Comparison and combined use of two sands constitutive models

 

Many studies have been and are being carried out on the stress-strain relationships in cohesionless soils. These

studies have produced various constitutive models: arnong these, the elastic non linear hyperbolic model and the elastoeplastie model with curved yield surface.

These two models, although so ditlerent in concept, can, however, he considered in part complementary. In the First, a simple constitutive equation permits the representation of the experimental total stress-strain diagram for drained triaxial

 

Many studies have been and are being carried out on the stress-strain relationships in cohesionless soils. These

studies have produced various constitutive models: arnong these, the elastic non linear hyperbolic model and the elastoeplastie model with curved yield surface.

These two models, although so ditlerent in concept, can, however, he considered in part complementary. In the First, a simple constitutive equation permits the representation of the experimental total stress-strain diagram for drained triaxial

tests in a range of dcviatoric stresses between 70 and 95% of failure. The second model, which analyses the components

of elastic and plastic strains in detail, is capable of describing complex load processes even after failure by using an

incremental analysis.

The parameters which must be evaluated for the application of Lade's model are subject to gross errors which it is hard

to check. This comes about because they result from a complex numerical processing of experimental data of diiferent

levels of accuracy.

It's possible to get over such ditliculty utilizing as input data not experimental values, directly measured, but values

from a simple elastic non linear stress-total strain relationship (litter model).

Thus the hyperbolic model is used in this paper as a lilter for the experimental data to which Lade's elasto—plastic model

will be applied. The criterion followed consists in making a comparison between two constitutive models of different

types and with different characteristics, and examining the theoretical consequences which arise from having filtered the

experimental data with one model before processing and using them for the calculation of the coefhcients of the other.

The result of such an operation is a serie of equations which permit the theoretical calculation of the components of strain

and of the parameters.

The calculated values that [all within the Hlter models most reliable range, agree very closely with the direct experimental

values and also with the empirical relations proposed by Lade,

In the range in which the filter model is less representative, where a direct comparison is possible there is

agreement between experimental and theoretical values; where, on the contrary, a direct comparison is impossible hccause

of the lack of reliable experimental values, asymptotic patterns are attained which, although cannot be exluded a

priori, require deeper critical attention.


  Many stu …


AUTORI: Vannucchi G.
RIG ANNO:1982 NUMERO:1
Numero di pagine: 7


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