1838
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Denmark
1. Follow Test Method 1 and 3.
2. For all categories of test, proof load:
P
p
=
ξ
(
γ
a
)
α
F
ad
(13)
where
F
ad
= max(F
ULS;d
; F
Serv;d
)
(14)
where all anchors are tested,
ξ
= 1,1
and
γ
a
= 1,3.
α
is a factor used to control reduced safety in
temporary situations, provided the risk of the
consequence justifies it. It may range from 0 to 1. For
permanent anchors
α
= 1
. For temporary anchors –
with small or no risk to human life or important
infrastructure
α
is typically set to 0,5.
Thus for permanent anchors:
P
p
= 1,1 x 1,3 F
ad
= 1,43 F
ad
(15)
For temporary anchors with less severe consequence
of failure:
P
p
= 1,1 x (1,3)
0,5
F
ad
= 1,25 x F
ad
(16)
3. Limiting criteria are based on a value of the creep rate
according to (informative) values in EN 1537:1999
France
1. Follow Test Method 3
2. Proof load for Investigation and Suitability tests
P
p
= 1,50 x F
serv;k
(17)
where
F
serv;k
is derived from calculation.
3. Suitability tests should demonstrate that the critical
creep load
P
c
≥
1,2 x F
Serv;k
(for permanent anchors)
and
P
c
≥
1,1 x F
serv;k
(for temporary anchors) where
P
c
is derived from the load corresponding to the end
of the first pseudo-linear part of the creep rate versus
anchor load plot found from an investigation or
suitability test.
4. Proof load for Acceptance tests:
P
p
= 1.25 x F
Serv;k
(permanent anchors)
(18)
or
P
p
= 1.15 x F
Serv;k
(temporary anchors)
(19)
Given the limits on
F
Serv;k
with respect to the critical
creep load, at these proof loads the ratio between test load
and creep load is independent of the application of the
anchor . It will be constant and approximately 1,04.
5. Limiting criteria based on the value of
α
3
at Proof load
P
p
and the value of
P
c
to check that
P
c
/ F
Serv;k
> 1,2
.
UK and Ireland
1. Follow Test Method 2 but also use Test Method 1.
2. Investigation tests - the anchor is normally loaded to
the point where the vertical asymptote of the
cumulative load loss k
l
vs load relationship may be
determined. An estimate of the anchor pull-out
capacity may also be made.
3. Proof Load for the suitability and acceptance tests
Pp = 1,5 x T
w
(20)
where
T
w
is derived from the stability and
serviceability requirements of the structure.
4. In both suitability and acceptance tests the limiting
criteria are based on the values of
k
l
at a)
P
p
= 1,5 x
T
w
and b)
P
p
= T
w
5.
Where Test Method 1 is adopted the limiting criterion
k
l
is translated into a creep displacement as shown in
Table 1, note b.
5 CONCLUSIONS
The aim in developing a new Section 8 for EC7 has been to
provide a rational framework for the design of ground anchors
as elements within an overall ground-structure design, while
accommodating the diverse practices of different countries. In
the opinion of the group responsible for the drafting, which
included the authors, this has been achieved. Some of the
values of factors and criteria will probably be refined during the
development of national annexes, though it is likely that
national practices will remain distinct for the time being.
Nevertheless, as with other aspects of Eurocodes, the existence
of a single agreed text gives the possibility of clearer
comparisons between national approaches, and so will hopefully
contribute to the development of a more unified approach in the
future.
6 ACKNOWLEDGEMENTS
The authors would like to acknowledge the contributions made
by their fellow members of TC250/SC7/EG1, Klaus Dietz,
Yves Legendre, Pierre Schmitt, Bernd Schuppener, Arne
Schram Simonsen, in the development of the new draft of
Section 8 of EC7.
7 REFERENCES
BS8081:1989. British Standard Code of practice for Ground
Anchorages.
British Standards Institution, London
DIN 4125 1990, Ground Anchorages – Design, construction and testing.
Deutches Institut für Normung
EN 1537:1999. Execution of special geotechnical work – Ground
anchors.
CEN, Brussels
EN 1997-1:2004/prA1:2012 Eurocode 7 – Geotechnical design – Part 1:
General rules.
CEN, Brussels
Littlejohn G.S. 1970. Soil anchors.
Proceedings of the Ground
Engineering Symposium
ICE, London, 33-44
Littlejohn G.S. 2012. Personal communication
prEN ISO 22477-5 Geotechnical investigation and testing - Testing of
geotechnical structures - Part 5: Testing of anchorages (in draft)
CEN, Brussels
SIA V 191. 1995. Vorgespannte Boden- und Felsanker.
Schweizerischer
Ingenieur- und Architekten – Verein.
TA 95 1995. Ground Anchors – Recommendations for the design,
calculation, execution and control.
Comité Français de la
Méchanique des Sols et des Travaux de Fondations
