Application of HS model to deep excavations andfoundation rafts
Andrzej TrutyZACE Services
28.08.2009
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Major goals in modeling soil-structure interaction problems
Estimation of stress resultants in structures that interact withsoil
Assessment of deformations in the area close to theconstruction site (mainly in the urban areas)
Assessment of additional deformations due to pumping of thewater from the excavation zone
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Major problems
Simple constitutive models for soils do not include the effectof small strain stiffness
Only small part of soil adjacent to the structure undergoesmoderate or larger strain amplitudes while the other remainsin the range of small or very small strains
Stiffness of soil in these zones can be very different
Hence there is a strong need to have a relatively simple butpowerful to describe basic phenomenona exhibited by soils
1 densification2 stiffness stress dependency3 plastic yielding4 dilatancy5 strong stiffness variation with growing shear strain amplitude
in the regime of small strains (γ = 10−6 to γ = 10−3)
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Stiffness-strain relation for soils (G/Go (γ))
G - current secant shear modulus
Go - shear modulus for very small strains
Atkinson 1991
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Notion of tangent and secant stiffness moduli
Initial stiffness modulus Eo
Unloading-reloading modulus Eur
Secant stiffness modulus at 50 % of the ultimate deviatoricstress qf
0
50
100
150
200
250
0 0.05 0.1 0.15 0.2 0.25
EPS-1 [-]
q [k
pa] 1
Eo
1E50
1Eur
qf
0.5 qf
σ3=const
q50
qun
Remark: All classical soil models require specification of Eur
modulus (Cam-Clay, Cap etc..)Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
HS model
Double hardening elasto-plastic model (Schanz, Vermeer,Benz)Nonlinear elasticity for stress paths penetrating the interior ofthe elastic domain
0
100
200
300
400
500
600
0 100 200 300 400 500
p [kPa]
q [k
Pa]
Cap surface
Graphical representation of shear mechanism and cap surfaceAndrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Shear/cap yield surfaces in HS model
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Setting initial state variables: γPSo and pco
Given: σo , OCRFind: γPS
o and pco
0
100
200
300
400
500
600
0 100 200 300 400 500
p [kPa]
q [k
Pa]Cap surface
Shear mechanism
σSR
σο
Procedure:
Set effective stress state at the SR pointσSR
y = σyo OCR
σSRx = σSR
z = σy KSRo
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Setting initial state variables: γPSo and pco
Remarks
1 KSRo = KNC
o ≈ 1− sin(φ) in the standard applications(approximate Jaky’s formula)
2 KSRo = 1 for case of isotropic consolidation (used in triaxial
testing for instance)
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: engineering draft
E = 20000√
y kPa for y ≤ 20m
E = 60000√
y kPa for y > 20m
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: FE discretization
Interface wall-soil
Fictitious interface to modelimpermeable barrier
SeepageElements +Fluid head BC
SeepageElementsFluid head BC
x
y
30m 120m
90m
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: Bending moments
-35
-30
-25
-20
-15
-10
-5
0-600 -400 -200 0 200 400
M [kNm/m]
Y [m
[] HSHS-smallMC
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: Wall deflections
-35
-30
-25
-20
-15
-10
-5
0-0.04 -0.03 -0.02 -0.01 0
Ux [m]
Y [m
] HS-smallHSMCMeasurement
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: Deflection after 1-st excavationstep
-35
-30
-25
-20
-15
-10
-5
0-0.005 -0.004 -0.003 -0.002 -0.001 0
Serie1
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: Soil deformation in crosssection x =20m
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
00 0.01 0.02 0.03 0.04
Uy [m]
Y [m
] HSHS-smallMC
Vertical heaving of subsoil at last stage of excavation
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation in Berlin Sand: Settlements behind the wall
-0.02
-0.015
-0.01
-0.005
0
0.005
0.010 20 40 60 80 100 120 140
X [m]
UY
[m] HS
HS-smallMC
Settlements behind the wall at last stage of excavation
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
What could happen during pumping of the water (effect ofdepression curve)
-35
-30
-25
-20
-15
-10
-5
0-0.015 -0.01 -0.005 0 0.005 0.01
Ux [m]
Y [m
] HS-smallHSMC
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
What could happen during pumping of the water (effect ofdepression curve)
-35
-30
-25
-20
-15
-10
-5
0-500 -400 -300 -200 -100 0 100 200 300 400 500
M [kNm/m]
Y [m
[] HSHS-smallMC
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Schweiger’s report: class A predictions for wall deflectionsfrom different modeling groups
H. F. Schweiger. Benchmarking in geotechnics. part i: Results of benchmarking. part ii: Reference solution andparametric study. Technical Report CGG IR006 2002, Institute for Soil Mechanics and Foundation Engineering,Graz University of Technology, Austria, March 2002.
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Deep excavation problem (1) in Warsaw (Poland)
Diapraghm walls L=27m, h=80cm
Piles 10-12m φ = 0.8m
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
HEB profiles+temporary piles
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
3D view of a coarse model
RemarkOption Boreholes was used to map irregular subsoil stratigraphyonto regular continuum mesh
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Temporary piles and piles under 40-story building
A B
C
A B
C
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
S-curve for tertiaray clays: theory vs measurements
Warstwa 11b
0
100000
200000
300000
400000
500000
600000
0.000001 0.00001 0.0001 0.001 0.01 0.1
EPS-1 [-]
E-se
cant
[kPa
]
Pomiar p'=260 kPaPomiar p'=320 kPaZ_SOIL p'=260 kPaZ_SOIL p'=320 kPa
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Settlements (without piles under the 40-story building)
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Settlements (with piles under the 40-story building)
RemarkTemporary piles and piles under the high building are needed alsoto prevent uplifting of the foundation raft at the early stage ofconstruction
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Deep excavation problem (2) in WarsawWykop wykonany do poziomu pWykop wykonany do poziomu płłyty dennej.yty dennej.
RemarkThis analysis was carried out by MSc Agnieszka Gugulska (CracowUniversity of Technology)
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Top view
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
3D model
Stropy rozporowe
Słupytymczasowe
Rozpory stalowe
Podkładki Ściany szczelinowe
GGłłóówne elementy konstrukcyjne podziemnej czwne elementy konstrukcyjne podziemnej częśęści wysokiego budynku. ci wysokiego budynku. Model w programie Model w programie Z_SoilZ_Soil..
Płyta fundamentowa
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
3D model+boreholesModel oModel ośśrodka gruntowego w programie rodka gruntowego w programie Z_SoilZ_Soil..
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Calibrating HS model
Rys. 58- Zestawienie porównywanych krzywych typu S.
Podsumowanie
Z porównania krzywych wynika, że wartością parametru refurE , dzięki której otrzymano
wykres zależności ( )vE ε0 najbliższy rzeczywistemu, jest wartość ][5,31579 kPaE refur = .
3.2. Sprawdzenie poprawności wyznaczonych wartości parametrów dzięki modelowi
testu ściskania trójosiowego w programie Z_Soil.
Sprawdzenie poprawności wyestymowanych wartości parametrów używanych
w modelu HS-small polegało na porównaniu krzywych typu S, otrzymanych dzięki
modelowi testu ściskania trójosiowego wykonanego w programie Z_Soil, z krzywymi
wyznaczonymi przez firmę „Geoteko” na podstawie wyników rzeczywistych badań
ściskania trójosiowego. Test trójosiowy przeprowadzony został na trzech próbkach gruntów
warstwy geotechnicznej IIb w warunkach z odpływem przy wartościach naprężeń 3σ
równych 250, 300 i 400 [kPa]. Zestawienie odpowiednich krzywych wykonano
na rysunku 59.
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation up to level -1
Wykop wykonany do poziomu stropu drugiej kondygnacji podziemnej.Wykop wykonany do poziomu stropu drugiej kondygnacji podziemnej.
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation up to level -2
Wykop wykonany do poziomu stropu trzeciej kondygnacji podziemnejWykop wykonany do poziomu stropu trzeciej kondygnacji podziemnej..
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Excavation up to level -3
Wykop wykonany do poziomu pWykop wykonany do poziomu płłyty dennej.yty dennej.
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Results: bending moments
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Results: Settlements of the ground surface
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Results: Foundation raft settlements
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts
Conclusions
HS is a good model to predict deformations and stressresultants in soil-structure interaction problems, especiallydeep excavations
Calibration procedures are fully documented in the coursenotes
It has been verified for several types of cohesive soils
It includes the effect of small strain stiffness that is of primaryimportance in modeling deep excavations
In the most recent Z Soil upgrade v.9.11 the model wasslightly modified by changing the form of the cap surface
Andrzej Truty ZACE Services Application of HS model to deep excavations and foundation rafts