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| Titel |
Clays causing adhesion with tool surfaces during mechanical tunnel driving |
| VerfasserIn |
G. Spagnoli, T. Fernández-Steeger, H. Stanjek, M. Feinendegen, C. Post, R. Azzam |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027876
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| Zusammenfassung |
| During mechanical excavation with a tunnel boring machine (TBM) it is possible that clays
stick to the cutting wheel and to other metal parts. The resulting delays in the progress of
construction work, cause great economic damage and often disputes between the public
awarding authorities and executing companies. One of the most important factors to reduce
successfully the clay adhesion is the use of special polymers and foams. But why does the
clay stick to the metal parts? A first step is to recognize which kind of clay mineralogy shows
serious adhesion problems. The mechanical properties of clay and clay suspensions are
primarily determined by surface chemistry and charge distribution at the interfaces, which in
turn affect the arrangement of the clay structure. As we know, clay is a multi-phase material
and its behaviour depends on numerous parameters such as: clay mineralogy, clay fraction,
silt fraction, sand fraction, water content, water saturation, Atterberg limits, sticky
limit, activity, cation exchange capacity, degree of consolidation and stress state.
It is therefore likely that adhesion of clay on steel is also affected by these clay
parameters. Samples of clay formations, which caused problems during tunnel
driving, will be analyzed in laboratory. Mineralogical analyses (diffractometry,
etc.) will be carried out to observe which minerals are responsible for adherence
problems. To manipulate the physical properties, batch tests will be carried out in order
to eliminate or reduce the adhesion on tool surfaces through variation of the zeta
potential.
Second step is the performance of vane shear tests on clay samples. Different pore fluid
(distilled water, pure NaCl solution, ethanol and methanol) will be used to study the variation
of the mechanical behaviour of clay depending on the dielectric constant of the
fluids.
This project is funded by the German Federal Ministry of Education and Research
(BMBF) and the DFG (German Research Foundation) in the frame of the programme
GEOTECHNOLOGIEN. |
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