《Mining and Tailings DamsUNECE.ppt》由会员分享，可在线阅读，更多相关《Mining and Tailings DamsUNECE.ppt（50页珍藏版）》请在三一办公上搜索。
1、Avoiding tailings dam failures Good practice in prevention,Philip PeckUNEP GRID Arendal and IIIEE at Lund University,Intro&Limitations,Not an ordered,detailed or exhaustive overview of this topicA general scene-setter for discussions enfolding the guidelines under developmentMost focus upon the role
2、 of the TMF operation phase in ensuring SafetyApplication of checklist,procedures,proper maintenance for the achievment proper safety management,Some more brief background,Why are we here?,Tailings management facilities can and do fail!This can almost universally be prevented one key area that helps
3、 is Good practice in management&operationsBut please note the whole best practice lifecycle is intrinsicably interlinked.,Spain,Los Frailes:On April 25,1998,a tailings dam failure of the Los Frailes lead-zinc mine at Aznalcllar near Seville,Spain,released 4 to 5 million m3 of toxic tailings slurries
4、 and liquid into nearby Ro Agrio,a tributary to Ro Guadiamar.The slurry wave covered several thousand hectares of farmland,and it threatened the Doana National Park,a UN World Heritage Area,Tailings release cross-boundary river contamination,waterway pollution(Romania),Lack of monitoring and mainten
5、ance.,As I understand the procedure for development of these guidelines,This workshop is intended to review the first steps taken for this guideline in the light of:Comprehensive documentation that exists;Existing best practice;New demands placed by mining practice;New possibilities offered by techn
6、ological advances;Formal conditions placed by transboundary conventions(for example);And.,This brief presentation,Content in draft guideline at presentSome big examples of the events we wish to prevent,some small examples as well.Examples of extant literature:I anticipate that these guidelines will
7、extensively refer to,and cross-reference,the extensive body of work that describes best practice.Some of the content of existing guidelines that will be reflected in more detailand that I see as the general intent,An ethos for responsible management of the life cycle of TMFs.,A general ethos good ta
8、ilings management could be said to require that:Existing and future public health and safety are not compromised;Environmental resources are not subject to physical and chemical deterioration;The after-use of the site is beneficial and sustainable in the long term;Adverse socio-economic impacts are
9、minimised;andSocio-economic benefits are maximised.,A huge body of international knowledge&expertise,Geotechnical knowledge with engineering experience can enable safe tailings dams to be designed and constructedHowever,the rate of tailings dam failures has averaged 1.7 a year during the past 30 yea
10、rs this knowledge and experience has not been applied in every case.In order to improve the situation the International Commission on Large Dams with the United Nations Environmental Programme published ICOLD Bulletin Number 121 221 examples of incidents with tailings dams and discusses causes.Aims
11、to help those in charge of tailings dams to understand some of the simple mistakes that continue to occur.ICOLD(2001).Bulletin 121.Tailings dams:Risk of dangerous occurrences.Lessons learnt from practical experience.,Most of us have heard of the infamous sites,Italy,The Stava tailings dam failure(Tr
12、ento,Italy)On July 19,1985,a fluorite tailings dam of Prealpi Mineraia failed at Stava,Trento,Italy.200,000 m3 of tailings flowed 4.2 km downstream at a speed of up to 90 km/h,killing 268 people and destroying 62 buildings.The total surface area affected was 435 hectares.,images from http:/www.stava
13、1985.it/,Analysts conclude that the dams were constructed with an unacceptably low factor of safety and that the failure probably was triggered by a blocked decant pipe located within the tailings.,Tailings dump area Baia Mare Romania(circa 1998)new land for the city,recovery of significant quantiti
14、es of residual gold,Cyanide contaminated water release(Baia Mare,Romania),Baia Mare:On 30 January 2000,a breach in the tailings dam of the Aurul S.A.Baia Mare Company,released some 100 000 m of cyanide-rich tailings waste into the river system near Baia Mare in north west Romania.This spill released
15、 an estimated 50-100 tonnes of cyanide,as well as heavy metals,particularly copper,into the Somes,Tisza and finally into the Danube Rivers before reaching the Black Sea.,But also sites the world has not heard about?,Culvert failure under Sasa Mine Tailings Dam,Macedonia,50m,170m,Inappropriate design
16、 Lack of monitoring and maintenance.Circa 3Mt down the river,Heavy metals contamination of soil and food(Macedonia),Tailings slime in riverbed downstream of Sasa Mine,Macedonia,Circa 500 000t tailings washout,Fushe Arrez,Albania.,Lack of inspection,maintenance and repair of water diversion channels,
17、Copper tailings dam(Rreshen Albania).Simply waiting to fail,No monitoringWater diversion has failed Evidence of structural instability.High phreatic surface,Inappropriate tailings disposa threatens society and the environment!,Draft UNECE safety guidelines and good practices for TMFs I,Annex II:Oper
18、ation and ManagementThe TMF should be operated and managed on the basis of an operation manual,which is developed in the planning phase and progressively modified.Its aim is to effectively manage the risks/hazards at the TMFThe operation manual should contain:description of all monitoring procedures
19、 mechanisms for investigations:sampling locations,sampling frequency,checklists and compliance parameters procedures for reporting on non-compliance and failurescorrective actions to be applied in case of non-complianceemergency planassessment parameters for effectiveness and suitability of the oper
20、ation manual,Draft UNECE safety guidelines and good practices for TMFs II,Annex II:Operation and ManagementAny changes to operation manual should be subject to its performance analysis,which should be documented.The performance of the TMF should be assessed and described during significant seasonal
21、events and the data gathered should be used for rehabilitation planning.In case of TMF acid rock drainage potential the management plans should be developed to prevent,reduce and treat acid water generation.,But what does this mean in practice?,Societies and prevention of TMF accidents,In societies
22、that care about dam safety,the normal aims with their actions are:To,as far as possible,ensure that dam accidents with serious consequences will not occur.To be prepared to mitigate the consequences in case of dam accidents.To make the dam safety situation transparent to the public.How to achieve th
23、ose aims probably requires different methods in different societies.Recognise the dynamics of nature and technology AND society!,Management areas in best practice mining the Deming Cycle(Mining Association of Canada(MAC)1998.Guide to the Management of Tailing Facilities.),A FRAMEWORK TO MANAGE TAILI
24、NGSPolicy and Commitment PLANRoles and ResponsibilitiesObjectives Managing RiskManaging ChangeResources and SchedulingDO Implementing the PlanDO&CHECKOperational ControlFinancial ControlDocumentationCompetencyMonitoringCommunicationsCHECK&ACTCheckingCorrective ActionManagement Review for Continual I
25、mprovement,Key points of departure for all this work,1 There are too many failures involving mine waste containment structures.2 The reliability of mine waste containment structures is among the lowest of earth structures andrisk-taking on the part of all stake-holders is excessive.3 Design and perf
26、ormance requirements have changed in recent years.It is no longer just a question of having relevant government permits.4 The technical requirements for design,construction and performance have never been morechallenging.5 The geotechnical engineer is capable of responding to the needs of the mining
27、 industry giventhe appropriate fiscal and technical management environment.6 The role of geotechnical engineering is not restricted to the design and construction of passivecontainment;it has much to offer in the development of new processes for waste management.7 Design for lease closure is geotech
28、nically intensive.8 Mine waste materials are complex;sometimes they behave better than expected.9 Mine waste materials are complex;sometimes they behave worse than expected.10 Case histories reveal that risk is not generated by technical limitations alone.The geotechnical performance of a man-made d
29、eposit depends not only on its composition,but also on how it isplaced.The control exercised by placement method should not be underestimated.Conclusion 11 A well-intentioned corporation employing apparently well-qualified consultants is not adequate insurance against serious incidents.,CRITICAL OPE
30、RATION ASPECTS,IMPROVING TAILINGS DAM SAFETY:Critical Aspects of Management,Design,Operation and Closure ICOLD COMMITTEE ON TAILINGS DAMS,General points(after ICOLD)The operation phase of a tailings dam often continues for several decades.The conditions pertaining to assumptions made at the design s
31、tage may change,sometimes quite radically,during the operation phase.Essential,both for ensuring compliance with the original design and to accommodate operating variations,that the operation be given a high level of priority from management and operators.This DEMANDS regular internal inspections,ex
32、ternal safety inspections and external,independent operation reviews,particularly after a significant incident(s)on a dam.,Pre-deposition Construction(ICOLD),Monitoring of:operations associated with the construction of pre-deposition works of a tailings dam for compliance with design standards const
33、ruction of perimeter starter walls,under-drainage facilities,decant facilities and other dam components.,Operation management I(ICOLD),A TMF is key factor in the overall operation of the mine or industrial process it is not a side issue.Therefore essential to have:continuous support of the operation
34、 process from managementdetailed attention to the management of the tailings deposition process by trained,competent personsformal,detailed Operating Manualupdated on a regular basis to accommodate any changes in design or operation parameters according to:visual inspectionsmonitoring reports,Operat
35、ion Management II Critical factors(ICOLD),Constant operational control of the decant facilityMaintenance of internal beach widthMaintenance of storm freeboardControl of beach slopesMeasurement of seepage discharge and turbidityMeasurement of the internal phreatic surface within the dam wallPore pres
36、sure measurementRecording of movements in the dam wallThese factors should also be addressed in the post closure phase of the dam.,Operation Management II Critical factors 2(ICOLD),Recording of seismic eventsRecording of delivered tailings particle size distributionEnsuring that the deposition proce
37、ss achieves adequate particle size segregation on the beachesRegular monitoring of the behaviour of walls and beaches and physical properties of the deposited tailings,and the deposition procedures.Management and maintenance of tailings delivery systemsRegular updating of monitoring response plans.M
38、anagement of all data.These factors should also be addressed in the post closure phase of the dam.,Tailings Dam Surveillance(ICOLD),The following essential aspects of surveillance are critical to success:What and how to measure and controlVisual monitoring and controlInstrumentation monitoringAnalys
39、is and interpretation of dataEmergency preparednessChain of responsibility.Good surveillance includes the careful keeping of surveillance records+interpretation of these by experienced persons.There must be a clear path for reporting of deviances and a mechanism for motivating and implementing remed
40、ial actions where necessary.,Deposition Management(ICOLD),Tailings deposition requires specific attention,particularly in cases where the tailings product is being used to raise the outer wall of the tailings dam.The deposition process,in association with the supernatant pool elevation,controls:Beac
41、h LengthBeach slopeFreeboard and flood managementTailings consolidationThe tailings dam wall will rise with time as deposition progresses and must be raised evenly around the dam perimeter.By managing deposition layer thickness and deposition cycle time around the perimeter,more effective drying con
42、solidation can be achieved.These factors are all specific to each individual dammust be managed daily to ensure design compliancemust be an integral component of the surveillance process.,Operational Water Management(ICOLD),Management of the supernatant pool as part of the overall deposition managem
43、ent process,is a key aspect of operation and all aspects of the water balance must be monitored and controlled carefully.size and depth should always be kept to a practical minimumManagement of the pool to a minimum size and the associated surveillance to ensure that this is always controlled will a
44、chieve:Reduced seepageIncreased freeboard(larger beaches)Lower phreatic surfaces.,TMFs must be built with the long long term in mind we cannot forget closure,Requires a knowledge of environmental conditions,multi-objective planning,close supervision of construction,careful operational surveillance,a
45、nd ongoing monitoring after closure.Sound engineering remains the basis of safe structures long-term stability is ensured by a design that is intrinsically stable,self-repairing,and low-risk,and able to stand up to weather and other local influences.The concept is more about the design of a permanen
46、t landscape feature NOT a short-term facility.In all cases a monitoring and verification procedure is needed to confirm that this goal has truly been achieved.,An abundance of literature and work to support improvement,IMPROVING TAILINGS DAM SAFETY:Critical Aspects of Management,Design,Operation and
47、 ClosureICOLD COMMITTEE ON TAILINGS DAMS literature just on this topic of Operation&Managagement,An abundance of literature and work to support improvement Examples regarding water Mgt.,United States Committee on Large Dams(USCOLD)1994.Tailings Dam Incidents.International Commission on Large Dams(IC
48、OLD)1992.Selections of Design Flood Bulletin 82(http:/www.icold-icgb.org)Canadian Committee on Large Dams(CANCOLD)Guidelines for Flood Design Criteria Based on Consequence and Risk.Australian National Committee on Large Dams(ANCOLD)1986.Guideline on Design Floods for DamsSouth African National Commi
49、ttee on Large Dams(SANCOLD).Report No.3.Interim Guidelines on Freeboard for Dams.Mining Association of Canada(MAC)1998.Guide to the Management of Tailing Facilities.(http:/www.mining.ca)Kraftfretagens Riktlinjer fr Dammskerhet(RIDAS)2002.Hydropower Industry Dam Safety Guidelines.Swedenergy,Stockholm
50、:Birger Gustafsson AB ISBN 91-7622-174-1Reference to Operation,Surveillance and Maintenance Manual:Kraftfretagens Riktlinjer fr Dammskerhet(RIDAS)2002.Hydropower Industry DamSafety Guidelines.Swedenergy,Stockholm:Birger Gustafsson AB ISBN 91-7622-174-1,An abundance of literature and work to support
