Post on 04-Sep-2018
Antonio BobetPGS 2011
Seismic Design of Underground Structures using
the Free-field Method and other Misconceptions
(Chuto Industrial Inc., 1997)
Misconceptions
1.Underground structures are safe against earthquakes
2.Underground structures deform with surrounding ground
3.Deep structures are safer than shallow structures
4.Use Mononobe-Okabe method to estimate loads
Outline
1. Motivation
2. Current Design
3. Design of Underground Structures
4. Misconceptions
Motivation
(EQE, 1995)
Collapse of the Daikai Station
Motivation
(Chuto Industrial Inc., 1997)
(EQE, 1995)
Cross Section
Motivation
Damage to the Central Column
Motivation
(Chuto Industrial Inc., 1997)
Plan View of the Daikai Station
Motivation
(Iida et al., 1996)
Outline
1. Motivation
2. Current Design
3. Design of Underground Structures
4. Misconceptions
Current Design
Sources of damage
• Fault displacement
• Ground failure
• Ground Shaking
Dagbreek fault in matjhabeng mine - Israel
45 cm
Current Design
Sources of damage
• Fault displacement
• Ground failure
• Ground Shaking
Current Design
Sources of damage
• Fault displacement
• Ground failure
• Ground Shaking
Current Design
(Dowding, 1977;
71 cases – 42 damaged)
(Sharma and Judd, 1991;
192 cases – 94 damaged)
Current Design
Damage to mountain tunnels during the Chi-Chi
earthquake, Taiwan, 1999. Data from Wang et al., 2001
(57 cases – 49 damaged)
Current Design
Bantaki Tunnel, after Kobe Earthquake
Current Design
Longxi Tunnel, after 2008 Wenchuan
earthquake, China (courtesy of Dr. H. Yu)
Current Design
+
Static Dynamic
Current Design
Body Waves
Current Design
Shear Wave Impinging Tunnel
Current Design
Tunnel Deformation Modes
Current Design
Free-field Method: Racking Deformation
=
V
sV
“Thought experiment”
“stiff” tunnel
Current Design
“Thought experiment”
“stiff” tunnel
Current Design
“Thought experiment”
“stiff” tunnel “soft” tunnel
Current Design
“Thought experiment”
“stiff” tunnel “soft” tunnel
Current Design
ro
ro tunnel
= 4 (1- )2F
(1- )(3- 2)F +12(3- 4)
Vmax
VP
ro
ro tunnel
= 4 (1- )2F
(1- )(3- 2)F +12(3- 4)
Vmax
VS
F = E ro
3 1- s
2 E s Is 1- 2
C = 0
Current Design
Current Design
Free Field “errors”
New Station (one year later)
(Benedicto, 2001)
Current Design
Tunnel
(Benedicto, 2001)
Current Design
Outline
1. Motivation
2. Current Design
3. Design of Underground Structures
4. Misconceptions
Pseudo-static Analysis (Hendron and Fernández, 1983)
Design
Rectangular Structure in Infinite Elastic Medium
Design
Rectangular Tunnel
Design
Rectangular Structure in Infinite Elastic Medium
Design
Depth Effect
Design
Outline
1. Motivation
2. Current Design
3. Design of Underground Structures
4. Misconceptions
Misconceptions
1.Underground structures are safe against earthquakes
2.Underground structures deform with surrounding ground
3.Deep structures are safer than shallow structures
4.Use Mononobe-Okabe method to estimate loads
Seismic Design of Underground Structures using
the Free-field Method and other Misconceptions
(Chuto Industrial Inc., 1997)
Thank you
Antonio BobetPGS 2011