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Workshop of the TC302 - Forensic Geotechnical Engineering FAILURES, DISPUTES, CAUSES AND SOLUTIONS IN GEOTECHNICS 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

Dolexpert - Geotechnika 6 Numerical Analysis of Unusual Behaviour of Zermanice Dam (36 m, 1952 –1958, Czech Republic)Numerical Analysis of Unusual Behaviour of Zermanice Dam (36 m, 1952 –1958, Czech Republic) Tomaš Skokan Dalibor Kratochvil František Glac Jiri Svancara Dalibor Bilek Vaclav Torner Marta Dolezalova Ivo Hladik Vlasta Zemanova Stanislav Novosad Karel Pekarek TEAM: CASE STUDY: PROBLEM: Concerns about the stability of the concrete dam due to long-term tilting, heave and uneven displacements detected by monitoringConcerns 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 stagesDevelpoment 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

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

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

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

Dolexpert - Geotechnika 10 ZERMANICE DAM Heave of dam sections founded on weak marly shale [ mm]Heave of dam sections founded on weak marly shale [ mm] Heave [ mm ]

Dolexpert - Geotechnika 11 ZERMANICE DAM Tilt [mm/10 m height] - pendulum in Section 1 – 1’Tilt [mm/10 m height] - pendulum in Section 1 – 1’ Tilt [mm/10m ]

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

Dolexpert - Geotechnika 13 WORKING HYPOTHESIS based on the analysis of geological conditions and monitoring results andbased on the analysis of geological conditions and monitoring results and on the geological-historical study of Q. Zaruba (1956), which highlighted the crucial role of viscoplastic flow of the marly shale in formation of the valleyon the geological-historical study of Q. Zaruba (1956), which highlighted the crucial role of viscoplastic flow of the marly shale in formation of the valley 1.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. 2.The visco-plastic parameters of the marly shale could be estimated by simulating the rheological process of the formation of the valley. ZERMANICE DAM, 36 m,

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 parameters1a : calibration of mechanical / hydraulic parameters 1b : stability analysis1b : stability analysis 1c : calibration of thermal parameters1c : calibration of thermal parameters Dam section on the teschenite 2a : calibration of mechanical / hydraulic parameters2a : calibration of mechanical / hydraulic parameters 2b : stability analysis2b : stability analysis

Dolexpert - Geotechnika 15 -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 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 MODELLING CONCEPT (continued)

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

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

Dolexpert - Geotechnika 18 REGIONAL FEM MODEL AND SOLUTION STRATEGY 2D FEM MESH EXCAVATION STAGES SIMULATING THE EROSION OF THE VALLEY m SOLUTION STRATEGY: elastoplastic simulation of the process using strength reduction method elastoplastic simulation of the process using strength reduction method determination of the viscoplastic parameters c vp,  vp,  determination of the viscoplastic parameters c vp,  vp,  viscoplastic simulation of the process  delayed collapse resulting in sliding viscoplastic simulation of the process  delayed collapse resulting in sliding

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 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 Section 2 - 2’: calculated 8.6 mm / measured 10.5 mm DOF = Horizontal displacements [m]

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 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) 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 2060prediction 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 bysuperposition of the viscoplastic flow across the valley induced by erosion of the riverbed and viscoplastic flow along the valley induced by reservoir filling (reservoir operation from 1959 to 2000) 2 1’ 1 2’

Dolexpert - Geotechnika 25 1.The unusual performance of the dam is caused by superposition of viscoplastic flow of marly shale in two directions: along the valley induced by reservoir filling and across the valley induced by the erosion of the riverbed in geological time. 2.Heave of the dam is caused by viscoplastic flow across the valley, while tilting a differential movements occur due to viscoplastic flow along the valley. 3.No immediate safety measures but only extension of the downstream embankment to damp the viscoplastic flow along the valley was recommended. 4.The analysis confirms that measuring and modelling are effective tools for pinpointing cause of distress of civil engineering structures. CONCLUSIONS

Dolexpert - Geotechnika 26 APPENDIX

Dolexpert - Geotechnika 27 BASIC RELATIONS OF THE PDEP MODEL (1) (Dolezalova 1985, 1992) Stress path groups Stress path identifiers and switch functions Region with different constitutive relations of Molenkamp’s Double Hardening Model(1983) Relations for calculating tangential deformation characteristics E t, t

Dolexpert - Geotechnika 28 BASIC RELATIONS OF THE PDEP MODEL (2)  c, ,  res, ,  t - cohesion, angle of shearing resistance, residual angle of shearing resistance, angle of dilation, tensile strength  E p, E unl, E ten, E max - tangent deformation modulus at loading, unloading, tension and the maximum tangent deformation modulus  p, max - initial and maximum tangent values of Poisson´s ratio  i 0, ,  o - initial shear strength mobilization, factor determining the minimum tangent modulus (E min =  E p ) and referent pressure Calculation of E t, t Parameters: ; ; Mohr- Coulomb yield and failure criterion - shear strength mobilization

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

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/  ) y = 1,.... k ; k – number of surfaces 2. Viscoplastic flow with two surfaces 3.Parameters to be determined: viscoplastic threshold F  c vp,  vp  10 to 20 % of strength viscoplastic threshold F  c vp,  vp  10 to 20 % of strength fluidity parameter   viscoplastic strain rate overstress overstress  fluidity parameter of rock salt