News Article

Workshop: The “Big Five”: Numerical Modeling of Cave Mining

Itasca is offering a workshop at the upcoming MassMin2020 virtual conference. Engineering consultants from three offices (IAus, ICSpA, and ICG) will be reviewing the “Big Five” geomechanical challenges associated with mass mining: caveability, ground subsidence, infrastructure stability, fragmentation, and gravity flow. Each session will include a brief background theory, numerical modeling methodologies, and their application to mining projects.

Who Should Attend?

This workshop is an overview designed for geomechanical and mining engineers, geoscientists, managers, and academics interested in learning more about numerical modeling of mass mining for panel, block, and sublevel caving and pit-to-underground transition.

Description

Accurate simulation of the caving process is complex due to the wide range of mechanisms to be captured, including stress redistribution around the cave, rock mass failure in advance of the cave, reduction in strength from peak to residual, dilation and bulking, material flow in the cave column, crater development, and crater slope failure.

This workshop will provide an overview of a variety of numerical modeling methods used to simulate cave mining in practice. The workshop is organized into five sessions, one for each of the Big Five geomechanical challenges in cave mining. Each session will consist of a brief introduction to relevant theory and background, Itasca’s approach to numerical modeling and engineering design, followed by applications or cases demonstrating the approach in practice. A 10-minute Q&A session will be open at the end of each session.

Date: December 8, 2020

Hours: 15:00 – 19:00 hr Santiago, Chile Time (12:00 noon - 4 pm CST)

Official language: English with simultaneous translation into Spanish

Brief descriptions of each session follow:

CAVEABILITY

Is the orebody going to cave and, if so, how? The ability to forecast cave propagation by understanding the evolving size and shape of seismogenic, yielded, and mobilized zones associated with caving is critical to the mine design. This establishes critical hydraulic radius and the potential for hang-ups and air gap formation, and is important to understand likely cave propagation rates and to define cave limits.

GROUND SUBSIDENCE

How might the underground cave impact the ground surface? Caving-induced subsidence may put mine infrastructure at risk, while changes in the surface landscape may be dramatic and can lead to high environmental impact. A major concern during the planning and execution of underground mining is the impact of ground movements on adjacent buildings and utilities. Another aim of defining the subsidence zones is to assess stand-off distances for the siting of mine shafts and other infrastructure.

Caving-induced surface subsidence is typically characterized by three key zones: the crater, the fractured zone, and the zone of continuous subsidence. The limits and shapes of these zones are mainly controlled by the overburden lithology spatial distribution and its associated rock mass strength, in-situ stress, the presence of major structures, preferred joint orientations, topography, and footprint depth and shape.

INFRASTRUCTURE STABILITY

How are underground excavations affected by cave propagation? Prediction of the redistribution of stresses associated with caving assists in assessing the stability and ground support effectiveness of undercut and extraction-level development and other critical infrastructure in both high- and low-stress environments. Seismicity and rockbursting hazards and working with mega-models consisting of tens to hundreds of millions of zone simulations will also be discussed.

FRAGMENTATION

What is the range of fragment size at the drawpoint and likelihood of hang-ups? Prediction of fragmentation, including secondary fragmentation, is critical to operational productivity and recovery.

Primary fragmentation is estimated based on the concept of Synthetic Rock Mass (SRM), where the geotechnical data is used directly to simulate the rock mass, including veins and explicit jointing. The rock mass is then subjected to cave back stresses, and the resulting fragments are tracked to derive a primary fragmentation curve. Subsequent material flow modeling utilizes an attrition law to predict how primary fragments degrade into secondary fragments as a function of rock block strength and draw.

GRAVITY FLOW

How is the caved material moving inside the cave and what is the impact on cave propagation, recovery, and dilution? Best practices using a coupled approach between continuum codes and flow codes will be reviewed. In addition to numerical simulation, Bin theory, Laubscher’s empirical method, and full-scale marker trials will be discussed.

Registration

You can register for the workshop via the MassMin2020 workshop web page. Space is limited.

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