IJMTES | International Journal of Modern Trends in Engineering and Science
ISSN: 2348-3121
DYNAMIC ANALYSIS OF THREE DIMENSIONAL
SOIL COLUMN MODEL USING OPEN SEES
V.Yogeshwaran1
1
(Department Civil Engineering, Rathinam Technical Campus, Coimbatore, India, [email protected])
______________________________________________________________________________________________________
Abstract— In this project three dimensional soil column model imposed to seismic loading has been analyzed with the help of Open
System for Earthquake Engineering Simulation (Open SEES). The Open SEES is developed by PEER (Pacific Earthquake Engineering
Research). In this analysis soil to soil pressure (Effective Stress), excess pore water generation (pressure exerted by water which is present
inside the voids), dissipation of pore water pressure, settlement were investigated. To impose the seismic loading the three past real time
earthquakes are taken such as Imperial Valley (Mexico), Tabas (Iran), and Valdivia (Chile). The Peak Ground Acceleration (PGA) for these
seismic loading are 0.57g, 1.0g, 0.31g respectively. The time period for ground acceleration has been considered as 20 sec, 25 sec and 20
sec respectively. The effective pressure, pore water pressure, settlement are investigated from the results.
Keywords— Pore Water Pressure, OPEN SEES, Peak Ground Acceleration
_________________________________________________________________________________________________________________
1. INTRODUCTION
Earthquake is the most dangerous thing in this world. It is
produced many reasons such as volcanic eruption and the
movement of plate boundaries. Damages due to earthquake
are uncountable; they are loss of life, damages for the
properties and buildings. The damage for the buildings is
mainly due to the changes in the soil strength. The building
get failed due to failure of the substructure and the settlement
of the soil during earthquake. The settlement of the soil is
due to liquefaction happened during earthquake.
elements are in cube shape (brick element). Each node has
seven degrees of freedom. Solid elements were represented
by the 3D eight node brick elements in Open SEES. All the
nodes are fixed against Y – direction (second degree of
freedom). The nodes on the lower boundary are fixed against
movement in all direction and the bottom sides are
considered as impermeable and top side is permeable.
2. 3D SOIL COLUMN
It is a 3D soil column model, the depth, thickness and width
of the soil column model is 10m, 1m, 1m respectively. The
soil column consists of ten brick elements, each element has
8 nodes. The nodes have seven degree of freedom, first three
degree of freedom denotes the X –axis, Y –axis, Z – axis
displacement respectively, and the fourth degree of freedom
denotes the pore water pressure, and the remaining degree of
freedom denotes rotation. The 3D soil column model is
assumed as Isotropic, homogeneous, and it has uniform
permeability along the depth and the drainage is allowed in
the top surface.
Fig 2. Schematic representation of brick element
3. NUMERICAL ANALYSIS
The gravity analysis is conducted as a variable transient
analysis for 300 steps with a time step of 1. Material is
entirely elasto – plastic constructive behavior. The selfweight of the soil elements is acting downward direction,
which is acting as a load for gravity analysis. Therefore, no
loading object is required. The analysis is conducted using
the Newmark integrator such as gamma and beta coefficients are 0.7 & 0.3 respectively. The model is analyzed
by applying the seismic loading. The seismic loading data is
taken from the time history of certain earthquake; takes
places where the earthquake happened in Imperial Valley
(Mexico), Tabas (Iran) and Valdivia (Chile).
4. RESULTS AND DISCUSSION
Fig 1. Three Dimensional model of soil column
The geometry of the element mesh has ten brick element.
The size of the each element is 1m in all direction. In this
there are 10 elements in the vertical direction and the
Volume: 04 Issue: 03 2017
A. Imperial Valley Earthquake (Mexico)
The earthquake happened in Imperial Valley in
Mexico in the year 1979, the magnitude of the earthquake is
6.5, and the intensity of the earthquake is 9. From the Fig. 3,
we can see the Peak Ground Acceleration occur between 7 to
8 sec time intervals. The Peak Ground Acceleration Value is
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IJMTES | International Journal of Modern Trends in Engineering and Science
0.57g. The acceleration time history is 20 sec for Imperial
Valley seismic loading. Fig. 4, represents the shear stress
distribution with respect to time for Imperial Valley. The
shear stress will cause the settlement. The maximum shear
stress is occur at the time period of 20 sec. The maximum
shear stress value is 145 Kpa. Fig. 5 shows the shear strain
distribution for Imperial Valley. The maximum shear strain
is nearly 0.004, occur at the time period of 15 sec. because
the Peak Ground Acceleration is occurred at that time is 0.4g
(Fig. 3).
ISSN: 2348-3121
Fig 7. Shows the effective vertical stress distribution for
Imperial Valley earthquake. The effective vertical stress is
3120 Kpa at the time period of 6.8 sec. Because the ground
acceleration is reached to 0.38g. Then the effective vertical
stress is decreased with respect to time and the effective
vertical stress is 1520 Kpa at the time period of 6 sec. Fig 8,
gives the pore pressure distribution for Imperial Valley, from
this figure, initially the pore water pressure will be equal to
hydro static pressure at t = 0 sec, and then the pore water
pressure get suddenly increased (at t=6.9 sec, t=7sec, t=7.2
sec) because at that time only the earthquake will reach the
Peak Ground Acceleration (PGA=0.57g). This can be
observed from the acceleration data of the Imperial Valley
earthquake in Fig 3. Then the pore water pressure come back
to hydrostatic pressure at t=50 sec.
Fig 3. Acceleration Time History Data of the Imperial Valley Earthquake
Fig 7. Effective vertical stress distribution with respect to depth for Imperial
Valley (Mexico)
Fig 4. Shear stress distribution with respect to time for Imperial Valley
(Mexico)
The pore water pressure, effective distribution at 10m depth
as shown in Fig 6. The pore water pressure is indicated by
red line by observing that we come to know initially the pore
water pressure will be equal to hydrostatic pressure and it get
increased suddenly at the time of Peak Ground Acceleration
(PGA = 0.57g), then it gradually decreases and again attain
the hydrostatic pressure, and the effective vertical stress is
denoted by green line in the Fig 6. Initially effective stress
between the soil grains will be high, at the time of seismic
loading effective stress become zero.
Fig 5. Shear strain distribution with respect to time for Imperial Valley
(Mexico)
Fig 6. Different stress distribution at 10m depth for Imperial Valley
(Mexico)
Volume: 04 Issue: 03 2017
Fig 8. Pore pressure distribution with respect to depth for Imperial Valley
B. Tabas Earthquake (Iran)
Tabas earthquake was a huge earthquake measuring
7.8 on the Richter scale which struck on September 16, 1978
in central Iran. The death toll was approximately 15,000 and
the worst damage was to the town tabas, which was at the
epicenter of the quake and completely flattened. Fig 9, shows
the acceleration history in the form of graph. From the above
graph we can see that the Peak Acceleration occur between 5
to 6 sec time interval (PGA=1g). The acceleration time
history data is taken for 25 sec. comparing to other
earthquake, maximum ground acceleration is for tabas
earthquake. Fig 10, shows that initial shear stress is low, at
the time of peak acceleration (PGA=1g). It reaches peak
value of 230 Kpa, at that time shear stress is greater than
shear strength of the soil, so the soil get failed due to shear
stress.
Fig 9. Acceleration time history of the Tabas (Iran) Earthquake
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IJMTES | International Journal of Modern Trends in Engineering and Science
ISSN: 2348-3121
Fig 10. Shear stress distribution with respect to time for Tabas (Iran)
In Fig 11, we can observe that initially shear strain is zero
and at the time (t=5.5sec) of Peak Ground Acceleration
(PGA=1g) shear strain become high, the value of shear strain
is 0.025. After 25 sec the strain will be constant because the
acceleration time history is taken for up to 25 sec. There is
no loading is given after 25 sec. So only the strain will
maintain the constant rate. Fig 12, gives the pore water
pressure, effective stress distribution at 10m depth. The pore
water pressure is indicated by red line by observing that
initially the pore pressure will be equal to hydrostatic
pressure and it get decreased suddenly at the time of Peak
Acceleration (PGA=1g), then it gradually decreases and
again attained the hydrostatic pressure and the effective
vertical stress is denoted by green line. Initially effective
stress between the soil grains will be high, at the time of
seismic loading effective stress becomes zero.
Fig 13. Effective vertical stress distribution with respect to time for Tabas
(Iran)
Fig 14. Pore pressure distribution with respect to depth for Tabas (Iran)
C. Valdivia earthquake (Chile)
The Valdivia earthquake is the most powerful
earthquake recorded in earth, rating 9.5 on the moment
magnitude scale. Fig 15, shows the maximum acceleration
occur between 2 to 3 sec time intervals. The acceleration
time history is taken for 20 sec.
Fig 11. Shear strain distribution with respect to time for Tabas (Iran)
Fig 15. Acceleration time history of Valdivia Earthquake
Fig 16, shows that, initially shear stress is low, at the time of
Peak Acceleration (PGA=0.31g) and it reaches peak value of
200 Kpa at that time shear stress is greater than shear
strength of the soil, so the soil get failed due to shear stress.
The shear stress reaches the value at 705 Kpa at a time
period of 5 sec. during that time the ground acceleration is
attain the maximum value.
Fig 12. Different stress distribution at 10m depth for Tabas (Iran)
Fig 13, represents the effective vertical stress distribution.
From this the pore pressure is increased to 45 Kpa at the time
period of 5.5 sec, and the effective vertical stress for the time
period of 5.7 sec, 7.4 sec are 35 Kpa and 20 Kpa
respectively. Fig 14, shows the pore water pressure is equal
to hydrostatic pressure at t=0 sec, and then the pore water
pressure get suddenly increased (at t =5.5 sec, t = 5.7 sec, t =
7.5 sec) because at that time only the earthquake will reach
the Peak Acceleration (PGA=1g) this can be observed from
the acceleration data of the Tabas earthquake (Fig.9), then
the pore water pressure come back to hydrostatic pressure at
t = 97 sec
Volume: 04 Issue: 03 2017
Fig 16. Shear stress distribution with respect to time for Valdivia (Chile)
Fig 17, shows that, initially shear strain is zero and the time
(t = 3.7sec) of Peak Ground Acceleration (PGA = 0.31g)
shear strain become high, the value of shear strain is 0.005,
Fig 18, shows the pore water pressure, effective stress
distribution at 10m depth. In this diagram initially the pore
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IJMTES | International Journal of Modern Trends in Engineering and Science
water pressure will be equal to hydrostatic pressure and it get
increased suddenly at the time of Peak Ground Acceleration
(PGA=0.31g), then it gradually decreases and again attain
the hydrostatic pressure. The effective vertical stress is
shown in this figure, initially the effective stress become
zero.
ISSN: 2348-3121
Ground Acceleration a sudden settlement takes place and
after that there is no settlement takes place.
Fig 21. Settlement of soil column for three different kinds of seismic loading
5. CONCLUSION
Fig 17. Shear strain distribution with respect to time for Valdivia (Chile)
Fig 18. Different stress distribution at 10m depth for Valdivia (Chile)
The settlement for three different seismic loading namely
Imperial Valley, Tabas, and Valdivia are 0.0215m, 0.127m,
0.564m respectively. The settlement can occur due to the
application of shear loading, and it plays an important role in
failure of soil. The shear loading can resist by improving the
strength of the soil or increasing the cohesion of the soil, or
increasing the angle of internal friction of the soil. Some
mechanical methods are also available to resist the settlement
such as vibro floating, vibro compaction. By introducing this
method the effective stress is do not reduce and the density
of the soil is also will increase. So the settlement is reduced.
REFERENCES
[1]
Fig 19. Effective vertical stress distribution with respect to time for Valdivia
(Chile)
Fig 19, shows the effective vertical stress and it reaches the
maximum value at the time period of 3.7 sec, then it is
reduced.
Fig 20, gives the pore water pressure distribution. From this
initially pore water pressure is equal to hydrostatic pressure
at t=0 sec, and then it is suddenly increased (at t=3.7 sec,
t=3.8 sec, t=3.9 sec), because at that time only the
earthquake will reach the Peak Ground Acceleration
(PGA=0.31g). This can be observed from the acceleration
data of the Valdivia Earthquake (Fig. 15), then the pore
water pressure come back to hydrostatic pressure at t = 80
sec.
Fig 20. Pore pressure distribution with respect to depth for Valdivia (Chile)
Fig 21, shows the settlement details of the soil. From this
initially there is no settlement, and at that time of Peak
Volume: 04 Issue: 03 2017
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