Tribocorrosion challenges in tunnel boring machinery (TBM)
Visualitza/Obre
Tipus de documentProjecte/Treball Final de Carrera
Data2015-11
Condicions d'accésAccés obert
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continguts d'aquesta obra estan subjectes a la llicència de Creative Commons
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Reconeixement-NoComercial-SenseObraDerivada 3.0 Espanya
Abstract
Tunnel Boring Machines (TBM) are used to bore tunnels, a specific area of interest for TBMs
is their cutter heads, which is a massive steel structure with hardened steel disc cutters
attached. The disc cutters can encounter all types of geology (i.e. from soft clays, slits, sands
etc., to soft rock and extremely hard rock) and environments (i.e. dry, wet, seawater or
chemical additives). These geologies and environments cause the disc cutters to be
continuously exposed to degradation in form of wear/abrasion, corrosion and fatigue, being
abrasion the dominant mechanism. Replacing the disc cutters is a considerable part of the
total tunnelling costs. Therefore, a better understanding of the degradation mechanisms
occurring during tunnel boring in different geology and environments can contribute to
reducing the disc cutter wear and consequently, reducing the tunnelling costs by enlarging
their lifetimes.
In this project, the tribological performance of steels used in the disc cutters of Tunnel Boring
Machines (TBM) has been assessed using different tests and environments close to the
TBM working conditions in order to find the best way of predicting on-site wear mechanisms.
Rock and soil tunnelling processes have been assessed. Rock/soil and water samples were
obtained from field (i.e. active tunnel boring projects) in order to reproduce more realistic
results. Three different tribological tests, reciprocal ball-on-plate, rubber wheel and
hyperbaric soil ground abrasion tests have been used in this work.
The reciprocal tests were done by rubbing steel balls onto the rock obtained from tunnel
boring sites. The tests were performed in dry conditions, water (from the same site), and a
mixture of water and conditioning additives designed for use in hard rock tunnel boring. After
the tests no measurable weight loss was observed on the steel balls, however the liquid
environment and the conditioning additives changed the wear mechanism on the steel
surface as compared to the dry conditions. The water and additives also provided some
lubrication, being the additives the best lubricant. The rubber wheel tests were performed in
different combinations of water, sand and conditioning additives. The tests showed that
adding the additives to the sand and water mixture significantly reduced the weight loss
however some additives caused pitting. The hyperbaric soil ground abrasion tests were
performed in dry and wet conditions and showed similar weight loss. However, SEM pictures
revealed that in the test with sand saturated in water, both abrasion and corrosion occurred.
While in the dry test, only abrasion occurred. This indicates that in this test the hardness of
the steel and abrasiveness of the sand is more decisive for the weight loss than the
corrosivity of the solution.
MatèriesSteel -- Corrosion, Drilling and boring -- Materials, Acer -- Corrosió, Tuneladores -- Materials
TitulacióENGINYERIA DE MATERIALS (TITULACIÓ CONJUNTA AMB LA UB) (Pla 2003)
Fitxers | Descripció | Mida | Format | Visualitza |
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PFC tribocorrosion TBM.pdf | Report | 13,45Mb | Visualitza/Obre |