Rocks & Slope Stability
Issue #43: Focus on Rock Engineering and Slope Stability
International slope stability research
The never-ending quest to go further, faster and higher not only applies to professional sports and space science, but is also a trend reflected in the mining industry. As rich, near-surface mineral deposits are depleted and environmental and social awareness grows, mining operators move to greater depths, pit slopes are getting higher, and modern technologies are used to excavate rocks at a much faster pace than ever before. read full article…
Geotechnical characterisation
The geological and geotechnical models are foundations of any mine design. These models could also be the leading sources of technical risks for mining projects. In order to minimise these risks, it is necessary to reduce the uncertainty in understanding the geological context of the deposit. With ever more sophisticated computer tools, it is possible to tackle more complex tasks in shorter times than before. read full article…
Risk aware!!!
The word “risk” is widely used when people perceive a hazardous event, resulting in widely different perceptions of risk. The technical definition of risk as used in geotechnical engineering is: Risk = P(event) x Consequences. Slope design for large open-pit mines presents unique challenges to the engineer that are captured in the oft-quoted maxim that “the objective is to have the slope fail the day after the last truckload of ore leaves the pit rim”. read full article…
3D modelling structurally controlled weak rock masses using blockiness
Design of deep open pits in structurally complex, weak deformable rock masses is a challenge. Recently, SRK in conjunction with HTA Consulting, engaged in assessing the slope stability for such a proposed pit. Experience has shown that incorporation of the Geotechnical Blockiness Index (GBI) within the 3D geotechnical domain model improves our ability to simulate pit design performance. read full article…
Estimating rock mass strength
Estimating rock mass strength (RMS) remains one of the challenges facing rock mechanics practitioners. The infinite variability of geology, weathering and alteration processes, the influence of mining and the inability to test rock mass strength directly, all pose great challenges to making reliable estimates. The experience of the practitioner, therefore, plays a crucial role in such estimates. read full article…
Itabirite iron ore bodies: Generic geotechnical models
SRK has recently been involved at the feasibility and pre-feasibility level studies on a number of large-scale iron ore projects in west and central Africa and Brazil. Experience across these locations has highlighted a number of similarities that should be considered when generating a geotechnical model in itabirites. read full article…
Safe and rapid development for major underground mines: Trends for the future
Rapid development techniques maximise activity at the tunnel face and advance completion rates without compromising safety. Good project planning should prepare for both expected ground conditions and unexpected variations in the rock mass to be excavated. This will reduce delays and mitigate the effect of poor ground conditions, which can slow advance rates by 50%. It is no surprise that poor ground slows advance rates. read full article…
Mining challenges in permafrost environments
The Kumtor gold project is located in the mountainous terrain of the Tien Shan Mountains in the Kyrgyz Republic, at an altitude of around 4000m. The mean annual temperature is minus 8°C. Locating and designing an exploration decline to access and explore the mineralised horizon below the operating open pit proved to be a challenging experience as a result of poor ground conditions, widespread glaciation and location of the waste dumps. read full article…
Shea Creek uranium project
The Shea Creek Project, owned jointly by AREVA Resources Canada Inc. and UEX Corporation, with AREVA acting as project operator, is an advanced uranium project located approximately 700km NNW of Saskatoon and approximately 30km east of the Alberta border, within the western Athabasca Basin of northern Saskatchewan. The property is underlain by two dominant lithologies: metamorphic basement rocks of Archean and Paleoproterozoic granitoid, covered by Proterozoic flat-lying to shallow-dipping, post-metamorphic quartz sandstone. read full article…
Integrating structural geology and geotechnics, Los Caracoles Dam
The Los Caracoles is a 140m high hydropower water dam, located in San Juan Province, Argentina, in an arid region of high seismic activity. The spillway system consists of two large parallel tunnels while the gateway structure is formed by two twin boxes, each 30m high, excavated in the upstream slope of the abutment. Natural stability relies in the continuity of the rock layers along the entire slope and into the foundation levels but this continuity would be altered by the gateway excavation. read full article…
Use of photogrammetric mapping techniques for slope stability
For pit slope design, geotechnical data is typically collected by mapping the benches to supplement data collected from boreholes. Where an open pit has been in operation for some years, bench faces are often difficult to access and, increasingly, access is being restricted to reduce the risk of exposure to rockfall hazards. In order to address these issues, photogrammetry is being used more frequently. read full article…
Assessing geotechnical management using the Ground Blockiness Index (GBI)
Risk management and risk assessment are important processes, and should be applied to both the development of mining studies and the implementation of designs. SRK has completed a risk assessment as part of the cutback feasibility study and practical design for the Damang pit in Ghana. For operational risk management, reliable field data needs to be collected. By using the Geotechnical Blockiness Index (GBI) in our field mapping, SRK applied a rapid rock mass characterisation tool to accelerate assessment at Damang. read full article…
UDEC modelling
The Universal Distinct Element Code (UDEC), developed by the ITASCA Consulting Group, is a “distinctive element program for discontinuum modelling”. UDEC simulates the response of discontinuous media (different rock types) when they are subjected to either static or dynamic loading. Linear or non-linear force-displacement causes movement in both normal and shear directions. read full article…
Antamina geological modelling, Peru
The Antamina Cu-Zn mine which lies in the high Andes of Peru, 270km north of Lima, is operated by Compañía Minera Antamina S.A., for a consortium of owners including BHP Billiton, Xstrata, Teck Resources, and Mitsubishi Ltd. An expansion of the mine has been recently approved which takes advantage of a 75% increase in reserves; the current extraction rate of 94,000 tonnes/day will be increased by 38% by 2012, with a corresponding extension of the mine life to 2029. With a rapidly expanding open pit in mountainous terrain, it is imperative to have a good understanding of the structural and lithological architecture, to ensure continuing safe and profitable extraction of the orebody. read full article…
Koidu vertical pit, Sierra Leone
The Koidu Kimberlite Project is situated in the Kono District of Sierra Leone, approximately 330 km east of the capital city, Freetown. The mining lease area is 4km2 and comprises two kimberlite pipes, four dyke zones and a number of blows off the dykes. In 2003, Koidu Holdings established operations on the property and began dewatering and removing silt from the existing 30m excavation of the No.1 Pipe. read full article…
Numerical analyses for evaluating pit wall and underground stability at Ok Tedi
A staged numerical analysis program was conducted for the final pit and proposed underground mining excavations at Ok Tedi Mine in Papua, New Guinea. The analyses were conducted to evaluate the performance of the final east and west pit walls, and the stability of the underground mining excavations beneath these walls, as mining progresses. These evaluations were intended to facilitate the design and to assist with decision-making concerning the viability of the underground mining project. read full article…
Blasting program optimises pit slope performance
Barton Mines, a garnet mining operation in upstate New York, contracted SRK to conduct a slope stability evaluation of the active Ruby Mountain pit. Three geotechnical coreholes were planned, along with cell mapping of the pit exposures to provide data for the slope stability analyses. During our site investigation, it became apparent that rock mass characteristics would not limit the slope design. The rock was relatively uniform lithology, and of relatively high strength. read full article…
Economic success in underground soft rock mining
The economic success of industrial mineral projects,such as potash, often depends on recovering high tonnages at low cost. These deposits are often tabular and, are subjected to the full weight of the overburden, are of relatively low strength, which makes underground high extraction problematic. Most of the tools and techniques available to the mining and rock mechanics engineer are based on the experiences of practitioners in hard rock mining. read full article…
Probabilistic stability analysis for pit slope optimisation at Jwaneng diamond mine, Botswana
The Jwaneng Mine is situated in the Republic of Botswana, approximately 160 km west of Gaborone. The open pit has a general NNE-SSW orientation, with waste dumps located to the west and the process plant area to the east. The excavation of the Cut 8 pit will remove part of the plant area. The current pit has a depth of 330m while the planned pit will have a depth of 645m. SRK carried out a detailed probabilistic stability analysis of the east slope to optimise the design of Cut 8 and ensure adequate performance of the slope and integrity of the plant installations in its vicinity. read full article…
Geotechnical design considerations for mine shafts
The design, development and operation of a shaft system is a critically important element in mining, and needs specialised technical input. Experience has shown that the consequences of damage to shaft systems caused by geotechnical factors are serious and costly. Control of ground conditions is a key factor in the design and sinking of shafts, as these conditions may vary considerably throughout the length of a shaft and require specific technologies to ensure safety and functionality. read full article…
Geotechnical investigation for Kwatebala copper open pit, DRC
Kwatebala is located 12km west-northwest of Fungurume in the Katanga Province of the Democratic Republic of Congo. The topography of the area is characterised by gently rolling hills with pronounced ridges which are frequently associated with copper mineralisation. These ridges have areas of open grassland, known as copper clearances, but are mostly covered with moderately dense bush. Kwatebala is a 1900m long east-west trending ridge that rises from the surrounding valleys to an altitude of 1503m. read full article…
Auditing the ground control management plan
SRK has developed an audit procedure for Ground Control Management Plans (GCMP) designed for open pit and underground operations. The audit procedure is based on guidelines provided by the Western Australian Department of Minerals and Petroleum (DMP), published in 1997 and 1999, relating to geotechnical considerations for both open pit and underground operations. The original intent of the guidelines was to “provide examples of good geotechnical engineering practice and assist mining operators in achieving compliance with the Mines Safety and Inspection Regulations 1995 (MISR 1995).” read full article…
Rapid characterisation of slope instability using LiDAR
Following a multi-bench structural instability along the primary haul road for an operating open-pit copper mine, SRK was tasked with rapidly evaluating geologic structure in the area and subsequently assessing pit slope stability. It was important to determine whether significant pit slope design modifications were necessary for further mining and whether safe transport through the area would be possible. read full article…
Slope stability – fundamental concepts
Despite the widespread availability of software programs using sophisticated numerical methods, the physical principles of slope engineering should not be forgotten. Simple, well considered engineering judgment based on fundamental principles, which identify all potential mechanisms of failure and account for the stability of each mechanism in the design, are critical. Recently, SRK was involved in reviewing the design of a 15m high gabion structure that collapsed. read full article…
Weathered rock masses
SRK’s rock mechanics engineers have recently undertaken open-pit design studies for rock masses hosted within saprolites and highly weathered bedrock. One such example is Oromin Explorations Ltd. Sabodala gold project in Senegal. Since 2006, SRK has designed a series of field programs to satisfy geotechnical, structural and hydrogeological objectives for scoping, pre-feasibility, and feasibility studies. Geologically, the project is characterised by steeply dipping, shear-hosted gold veins set within Precambrian greenstones. read full article…
Slope design in challenging conditions at El Teniente, Chile
The El Teniente mine complex, owned and operated by the National Copper Corporation of Chile (CODELCO), is located about 80 km south of Santiago, Chile in the Andes Mountains, at 2,500 meters above sea level. The complex includes a series of underground operations that use block caving and panel caving to extract copper. To provide flexibility in production rates and for strategic planning purposes, CODELCO is currently evaluating the Rajo Sur project at a pre-feasibility engineering level. read full article…
Integrating structural geology and geotechnics at Venetia diamond mine
At the Venetia diamond mine in northern South Africa, owned by De Beers, the country rock structural geology has been under investigation since before the mine was opened in 1994. This includes academic research alliances to better understand the complex structural deformation history of the mine area. These alliances are with the University of Johannesburg, Tect Consulting and more recently the University of Pretoria. It is located within the Central Zone of the Limpopo Belt, which is a multiply-deformed orogenic zone between the Kaapvaal and Zimbabwean cratons, formed during the Archean and Paleoproterozoic. read full article…
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