2881
Creep and long-term bearing capacity of a long pile in clay
Fluage et capacité portante à long terme d’un long pieu dans de l’argile
Ter-Martirosyan Z.G., Ter-Martirosyan A.Z., Sidorov V.V.
Moscow State University of Civil Engineering, Moscow,Russia
ABSTRACT: A rheological equation is proposed to describe shear deformations in party saturated hardening-softening clay soil,
based on modification of Maxwell rheological model. It is shown that the proposed equation describes creep, relaxation and kinematic
shear with identical parameters, including decaying, stable and progressive creep, depending on shear stress intensity.
RÉSUMÉ : Une équation rhéologique est proposée pour décrire les distorsions au sein d’une argile partiellement saturée, avec
durcissement et radoucissement, basée sur une modification du modèle rhéologique de Maxwell. Il est montré que l'équation proposée
décrit le fluage, la relaxation et le cisaillement cinématique avec des paramètres identiques, y compris la diminution stable et
progressive du fluage, en fonction de l'intensité de la contrainte de cisaillement.
KEYWORDS:long-time bearing capacity, hardening, softening, kinematic shear,stress relaxation, progressive creep.
1 INTRODUCTION
1.1
Investigation of clay soils in shear [1…16] shows that
rheological curves can be summarized for static loading
(
const
) as creep curves (Fig.1, а); for kinematic
loading (
const
,
const
1
) as curves
,(
)(
t
(Fig. 1, b); for given fixed strain value (
const
)0(
)
f
,
const
t
)(
) as relaxation curves
) , (
)
0
f
(Fig. 1,
c), with
(
t
and
as shear and compression stresses,
and
as shear strain and its rate,
– as shear strain rate,
t - time.
In each case the curves are quantified as empirical
dependencies, based on rheological models [1…16].
(a)
(b)
(c)
Fig.1. Rheological curves:
g-term strength, (τ
1
< τ
2
…<τ
а) creep and lon
– critical values
b) shear stresses τ(t) for different shear rates
7
of τ in case of γ
cr
= const);
const
, and
4 3 2 1
;
c) stress relaxation for different values of
(right) and limit
and
softening, depending on accumulated strain (Fig. 2).
F
,
1 – elastic element, 2
al strength, 3 – viscous
straight line of residual (long-term) shear strength (left)
The paper presents a rheological equation to describe shear
deformations of clay soil with strong rheological properties and
Maxwell rheological creep threshold
*
for strengthening
shear
i
ing
softening and shear structural strength properties:
– structur
g. 2. Maxwell rheological model, having strengthen
element.
The concept of simultaneous strengthening and softening of
deforming clay soil was repeatedly stressed by S.S.Vyalov,
M.N.Goldstein, G.I.Ter-Stepanayan, and it was also proved by
experiments [1…5].
