THE MONITORING OF GRAVITY DAMS: TWO TESTS IN SARDINIA, ITALY

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1 9.. FIG Working Week Rome, 7 may Dam and reservoir engineering surveying THE MONITORING OF GRAVITY DAMS: TWO TESTS IN SARDINIA, ITALY Speaker: Riccardo Monaci Authors: Riccardo Barzaghi Livio Pinto Riccardo Monaci DIIAR Politecnico di Milano, Italy STRUCTURE OF THE WORK PART : Monitoring network of gravity dams PART : Satellite technology Measures of crest displacement in two existing dams Experimetal GNSS network on Genna Is Abis Dam Modeling process of data series Crest displacement: comparison between pendulums and GPS measures Conclusions and future perspectives

Monitoring network of gravity dams PART : Satellite technology Measures of crest displacement in two existing dams Experimetal GNSS network on

2 9.. TECHNICAL DATA Classification: Height: Lenght: Max basin capacity: Water use: Management: Solid gravity dam 6 m 9 m Mm Drinking water supply, irrigation,flood lamination ENAS ENte Acque Sardegna TECHNICAL DATA Classification: Height: Lenght: Max basin capacity: Water use: Management: Hollow buttress gravity dam m 8 m 79 Mm Drinking water supply, irrigation, hydroelectric energy ENAS ENte Acque Sardegna

TECHNICAL DATA Classification: Height: Lenght: Max basin capacity: Water use: Management: Hollow

3 9.. PoliMi Model GENNA IS ABIS DAM MODELING PROCESS Jul 9 Jul 97 Jul 99 Jul Jul Jul Jul 7 Jul 9 π t π t π t S=a t + b + A cos + B sen + C cos + D sen T T T Crest displacement Ashlar Pendulums PoliMi Model π t T Statistics (mm) Standard deviation Time. step Max Period residual.88 Min(6 residual days). Annual average of daily air temperature Deterministic Model S=a T av year air +b T av water +c H+d H +e Crest displacement Ashlar Jul 9 Jul 97 Jul 99 Jul Jul Jul Jul 7 Jul 9 Positive values are crest displacement to downstream direction Pendulums Deterministic Model Statistics (mm) Water level Standard deviation.66 Max Tworesidual weeks moving average.9 of water temperature Min residual.8 PoliMi Model CANTONIERA DAM MODELING PROCESS π t π t π t S=a t + b + A cos + B sen + C cos + D sen T T T Crest displacement Ashlar Mar Mar 6 Mar 7 Mar 8 Mar 9 Mar Mar Pendulums PoliMi Model π t T Statistics (mm) Standard deviation.7 Max residual. Min residual. Deterministic Model S=a T av year air +b T av water +c H+d H +e Crest displacement Ashlar no Feb Feb 6 Feb 7 Feb 8 Feb 9 Feb Feb Positive values are crest displacement to upstream direction Pendulums Deterministic Model Statistics (mm) Standard deviation. Max residual.7 Min residual.8

Annual average of daily air temperature Deterministic Model S=a T av year air +b T av water +c H+d H +e Crest displacement Ashlar Jul 9 Jul 97 Jul 99 Jul Jul Jul Jul 7 Jul 9 Positive values are crest

4 9.. master stations REF REF roverstations A B C D GNSS MEASURES AND POLIMI MODEL ADJUSTED ON PENDULUMS Crest displacement Ashlar Aug 7 Feb 8 Aug 8 Feb 9 Aug 9 Feb GPS Pendulums PoliMi Model Statistics (mm) Mean,9 Std. deviation,8 Max residual,9 Min residual,7 Crest displacement Ashlar /9 Aug 7 Feb 8 Aug 8 Feb 9 Aug 9 Feb Aug GPS Pendulums PoliMi Model Statistics (mm) Mean, Std. deviation,87 Max residual,8 Min residual,6

5 9.. Analysis of pendulum observations for Genna Is Abis and Cantoniera dams led to some important conclusions: Pendulums are suitable instruments to characterize and control dams, because of their high accuracy and reliability Applied models fit properly data series, revealing in due time possible existing critical deformations GPS follows crest displacement data series very well, proving satellite positioning suitable for detection of slow deformation in civil engineering structures The GNSS technology can t replace traditional control instruments but can be used together with these other techniques to improve or design monitoring and alarm systemsof large dams, raging required accuracy with reasonable economic efforts. Thank you for your attention

well, proving satellite positioning suitable for detection of slow deformation in civil engineering structures The GNSS technology can t replace traditional control instruments but can be

6 9.. INSTALLED MONITORING INSTRUMENTS 8 extensometers (accuracy:. mm) 77 extensometers (accuracy:. mm) Collimation system pendulum chambers (ashlar no and /9) Each chamber contains two optical pendulums (a direct instrumentandaninvertedone) (accuracy:. mm) ASHLAR NO /9 ASHLAR NO Direct pendulum Inverted pendulum PENDULUM DATA SERIES 6 Crest displacement Ashlar /9 6 mm Oct 89 Oct 9 Oct 9 Oct 9 Oct 97 Oct 99 Oct Oct Oct Oct 7 Oct 9 6 Oct 89 Oct 9 Oct 9 Oct 9 Oct 97 Oct 99 Oct Oct Oct Oct 7 Oct 9 Crest displacement Ashlar mm Positive values are crest displacement to downstream direction 6

7 9.. INSTALLED MONITORING INSTRUMENTS 6 extensometers (rockmeters type) conventional extensometers mono axial joint meters pendulum chambers Each chamber contains two inverted pendulums and a direct instrument (accuracy:. mm) Pendulum chamber PENDULUM DATA SERIES 6 8 mm Crest displacement Ashlar 9 Feb Feb 6 Feb 7 Feb 8 Feb 9 Feb Feb 6 Crest displacement Ashlar mm Mar Mar 6 Mar 7 Mar 8 Mar 9 Mar Mar L asse MV è perpendicolare allo sbarramento e coincide con la direzione monte valle. Gli spostamenti sono negativi se diretti verso valle 7

mm) 7 9 7 8 9 7 9 Pendulum chamber PENDULUM DATA SERIES 6 8 mm Crest displacement Ashlar 9 Feb Feb 6 Feb 7 Feb 8 Feb 9 Feb Feb 6 Crest

8 9.. SELECTED MODELS PoliMi Set only as a function of time No physical quantities Predictive Period (6 days) πt πt πt S=a t + b + A cos + B sin + C cos + D sin T T T Time step πt T Deterministic It depends only on measured physical quantities Basedon cause effect correlations Annual average of daily air temperature Water level S=a T av year air +b T av water +c H+d H +e Two weeks moving average of water temperature PoliMi Model Genna Is Abis Dam FAST FOURIER TRANSFORM (FFT) Amplitude (mm*day) Fourier spectra Ashlar,,,,6,8, Frequency (days ) F =,7 days T = 69 days Linear trend F = T = Linear trend F =, days T = 8 days Linear trend Amplitude (mm*day) Fourier Spectra Ashlar /9,,,,6,8, Frequency (days ) F =,7 days T = 69 days Linear trend F = T = Linear trend F =, days T = 8 days Linear trend 8

of water temperature PoliMi Model Genna Is Abis Dam FAST FOURIER TRANSFORM (FFT) Amplitude (mm*day) Fourier spectra Ashlar,,,,6,8, Frequency (days ) F =,7 days T = 69 days Linear trend F = T = Linear

9 9.. Come scegliere le grandezze fisiche da inserire nel modello? Letteratura di settore e analisi di modelli già esistenti Leggi fisiche e della meccanica delle strutture Choice of proper physical variables Coefficienti di correlazione tra le variabili Temperatura aria ΔT aria acqua Temperatura media acqua Quota invaso Concio X Concio /9 X,6,78,,6,8,88,,99 Temperatura ( C) Concio direzione X Diga Genna Is Abis lug 9 lug 97 lug 99 lug lug lug lug 7 lug 9 Spostamento (mm) Temp media acqua Misure pendoli REF Rocky outcrop 7 9 Rocky outcrop REF 9

variables Coefficienti di correlazione tra le variabili Temperatura aria ΔT aria acqua Temperatura media acqua Quota invaso Concio X

10 9.. REF 7 9 REF Concrete gravity dam Hollow buttress gravity dam Arch dam Quaira Dam (BZ) Malga Bissina Dam (TN) Cancano Dam (SO)

11 9.. GNSS =Global Navigation Satellite System VANTAGGI Rilevamento in continuo Dati in formato digitale Assenza di operatori sul posto Trasmissione dati in remoto Costo contenuto SVANTAGGI Precisione conseguibile (millimetrica) Visibilità dei satelliti Rumore ambientale Nonostante la precisione millimetrica è possibile sfruttare la tecnologia GNSS per il monitoraggio delle grandi dighe? È una procedura che cerca di ricostruire l andamento di una determinata serie storica di misure mediante l impiego di una equazione matematica. MODELLI UTILIZZATI PRESENTI IN LETTERATURA SINTETIZZATI EX NOVO Carosio Dupraz De Sortis Paoliani Modelli predittivi Modelli fisicamente basati

tecnologia GNSS per il monitoraggio delle grandi dighe?

12 9.. Stazione totale Pendulums Collimation systems Extensometers STRUMENTI TOPOGRAFICI CLASSICI Stazioni totali Collimatori Estensimetri Pendoli STRUMENTI TOPOGRAFICI MODERNI Apparati GNSS

13 9.. ANALISI DELLE SERIE STORICHE (mm),,,,, Spostamenti MV al coronamento (//8) Misure pendoli corrette (mm),,,, 7 Spostamenti MV al coronamento (//8) Misure pendoli corrette Modello parabolico

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