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SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Dedi Apriadi, Ph.D.
Faculty of Civil and Environmental Engineering
Institut Teknologi Bandung
Introduction of Soil Dynamics & Earthquake Engineering
Dynamic Soil Properties
Dynamic Soil Properties
• Shear Modulus, Gs or Vs and Damping
Ratio, D
• The properties depend on:
– Soil Type
– Confining Stress
– Void Ratio
– Strain Level
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Linear Elasticity
• Linear (approximation): if the stiffness or
modulus is constant along increasing of stress
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
stiffness k
Non-linear Elasticity
• Non-Linear: if the stiffness or modulus is not
constant along increasing of stress (but function
of strain)
Nonlinearity
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
f
y
• Elastic: if the state of stress is a function of the
current state of deformation only (no permanent
strain is allowed)
Linear & Non Linear Elasticity
• Mechanical behavior is completely reversible
• Unloading follows the loading curve
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Isotropic & Anisotropic Material
• Isotropic:
- If its mechanical properties are the
same in all geometric directions.
- Constitutive relationships for these
isotropic materials should be invariant
to transformations of the coordinate
system.
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
• Anisotropic:
If its mechanical properties are not the same in all
geometric directions.
Inherent or cross-anisotropic: due to depositional process of materials
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Isotropic & Anisotropic Material
Linear Soil Stiffness
Parameters relationships
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Non-Linear Soil Stiffness
Stiffness changes with increasing of shear stress
Gt
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Monotonic loading
Non-Linear Soil Stiffness
Stiffness changes with increasing of shear stress
Gs
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Monotonic loading
Non-Linear Soil Stiffness
Stiffness changes with
increasing of shear stress
Gs
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Cyclic loading
Non-Linear Soil Stiffness
Stiffness degradation curves
F’ =G/Gmax
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Field testDedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
• Allows the properties of the soil is measured
in their existing state condition such as stress,
chemical, thermal and structural conditions.
• Do not require sampling
• Some specific properties are not measured
directly but by theoretical analysis or
empirical correlations.
Field testDedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
1. Low strain tests (shear strain below
0.001%): seismic geophysical surveys such
as seismic reflection or refraction, SASW,
seismic cross-hole, seismic down (up)-hole
2. High strain tests: SPT, CPT, Pressuremeter
test, S-CPT
Crosshole TestingOscilloscope
PVC-cased Borehole
PVC-cased
Borehole
Downhole
Hammer
(Source) Velocity
Transducer
(Geophone
Receiver)
t
x
Shear Wave Velocity:
Vs = x/t
Test
Depth
ASTM D 4428
Pump
packer
Note: Verticality of casing
must be established by
slope inclinometers to correct
distances x with depth.
Slope
InclinometerSlopeInclinometer
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Laboratory testsDedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
1. Low strain tests (shear strain below
0.001%): Resonant Column Test, Bender
element test
2. High strain tests: Cyclic Triaxial Test, Cyclic
Simple Shear Test etc
3. Model tests: Shaking table, Centrifuge test
Gmax or Vs Correlations: Other TestsDedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other TestsDedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other TestsDedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other Tests
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other Tests
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other Tests
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other Tests
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Gmax or Vs Correlations: Other Tests
Factors Influencing Damping Ratio
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Factors Influencing Damping Ratio
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Factors Influencing Damping Ratio
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Factors Influencing Damping Ratio
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
Dedi Apriadi – SI 4121 Pengantar Dinamika Tanah dan Rekayasa Gempa
TUGAS 4
Suatu profil tanah
Rigid Rock
Soft NC Clay
= 22 kN/m3
Vs = 780 m/det
= 15 kN/m3
Su = 5 kN/m2
PI = 45
Vs = 110 m/det
Tentukan:
1. Nilai initial modulus geser Gmax atau G0 dan damping ratio 0 untuk setiap lapisan dengan
menggunakan
- Data Su
- Vs hasil pengukuran dengan SDH tes
Kurva variasi G/Gmax dan damping ratio untuk lapisan batuan dalam gambar di atas.
2. Frekuensi natural dari lapisan soft clay
0
0.2
0.4
0.6
0.8
1
1.2
0.0001 0.001 0.01 0.1 1
G/G
MA
X
STRAIN (%)
G/Gmax
0
1
2
3
4
5
0.0001 0.001 0.01 0.1 1
DA
MP
ING
(%
)
STRAIN (%)
Damping Ratio (%)30 m
References
Dedi Apriadi – SI 6121 Dinamika Tanah dan Rekayasa Gempa
1. Kramer, S.L., Geotechnical Earthquake Engineering, Prentice Hall, 1996,
Chapter 9.
2. Das, B.M., Principles of Soil Dynamics, CENGAGE Learning, 2011.
3. Stewart, J., Geotechnical Earthquake Engineering, UCLA, 2007.
4. Bozorgnia, Y., and Bertero, V.V., Earthquake Engineering, from
Seismology to Performance Based Engineering, CRC Press, 2007.