Analysis of Groundwater Management Options for the Mir Mine

The Mir diamond mine is located in Eastern Siberia, Russia, where artic conditions are present year-round.
Itasca Consultants GmbH works on the construction of a comprehensive groundwater flow model using MINEDW to predict the pumping rates for the active dewatering option. A high-level trade-off study on the costs, benefits, and risks of all three groundwater management options are also presented in the paper.
The current mining operation consists in underground mining, which follows past open-pit operations. The surface diameter and the depth of the open pit are approximately 1,200 meters (m) and 525 meters below ground surface (mbgs), respectively. The underground mining has been suspended since August 2017 because of an inflow incident. The confined aquifer is approximately 110 m thick in the Mine area and has a water pressure of approximately 2.0 mega-pascal (MPA) near the pit and has very high salinity. Prior to the inflow incident, the groundwater was pumped from several pumping stations in the underground mine workings and injected into the same aquifer seven kilometers north-east of the open pit. The unique aquifer conditions, the extreme climatic conditions, and the need of re-injection of the mine water post challenges to the management of the groundwater and recommission of the Mir mine.

Modelling over-boring and extension of a tunnel with surrounding excavations

As part of phase four in the extension of the ANDRA Meuse/Haute-Marne Underground Research Laboratory, a safety niche (called GT1) will be over-bored into a larger section, then extended. The tunnel axis is 16 m from an auxiliary shaft (named PX). Two perpendicular drifts, called GLN and GLE, connect these 2 excavations (Fig 1). Itasca Consultants S.A.S. was asked to verify how these works affect the support of existing structures:

• PX (built in 12/2004) then the shaft station (01/2005);
• GLE and GLN (02/2005), the GT1 niche (08/2005), supported by HA20 bolts;
• TH34/58 steel arches, and steel frames at GLE/GLN and GLN/GT1 intersections;
• Concrete liners of PX and the shaft station (03/2006)

Excavation phases separated by creep periods are simulated using the HB-Lemaitre elasto-viscoplastic model in FLAC3D. Stress and damage states around excavations and resulting resultants in supports are successively reproduced. These states as well as the displacement field and convergences at typical cross-sections are examined in the short term, after over-boring and extension of GT1, then in the long term, after
20 years of creep (Fig 2).

• Axial forces in bolts reach the elastic limit, bolt extension is under 5%;
• Steel arches reach the sliding limit force (250kN). The plastic moment is reached in the vault for GLN (// sh) and in the sidewall for GLE and GT1 (// sH);
• Resultants in the PX liner are inside envelop curves, with a safety factor of 1.5;
• Compared to the current state, the planned works related to GT1, and subsequent 20-year creep, do not induce significant changes of the resultants in the frames;
• In terms of displacement, convergence, stress state and damage, the effects of over-boring GT1 are negligible.

Next FLAC/DEM Symposium We are glad to announce that the next FLAC/DEM Symposium will take place in the University of Wien (Austria) on February 17 to 20, 2020. We look forward to receiving abstracts regarding your recent projects. More information on the event will be soon posted on our websites.

• PFC 6.0 is now available!

Version 5.0 was a major overhaul of the PFC software, introducing a user-friendly graphical interface, advanced FISH/Python scripting APIs, a generalized contact logic, multithreading. It set the foundation for a general and extensible framework for DEM simulations.

PFC 6.0 continues advancing DEM capabilities by adding new model components (convex blocks) and greatly improving the coupling with continuum models and structural elements as implemented in FLAC3D. These added features open a wide range of new applications:

• For Rock/Soil Mechanics:
  • Coupled with FLAC3D, PFC can now be used for site-scale geotechnical models, and provide the ability to capture failure initiation and propagation at a fine resolution at region(s) of interest, using a fully dynamic, explicit finite-difference time-iteration scheme.
  • The addition of convex rigid blocks allow for zero-porosity intact rock mass modeling, with the ability to add features (fractures, gaps.) at the contact scale.
• For Granular Systems:
  • Rigid blocks add the ability to capture shape and inertia of the objects accurately. They are more accurate and computationally more efficient than clumps.

Click here for a detailed overview of the new features implemented in version 6.0.

Current Updates:

Itasca will host introductory training courses in Europe:

Please visit www.itascacg.com/training for full details or contact directly the office responsible for the training.

For users who envisage the need for substantial amounts of assistance, consulting support or customized training course are available.
Feel free to contact us if you have specific needs: we adapt our offer to your needs.