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1.
Farrokhzad Farzad MotahariTabari SeyedArmin Abdolghafoorkashani Hamid Tavakoli Hamidreza 《Geotechnical and Geological Engineering》2021,39(6):4071-4091
Geotechnical and Geological Engineering - Soil nailing is an in-situ soil reinforcement technique that is used to enhance the stability of land slopes, retaining walls and excavations. This... 相似文献
2.
We present a simple modelling method to estimate the volume of available groundwater in the freshwater lens of atoll islands under steady-state conditions. Model inputs include annual rainfall depth, island width for cross-sections along the length of the island, aquifer hydraulic conductivity, and depth to the contact between the upper sand aquifer and the lower limestone aquifer. The methodology is tested for nine islands of varying size in the Maldives and Micronesia. Sensitivity analysis indicates that lens volume on large islands typically is governed by the depth to the discontinuity, whereas lens volume for smaller islands is governed by rainfall rate and hydraulic conductivity. Volume curves, which relate lens volume to lens thickness, are developed for each of the nine islands and for three generic island shapes to allow rapid estimation of lens volume given field-estimated lens thickness. The methods presented in this study can be used for any small atoll island. 相似文献
3.
A. Mohammadzadeh M. J. Valadan Zoej A. Tavakoli 《Journal of the Indian Society of Remote Sensing》2009,37(2):173-184
Manual extraction of road network by human operator is an expensive and time-consuming procedure. Alternatively, automation
of the extraction process would be a great advancement. For this purpose, an automatic method is proposed to extract roads
from high resolution satellite images. In this study, using few samples from road surface, a particle swarm optimization is
applied to a fuzzy-based mean calculation system to obtain road mean values in each band of high resolution satellite colour
images. Then, the images are segmented using the calculated mean values from the fuzzy system. Optimizing the fuzzy cost function
by particle swarm optimization enables the fuzzy approach to be the best mean value of road with sub-grey level precision.
Initially, this method was applied to simulated images where the calculated mean values are consistent with the hypothetic
mean values. Application of the method to IKONOS satellite images has shown a prospective outcome for automatic road extraction.
Mathematical morphology is subsequently used to extract an initial main road centreline from the segmented image. Then, small
redundant segments are automatically removed. The quality of the extracted road centreline indicates the effectiveness of
the proposed approach. 相似文献
4.
Mohsen Tavakoli Florimond De Smedt Thomas Vansteenkiste Patrick Willems 《Natural Hazards》2014,71(3):2127-2142
This study investigates how extreme flows in the Grote Nete watershed located in the Flanders region of Belgium will respond to climate change and urban growth using the hydrological model WetSpa. Three climate change scenarios (low, mean and high), three urban development scenarios (low, medium and high) and the nine combined climate–urban change scenarios are considered. The results indicate that extreme low flows would decrease noticeably by climate change, while they would be less sensitive to urban development. On the other hand, extreme peak flows are predicted to increase considerably due to both climate change and urban growth. It is concluded that coupling the effects of land use change with climate change may lead to severe increase in the frequency river floods in winter as well as the frequency of extreme river low flows in summer. 相似文献
5.
Deep massive sulphide exploration using 2D and 3D geoelectrical and induced polarization data in Skellefte mining district,northern Sweden 
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下载免费PDF全文 Saman Tavakoli Tobias E. Bauer Thorkild M. Rasmussen Pär Weihed Sten‐Åke Elming 《Geophysical Prospecting》2016,64(6):1602-1619
Geoelectrical and induced polarization data from measurements along three profiles and from one 3D survey are acquired and processed in the central Skellefte District, northern Sweden. The data were collected during two field campaigns in 2009 and 2010 in order to delineate the structures related to volcanogenic massive sulphide deposits and to model lithological contacts down to a maximum depth of 1.5 km. The 2009 data were inverted previously, and their joint interpretation with potential field data indicated several anomalous zones. The 2010 data not only provide additional information from greater depths compared with the 2009 data but also cover a larger surface area. Several high‐chargeability low‐resistivity zones, interpreted as possible massive sulphide mineralization and associated hydrothermal alteration, are revealed. The 3D survey data provide a detailed high‐resolution image of the top ～450 m of the upper crust around the Maurliden East, North, and Central deposits. Several anomalies are interpreted as new potential prospects in the Maurliden area, which are mainly concentrated in the central conductive zone. In addition, the contact relationship between the major geological units, e.g., the contact between the Skellefte Group and the Jörn Intrusive Complex, is better understood with the help of 2010 deep‐resistivity/chargeability data. The bottommost part of the Vargfors basin is imaged using the 2010 geoelectrical and induced polarization data down to ～1‐km depth. 相似文献
6.
Nader Davoudi Hamid Reza Tavakoli Mehdi Zare Abdollah Jalilian 《Acta Geophysica》2018,66(6):1359-1373
The main goal of this article is to decluster Iranian plateau seismic catalog by the epidemic-type aftershock sequence (ETAS) model and compare the results with some older methods. For this purpose, Iranian plateau bounded in 24°–42°N and 43°–66°E is subdivided into three major tectonic zones: (1) North of Iran (2) Zagros (3) East of Iran. The extracted earthquake catalog had a total of 6034 earthquakes (Mw?>?4) in the time span 1983–2017. The ETAS model is an accepted stochastic approach for seismic evaluation and declustering earthquake catalogs. However, this model has not yet been used to decluster the seismic catalog of Iran. Until now, traditional methods like the Gardner and Knopoff space–time window method and the Reasenberg link-based method have been used in most studies for declustering Iran earthquake catalog. Finally, the results of declustering by the ETAS model are compared with result of Gardner and Knopoff (Bull Seismol Soc Am 64(5):1363–1367, 1974), Uhrhammer (Earthq Notes 57(1):21, 1986), Gruenthal (pers. comm.) and Reasenberg (Geophys Res 90:5479–5495, 1985) declustering methods. The overall conclusion is difficult, but the results confirm the high ability of the ETAS model for declustering Iranian earthquake catalog. Use of the ETAS model is still in its early steps in Iranian seismological researches, and more parametric studies are needed. 相似文献
7.
Post-Cyclic Undrained Behavior of Compacted Composite Clay Subjected to Various Cyclic Loading Paths
H. R. Tavakoli A. Shafiee M. K. Jafari 《Geotechnical and Geological Engineering》2011,29(6):1085-1097
Using a sequential procedure of undrained cyclic and post cyclic tests, the strength and stiffness degradation characteristics
of compacted composite clays are studied immediately after various cyclic loading paths by triaxial and hollow cylinder tests.
The effects of cyclic loading paths, sand contents, cyclic loading amplitude and confining pressure on the post-cyclic mechanical
behavior of the composite clays are evaluated. The results point out different peculiarities which can be of interest in assessing
the mechanical behavior of the composite clays under post seismic shaking. The results show that effect of cyclic loading
on post cyclic pore water pressure build-up is significant when pore water pressure build-up is considerably lower than the
associated value in monotonic loading. The effect of sand content and cyclic loading path on degradation of stiffness is more
remarkable than shear strength. Test results also reveal that the effect of sand content on the post cyclic pore water pressure
build-up is minor. However, when the aggregate content increases the shear strength increases. 相似文献
8.
Asskar Janalizade Choobbasti Meysam Saadati Hamid Reza Tavakoli 《Arabian Journal of Geosciences》2012,5(6):1307-1315
The performance of pile foundations in liquefiable soil subjected to earthquake loading is a very complex process. The strength and stiffness of the soil decrease due to the increase in pore pressure. The pile can be seriously destroyed by the soil liquefaction during strong earthquakes. This paper presents the response of vertical piles in liquefiable soil under seismic loads. A finite difference model, known as fast Lagrangian analysis of continua, is used to study the pile behavior considering a nonlinear constitutive model for soil liquefaction and pile?Csoil interaction. The maximum lateral displacement and maximum pile bending moment are obtained for different pile diameters, earthquake predominant frequencies, Arias intensities, and peak accelerations. It is found that the maximum lateral displacement and the maximum pile bending moment increase when the predominant earthquake frequency value decreases for a given peak acceleration value. 相似文献
9.
F. Nilforoushan F. Masson P. Vernant C. Vigny J. Martinod M. Abbassi H. Nankali D. Hatzfeld R. Bayer F. Tavakoli A. Ashtiani E. Doerflinger M. Daignières P. Collard J. Chéry 《Journal of Geodesy》2003,77(7-8):411-422
The rate of crustal deformation in Iran due to the Arabia–Eurasia collision is estimated. The results are based on new global positioning system (GPS) data. In order to address the problem of the distribution of the deformation in Iran, Iranian and French research organizations have carried out the first large-scale GPS survey of Iran. A GPS network of 28 sites (25 in Iran, two in Oman and one in Uzbekistan) has been installed and surveyed twice, in September 1999 and October 2001. Each site has been surveyed for a minimum observation of 4 days. GPS data processing has been done using the GAMIT-GLOBK software package. The solution displays horizontal repeatabilities of about 1.2 mm in 1999 and 2001. The resulting velocities allow us to constrain the kinematics of the Iranian tectonic blocks. These velocities are given in ITRF2000 and also relative to Eurasia. This last kinematic model demonstrates that (1) the north–south shortening from Arabia to Eurasia is 2–2.5 cm/year, less than previously estimated, and (2) the transition from subduction (Makran) to collision (Zagros) is very sharp and governs the different styles of deformation observed in Iran. In the eastern part of Iran, most of the shortening is accommodated in the Gulf of Oman, while in the western part the shortening is more distributed from south to north. The large faults surrounding the Lut block accommodate most of the subduction–collision transition. 相似文献
10.
Behrooz Tavakoli 《Journal of Seismology》2002,6(4):525-545
The sensitivity and overall uncertainty in peak ground acceleration (PGA)estimates have been calculated for the city of Tabriz, northwestern Iran byusing a specific randomized blocks design. Eight seismic hazard models andparameters with randomly selected uncertainties at two levels have beenconsidered and then a linear model between predicted PGA at a givenprobability level and the uncertainties has been performed. The inputmodels and parameters are those related to the attenuation, magnituderupture-length and recurrence relationships with their uncertainties.Application of this procedure to the studied area indicates that effects ofthe simultaneous variation of all eight input models and parameters on thesensitivity of the seismic hazard can be investigated with a decreasingnumber of computations for all possible combinations at a fixed annualprobability. The results show that the choice of a mathematical model ofthe source mechanism, attenuation relationships and the definition ofseismic parameters are most critical in estimating the sensitivity of seismichazard evaluation, in particular at low levels of probability of exceedance.The overall uncertainty in the expected PGA for an annual probability of0.0021 (10% exceedence in 50 yr) is expressed by a coefficient ofvariation (CV) of about 34% at 68% confidence level for a distance ofabout 5km from the field of the major faults. The CV will decrease withincreasing site-source distance and remains constant, CV = 15%, fordistances larger than 15 km. Finally, treating alternative models on theoverall uncertainty are investigated by additional outliers in input decision. 相似文献