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EPB machine excavation of mixed soils – Laboratory characterisation
Author(s) -
Oliveira Daniela Garroux G.,
Thewes Markus,
Diederichs Mark S.
Publication year - 2019
Publication title -
geomechanics and tunnelling
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.317
H-Index - 18
eISSN - 1865-7389
pISSN - 1865-7362
DOI - 10.1002/geot.201900014
Subject(s) - geotechnical engineering , soil water , concrete slump test , excavation , slump , geology , mining engineering , soil science , materials science , cement , metallurgy
Earth pressure balance (EPB) tunnel boring machines are shield machines that rely on their own excavated material as a support medium to maintain the support pressure at the face. This material also needs to have the necessary properties to be extracted, transported and, finally, disposed of. Whenever the natural material does not fulfil the necessary requirements, additives like water, foam, polymers, and fines, must be added, modifying the excavated ground to the desired conditions. The rheological properties of any excavated material, together with any additives, must be investigated and understood, as they will influence the flow behaviour of this conditioned material, directly affecting the machine operation and tunnel logistics. While studies assessing the flowability related to the EPB excavation of sand or clay soils are available, there is a lack of information on mixed soils. This paper presents the results from a testing campaign with mixed clay‐sand samples, aiming to reproduce a simplified tropical weathered mixed soil, investigating its flow behaviour when changing certain controlled variables: clay‐sand proportions, clay mineral, size of the clastic grain mixed with clay, water content, and additives (foam and polymers). Results from the tests conducted with a flow table, a slump test, and a rheometer device were compared, providing insights about the flow behaviour of the tested samples and its interaction with an EPB machine.