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MET
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Farimah MASROURI Professor in Geotechnical Engineering
LAEGO : Research Center In Geomechanics & Geoenvironmental Engineering
Nancy – UniversitéFrance
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Paris Nancy ~300 km
Nancy
90 min by TGV
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LAEGO : Research Center In Geomechanics & GeoenvironmentalEngineering
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Research teams
Rock Mechanics
Transfer in Porous media
Soil Mechanics
Systems & Risks
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Hydro-mechanical, Physical & Numerical Modelingof Soil Behavior
• Soil : Saturated, Unsaturated, Swelling or Rigid, Natural or Remolded -Treated
• Coupling : Hydraulic – Mechanical - Thermal & Chemical
• Multiscale : Lab (micro- et macroscopique ), in situ
• Aging & Time effects
Geotechnical EngineeringGeoenvironmental EngineeringConstruction Safety
Applications :
Soil Mechanics
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Swelling and shrinkage of unsaturated claysSwelling and shrinkage of unsaturated clays
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• When wetted, swelling soils can apply very high uplift pressures which can damage lightly-loaded structures.
• Expansive soils pose the greatest hazard in arid regions, which are much more susceptible to damage from expansive soils, than regions that maintain moist soil conditions throughout the year.
Expansive Clayey Soils
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2007
Small building in SenegalIndividual house in Tunisia
Arid Regions Swelling
Expansive soils damage foundations by uplift as the soils swell with moisture increases
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Buildings in Dakar - Senegal
Arid Regions Swelling
Expansive soils damage foundations by uplift as the soils swell with moisture increases
Photo : P. Berthelot2007
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Buildings in Dakar - Senegal
Arid Regions Swelling
Expansive soils damage foundations by uplift as the soils swell with moisture increases
Photos : P. Berthelot2007
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• Insurance companies pay out millions of euros yearly, to repair homes distressed by expansive soils (4,3 billions of euros between 1989 and 2006 ))
Global warming very long drought periods (1989-92, 1996-97, 2003, 2006,…) there are significant damages to foundations of light buildings
Shrinkage of clayey soils is considered as a natural hazard
France Shrinkage
Photos : R. Fabre2007
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• Surface evaporation and tree roots Differential water content
France Shrinkage
Photos : BRGM
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Influence of several wetting-drying cycles on the hydro-mechanical behaviour of clay soils
Analysis and modelling of drought propagation in the soil
11
22
ExamplesExamples ::
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Compacted swelling soil
Chou et Mou (1973)
Swellingaccumulation
Equilibrium stage
Alonso et al. (2005)
Mixture of bentonite/sand (80/20)
Shrinkageaccumilation
Equilibrium stage
Influence of several suction cycles on theHydro-mechanical behaviour of the swelling soils
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Mixture of two materials: 60% of bentonite + 40% of silt.
Characterisation of the tested materials (1/2)
2.672.632.71Specific Gravity (Gs)
14 -15--Shrinkage Limit(%)
22305Plasticity Index(%)
658137Plasticity Limit (%)
8711142Liquid Limit (%)
MixtureBentoniteSiltPhysical Property
Influence of several suction cycles on theHydro-mechanical behaviour of the swelling soils
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Initial states of the samples
12.7Dry unit weight (kN/m3)
1000
20 ± 2
37
70
10
15 ± 0.3
Loose samples
Height (mm)
Diameter (mm)
Parameters
Suction (MPa)
Compaction pressure (kPa)
Degree of saturation (%)
Water content (%)
Characterisation of the tested materials (2/2)
3000
20 ± 2
15.5
37
70
10
15 ± 0.3
Dense samples
11Influence of several suction cycles on theHydro-mechanical behaviour of the swelling soils
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Vertical net stress (kPa)
Suc
tion
(MP
a)
Followed stress paths
B8
A20
10
C
15
D
30
E
60F G H
0.01
3 cycles
11Influence of several suction cycles on theHydro-mechanical behaviour of the swelling soils
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11
Kassif & Ben Shalom (1971), Delage et al. (1992)
Suction Controlled Osmotic oedometer (0 to 8 MPa)
Influence of several suction cycles on theHydro-mechanical behaviour of the swelling soils
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0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0.01 0.1 1 10 100
Suction (MPa)
Void
ratio
(-)
Applied vertical stress=30 kPa, initial density=1.27 Mg/m3
Applied vertical stress=30 kPa, initial dry density=1.57 Mg/m3
L2 (initial density=1.27 Mg/m3)D2 (initial density=1.55 Mg/m3)
Applied vertical stress=30 kPa
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0.01 0.1 1 10 100
Suction (MPa)
Void
ratio
(-)
Applied vertical stress=15 kPa, initial density=1.27 Mg/m3
Applied vertical stress=15 kPa, initial dry density=1.57 Mg/m3L1 (initial density=1.27 Mg/m3)D1 (initial density=1.55 Mg/m3)
Applied vertical stress=15 kPa
15 kPa
Swelling accumulationDense sample
Loose sample
Shrinkage accumulation
30 kPaLoose sample
Shrinkage accumulation
Dense sample Swelling accumulation
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0.01 0.1 1 10 100
Suction (MPa)
Void
ratio
(-)
Applied vertical stress=60 kPa, initial density=1.27 Mg/m3Applied vertical stress=60 kPa, initial dry density=1.57 Mg/m3
L3 (initial density=1.27 Mg/m3)D3 (initial density=1.55 Mg/m3)
Applied vertical stress=60 kPaLoose sample
Shrinkage accumulation
Dense sample Swelling accumulation
Void ratio - Suction
60 kPa
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LAEGO LAEGO –– H. H. NowamoozNowamooz
Influence of several suction cycles on theHydro-mechanical behaviour of the swelling soils
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1. For the swelling soils submitted to several wetting and drying cycles, the factors influencing the volumetric deformation are :• the preconsolidation stress ;• the initial density and the water content.
2. After several suction cycles, an elastic state can be reached;
3. Intensity of the applied charge influences the necessary number of suction cycles to reach the equilibrium point.
Remarks 11
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– Fine graded soils Cam Clay
– Unsaturated soils BBM (Barcelona Basic Model)
– Swelling soils BExM (B. Expansive Model)Gens & Alonso (1992);
Alonso et al. (1999, 2005) : BExM
Hydro-mechanical behaviour of expansive soils22
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0,25em0,011κm
Micro / macro-structural coupling functions
Microstructural soil parameters
0,844 MPa30 MPa14 MPa
0,091,24
p0*
s0shkM
0,020,3150,2777
8,054×10-3 MPa-1
0,0150,609 MPa
κλ(0)rβκspc
f = 1×10-3 + 2×10-2 (1 - p* /p0)0,1fI = 0,5 + 9,9 (p* /p0 )1
Macro-structure soil parameters
0.25em0.011κm
0.844 MPa30 MPa14 MPa
0.091.24
p0*
s0shkM
0.020.3150.2777
8.054×10-3 MPa-1
0.0150.609 MPa
κλ(0)rβκspc
fD= 1×10-3 + 2×10-2 (1 - p* /p0)0,1fI = 0.5 + 9.9 (p* /p0 )1
Soil parameters (BExM)
Porosity n0= 0.385 Density ρs = 2.7 Mg/m3 Permeability k s = 1.66 10-6 m/s
Van Genuchten parameters : α = 27 MPa-1 ; m = 0.316 ; Sres = 0.2338
Hydro-mechanical behaviour of the swelling soilsunder shallow foundations
M. Mrad - H. Nowamooz - Laego
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– Objectives• Effect of wetting /drying (rain/drought) on the settlements of a
shallow foundation• Effect of a geo-membrane layer
Swelling soil
Rigid soil
Hydro-mechanical behaviour of the swelling soilsunder shallow foundations
M. Mrad - H. Nowamooz - Laego
backfill
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22
Propagation of Sr Without geo-membrane
Propagation of Sr With geo-membrane
Swelling soil
Rigid soil Soil deformations
Hydro-mechanical behaviour of the swelling soilsunder shallow foundations
M. Mrad - H. Nowamooz - Laego
Sr Propagation and soil strains
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Application to mine tailings :
Swelling pressure of treated tailingsHydraulic conductivity in Mine waste disposals…
Hydro-mechanical behaviour of the swelling soils
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Some of our recent papers in this field NOWAMOOZ H. & MASROURI F. “Relationships between soil fabric and suction cycles in compacted swelling soils“.International Journal of Engineering Geology – 2010 - 114 (3-4), pp. 444-455
NOWAMOOZ H. & MASROURI F. “Volumetric strains due to changes in suction or stress of an expansive bentonite/silt mixture treated with lime“. Comptes Rendus – Mecanique – 2010 – 338 (4), pp. 230-240.
NOWAMOOZ H. & MASROURI F. “Density-dependent hydromechanical behaviour of a compacted expansive soil”. International Journal of Engineering Geology. 2009. 106 (3-4), pp. 105-115
NOWAMOOZ H., MRAD M., ABDALLAH A, & MASROURI F. “Experimental and numerical studies of the hydromechanical behaviour of a natural unsaturated swelling soil”. Canadian Geotechnical Journal. 2009. 46 (4), pp. 393-410
NOWAMOOZ H. & MASROURI F. “Hydromechanical behaviour of an expansive bentonite/silt mixture in cyclic suction-controlled drying and wetting tests“. International Journal of Engineering Geology. 2008. 101 (3-4), pp. 154-164
MASROURI F., BICALHO K. & KAWAI K. “Laboratory hydraulic testing in unsaturated soils“. Geotechnical and Geological Engineering. 2008. Vol 26, 691-704.
DEVINEAU K., BIHANNIC I., MICHOT L., VILLIERAS F., MASROURI F., CUISINIER O., FRAGNETO G. & MICHAU N. "In situ neutron diffraction analysis of the influence of geometric confinement on crystalline swelling of montmorillonite". Applied Clay Science. Volume 31, Issues 1-2. 2006. 76-84. (ISSN : 0169-1317)
CUISINIER O. & MASROURI F. "Influence of complex hydromechanical loadings on the behaviour of a compacted expansive soil". Canadian Geotechnical Journal. Vol. 42. n° 3. 2005. 731-741. (ISSN 1208-6010)
CUISINIER O. & MASROURI F. "Hydromechanical behaviour of a compacted swelling soil over a wide suction range". International Journal of Engineering Geology. 2005. Vol. 81. n° 3 204-212. (ISSN : 0013-7952)
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