Effects of soil and fault properties on tunnel displacement induced by normal and reverse faults
As the world population increasing considerably in tandem with the growing cities, economies, and businesses, there is a need for effective and efficient public transportation. One of the fastest, and most convenient public transport is subway. However, it has become a major concern to geotechnic...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/92802/1/FK%202020%20102%20UPMIR.pdf |
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| Summary: | As the world population increasing considerably in tandem with the growing
cities, economies, and businesses, there is a need for effective and efficient
public transportation. One of the fastest, and most convenient public transport
is subway. However, it has become a major concern to geotechnical engineers
as the development and construction of subways are held underground where
faults exist. Several seismic events such as the earthquakes in Taiwan in 1999,
China in 2008, and Malaysia (Sabah) in 2015 caused by fault ruptures signify
the importance of this study. Although many studies have been conducted on
fault ruptures, most researchers only considered a free field (a field without
tunnels) and on homogeneous cohesionless soil (sand). In this study, a gigantic
physical model 1000 mm in height, 3000 mm in length, and 1000 mm in width
was fabricated in Geotechnical Engineering laboratory, Universiti Putra
Malaysia (UPM) to evaluate the influence of various soil properties on tunnels
affected by both normal and reverse faults, as well as the effects of various fault
angles and tunnel depths. Three different soil cohesion have been selected,
cohesionless soil , 10 kPa and 20 kPa which due to the reason that
cohesionless soil has been used in most of previous studies, and other studies
(in soil stability), cohesion values of less than 23 kPa has been used. Three
different soil friction angles have been investigated in this study,
27°, 33° and 39°. Previous studies have showed that range of soil friction angle
between 28° and 39° indicated density of up to 80%. Results revealed that
increasing the soil cohesion and friction angle resulted in reducing tunnel
displacements by as much as 64% and 39% respectively. Investigation on the
differences and similarities between normal and reverse faults revealed that
reverse faults can bring approximately 60% more tunnel displacements
compared to normal faults because a normal fault released less energy than a
reverse fault. Another aspect considered is the influence of fault angles in which results showed that vertical movements due to a fault angle of 90° could bring
major displacements of more than two times the displacements caused by a
fault angle of 30°. Evaluation of the effects of various distances between a
tunnel and a fault revealed that tunnel displacements could be reduced by more
than 22% when the tunnel is located 250 mm away from the fault. In addition,
finite element analyses were also performed using PLAXIS to simulate and
compare the results with physical model. The results of the current study could
be of benefit to society considering the fault ruptures. Many metropolitan cities
with underground structures are exposed to risks to many lives if fault ruptures
occurred. This study asserts that besides the structural design of a tunnel, the
geotechnical design also has a major impact on the safety and robustness of
the tunnel. It is also shown that geotechnical engineering aspects such as soil
properties, type of fault, tunnel depth, and fault angle have a strong influence
on tunnel damages in which those aspects were not considered in previous
research despite their importance. |
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