effect of subsurface barrier on seismic waves
TRANSCRIPT
Effects Of Subsurface Barriers On Seismic Waves
Group Members• Akshay M.
Krishnan• Ashwitha Reddy• Haseeb Tahir• Rohith Grandhi• Sagar Shah
Cee - 5464
Overview• Objectives• Background• Experiment• Theoretical Model• Results• Errors• Conclusion
Objectives
Study effects of change in subsurface conditions on wave propagation.
Develop an experiment to compare different subsurface conditions
Prepare a STRATA model for theoretical modeling
Compare results
Background
Waves
Compressional Waves• Sound waves• Seismic Waves
Longitudinal waves• Light waves
Experiment
1. Only Sand Sand layer
7” thick
2. Sand with wood layer Sand layer 3” thick Wood 0.75” thick Sand layer 3” thick
• 2’x1’ box of ply wood• Subjected to ground motion by the shake table• Ground Motion: Sine wave
Amplitude= 5cm Frequency 2 Hz.
• Used 2 Accelerometers to measure the Accelerations
Theoretical Model
StrataFree Software
Shear Velocity Velocity that relates shear between layers of flow.
Unit WeightWeight of Material
Shear Velocity
Theoretical Model Contd.
Damping Inelastic Darendeli & Stokoe Model
Shear Modulus Inelastic Darendeli & Stokoe Model
0.00E+00 1.00E+00 2.00E+00 3.00E+00 4.00E+000
0.20.40.60.8
11.2
Darendeli & Stokoe G/Gmax Model
StrainG
/Gm
ax
0.00E+00 1.00E+00 2.00E+00 3.00E+00 4.00E+000
5
10
15
20
25
Darendeli & Stokoe damping Model
Strain
Dam
ping
, %
Results
0 1 2 3 4 5-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Sand-only : surface acc. (in "g") - actual vs strata
Actual StrataTime (sec)
Acce
lera
tion
(g)
Results Contd.
0 1 2 3 4 5-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Sand-Wood : surface acc. (in "g") - actual vs strata
Actual Strata
Time (sec)
Acce
lera
tion
(g)
Results Contd.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Strata outputs : Sand-only vs. Sand-Wood
Sand-only : surface acc. (g) - output Strata Sand-Wood : surface acc. (g) - output Strata
Time (sec)
Acce
lera
tion
(g)
Errors Experiment was extremely scaled down Soil Properties depend on pressure
Centrifuges are used to conduct tests on soils The whole assembly acted as one rigid body Vibrations from the table movement affected the
readings Assumption of that waves will travel vertically
Conclusion
