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R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Prof. Riccardo Castellanza
Associate Professor Geotechnical Engineering
Department of Earth and Envinromental Sciences
Università degli Studi di Milano Bicocca
Geotechnical modelling (3D FEM based) for slope stability and underground geostructures - Lection 1
FEM applied to 3D stability analyses
35th PhD Cycle
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
1.Geotechnical modelling
2.FEM approach
3.Strength Reduction Method
4.Landslides case studies
5.Geo-structures case studies
6.2D demonstrative case
Outline
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
“Reason is like an eye staring at reality, greedily taking it in, recording its connections andimplications, penetrating reality, moving from one thing to another yet conserving all ofthem in memory, trying to embrace everything. A human being faces reality using reason.Reason is what makes us human. Luigi Giussani (1997) , “The Religious sense”, McGill-Queen’s University Press )
Geotechnical Modelling: the best starting points
“Modelling forms an implicit part of all engineering design but many engineers engage inmodelling without consciously considering the nature, validity and consequences of thesupporting assumptions. Many engineers make use of numerical modelling but may not havestopped to think about the approximations and assumpions that are implicit in thatmodelling – still less about the nature of the constitutive models that may have beeninvoked. ” David Muir Wood (2004), “Geotechnical Modelling”, Taylor&Francis
Aristotle said “ί έ ᾶ ᾕ ή ᾕ ίή”: any prediction is basedeither on a rational calculation or on intuitive perception. Although the latter has been fora long time the starting-point of any construction and still plays a relevant role in design, itis the former that allows the definition of the structure’s dimensions and safetyassessment. In fact, it allows rational prediction of the structure’s behavior in the differentconstruction phases and during its life. Roberto Nova (2012)”Soil mechanics”, Wiley- ISTE
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Geotechnical Modelling: main steps
Real case: description of phenomena
Model:
prediction of the behaviour
Work:
Making the job
Engineering Geology Geotechnical Engineering
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Geotechnical Modelling: main
Starting from focusing and observing the physical processes of the problem the following steps will be considered (based on my experience):Step 1: framing and defining the preliminary working hypothesisStep 2: topographic and hydro/geological surveys necessary to understand the boundary value problem (BVP). Definition of two-dimensional or three-dimensional geometric features to be included in the model,Step 3: performing the in situ and laboratory experimental campaign for the characterization of geomaterials based on the phenomenological models that will be used,Step 4: choice of constitutive and phenomenological models to be used, estimation of parameters and state variables on the basis of the experimental evidences, validation of the chosen theoretical frameworkStep 5: construction of the FEM model, execution of the numerical analyses in stages of the boundary value problem,Step 6: critical assessment of the results achieved by comparing them with simple analytical and/or empirical models.
Exp
erim
enta
lTh
eore
tica
lN
um
eric
alP
HA
SES
Geotechnical Modelling: main steps
Design and construction of the geotechnical project (e.g remediational measures)
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Starting from focusing and observing the physical processes of the problem the following steps will be considered (based on my experience):Step 1: framing and defining the preliminary working hypothesisStep 2: topographic and hydro/geological surveys necessary to understand the boundary value problem (BVP). Definition of two-dimensional or three-dimensional geometric features to be included in the model,Step 3: performing the in situ and laboratory experimental campaign for the characterization of geomaterials based on the phenomenological models that will be used,Step 4: choice of constitutive and phenomenological models to be used, estimation of parameters and state variables on the basis of the experimental evidences, validation of the chosen theoretical frameworkStep 5: construction of the FEM model, execution of the numerical analyses in stages of the boundary value problem,Step 6: critical assessment of the results achieved by comparing them with simple analytical and/or empirical models.
Exp
erim
enta
lTh
eore
tica
lN
um
eric
alP
HA
SES
Design and construction of the geotechnical project (e.g remediational measures)
Geotechnical Modelling: main steps
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Starting from focusing and observing the physical processes of the problem the following steps will be considered (based on my experience):Step 1: framing and defining the preliminary working hypothesisStep 2: topographic and hydro/geological surveys necessary to understand the boundary value problem (BVP). Definition of two-dimensional or three-dimensional geometric features to be included in the model,Step 3: performing the in situ and laboratory experimental campaign for the characterization of geomaterials based on the phenomenological models that will be used,Step 4: choice of constitutive and phenomenological models to be used, estimation of parameters and state variables on the basis of the experimental evidences, validation of the chosen theoretical frameworkStep 5: construction of the FEM model, execution of the numerical analyses in stages of the boundary value problem,Step 6: critical assessment of the results achieved by comparing them with simple analytical and/or empirical models.
Exp
erim
enta
lTh
eore
tica
lN
um
eric
alP
HA
SES
Design and construction of the geotechnical project (e.g remediational measures)
Geotechnical Modelling: main steps
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Starting from focusing and observing the physical processes of the problem the following steps will be considered (based on my experience):Step 1: framing and defining the preliminary working hypothesisStep 2: topographic and hydro/geological surveys necessary to understand the boundary value problem (BVP). Definition of two-dimensional or three-dimensional geometric features to be included in the model,Step 3: performing the in situ and laboratory experimental campaign for the characterization of geomaterials based on the phenomenological models that will be used,Step 4: choice of constitutive and phenomenological models to be used, estimation of parameters and state variables on the basis of the experimental evidences, validation of the chosen theoretical frameworkStep 5: construction of the FEM model, execution of the numerical analyses in stages of the boundary value problem,Step 6: critical assessment of the results achieved by comparing them with simple analytical and/or empirical models.
Exp
erim
enta
lTh
eore
tica
lN
um
eric
alP
HA
SES
Design and construction of the geotechnical project (e.g remediational measures)
Geotechnical Modelling: main steps
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Starting from focusing and observing the physical processes of the problem the following steps will be considered (based on my experience):Step 1: framing and defining the preliminary working hypothesisStep 2: topographic and hydro/geological surveys necessary to understand the boundary value problem (BVP). Definition of two-dimensional or three-dimensional geometric features to be included in the model,Step 3: performing the in situ and laboratory experimental campaign for the characterization of geomaterials based on the phenomenological models that will be used,Step 4: choice of constitutive and phenomenological models to be used, estimation of parameters and state variables on the basis of the experimental evidences, validation of the chosen theoretical frameworkStep 5: construction of the FEM model, execution of the numerical analyses in stages of the boundary value problem,Step 6: critical assessment of the results achieved by comparing them with simple analytical and/or empirical models.
Exp
erim
enta
lTh
eore
tica
lN
um
eric
alP
HA
SES
Design and construction of the geotechnical project (e.g remediational measures)
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
1) Geometry & experiments 2) theoretical framework
0ij
w iz
j i
h
x x
+ + =
1
2
h k
hk
k h
U U
x x
= − +
ij p
ij hk, ,ijhk
hkij
ij
Ct t
=
2
2
v
i
hk
tx
− =
Equilibrium solid scheleton
Compatibility
Constitutive model of soil/rock
Continuity equations fluid/soil
+ Boundary condition + Initial condition
FEM discretization + integration
new tunnel
3) numerical predictions
Geotechnical Modelling: main steps
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
0ij
w iz
j i
h
x x
+ + =
1
2
h k
hk
k h
U U
x x
= − +
2
2
v
i
hk
tx
− =
Equilibrium solid scheleton
Compatibility
Continuity equations fluid/soil
+ Boundary condition + Initial condition
new tunnel
This is the hearth of the geotechnical modeling
This is the body of the geotechnical modeling
ij p
ij hk, ,ijhk
hkij
ij
Ct t
=
Constitutive model of soil/rock
FEM discretization + integration
1) Geometry & experiments 2) theoretical framework 3) numerical predictions
Geotechnical Modelling: main steps
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
1.Geotechnical modelling
2.FEM approach
3.Strength Reduction Method
4.Landslides case studies
5.Geo-structures case studies
6.2D demonstrative case
Outline
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Numerical Solution to Boundary Value Problems
Prof. Ing. Riccardo Castellanza
The field equations which govern a typical soil mechanics problem –
expressing in mathematical terms the balance of mass for the pore fluid
(continuity equation), the balance of momentum for the solid skeleton
(equilibrium equations) and the strain-displacement compatibility
conditions, as well as the constitutive equations for the solid skeleton and
the pore fluid – were defined as a set of partial differential equations.
0ij
w iz
j i
h
x x
+ + =
1
2
h k
hk
k h
U U
x x
= − +
ijhk
hkijCt t
=
2
2
v
i
hk
tx
− =
i ij
j
hV k
x
= −
ij ij iju −
with:
ij p
ij hk, , =
hkij hkij
ij
C C
with:
where
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
14•Example: An acid solution, seeping through the pores, dissolves a part of the solid skeleton (e.g. bonds) and produce a gas (CO2).
Fully non linear
coupled system of
PDEs
•A complete theoretical study required a multiphase continuum approach with
Basic assumptions for modelling geotechnical environmental BVP
E1 Solid : Momentum Equilibrium Equations
E4 Fluid : Balance of Mass for water
E2 Solid : Kinematic Equations
E3 Solid : Constitutive equations
E5 Contaminant : Balance of mass for contaminant
species (diffusion, advection ad reactions )
+ Boundary and initial conditions
•In our approach we consider 3 different fields: 1) displacements, 2) pore pressure, 3) concentrations of chem. species
3 phases (solid,liquid,gas) and different species.
E6 Gas : Balance of Mass for gas
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020Prof. Ing. Riccardo Castellanza
Thus, in order to determine the quantities relevant to the design process
from an engineering viewpoint (i.e. displacement components at specific
points of the soil mass or the structures, earth pressures on retaining
structures, pore water pressure distributions, collapse load of foundations,
etc.), the set of governing partial differential equations is required to be
integrated, together with the chosen constitutive equations and the
appropriate initial and boundary conditions for the specific problem at hand
However, in almost all problems of practical interest, the integration of the
governing system of partial differential equations defined can only be
performed by means of approximate numerical methods.
Finite Element MethodFinite Difference Method
In the continuum approach…
the main methods are…
Numerical Solution to Boundary Value Problems
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
16
Prof. Ing. Riccardo Castellanza
The finite difference method essentially consists of the discretization of the governing partial
differential equations. According to this method, the derivative operator (i.e. the limit of the
difference quotient) is replaced by the difference quotient itself. The denser the chosen
discretization, the closer the results obtained are to the “exact” solution of the problem. ,
When the PDE is a second order elliptic partial differential equation, the finite difference
method proves to be very efficient .
Finite Difference Method
=Ah b
where A is a n x n matrix and h and b are two n-
component vectors, will be obtained.
Overall an algebraic system of n equations with
n unknowns of the kind:
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
17
Prof. Ing. Riccardo Castellanza
When hydraulic and static problems are coupled, the governing field
equations are no longer linear; the order of differentiation of the unknown
functions with respect to time increases and the equation governing the
evolution in space and time of the pore water pressure is parabolic. In this
case, the efficiency and accuracy of the finite difference method are
significantly reduced. For this reason, this approach has been practically
abandoned since the development of the finite element method (FEM).
Finite Element Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
18
Prof. Ing. Riccardo Castellanza
On the other hand, the FEM starts discretizing the continuous medium, and
substituting the unknown functions with some suitably selected approximating
functions with local support, characterized by a limited number of unknown
scalar coefficients representing the values of the unknown functions at some
specific points (e.g. the displacement nodal degrees of freedom).
Subsequently, these approximating functions are introduced into the field
equations, which are recast in integral form over the entire domain, and the
constitutive equations are enforced. The algebraic equations governing the
discretized problem then arise “naturally” as a consequence of the initial
discretization.
Finite Element Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
1.Geotechnical modelling
2.FEM approach
3.Strength Reduction Method
4.Landslides case studies
5.Geo-structures case studies
6.2D demonstrative case
Outline
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Strength Reduction Method
• Limit Equilibrium methods (2D and 3D):• Several methods available:
• Bishop’s modified method, • Spencer’s method, • Janbu’s generalized slice procedure …
• Soil mass is divided in slices and assumptions are made to satisfy equilibrium➢ The most likely failure mechanism is determined
• Finite element method (2D and 3D):• Equilibrium is obtained by continuum mechanics• No restriction regarding the geometries or the heterogeneities
(reinforcement) that can be considered
• No arbitrary assumption required for the shape of the failure surface• Various elasto-plastic soil models can be considered➢ Both safety factor and failure behaviour are determined
Approaches to slope stability assessment
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Differences between the two approaches
Finite Elements Limit equilibrium
Equilibrium Satisfied on the continuum Satisfied only for slices
Stresses Computed on the continuum Computed approximately on certain surfaces
Deformation Computed on the continuum Not considered
FailureYield condition checked in
every point of the continuum
Failure allowed only
on certain pre-defined
surfaces no check on yield
condition elsewhere
KinematicsThe failure mechanism
satisfies kinematic constraints
Kinematics are not
considered –
failure mechanisms
may not be feasible
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Increase of the applied load:• All material properties are kept constant (possibly weighted by a safety
factor)
• The load (weight of superstructure, groundwater level…) is increased until loss of stability
➢ The failure mechanism and the ultimate load are determined
• Reduction of the strength characteristics of the soil (c-f):• Self-weight and additional loads are applied at their nominal value
• The strength characteristics of the soil are reduced until loss of stability
➢ The failure mechanism and the safety factor on material propertiesare determined.
– The uncertainty is usually larger on material properties than on applied loads.
➢ The strength reduction method is preferred
Alternative finite element approaches
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Factor of Safety
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
How is instability (failure) determined in FE analysis?
• Non-convergence of a non-linear static analysis is a suitable indicator for instability (Griffiths and Lane, 1999)
• No convergence = No stress distribution can be found that is simultaneously able to satisfy both the plastic failure criterion and the global equilibrium
• Slope failure and numerical non-convergence occur simultaneously, and are accompanied by a drastic increase in the nodal displacements
• Criteria for non-convergence:• The Energy, Displacement or Force norms are monitored during
the incremental-iterative solution procedure.• A step is non-converged when the maximum number of iterations
(default value = 50) is reached without convergence of the norm.
➢ Accuracy in the determination of the stability limit is depending on the non-linear analysis controls :➢ Size of the safety factor steps and maximum number of steps➢ Maximum number of iterations➢ Type and value of the target convergence norm
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Strength reduction procedure
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Example 1:
• Parameters :
Benchmark Examples
1.2H 2H
H
Model mesh & dimensions
2 320 , 10 kN m , 20 kN m
10 m
0.05
c
H
c H
f
= = =
=
=
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Result contour plots:
Displacements on deformed shape
Maximum shear strain
Benchmark Examples
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Factor of Safety results : Comparison with equilibrium methods
Mogenstern & Price : 1.449
Janbu : 1.361
Bishop : 1.452 Spencer : 1.449
1.421.671.461.901.421.471.391.51
Q8Q4T6T3Q8Q4T6T3
GTSPhase2Software
Element type
FS
Benchmark Examples
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Example 2:
• Parameters :
Model mesh & dimensions
2H 2H
H
2H
H
1uc
2uc
2 3
1
1 2 1
0 , 50 kN m , 20 kN m
10 m
0.25, 0.6
u u
u u u
c
H
c H c c
f
= = =
=
= =
Benchmark Examples
Griffiths, D.V. and Lane, P.A., (1999) "Slope stability analysis by finite elements", Geotechnique, 49, 3, 387-403,
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Result contour plots:
Displacements on deformed shape
Maximum shear strain
Benchmark Examples
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Bishop : 1.505 Spencer : 1.505
Janbu : 1.393 Mogenstern & Price : 1.505
• Factor of Safety results : Comparison with equilibrium methods
1.391.351.35
Q8Q4T6T3Q8Q4T6T3
GTSPhase2Software
Element type
FS
Benchmark Examples
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Example 3:
– Parameters :
3D Examples
Model geometry Model mesh
Parameters
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
• Result contour plot:
Maximum shear strain
3D Examples
•Safety Factor 1.19 (see work tree)
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
1uc
2uc
SRM for Mohr Coulomb failure criteria
1 0tantan
SRFf
−
= f
ff
0
SRFf
C
cc =
[kPa]
[kPa]
ff0
f
0c
fc B
BA
A
' tan c= + f
Local level (in the Gauss point of the element)
Global level - BVP
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
ff 0
f
0c
fc
1 0tantan
SRFf
−
= f
ffLet’s define and
0
SRFf
C
cc =
if SRF SRFcf
Generalized SRM for Mohr-Coulomb failure criteria
Loss of convergence
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
ff 0
f
0c
fc
1 0tantan
SRFf
−
= f
ffLet’s define and
0
SRFf
C
cc =
if SRF < SRFcf
Generalized SRM for Mohr-Coulomb failure criteria
e.g. bonded geomaterials - rock
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
ff 0
f
0c
fc
1 0tantan
SRFf
−
= f
ffLet’s define and
0
SRFf
C
cc =
if SRF >SRFcf
Generalized SRM for Mohr-Coulomb failure criteria
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
ff
0f
0 0fc c= =
1 0tantan
SRFf
−
= f
ffLet’s define and
0
SRFf
C
cc =
if SRF SRFcf
Purely Granular soil
Generalized SRM for Mohr-Coulomb failure criteria
c
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
0 0f= =f f
1 0tantan
SRFf
−
= f
ffLet’s define and
0
SRFf
C
cc =
if SRF SRFcf
Purely Cohesive Soil/Rock
0c
fc
Generalized SRM for Mohr-Coulomb failure criteria
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Generalized SRM for other failure criteria (e.g. Hoek&Brown)
0.0
200.0
400.0
600.0
800.0
1000.0
-500 0 500 1000 1500 2000 2500 3000
[K
Pa]
[KPa]
Mohr-Coulomb failure loci
Hoek-Brown failure loci
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Generalized SRM for other failure criteria (e.g. Hoek&Brown)
0.0
200.0
400.0
600.0
800.0
1000.0
-500 0 500 1000 1500 2000 2500 3000
[K
Pa]
[KPa]
Mohr-Coulomb failure loci
Hoek-Brown failure loci
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Generalized SRM for other failure criteria (e.g. Nova model)
p’, p*
q
pt
ps
pm
f0: fresh rock
fw
: partially weathered
fu: uncemented soil
fwf
u
f0A
Bps
pt
pm
pc
pto
0.1.0
xd
pm.t.s
unbonded soilFresh rock
When the shrinking yield surface reaches point A, the stress-strain state move to Bfor respecting consistency.
EXAMPLE: Weathering (or SRM) in oedometric condition (initial stress A)
CHEMO-MECHANICAL
COUPLING
•Nova R., Castellanza R., Tamagnini C. (2003), A constitutive model for bonded geomaterials subject to mechanical and/or chemicaldegradation, Int. J. Num. Anal. Meth. Geomech.; 27(9), 705–732.
Strength Reduction Method
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
1.Geotechnical modelling
2.FEM approach
3.Strength Reduction Method
4.Landslides case studies
5.Geo-structures case studies
6.2D demonstrative case
Outline
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Starting point: include or not the failure surface(s)
A) Failure surface(s) known and prescribed B) Failure surface
undefined
C) Failure surfacepartially known
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: 3D geometry from DTM
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: 3D geometry from DTM
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: creation of the solid model of the chosen area
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: creation of the solid model of the chosen area
deposit Adeposit B
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Surf. 1A : deep surface between the intact rock and the deposit. It is obtained from the interpolation of 3D points (e.g. coring and geophysical measurements)
Case study #1: definition of deposit A surfaces
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Surf. 2A : intermediate surface obtained from the interpolation of 3D points (e.g. coring and geophysical measurements)
Case study #1: definition of deposit A surfaces
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: definition of deposit A surfaces
Surf. 2A : shallow surface obtained from the interpolation of 3D points (e.g. coring and geophysical measurements)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: definition of deposit B surfaces
Surf. 1B : deep surface between the intact rock and the deposit. It is obtained from the interpolation of 3D points (e.g. coring and geophysical measurements)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: definition of deposit B surfaces
Surf. 2B : intermediate surface. It is obtained from the interpolation of 3D points(e.g. coring and geophysical measurements)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: definition of deposit B surfaces
Surf. 2B : intermediate surface. It is obtained from the interpolation of 3D points(e.g. coring and geophysical measurements)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: definition of deposit B surfaces
Surf. 3B : shallow surface. It is obtained from the interpolation of known points (e.g. coring and geoelectic)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit B)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit B)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit B)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit B)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: subdivision of the solid (deposit B)
Check on 2D sections
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: definition of the deposits
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: mesh generation (dep. A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Deposit A: 3D analysis, c-f reduction - Fs > 2.5
Case study #1: SRM analysis and results (plastic strains)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Deposit A: 3D analysis, c-f reduction - Fs > 2.5
Case study #1: SRM analysis and results (plastic strains)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: mesh generation (deposit B)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Deposit B: 3D analysis, c-f reduction - Fs > 3.1
Case study #1: SRM analysis and results (plastic strains)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Deposit B: 3D analysis, c-f reduction - Fs > 3.1
Case study #1: SRM analysis and results (plastic strains)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Sez. A
Sez. B
Sez. C
Sez. A Sez. B Sez. C
Case study #1: 2D detail analysis (dep. A sections)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Sez. A Sez. B Sez. C
Case study #1: extraction of 2D surf. and rotation on x-y plane (sect. A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: extraction of 2D surf. and rotation on x-y plane (sect. A)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: material properties assignment
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: mesh of section A
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Plastic strains
Case study #1: SRM analysis and results of sect. A; Fs=1.68
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Displacements
Case study #1: SRM analysis and results of sect. A; Fs=1.68
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Sez. D
Sez. E
Sez. F
Sez. G
Case study #1: extraction of 2D surf. and rotation on x-y plane (sect. E)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: mesh of section E
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #1: mesh of section E
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
83
Dott. Ing. Riccardo Castellanza
Plastic strains
Case study #1: SRM analysis and results of sect. E; Fs=1.78
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
84
Dott. Ing. Riccardo Castellanza
Case study #1: SRM analysis and results of sect. E; Fs=1.78
Displacements (deformed)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
3D SRM Fs 2.5 (A) and 3.1(B)
Case study #1: SRM analysis and results (plastic strains)
2D SRM Fs beetwen 1.6 and 1.9
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont back-analysesCase study #2: Vajont landslide (1960-1963)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont landslide (1960-1963)9 october 1963, about 300ml m3 , about 2000 deaths
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont landslide (1960-1963)
before after
9 ottobre h 22.39’46’’
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont landslide (1960-1963)
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont landslide (1960-1963)
after
9 ottobre h 22.39’46’’
5
62
63
(a
(b
Modified by R. Selli, L. Trevisan, (1964)
Water level October 1963
Water level October 1961
lake level Groundwater level
5
62
63
(a
(b
Modified by R. Selli, L. Trevisan, (1964)
Water level October 1963
Water level October 1961
lake level Groundwater level
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #2: Vajont landslide (1960-1963)
after
9 ottobre h 22.39’46’’
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Progressive Shear strengthreduction until loss of
convergence
0
50
100
150
200
250
300
1214161820222426
coh
esi
on
[kP
a]
friction angle [deg]
Failure → progressive weakening
Ave. Material propertiesleading to a generalized
instability
3D FEM: ave material properties
3D effect of lake impounding on slope stability and activityThin shear zone along the 3D reconstruction of the failure zone→ Bistacchi et al.
Case study #2: Vajont back-analyses
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
3D Mesh
3D FEM: ave material properties Case study #2: Vajont back-analyses
prescribed failure surface
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont back-analyses
Landslides case studies
# 1/1: Lake level 700 m a.s.l.
(c=300 kPa, f=26°)
Displacement
Plastic strain
Displacement
Plastic strains
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
# 1/2: Lake level 700 m a.s.l.
(c=200 kPa, f=22°)
Displacement
Plastic strain
Case study #2: Vajont back-analyses
Landslides case studies
Displacement
Plastic strains
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont back-analyses
Landslides case studies
# 1/3: Lake level 700 m a.s.l.
(c=100 kPa, f=18°)
Displacement
Plastic strain
Displacement
Plastic strains
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont back-analyses
Landslides case studies
# 1/4: Lake level 700 m a.s.l.
(c=50 kPa, f=14°)
Displacement
Plastic strain
Displacement
Plastic strains
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont back-analyses
Landslides case studies
# 1/5: Lake level 700 m a.s.l.
(c=25 kPa, f=13°)
Displacement
Plastic strain
Loss of convergence
Displacement
Plastic strains
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Case study #2: Vajont back-analyses
Landslides case studies
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslide case studies
Case study #3: 3D rockslide
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: rockslide (in collaboration with Studio Associato Cancelli)
G. B. Crosta, C. di Prisco, G. Frigerio, P. Frattini, R. Castellanza, F. Agliardi (2013) Chasing a completeunderstanding of the triggering mechanisms of a large rapidly evolving rockslide, Landslides,
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D slope (in collaboration with Studio Associato Cancelli)
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
Real Failure Surface
MC: parameters:Friction angle : 27°
Cohesion c’ = 23 kPa
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
Real Failure Surface
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
G. B. Crosta, C. di Prisco, G. Frigerio, P. Frattini, R. Castellanza, F. Agliardi (2013) Chasing a completeunderstanding of the triggering mechanisms of a large rapidly evolving rockslide, Landslides,
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
Giovanni B. Crosta, Paolo Frattini, Riccardo Castellanza, Gabriele Frigerio, Claudio di Prisco, Giorgio Volpi, Mattia De Caro, Paolo Cancelli, AndreaTamburini, Walter Alberto, and Davide Bertolo, Investigation, Monitoring and Modelling of a Rapidly Evolving Rockslide: The Mt. de la Saxe CaseStudy, 349 Engineering Geology for Society and Territory - Volume 2. pp 349-354
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
1 0tantan
SRFf
−
= f
ff
0
SRFf
C
cc =
An higher reduction in cohesion than in the friction angle is more suitable for simulating the rock weathering
[kPa]
[kPa]
ff0
f
0c
fc B
BA
A
' tan c= + fSRM for Mohr Coulomb failure criteria
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
ff
0f
0c
fc
SRF SRFc f
cohesion
[kPa]
friction angle [°]
SRFc
coesione Cs
(kPa) SRFФ' Cs (°)
1.00 350 1.00 33.0
1.40 250 1.02 32.5
1.80 194 1.03 32.0
2.20 159 1.05 31.5
2.60 135 1.06 31.0
2.75 127 1.08 30.5
2.90 121 1.10 30.0
3.05 115 1.12 29.5
3.20 109 1.14 29.0
3.35 104 1.16 28.5
3.50 100 1.18 28.0
1 0tantan
SRFf
−
= f
ff0
SRFf
C
cc =
An higher reduction in cohesion than in the friction angle is more suitable for simulating the rock weathering.
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
SRFc
coesione Cs
(kPa) SRFФ' Cs (°)
1.00 350 1.00 33.0
1.40 250 1.02 32.5
1.80 194 1.03 32.0
2.20 159 1.05 31.5
2.60 135 1.06 31.0
2.75 127 1.08 30.5
2.90 121 1.10 30.0
3.05 115 1.12 29.5
3.20 109 1.14 29.0
3.35 104 1.16 28.5
3.50 100 1.18 28.0
1 0tantan
SRFf
−
= f
ff0
SRFf
C
cc =
An higher reduction in cohesion than in the friction angle is more suitable for simulating the rock weathering.
SRFC
Norm
aliz
ed
cohesive
and
fric
tionalst
rength
[%]
0
ff
f
0
c
c
R.Castellanza: Influence of material model on the settlement resultsProf. Ing. Riccardo Castellanza – FEM Course for PhD students – October 2020
Landslides case studies
Case study #3: 3D rockslide (in collaboration with Studio Associato Cancelli)
Giovanni B. Crosta, Paolo Frattini, Riccardo Castellanza, Gabriele Frigerio, Claudio di Prisco, Giorgio Volpi, Mattia De Caro, Paolo Cancelli, AndreaTamburini, Walter Alberto, and Davide Bertolo, Investigation, Monitoring and Modelling of a Rapidly Evolving Rockslide: The Mt. de la Saxe CaseStudy, 349 Engineering Geology for Society and Territory - Volume 2. pp 349-354