Phil de Graaf

De Beers

Fall of Ground management at Venetia is through Anglo American Plc slope safety critical controls. Each critical control has defined key performance indicators and standardised number metrics that are monitored and reported on. Through application of the hierarchy of controls, rockfall risk management is addressed in several elements of the slope s...

Venetia Open Pit Mine, after 30 years of production, will be transitioning to underground production in Q4 2022. This presents an interesting conundrum: aggressively maximise pit ore recovery and short-term revenue or follow a more conservative, high reliability slope design and defer ore to later underground recovery. Preferences are weighted towa...

The Large Open Pit project (LOP3) commissioned the development of a white paper, Guidelines for Structural and Geological Models, that provides structural geologists and geotechnical engineers working in open pit mines with guidance on the creation and evaluation of 3-D structural geology models, and the integration of such models with lithological...

For open pit mining, understanding and managing slope performance is critical for both operations and closure. Towards the end of mine life, achieving reliability of slope performance in operations often necessitates real-time implementation of active slope stabilisation controls. This situation changes significantly towards closure, when productio...

Interferometric synthetic aperture radar (InSAR) application has recently benefited from an increased number of service providers (with more diverse satellite constellations), advances in algorithm processing methods and, with reductions in costs, is becoming a widely accepted method of surface deformation monitoring in the mining industry. InSAR m...

Closure planning is a fundamental requirement for all existing and planned future mines. However, there are no accepted industry guidelines for how to assess options for open pit closure or for advancement of the closure plan in parallel stages with overall project development and operation. Ideally, closure planning needs to consider the site sett...

The De Beers Canada Victor Diamond Mine is located in the James Bay lowlands of Northern Ontario. This case study presents the evaluation of geotechnical stability and pit lake filling. The work was used to support decisions that informed risk assessments and the closure plan for two key phases: 1. Active closure, with personnel undertaking rehabil...

This paper discusses the engineering, hydrogeology, operational practices and TARPs that facilitated deeper mining and goodbye cuts at the De Beers Canada Victor Diamond Mine. A number of technical challenges related to water management and adverse geology late in the mine life were overcome in order to successfully meet and exceed the planned mini...

Working stress design (WSD) has long been used in geotechnical practice. However, in the past decade this has, to a significant extent, been replaced by limit state design (LSD) which is the basis for Eurocode 7, and presents a more robust approach in dealing with uncertainties. Factually, however, none of these approaches quantify the degree of un...

De Beers is currently developing closure plans for two open pit mines. At first glance they appear quite similar; both are relatively remote, have operated for 10 years, have similar pit dimensions (250-300 m deep and 1.5 km wide) and have Palaeozoic sedimentary host lithologies with weak upper units overlying more competent lower materials. Howeve...

The geometry and structural history of high-grade granite-gneiss units, which host the Venetia diatremes in South Africa, have been modelled in 3D using an implicit, rules-based, conditional geometrical technique. The volume contains a pervasive, dominant foliation, which forms the main plane of strength anisotropy in ongoing design and mining of t...

SYNOPSIS Namdeb's Southern Coastal mining operation is located in Southern Namibia, just north of the Orange River mouth. Diamonds were fi rst discovered in the area in 1928 and mining of diamondiferous onshore raised beaches has been the mainstay of Namdeb's production for nearly 90 years. The onshore beaches are now largely mined out but mining o...

The Southern Ridge Cutback 3 (STR3) at the Tom Price mine site will be the highest and steepest slope in Rio Tinto Iron Ore's Pilbara operation. Initial geotechnical assessment of the STR3 western slope using two-dimensional limit equilibrium methods recommended a substantial flattening of the design. This would have resulted in the deferral of 3.2...

Rio Tinto's Western Australian expansion, combined with mining within structurally complex geology and increasingly below the water table, presents challenges in effective slope management to ensure safe and economic mining. The Geotechnical Management System (GMS) was developed by Rio Tinto Iron Ore (RTIO) to manage geotechnical risks identified d...

A planar failure of approximately 600 kT occurred on the north wall of Centre Pit North (CEPN) at West Angelas Mine site in February 2010. The failure impacted a substantial resource of high grade iron ore and left a number of significant geotechnical hazards on and adjacent to the failure surface. These presented a series of challenges which had t...

Previous studies have indicated that a 40 m thick, at approximately 40 m depth, layer of Tertiary clay, will present significant challenges relating to slope and waste dump design as well as operational challenges (trafficability and handleability). Due to uncertainty over the confidence of parameters derived from triple tube sampling and testing,...

Slope Stability 2013, Brisbane, Australia 513 D.S. Lucas Mining One Consultants, Australia P.J.H. de Graaf Rio Tinto Iron Ore, Australia Rio Tinto Iron Ore's (RTIO) Tom Price open cut mine in the Pilbara region of Western Australia commenced in 1966 and had a cumulative production to mid 2012 estimated at over 800 Mt. The South East Prongs (SEP) pi...

Rio Tinto Iron Ore's (RTIO) Western Australian mine operations comprises 14 mines with a centralised 'Mission Control' Operations Centre (OC) in Perth, and currently delivers 237Mt/a ore from over 120 individual open pits. Operational challenges in terms of implementation of effective slope monitoring systems with appropriate visibility of system h...

Geotechnical design is characterised by a relatively large number of uncertainties, even if industry best practice is followed during the design process. Regulatory and corporate standards require appropriate geotechnical design and slope management. Rio Tinto Iron Ore (RTIO) have addressed this challenge by developing a geotechnical reconciliation...

Dewatering at the South East Prongs (SEP) pit has lowered in-pit water levels approximately 81 metres below the pre-mining water table. As a result a steep hydraulic gradient has developed behind the pit slope as the more permeable ore material has been dewatered and water levels (pore pressures) remain elevated in the less permeable waste rock mat...

A geotechnical data management system has been developed to manage drillhole and mapping data generated from in house and consultant administered field programs. This system comprises a data collection interface with integrated validation, processing and reporting functionality. Development of the database required careful consideration of how and...

Ongoing weathering of high rock slopes overlooking the DeCew Falls Generating Station No. 2 Powerhouse and transformer yard pose a risk to personnel and infrastructure. Originally designed and constructed as an unsupported cut slope more than 60 years ago, continued exposure to the elements has resulted in loosening, ravelling and undercutting of t...

The engineering and construction of an almost 10 metre deep, 20 metre diameter basement excavation, along with ancillary underpinning, tunnels, shafts, and raises to provide new underground space in the limestone bedrock forming the foundations of the Library of Parliament in Ottawa, Canada, without damage to the existing heritage building or disru...

Construction of a novel retaining wall and implementation, for the first time in Hong Kong, of high energy rock fall protection fences contributed to the successful completion of one of the most difficult highway realignment and widening programs ever undertaken in the Territory. The Tuen Mun Highway is one of the major arterial roads linking Hong...

The widening of the Tuen Mun Highway involved demanding aspects of site investigation, design and construction due to the combination of existing steep cut slopes, an extensive weak zone and heavy adjacent traffic. The application, for the first time in Hong Kong, of high energy rockfall protection fences and novel tie-back retaining wall design ar...

Due to the inherent strengths and weaknesses of existing cable bolt design tools it is necessary, to optimise the ultimate desgin, that a multifaceted approach be followed. This multifaceted methodology should be tailored to suite the specific engineering problem at hand. Ground conditions at each of the two field trials at Hudson Bay Mining and Sm...

Cable bolts are widely used as a principal means of support. The monitoring of the performance of reinforcement is critical in improving and optimising reinforcement designs. This paper presents case studies where Stretch Measurement to Assess Reinforcement Technology (SMART) instrumentation was used in conjunction with other observational, analyti...

Cable bolts are widely used as a principal means of support. The monitoring of the performance of reinforcement is critical in improving and optimising reinforcement designs. This paper presents a case study where Stretch Measurement to Assess Reinforcement Technology (SMART) instrumentation was used in conjunction other observational, analytical,...

The Delivery Tunnel North starts in Lesotho and continues into South Africa. It is divided into two sections by the Caledon and Little Caledon rivers. It runs through the mudrocks and sandstones of the Tarkastad Subgroup, and the Elliot and Molteno Formations. The tunnel was excavated by a double-shield tunnel boring machine, except for the section...

The purpose of Lesotho Highlands Water Project is primarily to supply water from Lesotho to the Pretoria-Witwatersrand-Vereeniging industrial region of South Africa. In addition, the hydroelectric scheme at Muela will supply enough electrical power to meet the needs of Lesotho. The project consists of a number of dams, reservoirs and tunnels, and a...