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Evaluation of undrained response from drained triaxial shear tests: DEM simulations and Experiments

Journal Article


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Abstract


  • The undrained shear response of monotonically loaded isotropically

    consolidated saturated sands can be characterised

    by a change in the excess pore pressure generation in the

    sample. The generation of positive and negative excess pore

    water pressures is related to contractive and dilative responses.

    The increase or decrease in pore water pressure

    continues until it reaches critical state (known as steady state

    for undrained tests). In general, Casagrande’s definition of

    critical state for sands has been utilised in most commonly

    used liquefaction analyses, and is referred to as the steadystate

    procedure (Castro, 1969; Casagrande, 1977; Castro &

    Poulos, 1977; Poulos et al., 1985). In the laboratory, consolidated

    undrained triaxial tests on both reconstituted and

    undisturbed samples are generally carried out to evaluate the

    steady state of sands (Poulos et al., 1985). However, it is

    very clear that steady-state determination from consolidated

    undrained tests with pore pressure measurements is sensitive

    to parameters such as initial effective confining pressure and

    initial fabric (Poulos, 1981; Been & Jefferies, 1985; Been et

    al., 1991; Castro et al., 1992). The most recent findings of

    De Gregorio (1990) indicate that critical state is influenced

    by the method of soil sample preparation (moist tamping,

    moist vibration or dry pluviation). This may be due to the

    volume change tendency caused by the difference in the

    fabric of the sand, which affects the critical-state response.

    Furthermore, such behaviour also depends on the loading

    system equipment’s capability to keep up with the potential

    for sample deformation, an important point with regard to

    potential differences in testing equipment from one laboratory

    to another. In this regard, Norris et al. (1997) developed

    a methodology to predict the undrained shear response of

    sands from drained triaxial tests carried out from isotropic

    rebound paths based on the effective stress concept. This

    method makes it possible for the majority of geotechnical

    firms to participate in the prediction of static liquefaction

    and residual strength by performing traditional drained tests

    with volume change measurements. Furthermore, this method

    also provides the condition and logic for the development

    of complete as against limited liquefaction (Norris et al.,

    1997).

    In the laboratory, drained triaxial shear tests were used to

    predict undrained behaviour using samples consolidated to

    the desired confining pressure and then rebounded to lower

    pressures. However, it is seldom possible in the laboratory to

    consolidate the assemblies along identical paths owing to the

    difficulty of preparing samples with the same initial fabric.

    In this technical note, the method proposed by Norris et

    al. (1997) is revisited using discrete element methods

    (DEM) (Cundall & Strack, 1979), by which means the

    sample preparation problem can be avoided. In addition,

    laboratory experiments on clean sands were carried out to

    validate the numerical simulation results using DEM.

UOW Authors


  •   T G, Sitharam (external author)
  •   Jayan Sylaja, Vinod
  •   B V, RaviShankar (external author)

Publication Date


  • 2008

Citation


  • Sitharam, T., Vinod, J. J S. & Ravishankar, B. (2008). Evaluation of undrained response from drained triaxial shear tests: DEM simulations and Experiments. Geotechnique: international journal of soil mechanics, 58 (7), 605-608.

Scopus Eid


  • 2-s2.0-57849088815

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=7172&context=engpapers&unstamped=1

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/4241

Has Global Citation Frequency


Number Of Pages


  • 3

Start Page


  • 605

End Page


  • 608

Volume


  • 58

Issue


  • 7

Place Of Publication


  • United Kingdom

Abstract


  • The undrained shear response of monotonically loaded isotropically

    consolidated saturated sands can be characterised

    by a change in the excess pore pressure generation in the

    sample. The generation of positive and negative excess pore

    water pressures is related to contractive and dilative responses.

    The increase or decrease in pore water pressure

    continues until it reaches critical state (known as steady state

    for undrained tests). In general, Casagrande’s definition of

    critical state for sands has been utilised in most commonly

    used liquefaction analyses, and is referred to as the steadystate

    procedure (Castro, 1969; Casagrande, 1977; Castro &

    Poulos, 1977; Poulos et al., 1985). In the laboratory, consolidated

    undrained triaxial tests on both reconstituted and

    undisturbed samples are generally carried out to evaluate the

    steady state of sands (Poulos et al., 1985). However, it is

    very clear that steady-state determination from consolidated

    undrained tests with pore pressure measurements is sensitive

    to parameters such as initial effective confining pressure and

    initial fabric (Poulos, 1981; Been & Jefferies, 1985; Been et

    al., 1991; Castro et al., 1992). The most recent findings of

    De Gregorio (1990) indicate that critical state is influenced

    by the method of soil sample preparation (moist tamping,

    moist vibration or dry pluviation). This may be due to the

    volume change tendency caused by the difference in the

    fabric of the sand, which affects the critical-state response.

    Furthermore, such behaviour also depends on the loading

    system equipment’s capability to keep up with the potential

    for sample deformation, an important point with regard to

    potential differences in testing equipment from one laboratory

    to another. In this regard, Norris et al. (1997) developed

    a methodology to predict the undrained shear response of

    sands from drained triaxial tests carried out from isotropic

    rebound paths based on the effective stress concept. This

    method makes it possible for the majority of geotechnical

    firms to participate in the prediction of static liquefaction

    and residual strength by performing traditional drained tests

    with volume change measurements. Furthermore, this method

    also provides the condition and logic for the development

    of complete as against limited liquefaction (Norris et al.,

    1997).

    In the laboratory, drained triaxial shear tests were used to

    predict undrained behaviour using samples consolidated to

    the desired confining pressure and then rebounded to lower

    pressures. However, it is seldom possible in the laboratory to

    consolidate the assemblies along identical paths owing to the

    difficulty of preparing samples with the same initial fabric.

    In this technical note, the method proposed by Norris et

    al. (1997) is revisited using discrete element methods

    (DEM) (Cundall & Strack, 1979), by which means the

    sample preparation problem can be avoided. In addition,

    laboratory experiments on clean sands were carried out to

    validate the numerical simulation results using DEM.

UOW Authors


  •   T G, Sitharam (external author)
  •   Jayan Sylaja, Vinod
  •   B V, RaviShankar (external author)

Publication Date


  • 2008

Citation


  • Sitharam, T., Vinod, J. J S. & Ravishankar, B. (2008). Evaluation of undrained response from drained triaxial shear tests: DEM simulations and Experiments. Geotechnique: international journal of soil mechanics, 58 (7), 605-608.

Scopus Eid


  • 2-s2.0-57849088815

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=7172&context=engpapers&unstamped=1

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/4241

Has Global Citation Frequency


Number Of Pages


  • 3

Start Page


  • 605

End Page


  • 608

Volume


  • 58

Issue


  • 7

Place Of Publication


  • United Kingdom