The end goal in open pit mining is to achieve reliable mine slopes that, if they fail, do not cause loss of life, equipment damage, sustained losses of production, or the inability to achieve published reserves. Over the years these requirements have been hampered by critical gaps in our knowledge and understanding of the relationships between the strength and deformability of jointed rock masses and the likely mechanisms of failure, with divided opinions on how to characterise the rock mass. Commonly, there has been an uncritical derivation of physical rock properties from empirical classification systems and an equally uncritical use of such physical properties in design analyses without a clear understanding of the geological framework. These inadequacies have been exposed by a number of spectacular large open pit slope failures, resulting in multiple fatalities, production losses, and unfavourable worldwide publicity. Collectively, they have demonstrated a need to step outside the box and reassess the fundamentals of rock mass strength and slope failure mechanisms from first principles.
The LOP Project slope design research tasks have been and continue to be directed at addressing these inadequacies by enabling the effective use of geological and geotechnical data in assessing rock mass characteristics, 3D modelling, and simulation of slope failure mechanisms, design analysis, and uncertainty analysis. The research tasks performed by the LOP project since 2009 have been drawn on the experience of the sponsors and a number of industry consultants and practitioners who have shared their knowledge and experience by contributing to several of the sections in the LOP Guidelines and Research Projects below.
Project Providers
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LOP Completed Projects
Stepsim4
Objectives: There is always variability in the length, spacing and orientation of discontinuities. Hence, in practice it may be preferable to use software such as STEPSIM for a probabilistic estimate for these equivalent shear strength parameters by considering the variability of parameters such as discontinuity persistency and strength. The “step-path” [Read more]
JointStats
Provider: CSIRO & The University of Queensland (JKMRC) Objectives: The JointStats software was initially produced by the Julius Kruttschnitt Mineral Research Centre (JKMRC), University of Queensland, as part of the International Caving Study research and technology transfer program. The original software accepted standard structural data from a face mapping [Read more]
OPS/ SiroModel
Provider: CSIRO Objectives: Development of the OPS/SiroModel, as part of the original Large Open Pit Mine Slope Stability Project (LOP I), allows the user to create a model of a section of an open pit excavation for slope stability analyses. It also includes a multi-function discrete fracture network (DFN) generator. [Read more]
Slope Model
Provider: ITASCA Objectives: A completely new code called Slope Model has been written as part of the Large Open Pit (LOP) Project. The code implements a version of the Synthetic Rock Mass (SRM) approach applied to the specific case of rock slopes. SRM allows movement on joints (sliding and [Read more]
LOP II Completed Projects
Quantifying Mining Induced Rock Mass Damage in Open Pits
Provider: Itasca Consulting Group Objectives: Open pit excavation results in disruption of the in-situ stress field with some stresses being relieved and others being increased. Damage to the rock mass behind open pit walls results from this stress redistribution and blasting practices. Damage to the rock mass from both [Read more]
LOP III On-going Projects
Dynamic slope stability and Seismic Risk
Objectives: Earthquakes have been responsible for initiating rock slope failures on sizes varying from minor landslides limited to one or more rock blocks up to major collapse involving whole mountainsides. However, while there are intense numbers of earthquake-triggered failures in natural slopes and tailing dams, [Read more]
Transient Pore Pressures in LOPs
Objectives: In conventional stability analyses, the strength properties of the rock mass or shear strength of a rupture surface on which sliding can occur are assumed to be constant over time. Failure is then explained through the influence of a triggering event, for example a [Read more]
Open Pit and Underground Interaction
Objectives: With more and more near surface deposits being depleted by open cast mining, many companies are studying the technical economic feasibility of underground mining. This involves mines that are currently active as well as re-opening mines that were closed. Implementing mine plans that include [Read more]
Mine Closure Guideline
Objectives:Closure planning is a fundamental requirement of all existing and planned future mines. The program for open pit Closure must consider the requirements of internal and external stakeholders, local regulatory requirements, global experience, leading practice and continuous improvement. This project focuses on the need for clarity [Read more]
Horizontal Drain Hole Programs for Slope Depressurization
Provider: BGC Engineering Inc. Objectives: Horizontal drain holes (HDHs) are often an integral part of the geotechnical engineer’s toolbox when pit wall performance is affected by porewater pressures. HDHs are commonly used or proposed for open pit depressurization systems; however, data to support the design, [Read more]
Guidelines for Structural and Geological Models in LOPs
Provider: SRK Consulting Objectives: The project aim is to providing direction on how to define a 3-D structural and geological model for use in open pit studies. The guidelines include the development of 3-D structural geology models, but is also inclusive of lithological and alteration [Read more]