2581
Technique of reinforced soil base calculation under fall initiation in ground mass
Technique du compte armé les raisons du sol à l'apparition des échecs à le massif du sol
Ponomaryov A., Zolotozubov D.
Perm national research polytechnical university, e-mail:
ABSTRACT: On the basis of carried out investigations, the authors obtained stress and strain development mechanisms of the
reinforced ground mass depending on the properties of soils, the characteristics of the reinforcing elements, the depth of their location
and their number. The obtained mechanisms allowed to propose the calculation methodology of the reinforced base surface settlement
in the territories expose to deformation. To evaluate the proposed method, it was compared with previously obtained results of the
experiments and calculations carried out with the help of BS8006, Giroud, Perrier, R.A.F.A.E.L methods and PLAXIS and Sofistik
programs.
RÉSUMÉ : À la base des études accomplies les auteurs ont reçu les mécanismes du développement de l'effort et l'effort de la masse
affermie de la raison en fonction des propriétés des sols, les particularités des éléments du renforcement, la profondeur de leur
situation et leur nombre. Les régularités reçues ont permis de proposer la méthode du compte le dépôt de la surface des raisons armées
sur les territoires exposés aux déformations. Pour estimer la méthode proposée, c'était en comparaison d'auparavant résultats acquis
des expériences et calculs accomplis avec l'aide de BS8006, Giroud, Perrier, les méthodes R.A.F.A.E.L et PLAXIS et les programmes
Sofistik.
KEYWORDS: reinforced soils, fall in ground mass, technique of calculation.
1 INTRODUCTION
When laying foundations of buildings and structures in areas
prone to possible vertical deformations (for instance, karstic and
technogenic dolines), it is necessary to provide measures to
prevent emergency situations.
The choice of measures depends on the type of security –
perfect or partial. When it is sufficient to provide only partial
security, geosynthetic material reinforcement of a ground base
is most commonly used. It is connected with the fact that
ground reinforcement is more economical as compared with
other methods. In the majority of case reinforcing of the bases
by geosynthetic materials apply at building automobile and
railways. Besides at building on karstic territories it is expedient
to reinforce geosynthetic materials of the bases low-charged
constructions, for example, low-rise buildings.
In Russia ground base reinforcement has not been used
widely so far due to various factors, including both the increase
in the cost of construction connected with the use of
geosynthetics and sufficiently large amount of excavation
works.
High quality geosynthetic materials themselves are not
cheap, and large volumes of excavation arise from the need of a
sufficiently deep placement of reinforcing layers. However, the
use of local materials and a well-tried technology of reinforced
base laying, as well as the increase in the safe upkeep of
buildings, give a good economic effect.
2 EXPERIMENTAL INVESTIGATIONS
Effective use of geosynthetics for reinforcement under ground
mass collapse is possible with the joint account of such factors
as physical and mechanical properties of foundation soil, tensile
properties of geosynthetics, the depth of reinforcing layers and
their number. The optimal choice of these parameters requires
rather complex calculations taking into account load –
elongation dependences. The existing methods (the method
outlined in the British Standard BS 8006, section 8.4 (BSI, 1995
– Fig. 1), the method of Giroud et al (1990), the method of
Perrier (1985); R.A.F.A.E.L. – method (Blivet et al, 2002) do
not consider the actual tensile force – relative deformation ratio.
They are applied for single-layer reinforcement. Being used to
solve geotechnical problems, software packages that implement
numerical methods give great inaccuracy, but at the same time
they allow to calculate more quickly and check more types of
reinforcement including those of multi-layer reinforcement.
Figure 1. BS 8006: Parameters used to determine reinforcement.
The study of reinforced bases under ground mass collapse
conducted by the authors allowed to obtain the mechanisms of
stress – strain development in the reinforced ground mass
depending on the foundation soil properties, the characteristics
of the reinforcing elements, their depth and quantity. The results
of S. Schwerdt’s investigations were also used in the study.
On the basis of the mechanisms obtained we proposed the
technique for calculating the reinforced base surface settlement
in areas prone to deformation. As in the above-mentioned
methods, the calculations were carried out for single-layer
reinforcement, but at the same time the change in elongation of
the geosynthetic reinforcing material depending on the load was
taken into account. To do calculations using this method it is
necessary to have load – elongation dependences which are
obtained when testing geosynthetics at rupture, in accordance
with ISO 10319:2008 (Fig. 2).
In the course of our studies we were doing experiments with
account of the current Russian regulations enabling to apply
tensile-testing machines to ensure the constant rate of bottom
