Åke Nilsson, Vattenfall Power Consultant. Vattenfall Power Consultant

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1 1 2 Åke Nilsson, Vattenfall Power Consultant Vattenfall Power Consultant

2 Svenska deltagare är: Åke Nilsson och Maria Bartsch Inre erosionsgruppen arbetar med att skriva rapporten: Guidelines on safety assessment on internal erosion Vattenfall Power Consultant 2

3 AUSSOIS, FRANCE, 5-27 APRIL 2005 WORKSHOP ON INTERNAL EROSION AND PIPING OF DAMS AND THEIR FOUNDATIONS AUSSOIS, FRANCE APRIL 2005 Internal erosion of dams and their Foundations by Taylor & Francis. Vattenfall Power Consultant 3

4 Workshop on Internal Erosion and Piping of Dams and Foundations, April 2005 Aussois France Filters and internal erosion in Swedish dams Åke Nilsson Hans Rönnqvist Internal erosion in the Porjus dam Risk assessment and proposal for upgrading Maria Bartsch The susceptibility of internal erosion in the Suorva dam Åke Nilsson Detection of internal erosion in embankment dams using temperatur, resistivity and SP mesurements Sam Johansson Vattenfall Power Consultant 4

5 Internal erosion beskrivningar händelseförlopp (R. Fell 2005) Vattenfall Power Consultant 5

6 Meeting 2006 Workshopen samlade drygt 60 deltagare från 14 länder. Ett 30-tal presentationer hölls under följande teman: Incidents and modes of failure assessment Experimental works and modelling Detection methods Vattenfall Power Consultant 6

7 Dokumentation från workshopen kan laddas ner från SwedCOLDs hemsida under rubriken Europaklubben. Vattenfall Power Consultant 7

8 WAC Bennet Dam 1996 Vattenfall Power Consultant 8

9 Vattenfall Power Consultant 9

10 Cross-hole seismic has been used successfully Vattenfall Power Consultant 10

11 Annual meeting 2008 Vattenfall Power Consultant 11

12 List of Participants Obergurgl 2008 Vattenfall Power Consultant 12

13 Jonathan Fannin, Prof. of Civil Engineering Evaluating the internal stability of soils Jonathan Fannin,, Prof. of Civil Engineering Maoxin Li, Ph.D. candidate University of British Columbia 21 April 2008, Obergurgl,, Austria Kenney and Lau method Vattenfall Power Consultant 13 and Kezdi method

14 Jonathan Fannin, Prof. of Civil Engineering Internal instability - Application of the methods Case 1: Stable Case 2: Unstable Gravel Coarse Sand Medium Fine Fines Silt Clay Boulder Cobble Gravel Coarse Medium Sand Fine Fines Silt Clay Percent smaller '' 1 1/2'' 3/4'' 3/8'' #4 #10 Mesh #20 #40 #60#100 #200 MV4-CORE-1 MV4-CORE-2 MV4-CORE-3 Percent smaller '' 1 1/2''3/4'' 3/8'' #4 Mesh #10 #20 #40#60#100#200 Test specimen Blended average Level layer Mass increment, H (%) MV4-CORE-1 MV4-CORE-2 MV4-CORE-3 1 Diameter, mm 0.1 UNSTABLE Mass passing, F (%) STABLE Mass increment, H (%) Diameter, mm STABLE 10 UNSTABLE Mass passing, F (%) Vattenfall Power Consultant 14

15 INTERNAL EROSION in foundation Dammsäkerhetshöjande åtgärder mot inre erosion vid Statkrafts anläggning Agnsjön Åke Nilsson Vattenfall Power Consultant, Sweden Vattenfall Power Consultant

16 Observationer nedströms dammen artesiska grundvattentryck koncentrerade läckage visst utflöde av material Vattenfall Power Consultant 16

17 Installation av vertikaldräner Vertikaldräner installerades med en speciell maskin ( dränstickare ) Vattenfall Power Consultant 17

18 Exempel på presentationer The internal erosion - the Mostiště rockfill dam - the levee at the Horka village JAROMÍR ŘÍHA Brno University of Technology, Czech Republic Vattenfall Power Consultant 18

19 Dam Mostiště basic parameters Dam type: rockfill with thin upstream loess core Crest length: 340,7 m, Max. height: 32,70 m Total reservoir volume: mil. m 3 Mz = 476,90 Mro = 477,58 Ms = 458,60 Mmax = 478,64 MBH = 479,80 Porucha 476,10 1 :1,751 :1,5 1 :1,21 1 :1,29 Jádro - prachovité hlíny Filtr I / Filtr II Hutněný kamenný zához Kamenná rovnanina Kamenná dlažba Nehutněný kamenný zához Zásyp materiálem z výkopu Údolní písčité až balvanité štěrky Podloží - granulit Injekční clona 1 :1, m Vattenfall Power Consultant 19

20 Subsidence of the dam crest at right abutment - 12 November 2004 Vattenfall Power Consultant 20

21 Vertical displacements along the dam crest Vattenfall Power Consultant 21

22 Uncovered road surface at the dam crest Vattenfall Power Consultant 22

23 Location of failure Mz = 476,90 Mro = 477,58 Ms = 458,60 Mmax = 478,64 Internal erosion Porucha 476,10 MBH = 479,80 1 :1,751 :1,5 1 :1,21 1 :1,29 Jádro - prachovité hlíny Filtr I / Filtr II Hutněný kamenný zához Kamenná rovnanina Kamenná dlažba Nehutněný kamenný zához Zásyp materiálem z výkopu Údolní písčité až balvanité štěrky Podloží - granulit Injekční clona 1 :1, m Vattenfall Power Consultant 23

24 Quantification of the existing defect Data 10th May th February 2004 Reservoir water level, (m) Seppage, (l/s) Hydraulic gradient Hypothetical pipe diameter (mm) Vattenfall Power Consultant 24

25 Causes of the incident Poor quality of clayey core material sandy layers Poor compaction of the upper part of the core relatively thin core inadequate compaction Filter zones missing at some parts of the dam Vattenfall Power Consultant 25

26 Immediate actions: Extraordinary action decrease of water level by 13m Removal of the 7 m wide section of side spillway Governor of the region proclaimed a state of emergency Tender proceedings selection of the contractor Vattenfall Power Consultant 26

27 Prognosis of piping progression Data Critical water level, (m) Time to beginning of internal erosion Leakage at the beginning of internal erosion Time to the seepage path (pipe) collapse (1000 year return period) 1 hour 0.7 l/s 4 hours Discharge at the time of leakage path collapse 200 m 3 /s Vattenfall Power Consultant 27

28 Jet grouting technology Vattenfall Power Consultant 28

29 Jet grouting Vattenfall Power Consultant 29

30 Inre erosion - Perspektiv på arbetet med svenska dammar Förebyggande generella åtgärder: Sverige: - Beräkning av ett dimensionerande läckage underlag för dimensionering av tåbankar (stödbankar) Utomlands: - Planer på instrumentering Åtgärder då läckage eller sjunkgropar inträffat: Sverige: - I många fall finns redan redan dränage och kontinuerlig läckagemätning. - Kompletterar med instrumentering - litar oftast på självläkning och tåbankar (katastrofsäkring). - instrumentering för övervakning. - injektering och i något fall slurry trench. Utomlands: Åtgärder för att stoppa initieringen av inre erosion - injektering, - slitsmurar, slurry trenches, jet-grouting, sponter etc.) - i kombination med instrumentering för övervakning. Vattenfall Power Consultant 30

31 Preliminärrapport European Working Group of ICOLD European Symposium of ICOLD on September 2007 in Freising, Germany 2007 Vattenfall Power Consultant 31

32 COUNTRIES MEMBERS Canada P. A. ZIELINSKI (Chairman) USA C.G. TJOUMAS (Vice-Chairman) Argentina F. GIULIANI Australia D. STEWART Austria E. NETZER Brazil F. DE GENNARO CASTRO Canada D.N.D. HARTFORD China Z. XU Czech Rep. J. POLACEK Finland R. KUUSINIEMI France M. POUPART Germany H.U. SIEBER USA David S. Bowles, Vattenfall Power Consultant 32 India Iran Italy Japan Korea Lesotho Netherlands Norway Pakistan Portugal Russia Serbia and Montenegro Spain Sweden Switzerland United Kingdom A.K. BAJAJ M. GHAEMIAN G. RUGGERI H. KOTSUBO T.S. YOO B.M. RAFONEKE J.P.F.M. (HANS) JANSSEN G. HOLM MIDTTOMME M. MUSHTAQ CHAUDRY A. SILVA GOMES E. BELLENDIR I. TUCOVIC J. DE CEA A. NILSSON M. BALISSAT A. HUGHES

33 ICOLD Committee on Dam Safety Arbetar med: - New Bulletin on Dam Safety Management - Dam Failures and Incidents Database POUPART, M. POUPART, France Vattenfall Power Consultant 33

34 USA TOTALT 77 BROTT I FYLLN IN GSDAMMAR År INRE EROSION 44% Läckning genom dammen 30 % 23 % Överströmning FLÖDEN 41% Läckning genom grunden 14% 6 % 9 % 18 % Erosion vid utskov Instabilitet Diverse Vattenfall Power Consultant 34

35 Databaser: - dammbrott, - incidenter Three ICOLD bulletins on this topic : 1974 Lessons from dam incidents : 290 events among which 90 failures 1983 Deterioration of dams and reservoirs : 1105 deterioration cases among which 107 failures 1995 : Dam failures statistical analysis (bulletin 99): 179 failures Other data bases exist Vattenfall Power Consultant 35

36 Proposal in M. POUPART, France Failures (~ 200) : should be a commitment for ICOLD ; Failures and Incidents (> 1000) : on a voluntary basis of each country, either with links from ICOLD Website to these national databases, or data transfer Vattenfall Power Consultant 36

37 First step collect the data into one data base 1974 Lessons from dam incidents (scan of 266 cases) Bulletin 99 (118 cases) Data collected by Dr NETZER (21 cases) achieved in 2006 and some other 405 cases of failures and incidents included Vattenfall Power Consultant 37

38 Dam Failures and Incidents Database - example Vattenfall Power Consultant 38

39 Dam Failures and Incidents Database - example Vattenfall Power Consultant 39

41 Proposal in 2008 Second step: Database - Incident In Sofia, decision to postpone this step due to: Lack of internal resources Insufficient involvement of national committees Confidentiality? (approval from dam owners. Vattenfall Power Consultant 41

42 Proposal in 2008 First step: Database - Dam Failures Reliability of data => Control and update by national committees: only the 22 new cases were sent to national committees ICOLD Website : work on progress with secretary general: Accessibility: members of ICOLD with password Three national committees do no want to have the an update of the Database for dam failures... where are we after SOFIA meeting? Vattenfall Power Consultant 42