint sets in a slope wall. The basic input is the statistical information of wall orientation, joint sets (dip and dip direction), bench face angle, bench height, cohesion and friction angle for the joints, and unit weight of the rock.

The main characteristics of the analysis are:

Identification of unstable wedges
Construction of cumulative distribution curves for the unstable volume and other geometrical parameters (see figure)
Calculation of berm widths based on a comparison between the spill length of the critical volume and the catchment criterion

Both SWISA and PFISA are run internally by Itasca as Excel spreadsheets, but, eventually, the two tools will be made commercially available to the geotechnical community. To see and find out more about SWISA and PFISA, please see the complete description at our web site.

Figure: Alternative design curves for different bench face angles showing the spill length determined from the cumulative volume distribution for an analysis with SWISA

Current Versions updated since December 1, 2007

New Feature Available in FLAC 6.0 Pre-Release

Automatic remeshing (or rezoning) logic is now available in the FLAC 6.0 pre-release for large- strain models, including dynamic simulations. This feature allows the model to pause cycling when a "bad geometry" error might cause a halt to the model run, rezone the model, and continue the simulation uninterrupted. A PDF file documenting the logic and a few demo examples and corresponding data files are included in the pre-release update available on our web site.

As bad-zone geometries threaten to halt the model, automatic remeshing performs a re-mapping of zones (preserving accuracy in the calculations) to restore integrity to the mesh and allow further cycling.

As of January 1, 2008, Loren Lorig will serve as Chief Executive Officer of HCItasca. Loren has spent the last nine years as General Manager of Itasca S.A., HCItasca's office in Chile. Loren is an engineer with more than twenty-five years of experience – 22 with Itasca – and his expertise has been recognized internationally. This past fall Loren was elected to serve as CEO by the HCItasca Board of Directors, after a two-year search for a candidate to replace his predecessor, John Markham (who will continue to serve HCItasca in the capacity of Chief Financial Officer). His experience will be a valuable asset in this time of transition, as new leadership will bring new opportunities and new directions to the company.

Reminder
The FLAC/DEM Symposium will be held August 25-27, 2008, in Minneapolis. Registration is now open. To register, please complete the Registration Form [fill-in PDF, 289k] and return it to the attention of Michele Nelson via email (mnelson@itascacg.com) or fax (+1-612-371-4717). Don't wait to register, or to reserve your on-site accommodations. A block of rooms has been held for the conference, but a number of them have already been taken. Visit the Symposium page for full details.

Introductory software training courses are coming this Spring. Registration for each class is limited, so don't delay signing up. More information - including course outlines and a registration form - is available on the Training page.

FLAC	April 7-9, 2008
FLAC3D*	April 14-16, 2008
3DShop	April 21-23, 2008
UDEC	April 28-30, 2008
3DEC*	May 5-7, 2008
PFC	May 12-15, 2008

* - For FLAC3D and 3DEC, one complimentary registration to the corresponding training course is included with the purchase of a new license.

Literature by HCItasca personnel recently published or acquired in the HCItasca library.

Andrieux, P. P., R. K. Brummer and H. Li O'Connor. (2007) "Elastic Versus Inelastic Numerical Modelling of Deep and Highly Stressed Mining Fronts," in Deep Mining 07 (Fourth International Seminar on Deep and High Stress Mining, November 2007, Perth, Australia), pp. 51-57, Y. Potvin, Ed. Perth: Australian Centre for Geomechanics.

Board, M., B. Damjanac and M. Pierce. (2007) "Development of a Methodology for Analysis of Instability in Room and Pillar Mines," in Deep Mining 07 (Fourth International Seminar on Deep and High Stress Mining, November 2007, Perth, Australia), pp. 273-282, Y. Potvin, Ed. Perth: Australian Centre for Geomechanics.

Hudyma, M. R., and D. Heal. (2007) "Proactive Versus Reactive Seismic Monitoring in Mines --- Results of a Seismic Monitoring Survey," in Deep Mining 07 (Fourth International Seminar on Deep and High Stress Mining, November 2007, Perth, Australia), pp. 207-219, Y. Potvin, Ed. Perth: Australian Centre for Geomechanics.

Mercier-Langevin, F., and M. R. Hudyma. (2007) "The Development and Implementation of a Comprehensive Seismic Risk Management Plan at Agnico-Eagle's LaRonde Mine," in Deep Mining 07 (Fourth International Seminar on Deep and High Stress Mining, November, 2007, Perth, Australia), pp. 221-232, Y. Potvin, Ed. Perth: Australian Centre for Geomechanics.