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Workshop of the TC302 - Forensic Geotechnical Engineering

Workshop of the TC302 - Forensic Geotechnical Engineering FAILURES, DISPUTES, CAUSES AND SOLUTIONS IN GEOTECHNICS 24-25 September 2010, Budapest, Hungary. UNDERSTANDING BEHAVIOUR OF DISTRESSED STRUCTURES THROUGH MEASURING AND MODELLING. MARTA DOLE Z ALOV A

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Workshop of the TC302 - Forensic Geotechnical Engineering

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  1. Dolexpert - Geotechnika

  2. Dolexpert - Geotechnika

  3. Dolexpert - Geotechnika

  4. Dolexpert - Geotechnika

  5. Workshop of the TC302 - Forensic Geotechnical Engineering FAILURES, DISPUTES, CAUSES AND SOLUTIONS IN GEOTECHNICS 24-25 September 2010, Budapest, Hungary UNDERSTANDING BEHAVIOUR OF DISTRESSED STRUCTURES THROUGH MEASURING AND MODELLING MARTA DOLEZALOVA Dolexpert – Geotechnika, Prague, Czech Republic • Robust numerical models fitting the long-term measurement results represent a powerfull tool for pinpointing causes of distress

  6. CASE STUDY: • Numerical Analysis of Unusual Behaviour of Zermanice Dam(36 m, 1952 –1958, Czech Republic) • PROBLEM: • Concerns about the stability of the concrete dam due to long-term tilting, heave and uneven displacements detected by monitoring • SOLUTION: • Develpoment of a 3D model of the dam and its foundation fitting the monitoring results and simulating the history of the dam including the distress stages TEAM: Stanislav Novosad Karel Pekarek Tomaš Skokan Dalibor Kratochvil František Glac Jiri Svancara Dalibor Bilek Vaclav Torner Marta Dolezalova Ivo Hladik Vlasta Zemanova Dolexpert - Geotechnika

  7. ZERMANICE CONCRETE DAM:reservoir of 26 mil. m3 for water supply of Ostrava industrial region OUTLINE OF THE PRESENTATION • The dam and dam site • Measurement results • Modelling concept • Stability assessment • Modelling formation of the valley • 3D model of the dam and its foundation • Conclusions Dolexpert - Geotechnika

  8. ZERMANICE CONCRETE DAM • geological conditions • properties of bedrock • characteristic cross sections of the dam Dolexpert - Geotechnika

  9. ZERMANICE CONCRETE DAM • deformation modulus of the bedrock • differential movements of the dam Dolexpert - Geotechnika

  10. ZERMANICE DAM • Heave of dam sections founded on weak marly shale [mm] Heave [mm] 1964 1970 1980 1990 2000 Dolexpert - Geotechnika

  11. ZERMANICE DAM • Tilt [mm/10 m height] - pendulum in Section 1 – 1’ Tilt [mm/10m ] 1966 1970 1980 1990 2000 Dolexpert - Geotechnika

  12. ZERMANICE DAM • Uneven horizontal displacements of the dam crest Section 1-1‘ on weak marly shale, 60 mm Horizontal displacement [mm] Section 2-2‘ on competent volcanic rock, 20 mm 1955 2000 Dolexpert - Geotechnika

  13. ZERMANICE DAM, 36 m, 1952-1958 • WORKING HYPOTHESIS • based on the analysis of geological conditions and monitoring results and • on the geological-historical study of Q. Zaruba (1956), whichhighlightedthe crucial role ofviscoplastic flow of the marly shale in formation of the valley • Possible reason of the unexpected behaviour of the dam is viscoplastic flow of the marly shale induced by reservoir filling causing overstress, which exceeded of visco-plastic threshold of the marly shale. • The visco-plastic parameters of the marly shale could be estimated by simulating the rheological process of the formation of the valley. Dolexpert - Geotechnika

  14. MODELLING CONCEPT - step-by-step simulation of the observed behaviour by a series of 2D FEM models • LOCAL 2D FEM MODELS • Dam section on the weak marly shale • 1a : calibration of mechanical / hydraulic parameters • 1b : stability analysis • 1c : calibration of thermal parameters • Dam section on the teschenite • 2a : calibration of mechanical / hydraulic parameters • 2b : stability analysis Dolexpert - Geotechnika

  15. MODELLING CONCEPT (continued) • calibration of rheological parameters REGIONAL 2D FEM MODELS 3a : erosion of the riverbed and bulging of the marly shale 3b : viscoplastic flow of disturbed shale during construction of the dam 3c : influence of the reservoir on viscoplastic flow of the disturbed shale during operation of the dam 3D FEM MODEL 4 : synthesis, safety assessment and prediction of the dam performance Dolexpert - Geotechnika

  16. ZERMANICE DAM: stability assessment • Section of the dam on weak marly shale • Strain localization and slip at strength reduction factor F = 2.5 Dolexpert - Geotechnika

  17. FORMATION OF THE LUCINA RIVERBED IN GEOLOGICAL TIME • Geological-historical study of Academic Zaruba, 1956: • erosion of the valley, depth: 25 m • viscoplastic flow and bulging of marly shale • sliding, breaking and subsidence of the teschenite sill: ~ 13 m • duration of the event cca 15 000 years Teschenite sill before erosion of the riverbed (–25 000 B.C.) Pleistoceneous gravel Teschenite Cretaceous marly shale Teschenite blocks after erosion of the riverbed (–10 000 B.C.) Dolexpert - Geotechnika

  18. REGIONAL FEM MODEL AND SOLUTION STRATEGY 2D FEMMESH • SOLUTION STRATEGY: • elastoplastic simulation of the process using strength reduction method • determination of the viscoplastic parameters cvp,jvp,G • viscoplastic simulation of the process delayed collapse resulting in sliding 0 1800 m EXCAVATION STAGES SIMULATING THE EROSION OF THE VALLEY Dolexpert - Geotechnika

  19. FEM SIMULATION OF THE VISCOPLASTIC FLOW ACROSS THE VALLEY • excavation of the riverbed simulating erosion • viscoplastic flow and bulging of the soft marly shale due to overstress induced by erosion • washing away the disturbed marly shale from the riverbed Dolexpert - Geotechnika

  20. RESULTS OF THE FEM SIMULATION • bulging of the marly shale and subsidence of the teschenite blocks due to erosion of the riverbed • cumulated displacement vectors Teschenite blocks: horizontal displacement of 14 m and subsidence of 10 m (10 to 13 m according to the geological study) Dolexpert - Geotechnika

  21. 3D MODEL OF ZERMANICE DAM • horizontal displacements induced by the first filling of the reservoir • Section 1 - 1’: calculated 18.5 mm / measured 15.5 mm • Section 2 - 2’: calculated 8.6 mm / measured 10.5 mm Horizontal displacements [m] DOF = 389 656 Dolexpert - Geotechnika

  22. 3D MODEL OF ZERMANICE DAM • highly uneven horizontal movements of the dam sections • founded on soft marly shale and on competent teschenite • comparison of the calculated and measured displacements due to • viscoplastic flow of the marly shale(1959 – 2000) Dolexpert - Geotechnika

  23. 3D MODEL OF ZERMANICE DAM • prediction of the horizontal movements of the dam sections on the soft marly shale up to 2060 Dolexpert - Geotechnika

  24. 3D MODEL OF ZERMANICE DAM • superposition of the viscoplastic flow across the valley induced by • erosion of the riverbed and viscoplastic flow along the valley induced byreservoir filling (reservoir operationfrom 1959 to 2000) 2’ 2 1’ 1 Dolexpert - Geotechnika

  25. CONCLUSIONS • The unusual performance of the dam is caused by superposition of viscoplastic flow of marly shalein two directions: along the valley induced by reservoir filling and across the valley induced by the erosion of the riverbed in geological time. • Heave of the dam is caused byviscoplastic flow across the valley, while tilting a differential movements occur due to viscoplastic flow along the valley. • Noimmediate safety measures butonly extension of the downstream embankment to damp the viscoplastic flow along the valley was recommended. • The analysis confirms that measuring and modelling are effective tools for pinpointing cause of distress of civil engineering structures. Dolexpert - Geotechnika

  26. APPENDIX Dolexpert - Geotechnika

  27. BASIC RELATIONS OF THE PDEP MODEL (1)(Dolezalova 1985, 1992) Stress path identifiers and switch functions Stress path groups Relations for calculating tangential deformation characteristics Et, nt Region with different constitutive relations of Molenkamp’s Double Hardening Model(1983) Dolexpert - Geotechnika

  28. BASIC RELATIONS OF THE PDEP MODEL (2) Calculation of Et, nt Mohr- Coulomb yield and failure criterion ; - shear strength mobilization ; Parameters: • c, j, jres, y, st - cohesion, angle of shearing resistance, residual angle of shearing resistance, angle of dilation, tensile strength • Ep, Eunl, Eten, Emax - tangent deformation modulus at loading, unloading, tension and the maximum tangent deformation modulus • np, nmax - initial and maximum tangent values of Poisson´s ratio • i0, s, so- initial shear strength mobilization, factor determining the minimum tangent modulus (Emin = d Ep) and referent pressure Dolexpert - Geotechnika

  29. ZERMANICE DAM • 2D FEM model of the dam section on disturbed marly shale embankment dam foundation slab disturbed marly shale partly disturbed marly shale grout curtain marly shale Deformational and strength characteristics of marly shale 1 – marly shale 2 – partly disturbed marly shale 3 – disturbed marly shale Dolexpert - Geotechnika

  30. MULTIFACE VISCOPLASTIC FLOW 1.Viscoplastic strain rate (Perzyna, 1966; Zienkiewicz & Pande, 1977) Q– viscoplastic potential F– viscoplastic threshold (yield surface)  – fluidity parameter (1/h) y = 1, .... k ; k– number of surfaces 2. Viscoplastic flow with two surfaces • Parameters to be determined: • viscoplastic threshold Fcvp , jvp10 to 20 % of strength • fluidity parameter  » fluidity parameter of rock salt viscoplastic strain rate overstress Dolexpert - Geotechnika

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