THESIS
2020
xvi, 184 pages : illustrations (some color) ; 30 cm
Abstract
Deep geological disposal is regarded as one of the most practical ways for the stratum disposition of
the high-level radioactive waste (HLW). Moreover, it is known that soft rock is one of the most suitable
host rocks for geological disposal because of its low water permeability and little cracks. However,
there is lack of understanding of the influence of temperature on soft rock which is generated by HLW
for long-term. Therefore, it is in demand to establish the way to evaluate the soft rock behavior under
thermal loading. Even though previous studies have been revealed the mechanical behavior of soft
rock subjected to high temperature and developed constitutive models to describe its behavior, long-term
stability of tunnel, especially tunnel creep behavior, under high temperat...[
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Deep geological disposal is regarded as one of the most practical ways for the stratum disposition of
the high-level radioactive waste (HLW). Moreover, it is known that soft rock is one of the most suitable
host rocks for geological disposal because of its low water permeability and little cracks. However,
there is lack of understanding of the influence of temperature on soft rock which is generated by HLW
for long-term. Therefore, it is in demand to establish the way to evaluate the soft rock behavior under
thermal loading. Even though previous studies have been revealed the mechanical behavior of soft
rock subjected to high temperature and developed constitutive models to describe its behavior, long-term
stability of tunnel, especially tunnel creep behavior, under high temperature is not well
investigated. The main objective of this research is to gain a better understanding of soft rock tunnel
long-term behavior under thermal environment. Furthermore, this study aims to validate a newly
proposed thermo-elastoplastic constitutive model by conducting the class C-predictions.
Triaxial compression tests and triaxial creep tests with artificial soft rock were carried out to
investigate the mechanical behavior of itself and gain parameters for class C-predictions. A total of
four tunnel modelling experiments at 20 and 60°C which consist of loading failure test and creep
failure test were also conducted using artificial soft rock. Tunnel deformation, deviatoric strain on
tunnel model surface and temperature history were measured during the test. Moreover, experiment
data which is gained through this research is simulated with the proposed constitutive model.
The element test results reveal that the artificial soft rock used in this research can simulate the
fundamental mechanical behavior of sediment soft rock and contributed to gain parameters for class
C-predictions. It is also shown that increase of temperature weaken tunnel stability and shorten the
tunnel failure time in tunnel modelling experiment. Temperature seems to have larger influence on
creep failure time than loading failure time. Furthermore, tunnel model experiment results imply that
the different loading method between tunnel failure test and tunnel creep test results in different
destruction modes.
Even though class C-predictions results show that the constitutive model can capture the features of
mechanical behavior of soft rock at element level, it is found that expanding it to FEM has some
problems. In this study, computed result is presented mainly in order to interpret the gained
experimental data.
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