2862
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1 – loading, 2 - unloading
Figure. 9. Pile 5 side test diagram
3 PRACTICAL APPLICATION OF PILE TEST RESULTS
As was mentioned above, analysis of pile footings of MIBC
Moskva-CITY sky-scrapes mainly consists in determination of
pile side and tip resistances (maximum values and their depend-
ence on displacements). Analysis of such piles can be done nu-
merically with the help of 3D software.
The analytical soil model, developed for such analysis, shall
be verified by solutions of test problems. The test problems in
this case are single pile tests. In the process of test solutions
design parameters are specified (side resistance as well as soil
strength and deformation parameters).
Figure 10 gives analytical and test data of pile tests, obtained
by submersible jacks at site 11.The numerical simulation was
done with the help of PLAXIS 2D 8.2 software. The analytical
model was the ideal elasto-plastic model with Mohr-Coulomb
strength criterion.
The following assumptions and prerequisites were adopted
for the analysis:
-
the input values of physico-mechanical parameters of
geotechnical elements were adopted as for the 2nd limit state
analysis;
-
static loads alone were adopted for the analysis.
Shock, dynamic, vibration and other technological loads and
actions due to construction operations were not taken into con-
sideration;
-
pile material was considered elastic.
In order to harmonize the results of tests and analyses there
were used improved parameters of surrounding soil. 3 inter-
linked parameters: E, φ and с were selected. There were done
several analyses, in which soil parameters were chosen as ap-
proximation of experimental data by analytical data, which were
upper and lower jacks plates displacements and variation of
forces and deformations in the pile at different levels along the
pile length.
Final results are presented on Figure 10. Their comparison
with experimental data showed their sufficient proximity: the
scatter does not exceed 10%. The analyses showed that with
practically identical soil strength parameters the soil stiffness
modulus values, obtained from the analyses is times greater than
the one, obtained from geotechnical investigations, that was
further accounted for in soil analysis.
Figure 10. Data from pile tests by Osterberg method, compared with
numerical simulation data.
4 CONCLUSIONS AND RECOMMENDATIONS
Pile side and tip resistance rather than a single pile bearing
capacity are important for designing MIBC «Moskva-CITY»
footings.
Side and tip resistance can be determined by tests of pile
fragments, separate side and tip tests by means of a specially
developed method, described in the paper, or by means of pile
tests with gauges, installed in the pile body, to measure distribu-
tion of forces along pile length.
It is recommended to verify pile footing interaction with soil
and to verify the analytical model, using single piles test data.
It is recommended to verify the values of design mechanical
soil properties, obtained from geotechnical survey, by back
analysis, using single pile tests.
It is admissible to adopt cast pile side surface resistance
equal to 1,8МPа (180t/m2) for Suvorovsky and Podolsk-
Myachikovsky medium-strength and strong limestones.
In order to activate cast pile tips it is necessary to apply spe-
cial measures to clean and to compact borehole bottom face, e.g.
to grout pile tip – soil interface, to compact the bottom face by
filling rubble or by stiff concrete ramming, etc.
5 REFERENCES
Osterberg J. O. New Device for Load Testing Driven Piles and Drilled
Shafts Separates Friction and End Bearing/ Proceeding: Internatio-
nal Conf. on Pilling and Deep Foundation, London, A.A. Balkena,
1989
State Standard 5686-94 “
Methods of field pile tests”
Petrukhin V.P., Shulyatjev O.A., Kolybin I.V., Mozgacheva O.A., Bez-
volev S.G., Kisin B.F. Construction of MIBC «Moskva-CITY»/
Russian Architectural and Building Construction Encyclopedia,
v.XII. Underground Construction, 2008.
Kharichkin A., Syuljatjev O., Besvolev Stepan. Soil-Pile Interaction in
Pile Foundation and Pile Reactions Monitoring/ International Con-
ference on Deep Foundations – CPRF and Energy Piles. Frankfurt
am Main, 2009.
Analysis of a High-Rise Tower on Site №2-3 of MIBC Moskva-CITY.
High-RiseBuildings. №1/11, 2011.
Zaretsky Yu.K., Karabajev M.I. Analysis of Test Piles-Ground Interac-
tion and Comparison with Test Data. Messenger of Moscow State
Construction University, №1, 2006.
Duzceer R, Gokalp A., Adatepe S. Load Testing and Bearing Capacity
of Bored Piles in Limstone/ Proceeding of the 17 International Con-
ference on Soil Mechanics and Geotechnical Engineering. Alexan-
dria, Egypt, 2009.
Petrukhin V.P., Shulyatjev O.A, Bokov I.A. Review of Pile Tip Pre-
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