Analysis of a deepseatedslopefailurein theAlpsTom Schanz, MariaDatcheva& Anke Spickermann, Laboratory of Soil MechanicsLaboratory of SoilMechanicsAcknowledgementsMichael Moser(Universität Erlangen)Yves Bonanomi(Sedrun, Schweiz)Florian AmannElektrowatt AG, Zurich)Peter Gußmann(KEM)AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsContents1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics1. Introduction• location• methods of field measurements and observations• processes and mechanisms influencing the slope instability• objective: obtain the geometry and the dimensions of the potential failure mass• rock mass run-off after four main scenarios1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary Numerikin derGeotechnikAK 1.6 16-17 October 2003, WeimarAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsMaximum deformationmeasured:85cm/year?6050Elevation [m]403020100-10GPSHigh precision measuring tape0102030405060Distance [m]708090100Tacheometric surveyNumerikin derGeotechnikAK 1.6 16-17 October 2003, WeimarAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsα>(90°-β) + ϕα... Inclinationof slopeβ... Inclinationof jointsϕ... Friction angle of jointsFlexural topplingBlocky topplingFlexural blocky topplingSketches taken fromdifferent literatureAK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnik1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary Analysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsFig. 1.1: Original situationFig. 1.2: Scenario33 322 250 m³Amann & Moser (2002)Fig. 1.3: Scenario 24 886 853 m³Fig. 1.4: Scenario115 095 617 m³AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsmainscenarios (Bonanomi, Amann& Moser, 2002)scenario1 = 15 095 617 m³scenario2 = 4 886 853 m³scenario3 = 3 322 250 m³scenario4 = 170 000 m³ 2400230022002100200019001800Szenario 4Szenario 2Szenario 11700160015001400171400171600171800172000172200172400172600172800173000173200Szenario 3Fig. 1.5: Scenario1 –4 , centralregionof theslopeAK 1.6 16-17 October 2003, WeimarFig. 1.6:Failuresurfacescenario1Failuresurfacescenario2Failuresurfacescenario3Failuresurfacescenario4Numerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsSize and locationof failure mass areneeded for this type of annalysis?Fig. 1.7: Visualisationof a Run-Out Analysis, first resultsLagrangian solutionof St. Venant`s equation (Meier, Schanz & Hungr, 2003)AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnik1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. SummaryAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics2. Geological situation• profil geometrielength= 1012 m height= 595 m • material→mineralogical composition→weathering→joints structure• loading→post glacial unloa-dingAmann & Moser (2002)Fig. 2.1: Isolines of displacements 1999,locationof the profile studiedAK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnik1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary Analysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics1.Joints (micro-meso)ÆSmeared approach2.Disturbed zones (macro)ÆDiscrete approachFig. 2.2: Analysedcross section of the slope (Amann& Moser, 2002)1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics3. Main assumptions• Distribution and thicknessof weathered zones• Material properties• Initial stresses –geological history1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics• Depth of weathered zones?Fig. 3.1: Geological situation (rock mass units, orientation of joints, current topography)AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnik1. Introduction2. Geological situation3. Main assumptions4. Numerical modelling5. Discussion6. Summary Analysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsFig. 3.2: Schemeof thetwomaindipdirectionsof thejoints1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. SummaryNumerikin derGeotechnikAK 1.6 16-17 October 2003, WeimarAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics• Material properties?Tab. 3.1: Summaryof theusedmaterial propertiesmaterial zonesYoung's modulus [MPa]density [kg/m³]friction angle [°]cohesion [MPa]friction angle [°](degradation)cohesion [MPa](degradation)dilatancy [°](degradation)Poisson's ratiogranite-gneiss90002500461,235gneiss8000250044135weak rocks1000250027027quartzite12000250045235disturbed zones3000250029029000001. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary 50,2550,2510,2550,2510,25AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics• Determination of initialstresses–geologicalhistory?Fig. 3.3: Initial stateFig. 3.4: Icereplacesrock on Fig. 3.5: Icereplacesrock onlayer1layer2Fig. 3.6: Icereplacesrock onlayer3 Fig. 3.7: Icereplacesrock onlayer4Fig. 3.8: Removingicelayer1Fig. 3.9: Removingicelayer2 Fig. 3.10: Removingicelayer3Fig. 3.11: Removingicelayer4 AK 1.6 16-17 October 2003, WeimarFig. 3.12: Currentstateof theslopeNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics4. Numericalmodelling• FEM •KEM →finite elementmethod(PLAXIS)→KinematicElementMethod(Gußmann)• Finite elementcontinuummodel→3D anisotropiccontinuum→Macro: disturbedzones-interfaceelements→Meso-micro: jointedrock model• Discretization →x-y-dimension: 2000 x 1000 m→4 slicesx 75 m = 300m in z-direction→4 x 2089 = 8356 15-node wedgeelements1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics•FEMmaterial zonesYoung's modulus[MPa]density [kg/m³]Poisson's ratioRinterjoint set 1friction angle [°]cohesion [MPa]dilatation angle [°]joint set 2friction angle [°]cohesion [MPa]dilatation angle [°]granite-gneiss900025000,250,6α1 = 85° ,461,216α1 = 85° ,461,216gneiss800025000,250,6α2 = 160°44114α2 = 30°44114weak rocks100025000,250,6quartzite1200025000,250,6270145215270145215Tab. 4.1: Material propertiesof calculationphase1 ... 91. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. SummaryAK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsTab. 4.2: Material propertiesof calculationphase10material zonesgranite-granite-gneissgranite-gneissweakquartzitegneissslightly gneissrocksweatheredweathered900025000,250,6461,216461,216900025000,250,335053505900025000,250,0135053505800025000,250,64411444114100025000,250,6270127011200025000,250,64521545215Fig. 4.1: Decreaseof theinterfacestrengthreductionfactorRinterYoung's modulus[MPa]density [kg/m³]Poisson's ratioRinterfriction angle [°] cohesion [MPa]dilatation angle [°] friction angle [°]cohesion [MPa]dilatation angle [°]joint set 1 α1 = 85° , α2 = 160°joint set 2 α1 = 85° , α2 = 30°AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics•KEMFig. 4.1: Geometryand rock layersusedin theKEM modelTab.4.1: Material propertiesmaterial zonesYoung's modulus [MPa]density [kg/m³]friction angle [°]cohesion [MPa]AK 1.6 16-17 October 2003, Weimargranite-gneiss90002500461,2gneiss80002500441weak rocks10002500270quartzite120002500452disturbed zones30002500290Numerikin derGeotechnik1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. SummaryAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics5. Discussion→Resultsof FEM -calculationFig. 5.1: Total displacementscontours in equilibriumwithgravitationalforces AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnik1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary Analysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanicsFig. 5.2: Locationof theconsideredthreeslopeintersections 1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics1000800U total A-AUx A-AU total B-BUx B-BU total C-CUx C-CK0= σ`hh/ σ`yy1000K0 in x A-AK0 in z A-AK0 in x B-BK0 in z B-BK0 in x C-CK0 in z C-C800height [m]400height [m]6006004002002000-20-10010203040displacements U [cm]5060700-8-6-4-20K02468Fig. 5.3: Total displacementsand displacementsin x-direction forthethreeslopeintersectionsFig.5.4: K0 factorforthethreeslopeintersectionsAK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics→Resultsof KEM –calculation 1 (identical constitutive parameters) factorof safety F=2.42Fig. 5.5: Thegeometryof theslipsurfaceobtainedwithKEM 1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics→Resultsof KEM –calculation 2 (modified constitutive parameters)cohesionisreduced75%factorof safety F=1.59Fig. 5.5: Thegeometryof theslipsurfaceobtainedwithKEM 1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary AK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnikAnalysis of a deepseatedslopefailurein theAlpsLaboratory of SoilMechanics6. Summary• to evaluatethepotential hazard, itisessential to understandthe geologicalsituationand mechanismsdrivingtheslopeinstability• theanalysesbaseon importantassumptionsbecauseof missing information• thefinite elementanalysiswas comparedwiththepredictions doneusingkinematicelementmethod→approximatlysamelocationof theslipline = slidingmass•improveddata–morerealisticresultscanbeobtainedincluding time dependencyfracturingrock degradationphenomenaNextStep:Performingdetailed „Run-out“analysiswithdeterminedfailuremassAK 1.6 16-17 October 2003, WeimarNumerikin derGeotechnik1. Introduction2. Geologicalsituation3. Main assumptions4. Numericalmodelling5. Discussion6. Summary