615
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Correction of soil design parameters for the calculation of the foundation based
on the results of barrettes static load test
Correction des paramètres de conception du sol pour le calcul sur la base des résultats de test
de barrettes de charge statique
Shulyatiev O., Dzagov A., Bokov I., Shuliatev S.
Gersevanov institute for soil bases and underground structures, e-mail:niiosp35@yandex.ru.
ABSTRACT: Geotechnical investigations and design works were being performed in 2008-2010 for the construction of Okhta-center
high-rise tower in St. Petersburg. Unique static load tests of 80 m deep barrettes were performed in 2010 as part of design process. 3
barrettes were tested simultaneously as a group and two were tested individually. The tests were planned in such a way as to get the
standard values of bearing capacity of barrettes, and to clarify the parameters of soil needed for the calculation of the barrette
foundation.The comparison of the bearing capacity values with the values calculated using Russian and foreign building codes is
provided. Limitations of currently used codes are shown.
RÉSUMÉ : Les études géotechniques et les travaux de conception ont été réalisées en 2008-2010 pour la construction du centre Okhta
haute tour à Saint-Pétersbourg. Uniques essais de charge statique de 80 m de profondeur barrettes ont été réalisées en 2010 dans le
cadre du processus de conception. 3 barrettes ont été testés simultanément en tant que groupe et deux ont été testés individuellement.
Les tests ont été planifiés de manière à obtenir les valeurs standard de la capacité portante des barrettes, et de préciser les paramètres
du sol nécessaires pour le calcul de la fondation barrette. La comparaison des valeurs de capacité portante avec les valeurs calculées à
l'aide des codes de construction russes et étrangères est fournie. Limites des codes actuellement utilisés sont affichés.
KEYWORDS:piles, barrettes, static load test, shaft friction, FEM, bearing capacity, high-rise building.
1 INTRODUCTION
In recent decades, in Russia there is a steady increase in the
number of tall buildings being built, of which a substantial part
is the building higher than 150 m.
Building heigher then 150m need a special approach to
design. Existing bulding codes in Russia and other countries as
well, can not fulfill the requirements of modern day high-rise
construction. For foundation constructions existing codes are
limited by relatively small depth of ground investigation and
testing loads.
In the current RF building codes plate loading test is
considered as the reference method for soil Young modulus
estimation. According to codes soil modulus determined by
other methods should be adjusted to plate loading test modulus.
It is not always possible, given the great depth of the soil used
as the bearing layer of high-rise building foundation.
This paper discusses the engineering properties of Vendian
clay as a bearing layer of Okhta tower high-rise building in St.
Petersburg. According to building design it’s pile foundation
will be embedded in Vendian clay layer lying deeper then 45 m
from ground surface.
Building design The project has a device for high-rise
building with pile foundation bearing on Vendian clay layer,
lying with a mark of -45 m B.S.V.
Laboratory tests on odometer and triaxial schemes were
made during ground investigations to study the properties of
Vendian clays. Given the depth of bearing layer pressuremeter
test were selected as in-situ test method.
Laboratory testing of soil extracted from great depth usually
complicated by disturbanceof soil samples, caused by stress
relief and preparation of samples for testing, and by the
complexity of high-precision measurements of deformation of
the sample (especially true for high stiffness soils).
Pressuremeter test, in turn, has no alternatives for soil testing
in-situ at greater depths. Design value of pressuremeter Young
modulus needs to be adjusted to plate loading test modulus, and
if that is not possible soil anisotropy factor needs to be
determined for conversion of soil modulus in the horizontal
direction to the modulus in the vertical direction.
Trial Barrette static test was scheduled as part of the pile
foundation design process. Given the high testing load
"Osterberg" method were considered economically effective.
Given specifics of the method, in addition to pile bearing
capacity assesment, one can provide design engineer with the
possibility of making “deep plate loading test”.
Figure1 .Location of test barretes.
Trial Barrettes were made from the surface of the soil. The
working part of a 65-m barrette was made of B40 grade
reinforced concrete. Barrettes were constructed by the
conventional technology - in the trenches, excavated under the
protection of bentonite slurry.
