18
1735-0522
316
Non-invasive Continuous Surface Wave Measurements for In Situ Damping Ratio Profiling of Soils
Haddad
A.
Shafabakhsh
Gh.
1
6
2007
5
2
93
103
03
11
2009
11
01
2014
Local site conditions have a strong effect on ground response during earthquakes. Two
important soil parameters that control the amplification effects of seismic motions by a soil column
are the soil hysteretic damping ratio and shear wave velocity. This paper presents the results of in
situ damping ratio measurements performed using continuous surface wave attenuation data at a
site in Semnan University campus and analysis used to obtain the near surface soils damping ratio
profile. Once the frequency dependent attenuation coefficients are determined, the shear damping
ratio profile is calculated using an algorithm based on constrained inversion analysis. A computer
code is developed to calculate the shear damping ratio in each soil layer. Comparisons of the in situ
shear damping ratio profile determined from continuous surface wave with cross hole independent
test measurements are also presented. Values of shear damping ratio, obtained using continuous
surface wave measurements, were less than the measured using cross hole tests, possibly because
of the higher frequencies used in cross hole tests.
317
Evaluation of Undrained Shear Strength of Loose Silty Sands Using CPT Results
Naeini
S.A.
Ziaie-Moayed
R.
1
6
2007
5
2
104
117
03
11
2009
11
01
2014
Series of undrained monotonic triaxial tests and cone penetration tests were conducted on
loose silty sand samples to study correlation between undrained shear strength of silty sands (Sus)
and piezocone test results. CPT tests were conducted at 27 silty sand samples in calibration
chamber. The results indicate that, in low percent of silt (0-30%), as the silt content increases, the
undrained shear strength (Sus) and cone tip resistance (qc) decreases. It is shown that, fines content
affects undrained shear strength (Sus) and cone tip resistance (qc) similarly. On the basis of obtained
results, equations were proposed to determine the normalized cone tip resistance (qc1n) and
undrained shear strength (Sus) of silty sand in term of fines content. Finally based on those
equations, a correlation between normalized cone tip resistance and undrained shear strength of
silty sand is presented. It is shown that the normalized undrained shear strength and normalized
cone tip resistance of loose silty sands (F.C. <30%) decreases with increase of silt contents.
318
Analysis of Buried Plastic Pipes in Reinforced Sand under Repeated-Load Using Neural Network and Regression Model
Moghaddas Tafreshi
S.N.
Tavakoli Mehrjardi
Gh.
Moghaddas Tafreshi
S.M.
1
6
2007
5
2
118
133
03
11
2009
11
01
2014
The safety of buried pipes under repeated load has been a challenging task in
geotechnical engineering. In this paper artificial neural network and regression model for
predicting the vertical deformation of high-density polyethylene (HDPE), small diameter flexible
pipes buried in reinforced trenches, which were subjected to repeated loadings to simulate the
heavy vehicle loads, are proposed.
The experimental data from tests show that the vertical diametric strain (VDS) of pipe embedded
in reinforced sand depends on relative density of sand, number of reinforced layers and height of
embedment depth of pipe significantly. Therefore in this investigation, the value of VDS is related
to above pointed parameters.
A database of 72 experiments from laboratory tests were utilized to train, validate and test the
developed neural network and regression model. The results show that the predicted of the vertical
diametric strain (VDS) using the trained neural network and regression model are in good
agreement with the experimental results but the predictions obtained from the neural network are
better than regression model as the maximum percentage of error for training data is less than
1.56% and 27.4%, for neural network and regression model, respectively. Also the additional set
of 24 data was used for validation of the model as 90% of predicted results have less than 7% and
21.5% error for neural network and regression model, respectively. A parametric study has been
conducted using the trained neural network to study the important parameters on the vertical
diametric strain.
319
Discrete least square method (DLSM) for the solution of free surface seepage problem
Rahmani Firoozjaee
A.
Afshar
M.H.
1
6
2007
5
2
134
143
03
11
2009
A meshless method namely, discrete least square method (DLSM), is presented in the
paper for the solution of free surface seepage problem. In this method computational domain is
discredited by some nodes and then the set of simultaneous equations are built using moving least
square (MLS) shape functions and least square technique. The proposed method does not need any
background mesh therefore it is a truly meshless method. Several numerical two dimensional
examples of Poisson partial differential equations (PDEs) are presented to illustrate the
performance of the present DLSM. And finally a free surface seepage problem in a porous media is
solved and results are presented.
320
Optimal Identification of Ground-Water Pollution Sources
Ghafouri
H.R.
Darabi
B.S.
1
6
2007
5
2
144
155
03
11
2009
11
01
2014
A new mathematical model for identifying pollution sources in aquifers is presented. The
model utilizes Lagrange Constrained Optimization Method (LCOM) and is capable to inversely
solve unsteady fluid flow in saturated, heterogeneous, anisotropic confined and/or unconfined
aquifers. Throughout the presented model, complete advection-dispersion equation, including the
adsorption as well as retardation of contaminant, is considered. The well-known finite element
method is used to discretize and solve the governing equations. The model verification is
implemented using a hypothetical example. Also, the applicability of the developed code is
illustrated by the real field problem of Ramhormoz aquifer in southwestern Iran.
321
Diagonal Compression Criterion on Compression Reinforcement Ratio in Flexural HSRC Members
Maghsoudi
A.A.
Akbarzadeh Bengar
H.
1
6
2007
5
2
156
167
03
11
2009
11
01
2014
Limit to the tension reinforcement ratio ( ρ) in flexural high strength reinforced concrete
(HSRC) members is based on the requirement that tension failure as sufficient rotation capacity are
ensured at ultimate limit state. However, the provisions for the total amount of longitudinal
reinforcement ratio ( ρ and ρ’) are not associated with any rational derivation. In this paper, a
quantitative measure to evaluate an upper limit to the compression reinforcement ratio ρBmax of
flexural HSRC members is proposed. The quantitative criterion to ρBmax can be derived from i) steel
congestion and ii) considerations that are related to the diagonal compression bearing capacity of
the members.
In this paper it is shown that, when shear loading is dominant, the limit to is set by the diagonal
compression criterion. Parameters that affect this limit are deeply investigated and the expressions
were derived for different end conditions, to provide an additional tool for a better design and
assessment of the flexural capacity of HSRC members.