Volumetric creep deformations

download Volumetric creep deformations

of 25

  • date post

    03-Apr-2018
  • Category

    Documents

  • view

    214
  • download

    0

Embed Size (px)

Transcript of Volumetric creep deformations

  • 7/29/2019 Volumetric creep deformations

    1/25

  • 7/29/2019 Volumetric creep deformations

    2/25

    2

    Contents

    Introduction / Description of the problem

    Effect of creep stress level

    Creep strains

    Laboratorial tests

    Effect of binder quantity

    Conclusions

  • 7/29/2019 Volumetric creep deformations

    3/25

    3

    A14 (IP3) soft soil of Baixo Mondego

    Introduction / Description of the problem

    Creep settlements of an embankment on soft soil (Portugal)

    Geotechnical design:couple stability-settlement analysis incorporating time effects

    Effects of time on the rheological behaviour of soft soils

  • 7/29/2019 Volumetric creep deformations

    4/25

    4

    log

    time

    q C

    q B

    q A

    qC

    > qB

    > qA

    1 3= ' 'q

    Material creep - deformation- irreversible- time dependent

    Creep Model

    Soil creep - sandy soil: rearrangement of soil particles- soft soils: viscosity effects

    Failure

  • 7/29/2019 Volumetric creep deformations

    5/25

    5

    Creep modelation

    Volumetric

    component

    Deviatoric

    component

    Creep Model

    Incorporated into an Elastoplastic Soil Model

    Taylors law

    C Secondary consol. coefficient

    e void ratio

    tv volumetric age

    ( )0/ 2.3

    1

    t ttv t

    v

    Cdt

    e t

    +=

    +, m Singh-Mitchells parameters

    Singh-Mitchells law

    ( )( )ult

    D31

    31

    -

    - =

    deviatoric stress level

    td deviatoric age

    A,

    ( )..m

    t t dt D is

    t d

    tAe dt

    t

    + =

  • 7/29/2019 Volumetric creep deformations

    6/25

    6

    Laboratorial Tests

    Unstabilized soft soil:- identification and characterization- oedometer tests

    Stabilized soft soil with CEM I 42.5R and Slag (75/25):

    - preparation of samples with = 70 and 50 mm- oedometer tests

    Creep volumetric study by oedometer tests

  • 7/29/2019 Volumetric creep deformations

    7/25

    7

    GG wwnatnat satsat ee natnat GranulomGranulom .. PlasticPlasticPlastic . OM. OM Unifined c uu(%) ((%) ( kNkN/m/m 33)) (%) (%)(%) (%) (%)(%) Classific. (kPa)(kPa)

    2.55 80 14.6 2.1 C = 8 - 12 wwLL = 71 7.7 OH of high < 25M = 71 wwPP = 43 plasticity

    S = 17 - 21 IP = 28

    Unstabilized soft soil

    Soft soil deposit of Baixo Mondego (thickness 20m):- geotechnical properties

    - chemical properties

    CaOCaO SiOSiO 22 Al Al22OO 33 FeFe 22OO 33 MgOMgO KK22O pH TOC ECECO pH TOC ECEC(%)(%) (%) (%)(%) (%) (%)(%) (%)(%) (%)(%) ((--) (%) () (%) ( cmolcmol +/kg)+/kg)

    0.74 62.00 16.00 4.80 1.10 3.00 3.5 2.79 11

  • 7/29/2019 Volumetric creep deformations

    8/25

  • 7/29/2019 Volumetric creep deformations

    9/25

    9

    Sample preparation

    Based on EuroSoilStab (2001) with the modificationsproposed by Correia (2011)

  • 7/29/2019 Volumetric creep deformations

    10/25

    10

    Oedometer test

    Curing time = 28 days

    Vertical pressure applied

    during the curing time = 48 kPa( v0 middle of deposit thickness)

    Stress ratio adopted:2 loading4 unloading

    (each stress increment = 24h)

  • 7/29/2019 Volumetric creep deformations

    11/25

    11

    Oedometer test

    Curing time = 28 days

    Vertical pressure applied

    during the curing time = 48 kPa( v0 middle of deposit thickness)

    Stress ratio adopted:2 loading4 unloading

    (each stress increment = 24h)

    Creep stress (14 days):

    (embankment of 4m high, = 22kN/m 3)136 kPa unstabilized

    88 kPa

    Unstabilized

    embankment

  • 7/29/2019 Volumetric creep deformations

    12/25

    12

    Oedometer test

    Curing time = 28 days

    Vertical pressure applied

    during the curing time = 48 kPa( v0 middle of deposit thickness)

    Stress ratio adopted:2 loading4 unloading

    (each stress increment = 24h)

    Creep stress (14 days):

    (embankment 4m high, = 22kN/m 3)136 kPa unstabilized448 kPa stabilized

    (DMC of = 0.8m, spaced 1.5m in

    a square pattern)

    400 kPa

    Stabilized

    embankment

  • 7/29/2019 Volumetric creep deformations

    13/25

    13

    Results

    One-dimensional compression curves

    0,5

    0,7

    0,9

    1,1

    1,3

    1,5

    1,7

    1,9

    2,1

    1 10 100 1000 10000 100000

    'v (kPa)

    e

    UnstabilizedStabilized

    'p =40kPa

    'p = 2500kPa

    (C r = 0,065; C c =0,57)(C r = 0,032; C c =1,00)Stabilized (C r = 0.032 C c = 1.00)

    Unstabilized (C r = 0.065 C c = 0.57)

    y = 40 kPa

    y = 2 500 kPa

    M e t a s t a b l e

  • 7/29/2019 Volumetric creep deformations

    14/25

    14

    Results

    Creep volumetric strains

    Stabilized

    1,4

    1,5

    1,6

    1,7

    1,8

    0 , 0 1

    0 , 1 0

    1 , 0 0

    1 0 , 0 0

    1 0 0 , 0

    0

    1 0 0 0

    , 0 0

    1 0 0

    0 0 , 0 0

    1 0 0 0

    0 0 , 0 0

    time (min)

    e

    UnstabilizedStabilized

    (C =0,023)(C =0,00075)

    Unstabilized

    C = 0.023

    C = 0.00075

    Stabilized

  • 7/29/2019 Volumetric creep deformations

    15/25

    15

    Results : effect of creep stress level(binder quantity = 125kg/m 3)

    One-dimensional compression curves

    0,6

    0,8

    1,0

    1,2

    1,4

    1,6

    1,8

    2,0

    2,2

    1 10 100 1000 10000 100000 'v (kPa)

    e

    Unstabilized

    Stabilized100 kPa

    1,690

    1,695

    1,700

    1,705

    1,710

    1,715

    1,720

    100 1000 10000

    '

    creep = 100 kPa

    creep

  • 7/29/2019 Volumetric creep deformations

    16/25

    16

    One-dimensional compression curves

    0,6

    0,8

    1,0

    1,2

    1,4

    1,6

    1,8

    2,0

    2,2

    1 10 100 1000 10000 100000 'v (kPa)

    e

    Unstabilized

    Stabilized100 kPa248 kPa448 kPa

    1,670

    1,675

    1,680

    1,685

    1,690

    1,695

    1,700

    100 1000 10000

    '

    creep = 448 kPa

    creep

    Results : effect of creep stress level(binder quantity = 125kg/m 3)

  • 7/29/2019 Volumetric creep deformations

    17/25

    17

    One-dimensional compression curves

    0,6

    0,8

    1,0

    1,2

    1,4

    1,6

    1,8

    2,0

    2,2

    1 10 100 1000 10000 100000 'v (kPa)

    e

    Unstabilized

    Stabilized100 kPa248 kPa448 kPa848 kPa

    1248 kPa1648 kPa

    1,650

    1,655

    1,660

    1,665

    1,670

    1,675

    1,680

    100 1000 10000

    '

    creep = 1648 kPa

    creep

    Results : effect of creep stress level(binder quantity = 125kg/m 3)

  • 7/29/2019 Volumetric creep deformations

    18/25

    18

    Creep volumetric strains

    0,000

    0,005

    0,010

    0,015

    0,020

    0,025

    0,030

    0,0350,01 0,1 1 10 100 1000 10000 100000

    Time (min)

    e100 kPa248 kPa448 kPa848 kPa1248 kPa1648 kPaEOP

    C = 0.00075

    C = 0.00102

    C = 0.00160C = 0.00274

    C = 0.00292

    C = 0.00051

    Results : effect of creep stress level(binder quantity = 125kg/m 3)

  • 7/29/2019 Volumetric creep deformations

    19/25

    19

    C = 1.67x10-6 . ' creep + 322.7x10

    -6

    (R = 0.970)

    0

    0,001

    0,002

    0,003

    0,004

    0 250 500 750 1000 1250 1500 1750

    ' creep (kPa)

    C

    Secondary consolidation coefficient vs creep stress

    Results : effect of creep stress level(binder quantity = 125kg/m 3)

    creep < y

  • 7/29/2019 Volumetric creep deformations

    20/25

    20

    Results : effect of binder quantity(creep stress = 448kPa)

    One-dimensional compression curves

    creep

    0,6

    0,8

    1,0

    1,2

    1,4

    1,6

    1,8

    2,0

    2,2

    1 10 100 1000 10000 100000 'v (kPa)

    e

    Unstabilized

    75 kg/m3125 kg/m3Stabilized

    1,610

    1,620

    1,630

    1,640

    1,650

    1,660

    100 1000

    75 kg/m3

    creep

  • 7/29/2019 Volumetric creep deformations

    21/25

    21

    Results : effect of binder quantity(creep stress = 448kPa)

    One-dimensional compression curves

    creep

    0,6

    0,8

    1,0

    1,2

    1,4

    1,6

    1,8

    2,0

    2,2

    1 10 100 1000 10000 100000 'v (kPa)

    e

    Unstabilized

    75 kg/m3100 kg/m3125 kg/m3250 kg/m3400 kg/m3

    Stabilized

    1,300

    1,310

    1,320

    1,330

    1,340

    1,350

    100 1000

    400 kg/m3

    creep

  • 7/29/2019 Volumetric creep deformations

    22/25

    22

    Creep volumetric strains

    0,00

    0,02

    0,04

    0,06

    0,08

    0,10

    0,12

    0,01 0,1 1 10 100 1000 10000 100000

    time (min)

    e

    75 kg/m3100 kg/m3125 kg/m3

    250 kg/m3400 kg/m3EOP

    C = 0.00636

    C = 0.00149C = 0.00102C = 0.00062C = 0.00055

    Results : effect of binder quantity(creep stress = 448kPa)

  • 7/29/2019 Volumetric creep deformations

    23/25

    23

    Secondary consolidation coefficient vs binder quantity

    0

    0,002

    0,004

    0,006

    0,008

    0 100 200 300 400 500

    Binder quantity (kg/m3

    )

    C

    Results : effect of binder quantity(creep stress = 448kPa)

    250

  • 7/29/2019 Volumetric creep deformatio