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Underground Expansion of Drents Museum
The use of PLAXIS in pre- and postdiction analyses
PLAXIS PDC meeting
February 15, 2013
Marco Peters
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Contents
Project description
Soil investigation
Excavation methodsExcavation methods
Retaining wall types
PLAXIS prediction analysis
PLAXIS postdiction analysis
Why prediction analysis?
– To predict the displacements of the monumental buildings during excavations
– To determine design and phasing in order to respect the displacement requirements
Why postdiction analysis?
– To verify the design principles and assumptions
– To control and/or reduce risks and to optimise where possible

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Project description
Located in historical rich part of Assen
Museum exists of several monumental buildings
Situation 2009
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Project description
Expansion necessary due to growing number of visitors
Preserving the monumental view and park
Expansion underground: one large exposition hall on southern sideExpansion underground: one large exposition hall on southern side
Location: under former parking place and under the Coach House
Area: 2,500 m²

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Project description
Underground connection to main building (Bailiff’s House)
Indoor excavation
Exposition hall under monumental Coach House
Temporally relocation of the Coach House
Original crack of course…Original crack of course…Original crack of course…Original crack of course…
(also gas extraction??)(also gas extraction??)(also gas extraction??)(also gas extraction??)
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Soil Investigation
Field tests:
– 31 CPT’s + friction and piezo cone (20 à 30 m)
– 4 machinal bore holes (11 à 15 m)
Indoor excavationIndoor excavation
Bailiff’s HouseBailiff’s House
– 4 machinal bore holes (11 à 15 m)
– 8 piezo meters (tubes in bore holes)
Laboratory tests:
– 12 volume weight + water contents
– 12 classifications
– 8 CU-TA triaxial tests + unload reload steps
Original locationOriginal location
Coach HouseCoach House

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Soil Investigation
Soil type (DKM 23)
Top
[m+NAP]
Sand, moderate, slightly clayey +10.0Sand, moderate, slightly clayey +10.0
Boulder Clay (Keileem) +8.5
Sand, loose/moderate +7.2
Sand, dense with gravel +5.0
Pot Clay +1.5
Sand, moderate -1.5
Pot Clay -5.5
Sand, dense with gravel -9.5
UndergroundUndergroundUndergroundUnderground
obstacles?obstacles?obstacles?obstacles?
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Soil Investigation
Schematised geotechnical profile

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Soil Investigation
γ γ φ
Characteristic soil parameters (Hardening Soil, drained)
Soil type γ
[kN/m3]
γsat
[kN/m3]
c’
[kPa]
φ’
[ o ]
E50
ref
[MPa]
Eur
ref
[MPa]
m
[ - ]
OCR
[ - ]
water head
[m+NAP]
Sand, slightly clayey 17 19 0 30 40 160 0.5 - +9.8
Boulder Clay (Keileem) 20.4 20.4 0 27.3 8.1 45.8 0.8 1.0 +9.8
Sand, moderate 18 20 0 32.5 45 180 0.5 - +9.8
Sand, dense with gravel 19 21 0 35 100 400 0.5 - +9.8
Pot Clay 18.1 18.1 9.8 17.0 9.8 25.3 0.8 2.5 +9.3
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Excavation methods
Two compartments:
– Excavation A: Exposition Hall and Coach House (outside)
– Excavation B: Underground entrance Bailiff’s House (inside)– Excavation B: Underground entrance Bailiff’s House (inside)

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Excavation methods
Excavation A (outside):
– Polder principle by using Pot Clay layers as water resisting layers
– In situ concrete floor (dry) with anchor piles (final situation)– In situ concrete floor (dry) with anchor piles (final situation)
– Deep sheet piles to reach the deeper continuous Pot Clay layer (passing sand/gravel)
– Low vibration soil mix wall near museum
– Strict deformation requiries existing foundations
– Horizontal support (struts) on two levels
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Excavation methods
Excavation B (inside):
– Underwater concrete floor with anchor piles
– Retaining walls: jet grout walls under foundation
– Strict deformation requiries existing foundations
– Horizontal support by anchoring above groundwater level

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Retaining wall types
Excavation A (outside, away from buildings):
Steel sheet piles:Steel sheet piles:
– AZ25, tip level on NAP -6.5 m
– Vibration test with different installation methods, according to SBR-A
– Chosen method: installing sheet piles after pre-drilling
– Minimum distance of museum buildings: 30 m
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Retaining wall types
Excavation A (outside, near buildings):
Soil mix wall:Soil mix wall:
– 550 mm thick, tip level on NAP -5.0 m
– HEB 320-profiles, spacing a = 1.0 m
– Strip dimensions depending on maximum allowed foundation deformations
– Section width ≈ 2.2 m
– Spacing between two fresh strips ≈ 1.8 m (overcut = (2.2 – 1.8)/2 = 0.2 m)
a = 1.0 m
A = 1.0 -0.3 = 0.7 m
d = 0.55 md = 0.55 m
D = 0.4 m
a a

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Retaining wall types
Excavation B (inside):
Jet grout wall:Jet grout wall:
– Wall thickness 1000 - 1500 mm thick, tip level on NAP -1.7 m
– Two rows of columns in triangular mesh of 0.6 – 0.7 m
– Grout diameter = 900 mm
– Overcut = 0.2 – 0.3 m
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PLAXIS prediction analysis
Excavation A - sheet pile wall: design ULS + SLS only with D-Sheet Piling
Excavation A - soil mix wall: design ULS with D-Sheet Piling, SLS with PLAXIS 2D
Excavation B – jet grout wall: design ULS with D-Sheet Piling, SLS with PLAXIS 2DExcavation B – jet grout wall: design ULS with D-Sheet Piling, SLS with PLAXIS 2D

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PLAXIS prediction analysis
Modelling soil mix wall for deformation analysis (SLS):
– Linear Elastic model
– model width: 0.6 m (real width: 0.55 m)– model width: 0.6 m (real width: 0.55 m)
– during casting: estimated stiffness for 2D-prediction: Efresh ≈ 5 to 10·103 kPa, Rint = low
– after hardening: E = ELE, Rint = 0.95
– uncracked situation (not used here):
– soil mix: Emix = 5.0·106 kPa, I = 0.553/12, EImix = 6.93·103 kNm2/m
– steel profile HEB320 (spacing 1.0 m): EIs = 6.93·103 kNm2/m
– PLAXIS: ELE = (EImix + EIs) / (0,63/12) = 7.45·106 kPa
– cracked situation:
– soil mix: Emix = 0 kNm2/m
– steel profile HEB320 (spacing 1.0 m):– steel profile HEB320 (spacing 1.0 m):
EIs = 6.93·103 kNm2/m
– PLAXIS: ELE = (0 + EIs) / (0.63/12) = 3.60·106 kPa
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PLAXIS prediction analysis
Modelling struts:
– modelled as elastoplastic anchors
– first level NAP +11.9 m (top H-profiles above greenfield):– first level NAP +11.9 m (top H-profiles above greenfield):
– EA = 2.1·106 kPa
– spacing = 1.0 m
– Np = 500 kN
– second level NAP +8,3 m:
– EA = 2.1·106 kPa
– spacing = 1.0 m
– Np = 1000 kN
Modelling anchor piles:
– from floor to sand layer (NAP -12.0 m): Ischebec Ø 88.9 x 7.1 mm– from floor to sand layer (NAP -12.0 m): Ischebec Ø 88.9 x 7.1 mm
– elastoplastic node-to-node anchor, EA = 416·103 kN
– Np = 548 kN, spacing: 3.0 x 3.0 m
– from NAP -12.0 to tip NAP -17.0 m: grout
– elastoplastic geogrid, EA = 139·103 kN/m
– Np = 183 kN/m, spacing: 3.0 m

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PLAXIS prediction analysis
(1004)(1005) (1004)(1005)
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PLAXIS prediction analysis
Prediction results vertical displacement foundation near soil mix wall
(1004)(1005)

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PLAXIS prediction analysis
Excavation A - sheet pile wall: design ULS + SLS only with D-Sheet Piling
Excavation A - soil mix wall: design ULS with D-Sheet Piling, SLS with PLAXIS 2D
Excavation B – jet grout wall: design ULS with D-Sheet Piling, SLS with PLAXIS 2DExcavation B – jet grout wall: design ULS with D-Sheet Piling, SLS with PLAXIS 2D
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PLAXIS prediction analysis
Modelling jet grout wall for deformation analysis (SLS):
– Mohr Coulomb model
– grout wall width: 1.0 – 1.5 m (average: 1.30 m– grout wall width: 1.0 – 1.5 m (average: 1.30 m
– ultimate compressive strength (UCS = fc) soil dependent (Van der Stoel (2001)):
2,0≈ν
– used Mohr Coulomb model soil parameters for jet grout wall:
Soil type
UCS fc;min
[MPa]
UCS fc;max
[MPa]
Clay 2 - 3 7
Silt 5 15
Sand 10 40
Gravel 10 40
cfàc ⋅≈ 3,02,0'
0
50' àsoil +≈ϕϕ
5,0
;50 800 csand fE ⋅≈
67,0
;50 500 cclay fE ⋅≈
Soil type
fc;av
[MPa]
γsat
[kN/m3]
c’
[kPa]
φ’
[ o ]
E50
[MPa]
Sand, slightly clayey 10 20 2000 35 2530
Boulder Clay (Keileem) 5 20 1000 30 1470
Sand, dense with gravel 15 20 3000 35 3098
Pot Clay 3 18 600 25 1044

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PLAXIS prediction analysis
Modelling anchors:
– anchor (north+east) NAP +9.0 m (lsteel ≈ 6 m): Ischebec Ø 30 x 11 mm
– elastoplastic node-to-node anchor, EA = 95·103 kN– elastoplastic node-to-node anchor, EA = 95·10 kN
– Np = 260 kN, spacing: 1,4 m
– anchor (west) NAP +9.8 m (lsteel ≈ 7 m): Ischebec Ø 40 x 20 mm
– elastoplastic node-to-node anchor, EA = 150·103 kN
– Np = 425 kN, spacing: 1,4 m
– grout (lgrout ≈ 5 m): Ø 120 mm
– elastoplastic geogrid, EA = 68·103 kN/m
– Np = 150 kN/m, spacing: 1.4 m
Modelling anchor piles:
– from floor to sand layer (NAP -12.0 m): Ischebec Ø 88.9 x 7.1 mm– from floor to sand layer (NAP -12.0 m): Ischebec Ø 88.9 x 7.1 mm
– elastoplastic node-to-node anchor, EA = 416·103 kN
– Np = 548 kN, spacing: 2.2 x 2.2 m
– from NAP -12.0 to tip NAP -17.0 m: grout
– elastoplastic geogrid, EA = 190·103 kN/m
– Np = 250 kN/m, spacing: 2.2 m
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PLAXIS prediction analysis
(1005) (1005)

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PLAXIS prediction analysis
Prediction results vertical displacement foundation at jet grout wall
(1004)
(1005)
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PLAXIS prediction analysis
Monitoring results soil mix wall + jet grout wall
– Measured vertical displacements
– Reference measurements: August 2009– Reference measurements: August 2009
– Last measurements: October 2010
Time Stages soil mix wall
(excavation A)
Stages jet grout wall
(excavation B)
excavation A/B
[m+NAP]
water in pit A/B
[m+NAP]
uv;1004
[mm]
uv;1005
[mm]
Aug 2009 0. Reference 0. Reference +11.5 / +11.3 +9.3 / +9.3 0 0
Sept 2009 1. Installation wall +11.5 / +11.3 +9.3 / +9.3 - -
Dec 2009 2. Struts 1 +9.5 / +11.3 +9.3 / +9.3 -9 -5
(Dec 11th) +9.5 / +11.3 +9.3 / +9.3 -10 -6
(Dec 15th) +9.5 / +11.3 +9.3 / +9.3 -9 -6
(Dec 17th) +9.5 / +11.3 +9.3 / +9.3 -9 -5
Mar 2010 1. Installation wall +6.5 / +11.3 +9.3 / +9.3 - -
Apr 2010 4. Excavation max. (dry) +5.0 / +11.3 +4.7 / +9.3 -9 -4
May 2010 5. Anchor piles +5.0 / +11.3 +4.7 / +9.3 -10 -5
Jun 2010 6. Concrete floor +5.4 / +11.3 +4.7 / +9.3 - -
Aug 2010 2. Excavation max. (wet) +5.4 / +4.2 +4.7 / +9.3 - -
Oct 2010 7. Anchored floor +5.4 / +4.2 +4.7 / +9.3 -9 -5
Nov 2010 3. Anchor piles + OWB +5.4 / +5.0 +4.7 / +8.8 - -
Dec 2010 4. Anchors 1+2 +5.4 / +5.0 +4.7 / +8.8 - -
Jan 2011 8. Water loading floor 5. Dewatering pit +5.4 / +5.0 +5.0 / +4.2 - -

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PLAXIS prediction analysis
Interaction settlement and heave of both excavations A + B
Σ u = a · u + b · uΣ uy;1004 = a · uy;1004;excavation A + b · uy;1004;excavation B
Σ uy;1005 = c · uy;1005;excavation A + d · uy;1005;excavation B
where:
a = influence excavation A (soil mix wall) on settlement 1004
b = influence excavation B (jet grout wall) on settlement 1004
c = influence excavation A (soil mix wall) on settlement 1005
d = influence excavation B (jet grout wall) on settlement 1005
As a consequence of the 3D-situation:As a consequence of the 3D-situation:
– a = 1 (direct impact)
– b = 0 - 0.5 (impact is limited due to stiffer corner with three walls)
– c = 1 (direct impact)
– d = 0.5 - 1 (impact could be reduced due to limited pit dimensions in 3D)
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PLAXIS prediction analysis
Superposition prediction results from both excavations

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PLAXIS prediction analysis
Conclusions prediction analyses:
– both measured and predicted displacements do not exceed the maximum allowable
displacement limit of 10 mm (or rotation of 1 : 500);displacement limit of 10 mm (or rotation of 1 : 500);
– measured settlement during casting of fresh soil mix wall is higher than predicted,
settlement can be fitted in postdiction by changing stiffness of fresh soil mix;
– in excavation A, settlement is dominant and in excavation B, heave (or swell) is
dominated;
– in both excavations, vertical displacements at the foundations are dominating the
horizontal displacements;
– because of 3D-situation, there is an interaction between settlements from both
excavations (superposition of settlements and heave);
– the superposition of the two 2D-sections should be verified by 3D-modeling;– the superposition of the two 2D-sections should be verified by 3D-modeling;
– calculated heave or swell is rather high, postdiction with HS-small strain model might lead
to better approach.
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PLAXIS postdiction analysis
Postdiction 1: 2D-analysis to fit Efresh for soil mix wall
Postdiction 2: 3D-Tunnel analysis to verify the superposition of the two 2D-planes
Postdiction 3: 2D-analysis with Hardening Soil small strain modelPostdiction 3: 2D-analysis with Hardening Soil small strain model
Postdiction 4: 3D-analysis with Hardening Soil small strain in 2012

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PLAXIS postdiction analysis #1
Adapting (fresh) soil mix wall for deformation analysis (SLS):
– Linear Elastic model
– model width: 0.6 m (real width: 0.55 m)– model width: 0.6 m (real width: 0.55 m)
– during casting: estimated stiffness for 2D-prediction: Efresh ≈ 5 to 10·103 kPa (av.: 7.5 MPa)
– low value Rint = 0.2 (comparing to Rint;final = 0,95)
– sensitivity analysis Efresh to fit measured settlement 1004: Efresh = 4·103 kPa with Rint = 0.2
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PLAXIS postdiction analysis #1
(1004)(1005) (1004)(1005)

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PLAXIS postdiction analysis #1
Superposition postdiction results from both excavations
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PLAXIS postdiction analysis #2
Postdiction 1: 2D-analysis to fit Efresh for soil mix wall
Postdiction 2: 3D-Tunnel analysis to verify the superposition of the two 2D-planes
Postdiction 3: 2D-analysis with Hardening Soil small strain modelPostdiction 3: 2D-analysis with Hardening Soil small strain model
Postdiction 4: 3D-analysis with Hardening Soil small strain in 2012

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PLAXIS postdiction analysis #2
Modelling in 3D-Tunnel (2010):
– verifying superposition of both excavations
– calculation only with Hardening Soil (HS-small strain was not available yet)– calculation only with Hardening Soil (HS-small strain was not available yet)
– excavations only rectangular
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PLAXIS postdiction analysis #2
Vertical displacements on surface level (foundation settlement)
Installation soil mix wall Maximum excavation A (dry) Dewatering excavation BInstallation soil mix wall Maximum excavation A (dry) Dewatering excavation B

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PLAXIS postdiction analysis #2
Calculation results from 3D-Tunnel:
– calculated settlement from excavation A correspond well with measured displacements
– significant influence of heave/swell from excavation B on both calculation points
-0,010
-5,e-3
0,000
Uy [m]
Vertical displacement 3DT
Point 1004
Point 1005
– significant influence of heave/swell from excavation B on both calculation points
– influence of swell on settlement front wall museum overestimated
0 20 40 60 80 100
-0,020
-0,015
Step
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PLAXIS postdiction analysis #3
Postdiction 1: 2D-analysis to fit Efresh for soil mix wall
Postdiction 2: 3D-Tunnel analysis to verify the superposition of the two 2D-planes
Postdiction 3: 2D-analysis with Hardening Soil small strain modelPostdiction 3: 2D-analysis with Hardening Soil small strain model
Postdiction 4: 3D-analysis with Hardening Soil small strain in 2012

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PLAXIS postdiction analysis #3
Adapted parameters soil layers under excavation (Hardening Soil small strain):
– γ0,7 = 1·10-4
– G ref ≈ (1 to 4) · E ref
Soil type
E50
ref
[MPa]
Eur
ref
[MPa]
m
[ - ]
G0
ref
[MPa]
γ0,7
[ - ]
Sand, slightly clayey 40 160 0.5 - -
Boulder Clay (Keileem) 8.1 45.8 0.8 137 1·10-4
Sand, moderate 45 180 0.5 56 1·10-4
– G0
ref ≈ (1 to 4) · Eur
ref
– Assumed stiffnesses:
– sand: G0
ref ≈ 1.25 · Eur
ref
– clay: G0
ref ≈ 3 · Eur
ref
Sand, dense with gravel 100 400 0.5 500 1·10-4
Pot Clay 9.8 25.3 0.8 76 1·10-4
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PLAXIS postdiction analysis #3
(1004)(1005) (1004)(1005)

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PLAXIS postdiction analysis #3
(1005) (1005)
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PLAXIS postdiction analysis #3
Superposition postdiction results from both excavations

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PLAXIS postdiction analysis #4
Postdiction 1: 2D-analysis to fit Efresh for soil mix wall
Postdiction 2: 3D Tunnel-analysis to verify the superposition of the two 2D-planes
Postdiction 3: 2D-analysis with Hardening Soil small strain modelPostdiction 3: 2D-analysis with Hardening Soil small strain model
Postdiction 4: 3D-analysis with Hardening Soil small strain in 3D-2012
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PLAXIS postdiction analysis #4
Modelling in 3D-2012:
– verifying superposition of both excavations (comparing to 3DT)
– checking the vertical displacement for the whole foundation– checking the vertical displacement for the whole foundation
– calculation with HS-small strain

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PLAXIS postdiction analysis #4
Vertical displacements on surface level (foundation settlement)
Installation soil mix wall Maximum excavation A (dry)Installation soil mix wall Maximum excavation A (dry)

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PLAXIS postdiction analysis #4
Vertical displacements on surface level (foundation settlement)
Dewatering excavation B Freatic water under concrete floor excavation ADewatering excavation B Freatic water under concrete floor excavation A
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PLAXIS postdiction analysis #4
Calculation results from 3D-2012:
– calculated settlement from excavations correspond well with measured displacements
– swell is reduced by 20 to 30%, but is still slightly overestimated comparing with measured– swell is reduced by 20 to 30%, but is still slightly overestimated comparing with measured
displacements (about 25% more settlements at point 1004)
correction reference = 1,5 mm

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Conclusions PLAXIS pre- and postdictions
Conclusions 2D-and 3D-analyses:
– Both measured and predicted displacements do not exceed the maximum allowable
displacement limit of 10 mm (or relative rotation of 1 : 500).
– Effect of fresh soil mix dominates the settlement, a realistic (average) stiffness is essential– Effect of fresh soil mix dominates the settlement, a realistic (average) stiffness is essential
to make a proper prediction.
– Verification superposition of two 2D-plane strain with 3D-analyses is satisfactory.
– Modelling with HS-small leads to better approach, especially for the effect of excavation B.
– Assumed values for G0
ref seem to be proper values (after some sensitivity analyses).
– With HS-small strain model, maximum heave or swell is reduced by 20 à 30%.
– Swell is slightly overestimated (but other effects might have led to measured settlement).
Recommendations:
– Installation of soil mix walls might lead to small but significant displacements.– Installation of soil mix walls might lead to small but significant displacements.
– To define Go from CU-tests more punctually, smaller strains have to be investigated.
– Further analysis of swell in general is recommended.
(special attention to undrained and consolidation behaviour might be useful during the different stages,
especially to make distinction to different swell mechanisms - initial volume-constant and elastic swell,
primary swell with degree of consolidation, secondary swell etc. - this is one of the investigation topics of
CUR committee C202).
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Project team
Client: Provincie Drenthe
Project developer: Draaijer & Partners
Main contractor: Geveke Bouw BV (TBI)Main contractor: Geveke Bouw BV (TBI)
Structural design: IB Wassenaar BV
Geotechnical design & consult: Grontmij Nederland BV
Contractor underground constructions: Franki Foundations Group (Besix)
Soil investigation: Grontmij Terreinonderzoek & IJB Geotechniek BV
Laboratory investigation: Fugro Materiaalkundig Laboratorium
Sheet pile vibration analysis: Sterk Heiwerken
Monitoring: Mug Ingenieursbureau BV
Architect: Erick van Egeraat (DbEVE)

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For further questions, please contact:
Marco Peters
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Marco Peters
T +31 30 220 76 13
E marco.peters@grontmij.nl