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COMMISSION INTERNATIONALE DES GRANDS BARRAGES
------- VINGT-CINQUIÈME CONGRÈS
DES GRANDS BARRAGES Stavanger, Juin 2015
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THE DEVELOPMENT OF GRG – GEOTECHNICAL RISK MANAGEMENT PROGRAMME FOR VALE(*)
Joaquim Pimenta de ÁVILA
Director, M.Sc. – Pimenta de Ávila Consultoria Ltda.
Felipe Figueiredo ROCHA Project Manager – Pimenta de Ávila Consultoria Ltda.
Marilene LOPES
Project Engineer, M.Sc. – VALE.
Camila Moreira QUEIROZ Civil Engineer, M.Sc. – VALE.
Lucas Samuel Santos BRASIL
Civil Engineer, M.Sc. – Pimenta de Ávila Consultoria Ltda.
Daniel Claudino Ramos PENNA Civil Engineer, M.Sc. – Pimenta de Ávila Consultoria Ltda.
Karla Cristina Araújo Pimentel MAIA
Civil Engineer, D.Sc. – Pimenta de Ávila Consultoria Ltda.
Teresa Cristina FUSARO Consultant, M.Sc.– Pimenta de Ávila Consultoria Ltda.
BRAZIL
(*) Le développement d’un programme de GRG – Gestion des risques géotechniques pour VALE
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1. INTRODUCTION
There are many risks related to the mineral industry, such as health and safety, environmental and business risks. Among these, the geotechnical risks can be considered one of the most important and can be related to different business areas such as mining and logistics, including railroads and ports.
Even though any accident or geotechnical incident can cause
consequences of great magnitude in several categories, both internally and externally to the company, in many cases, the actions related to geotechnical problems are taken in a corrective way. Although in recent years the scenario regarding the manner in which the geotechnical aspects are treated within the mining industry in Brazil has changed and improved, the activities associated with the production are still prioritized and there is still a certain gap in decision making on matters related to the safety of geotechnical structures.
Brazilian mining company VALE is a global producer of iron ore. Its main
activities include iron ore, alumina and bauxite production; sea and rail transport; and increasingly, hydroelectric generation. It also mines or produces manganese, ferroalloys, aluminum, gold, kaolin, potash, fertilizers and most recently, copper. Its transport activities include rail, ports and shipping. VALE employs more than 100,000 workers, with headquarters in Brazil and operations in more than 30 countries, as shown in Fig.1.
Fig. 1
VALE’s operations across the world Les opérations de VALE dans le monde
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VALE is committed to quality of life and environmental preservation in all of its regions of operation and has always been concerned with the safety of the geotechnical structures related to their business. The importance of these structures and the associated risks become explicit when the number and diversity of geotechnical structures is examined. A comprehensive inventory was conducted in 2011 and the number of structures in shown in Fig.2.
316
7858
190
2000
4000
6000
8000
10000
Num
ber o
f Str
uctu
res
Geotechnical Structures by Business Area
MiningRailroadsPorts
166
116
34
0
50
100
150
200
Num
ber o
f Str
uctu
res
Geotechnical Structures in Mining
Dams/LeveesWaste DumpsOpen-Pit Mines
Fig. 2
Number of geotechnical structures in VALE’s Iron Ore Business in Brazil in 2011 Nombre d’ouvrages géotechniques pour l’activité de minerai de fer de VALE au
Brésil en 2011
Within this context, VALE developed a research programme focused in the implementation of a Geotechnical Risk Management Programme, aiming to create a systematic process for identification, assessment and treatment of risks and to allow risk oriented decisions concerning the geotechnical structures. Pimenta de Ávila Consultoria, a Brazilian engineering and consultancy firm with large experience in the mining sector, was hired for the development of this programme.
2. THE DEVELOPMENT OF THE PROJECT
The GRG - Gerenciamento de Riscos Geotécnicos (Geotechnical Risk Management) was conceived to embrace VALE’s three large business areas that hold geotechnical structures: Mining, Railroads and Ports, restricted to the iron ore business in Brazil, as shown in Fig.3.
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Geotecnical Structures
Design
Construction
Operation
Closure
VALE'S BRAZILIAN IRON ORE BUSINESS
MINING
• Dams• Waste dumps• Mine pits• Industrial slopes• Retatining
structures• Natural slopes
RAILROADS
• Cutting slopes• Embankment
slopes• Natural slopes• Tunnels• Retainig
structures
PORTS
• Storage area• Cutting slopes• Embankment
slopes• Natural slopes• Breakwater
Fig. 3
Scope of GRG – Geotechnical Risk Management Champ d'application de la GRG- Gestion des Risques Géotechniques
Given the wide range of development-related activities of the GRG -
Geotechnical Risk Management and the size of the project, VALE set as a priority the development of the GRG for geotechnical structures (dams, tailings dams and open pit mines) that are in the operational phase. Therefore, the GRG project did not move forward with greater detail for other geotechnical structures and other stages of their life cycle.
The development of the GRG Project was structured in four phases or
cycles, as shown in Fig. 4.
Fig. 4 GRG: Phases of the project
GRG: Phases du projet The first phase (Characterization) was executed and completed in 2011. It
consisted of a diagnosis of the IT systems related to geotechnical and / or risk management already used in VALE, as well as of the existing methodologies and processes used to manage the geotechnical risks.
The second phase (Development) is under development by Pimenta de
Ávila Consultoria Ltda, and has started in 2013. It consists basically in the development of processes and methodologies that will support the risk management of VALE’s geotechnical structures and was divided in three dimensions: methodological basis, technical application and training. In this phase, the programme was structured and the procedures, guidelines and methodologies to be followed for each business area were elaborated. The basis
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for the computational system that will support GRG were developed, emphasizing that the software will be the final product to be generated.
The third phase (Implementation) consists of the implementation of the GRG in selected operational areas, planned for 2015. In this phase, the involvement of VALE’s IT is essential, as well as the training of the staff that will use the system and the methodologies defined in the GRG. At this stage the system will be loaded with the information necessary for its operation.
The fourth phase (Operation) is the use of the GRG system in the day-to-day activities of the technical staff of VALE, so that the results can guide decision-making and minimize the risks of geotechnical structures, and is scheduled for 2016.
3. STRUCTURING THE GRG: GEOTECHNICAL RISK MANAGEMENT PROGRAMME
The first step of the development was to establish the methodological basis that would be used in the project, defining the tools, guidelines, methodologies and processes that would guide the activities of risk management of geotechnical structures within the context of the GRG. To accomplish this target, a vast literature review of issues related to risk management and of other mining companies’ good practice was conducted, as well as the expertise of Pimenta de Ávila Consultoria in works of similar nature was considered.
In the specific case of dams, tailings dams, waste dumps and open pit
mines, objective of this article, all data collected in the first phase of the project was analyzed and the information about all geotechnical structures of the iron ore business was consolidated, including the consolidation of previous audit data (FMEA worksheets and recommendations’ spreadsheets) of all structures since 2002.
The internal context of VALE was studied to understand the needs and
targets of the company with the implementation of this project. Currently, VALE’s business plan is elaborated using, among other information, risk evaluations. Therefore, it was considered important to have an monetary evaluation of the geotechnical risks.
So that the project was compatible with the risk management methods
used internationally and internally to VALE, the concepts of ISO 31.000/2009 were used, following the steps showed in Fig.5 and summarized in the next items.
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Fig. 5
Risk management according to ISO 31.000:2009 [1] Gestion des risques selon la norme ISO 31.000: 2009
3.1. ESTABLISHING THE CONTEXT
In general terms, this phase articulates objectives, defines external and internal influences and sets the scope and risk criteria for the risk process, and has two major outputs: the proposal of a geotechnical risk policy and of an organizational structure.
All information about risk policy and risk management standards applied by
VALE was consolidated and discussed with the department responsible for development of frameworks and guidance on enterprise risk management. Taking into account the existing policies and standards, guidelines for establishing the Geotechnical Risk Policy were proposed and are being evaluated by VALE.
Considering the size and complexity of VALE, the organizational model is
regarded as a key point to enable the implementation and operation of GRG. To allow the definition of an organizational model for geotechnical risk management, the current model adopted (staff, organizational structure, roles, responsibilities, inter-relationships between areas, etc.) was analyzed and meetings with managers and directors were conducted.
An organizational structure was proposed, defining a technical team and
minimum training required for the operation of GRG. Based on the discussions during these years of development of GRG, it is considered essential to structure a specific area or team that will be responsible for the programme. Given the large demand of the operational areas, their main function would be to provide inputs (risk identification) to this specialist area (e.g. Office of Risk), which would be responsible for managing the process as a whole.
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3.2. RISK IDENTIFICATION
The activities of geotechnical structures management consist, ultimately, in the permanent management of the risks involved in the construction and operation of these structures. This risk management permeates the various operating levels of the company, although there is not always awareness of the importance of the actions and decisions taken in relation to the risks involved.
It is important to notice that much of the monitoring of geotechnical
structures activities is embedded in routine operation. Visual inspections and measurements / analysis of instrumentation data can detect anomalies that increase the risks posed by the structures and, on the other hand, the execution of works of repair and / or improvements can reduce them. This process is currently managed by a computational system (GEOTEC) that controls the routine activities, registers anomalies and controls action plans defined for their correction, as shown in Fig. 6.
Fig. 6 Activities controlled by GEOTEC system
Activités contrôlées par le système GEOTEC Thus, the GRG and GEOTEC can be considered complementary systems.
The identification of risks will continue happening during the visual inspections, instrumentation data analysis and periodical qualitative risk analysis (FMEA). Additionally, they will be identified by “risk specialists” that will be able to aggregate all information regarding a specific structure and conduct the risk assessment, as shown in Fig. 7.
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Fig. 7 Identification of risks
Identification des risques 3.3. RISK ANALYSIS - PROBABILITIES
Risk analysis involves understanding the risks and how they may impact the organization. It is expressed in terms of the consequence and likelihood [1].
Considering the needs of VALE of a monetary quantification of risks, it was decided to evolve from the qualitative risk analysis method already used by VALE (Failure Mode and Effect Analysis - FMEA) to a quantitative risk analysis of dams, waste dumps and open pit mines.
The standardization of components, failure modes and their causes was
the first step to come out with a generic fault tree that could represent the basic final failure modes for these structures. It should be noted that the seismic activity in Brazil is of very low intensity, consequently, failure modes caused by this phenomenon were not considered in this fault tree.
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Fig. 8
Fault Tree for geotechnical structures’ failure modes within the context of GRG. Arbre pour les modes de défaillance des ouvrages géotechniques dans le
contexte de la GRG.
In designing risk analysis for a particular dam, the entire range of plausible dam failure exposure scenarios should be studied. This means to consider all possible failure modes over the entire range of initiating event conditions and all exposure conditions affecting the population at risk. Nevertheless, for practical reasons, only a finite number of failure scenarios can be considered.
Therefore, the process of risk analysis proposed within the context of GRG
begins with a preliminary qualitative risk analysis using FMEA, method that has already been used by VALE to identify the possible failure modes for dams. The information gathered at this phase should be used to define the scenarios to be analyzed in the more detailed quantitative analysis.
A methodological basis for quantifying the probability of failure and
consequence costs was defined for each type of structure and associated failure modes. In the specific case of dams and tailings dams, the following procedures were used to define the probability of failure:
3.3.1. Overtopping The evaluation of the probability of failure due to dam overtopping is based
on flood hydrologic studies of the spillway. The methodology used considered rainfall-runoff and flood frequency analysis with the selection of the flood that results in dam overtopping.
Furthermore, in some cases, estimates of the probability of failure due to
overtopping can be performed through the development of an event tree in order to consider some events that associated with a precipitation of great magnitude may cause overtopping (e.g. obstruction of the spillway system, reduction of the damping flooding capacity due to inadequate waste disposal, disruption of geotechnical structures and / or natural slopes adjacent to the reservoir, among others).
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3.3.2. Slope Instability Probabilistic methods, such as, Monte Carlo, FOSM ("First Order Second
Moment") and Point Estimate Method [2] were applied to calculate the probability of failure due to slope instability.
The general calculation process of the Monte Carlo method, for example,
consists of the following steps: Identification of the key random variables that contribute to the variation
of the factor of safety; Estimation of characteristics of each random variable (mean, standard
deviations and probability density functions); Generation of N samples of random variables and creation o N sets of
random variables; Calculation of the factor of safety (slope stability analysis) for each set of
random variables, using limit equilibrium analysis; Calculation of the probability of failure. It is important to emphasize that probabilistic methods can be applied
whenever there is a mathematical formulation between the factor of safety (dependent variable) and the random variables. This mathematical formulation can be empirical, analytical or numerical. Furthermore, the minimum number of iterations for each method depends on the number of key random variables used in the analysis. Therefore, firstly it is recommended to apply the FOSM method and determine the relative contribution of each random variable to the total uncertainty. Then using only the random variables that contribute the most to the variance of the factor of safety, the Monte Carlo or Point Estimate methods can be optimized with a significant reduction in the time spent to perform the analyses.
Another important aspect is related to the fact that for the FOSM and Point
Estimate methods it is necessary to assume a probability density function to represent the factor of safety, whereas for Monte Carlo method this function is obtained as a result of the calculation process itself.
Finally, each probabilistic method has advantages and drawbacks.
However, the analyses performed so far showed that, in general, estimates of the probability of failure by the methods mentioned above are comparable and reflect the stability condition expected to the structures analyzed. More information about these methods can be found in a number of publications including Ang & Tang [3], Harr [4] and Baecher & Christian [5].
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3.3.3. Internal Erosion The term internal erosion is used generically to describe the process when
soil particles within an embankment dam or its foundations are carried downstream by seepage flow. The main mechanisms are described by Fell & Fry [6], and can be represented in a fault tree as shown in Fig.9.
Fig. 9
Fault tree indicating possible initiation forms of internal erosion Arbre de défaillances indiquant des formes possible d'initiation de l'érosion
interne
Event trees have been used to estimate the probability of failure due to internal erosion as this failure mode does not have a mathematical formulation that permits this calculation. Therefore, event trees can be elaborated for each one of the initial events presented in Figure 9, selected according to the qualitative risk analysis done previously.
In the context of GRG, event trees have been prepared in accordance with
the general sequence of events proposed by the USBR [7], comprising the following items:
Reservoir at or above the threshold level Initiation - Erosion starts Continuation - Unfiltered or inadequately filters exit exists Progression - Continuous stable roof and/or sidewalls Progression - Constriction or upstream zone fails to limit
flows Progression - No self-healing by upstream zone Unsuccessful detection and intervention Dam breaches (uncontrolled release of reservoir)
The estimate of the probability of each node of the event tree can be
performed, according to the failure mode under analysis and the information available, employing the methods below, alone or in combination:
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Based on probabilistic stability analysis; Using tables available in the literature, basically the ones proposed by
Fell [8], that evaluate the main factors of influence on the probability of occurrence of each event; and
Using engineering judgment and verbal descriptors in the case of inadequate technical reference for the case study, or when these references also feature descriptors for the probabilities.
To quantify the probability of unsuccessful detection and intervention, two
factors were considered: the Effectiveness of the Internal Control Environment and the Intervention Capacity.
For operational risks, and more specifically for geotechnical risks, the
existence of an effective internal control environment is critical to the success of decision-making that will allow risk reduction. So, in addition to having suitable and sufficient controls (adequate, sufficient and well documented monitoring activities), adequate tools for information management and assistance to decision-making are essential.
To evaluate the Effectiveness of the Internal Control Environment,
indicative of the capability to provide detection and intervention in order to avoid an accident, the following four levels are proposed: Informal, standardized, monitored and optimized, taking into account if monitoring is suitable, sufficient and supported by computerized system that integrates information from inspections and internal and external audits and risk analysis.
Regarding the Intervention Capacity, the following factors of influence
should be considered: Process’ evolution or breach formation time, suitability of access and response preparedness 3.3.4. Static Liquefaction
The probability of failure of tailings dams due to static liquefaction was
estimated for a case study using an event tree elaborated according to the methodology proposed by Olson [9]. In general terms, the following items can be considered in the analysis:
Initial event: rainfall, failure of natural slopes or waste dumps adjacent to
the tailings dam reservoir resulting in a rapid increase of the phreatic surface, construction of a raising dyke in a tailings dam causing excessive static loads;
Slope stability analysis: evaluation of the potential of the triggering event (increase in pore pressures) to cause slope instability;
Final result: flow failure due to liquefaction of the dam or foundation material.
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It should be observed that the probability of occurrence of the initial event can be estimated, for example, based on the return period of a rainfall or the probability of a natural slope to fail. The probability of the triggering event to cause slope instability can be evaluated using probabilistic methods, such as Monte Carlos approach. Finally, the probability of failure due to static liquefaction is obtained by multiplying the probabilities estimated for each node. 3.4. RISK ANALYSIS - CONSEQUENCES
The failure of a geotechnical structure can result in impacts of different magnitude and features for different consequence categories. Within GRG, the consequences are evaluated considering the following six categories, in accordance with VALE’s Risk Policy:
Economic: damage to buildings and their contents, vehicles, public /
private infrastructure, loss of production and income in the affected area;
Health and Safety: loss of life, injury, costs of medical care and treatment of affected persons;
Environment: damage to flora, fauna, watercourses, soil contamination; Regulation: increase in inspections, penalties, temporary and / or
permanent shutdown of the unit, difficulty in obtaining and / or renewing licenses;
Social: impacts on the society affected by the failure, changing of the routine, temporary withdrawal of access to health, education and leisure services; and
Company’s Image: negative repercussions in the media, protests of society and NGOs, fall in stock price, among others.
Analysis of the consequences are based on different specific
methodologies, including the GIS software package HEC-FIA (Flood Impact Analyses) developed by the US Army Corps of Engineers. HEC-FIA calculates damages to structures and contents, losses to agriculture, and estimates the potential for life loss. The basic information added in HEC-FIA are dam break hydraulic simulation results and economic and population data of the downstream study area. The life loss computed by HEC-FIA includes consideration of the effectiveness of warning system, community response to alert, and evacuation of large populations. All damage assessment is computed for each structure using inundation area and hydrograph data [10].
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3.5. RISK EVALUATION
Risk evaluation involves making a decision about what should be done about the risk. It involves determining appropriate treatments for the risk, and what level of risk the organization can tolerate [1].
The development of tolerable risk guidelines is not an easy task and
requires an understanding of relative risk tolerance of an organization. Once the risks incurred by a project or operation are estimated, rational and sustainable decisions on risk mitigation are generally requested by clients wishing to adopt risk management methods and maximize the investment they have made by performing a risk assessment. These decisions can only be taken after an explicit risk tolerability function as defined by Oboni [11].
Tolerable risk curves were elaborated based on Whitman [12], ANCOLD
[13], USACE [14] and USBR [15] and are under appraisal by VALE’s management team. 3.6. RISK RESPONSE AND CONTROL
Once the risk assessment is concluded, the next phase of the process will be the stage of treatment, which involves selecting one or more options to modify existing undesirable conditions. It is essentially a decision-making process and the following risk response strategies are usually considered: Avoid, Mitigate, Transfer or Accept (active or passive acceptance)
Within the context of GRG, different response treatments can be evaluated,
taking into account the probability and consequences of the event, risk value and residual risks. The decision making will be registered, as shown in Table 1:
Table 1
Example of Possible Risk Treatments and Decision Making Record Failure Mode: Internal erosion in the contact with embedded concrete galleryRisk: R= 9 x 10-4 x R$ 480.000.000,00 = R$ 432.000,00
Response strategy Possible TreatmentsTreatment
Estimated Cost Residual Risk Decision
Eliminate Total plugging of the gallery R$ 2.000.000,00 R$ 0,00 √
Mitigate Partial plugging of the gallery R$ 1.000.000,00 R$ 100.000,00
Mitigate Increase monitoring by conducting annual inspections inside the gallery
R$ 20.000,00/year R$ 350.000,00
Accept Keep current monitoring R$ 0,00 R$ 432.000,00
Transfer Contracting na insurance R$ 496.800,00 -
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It must be emphasized that these are general treatment options, that may be suitable for a specific type of risk or not, depending on the evaluation of its tolerability. In other words, very high risk or those with possible life losses should not be accepted, while very low risks can be accepted and may not need to be eliminated. Thus, guidelines to assist in decision making were defined in accordance with acceptance curves approved by VALE. 3.7. COMMUNICATION
Risk communication is a critical component of an effective risk informed decision process and, therefore, it was integrated to the processes embraced by GRG.
The GRG holds an intrinsic communication flowchart. Each risk will be
approved by or communicated to a specific organizational level, following pre-established levels in accordance with VALE’s corporate risk policies.
Once a risk is inserted in the system, an action and approval pipeline is
started. The steps to be followed and the respective person in charge are already defined within the system:
Step 1 – Risk Identification Step2 – Risk Analysis and Approval Step 3 – Designation of the Risk Owner Step 4 – Designation of the Risk Controller Step 5 – Development of the Response Plan Step 6 – Residual Risk Analysis and Approval Step 7 – Response Plan Evaluation and Approval Step 8 – Waiting Execution Step 9 – In Execution Step 10 – Residual Risk Analysis and Approval Step 11 - Conclusion
The system also provides notifications (pending, alert and knowledge) to
the personnel involved and those ones defined in the risk evaluation process, such as, risks owners or risk controllers, if there are actions to be taken concerning the geotechnical risks identified.
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4. THE COMPUTATIONAL PROTOTYPE
The computational prototype of the GRG was developed in order to materialize the concepts and methods developed for dams, waste dumps and open pit mines. Basically, the prototype has two modules, as shown in Fig. 10:
Risk Management Module (Risk Identification, Analyses, Risk
Response and Management Panels); and Complementary Module (Documents and Procedures, Audits and
External Inspections, Control Panel and Dam Safety Plan required by Law 12.334/2010).
Fig. 10 Activities controlled by GRG system
Activités contrôlées par le système GRG
The computing prototype is now being integrated in VALE network and may become the official VALE Geotechnical Risk Management System itself (Portal GRG).
Some points to be highlighted in the Risk Management Module include the possibility of qualitative and quantitative analysis within the system, including the possibility of creation of event and fault trees. Fig. 11 and Fig.12 illustrate the risk registration and event tree creation screens in the GRG system.
Fig. 11 Risks’ registration within the GRG system
Enregistrement des risques dans le système GRG
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Fig. 12 Event Tree elaborated using the GRG system
Arbre d’événement élaboré à l'aide du système GRG All geotechnical risks are aggregated and displayed in a dashboard, which
allows the visualization of the aggregated risks considering different organizational levels and also to drill down to the list of risks associated with a specific structure. In the future, the tolerability curves will be included in the dashboard.
Fig. 12 Dashboard with aggregated risks
Tableau de bord avec les risques agrégés
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So far the structure of the GRG has been developed and consolidated for dams and open pit mines. However, other geotechnical structures will also be included, such as, embankment and cutting slopes found along railroads and ports.
5. TECHNICAL APPLICATIONS
The original scope of GRG did not include the development of technical applications. However, during the progress of development, the need and importance of carrying out practical applications of the processes and methodologies proposed in the GRG became evident, to identify the strengths and points that required improvements in the project. In accordance with VALE’s management team, it was decided to carry out quantitative risk analysis for a group of 6 dams and 2 open pit mines.
6. CONCLUSIONS
The activities of geotechnical structures management consist, ultimately, in the permanent management of the risks involved in the construction and operation of these structures. Although risk management permeates the various operating levels of a company, there is not always awareness of the importance of the actions and decisions taken in relation to the risks involved.
The geotechnical risk management can be greatly enhanced by having the base of knowledge supplied by risk assessments of dams and other geotechnical structures. Such knowledge creates a consistent basis for prioritizing risk reduction activities in a portfolio of facilities.
The GRG will supply a platform for a risk-informed internal environment. In the sphere of the GRG, the possible failure modes can be assessed, allowing the identification, analysis and quantification of the more likely hazard scenarios. Therefore, it will allow structured and logical decision-making regarding geotechnical risks reduction and communication to the adequate organizational levels.
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ACKNOWLEDGEMENTS
The authors thank VALE and Pimenta de Ávila Consultoria for the encouragement and constant support to the development of studies related to dam safety and risk analysis.
REFERENCES [1] ISO 31.000/2009. [2] ROSENBLUETH, E. Point Estimates for Probability Moments. National
Academy of Sciences of the United States of America, 1975. [3] ANG, A.H.S. & TANG, W. Probability Concepts in Engineering Planning
and Design: Basic Principles, 1975. [4] HARR, M.E. Reliability–Based Design in Civil Engineering, 1987. [5] BAECHER, G. B. & CHRISTIAN, J. T. (2003). Reliability and Statistics in
Geotechnical Engineering, 2003. [6] FELL, R. & FRY, J.J (eds.) Internal Erosion of Dams and Their
Foundations, 2007. [7] USBR. Chapter 16 – Internal Erosion. Best Practices and Risk
Methodology. http://www.usbr.gov/ssle/damsafety/Risk/methodology.html, 2012.
[8] FELL, R., MACGREGOR, P., STAPLEDON, D., BELL, G. Geotechnical Engineering of Dams, 2005.
[9] LEHMAN, William; NEEDHAM, Jason. Consequence Estimation Dam Failures, in Innovative Dam and Levee Design and Construction for Sustainable Water Management. 32nd Annual USSD Conference, 2012.
[10] OLSON, S.M. Liquefaction Analysis of Level and Sloping Ground Using Field Case Histories and Penetration Resistance. Ph.D. thesis, University of Illinois at Urbana-Champaign, 2001.
[11] OBONI, Franco - What You Need to Know About Risk Management Methods, 2013
[12] WHITMAN, R.V. Evaluating Calculated Risk in Geotechnical Engineering. The Seventeenth Terzagui Lecture, 1981.
[13] ANCOLD [14] USACE. Interim Tolerable Risk Guidelines for US Army Corps of
Engineers Dams. USSD Conference, 2009. [15] USBR. Interim Dam Safety Public Protection Guidelines - A Risk
Framework to Support Dam Safety Decision-Making. http://www.usbr.gov/ssle/damsafety/documents/PPG201108.pdf, 2011.
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SUMMARY
This paper presents the development of a Geotechnical Risk Management Programme for VALE, a global mining company, from a broad perspective with application to dam safety. The main objective is to provide a rigorous, systematic and thorough process to support the management of geotechnical structures safety, in special the risks associated with dams and tailings dams. The methodological basis and the computational prototype developed embrace all activities related to risk management: risk identification, analysis, evaluation and treatment, allowing risk-informed decisions, prioritizing evaluations and risk reduction activities. In accordance with the company’s Risk Policies, all risks were evaluated in monetary terms, taking into account economical, health and safety, environmental, regulatory, social, and company’s image consequences.
RÉSUMÉ
Cet article présente le développement d’un programme de gestion des risques géotechniques pour VALE, une compagnie minière internationale, dans une perspective globale avec application à la sécurité des barrages. L’objectif principal est de fournir un processus rigoureux, systématique et approfondi pour assister la gestion de la sécurité des ouvrages géotechniques, en particulier les risques liés aux barrages, notamment de stériles miniers. La base méthodologique et le prototype numérique développé embrassent toutes les activités liées à la gestion des risques : identification, analyse, évaluation et traitement, permettant des décisions en toute connaissance des risques, et en indiquant les priorités des évaluations et des activités de réduction des risques. En conformité avec les politiques de risque de l’entreprise, tous les risques ont été évalués en termes monétaires, en tenant compte des conséquences sur l’économie, la santé et la sécurité, l’environnement, la réglementation, la société et sur l’image de l’entreprise.
