Simultaneous Effects of Joint Spacing and Orientation on TBM Cutting Efficiency in Jointed Rock Masses     

Hadi Bejari  Jafar Khademi Hamidi 《Rock Mechanics and Rock Engineering》2013,46(4):897-907

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Deriving an intelligent model for soil compression index utilizing multi-gene genetic programming     

Danial Mohammadzadeh S  Jafar Bolouri Bazaz  S. H. Vafaee Jani Yazd  Amir H. Alavi 《Environmental Earth Sciences》2016,75(3):262

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Environmental geochemistry of Cu, Zn and Pb in sediment from Qeshm Island-Persian Gulf, Iran: a comparison between the northern and southern coast and ecological risk     

Golshan Shirneshan  Alireza Riyahi Bakhtiari  Seyed Jafar Seyfabadi  Samar Mortazavi 《Geochemistry International》2013,51(8):670-676

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Dynamic response of a thick plate on viscoelastic foundation to moving loads     

Musharraf Zaman  Michael R. Taheri  A. Alvappillai 《国际地质力学数值与分析法杂志》1991,15(9):627-647

A finite element algorithm is presented to evaluate the dynamic response of pavements including aircraft-guideway-foundation interaction. The pavement-foundation system is modeled by a series of thick plate elements supported by discrete springs and dashpots at the nodal points representing the viscoelastic foundation. The moving aircraft loads are represented by masses each supported by a spring and dashpot suspension system and having a specified horizontal velocity and acceleration. The accuracy of the algorithm is verified by comparing the finite element solution with available analytical results. A parametric study is conducted to determine the effects of various parameters on the dynamic response of pavements to moving loads.  相似文献   

On the free oscillations of a laterally heterogeneous earth model     

Jafar Arkani-Hamed 《Pure and Applied Geophysics》1972,95(1):5-17

Summary The equations of motion for the free oscillations of a heterogeneous spherical earth model are derived. It is found that the lateral variations of density and elastic moduli couple the odd(even) harmonics of the spheroidal oscillations with themselves as well as with the even (odd) harmonics of the torsional oscillations.List of symbols r, , Spherical coordinates;r is the radial distance from earth's center, is the co-latitude, and is the east longitude - r Space vector denoting a point with coordinatesr, , and - Gradient operator - ² Laplacian operator - _ij Kronecker's delta function - I Identity matrix - i   相似文献   

Subduction of continental margins and the uplift of high-pressure metamorphic rocks     

Andrew Hynes  Jafar Arkani-Hamed  Reinhard Greiling 《Earth and Planetary Science Letters》1996,140(1-4):13-25

The mechanism by which high-pressure metamorphosed continental material is emplaced at high structural levels is a major unsolved problem of collisional orogenesis. We suggest that the emplacement results from partial subduction of the continental margin which, because of its high flexural rigidity, produces a rapid change in the trajectory of the descending slab. We assume a two-fold increase in effective elastic thickness of the lithosphere as the continental margin approaches the subduction zone, and calculate the flexural profile of a thin plate for progressive downward migration of the zone of increased rigidity. We assess the effect of changes in the flexural profile on the overlying accretionary prism and mantle wedge as the continent approaches by estimating the extra stresses that are imposed on the wedge due to the bending moment exerted by the continental part of the plate. The wedges overlying the subduction zones, and the subducting slab itself, experience substantial extra compressional stress at depths of around 100 km, and extensional stress at shallower depths, as the continental margin passes through the zone of maximum curvature. The magnitudes of such extra stresses are probably adequate to effect significant deformation of the wedge and/or the descending plate, and are experienced in a time interval of less than 5 m.y. for typical subduction rates. The spatial variation of yield stresses in the region of the wedge and descending slab indicates that much of this deformation may be taken up in the crustal part of the descending slab, which is the weakest region in the deeper parts of the subduction zone. This may result in rapid upward migration of the crust of the partially subducted continental margin, against the flow of subduction. High-pressure metamorphosed terranes emplaced by the mechanism envisaged in this paper would be bounded by thrust faults below and normal faults above. Movement on the faults would have been coeval, and would have resulted in rapid unroofing of the high-pressure terranes, synchronous with arrival of the continental margin at the subduction zone and, therefore, relatively early in the history of a collisional orogen.  相似文献   

Variography of ores from the Rubtsovsk massive-sulfide copper-lead-zinc deposit (Altai Territory)     

N. N. Shatagin  Sharif Jafar  B. M. Chekalin 《Moscow University Geology Bulletin》2007,62(6):376-382

Construction of variograms (variation diagrams) of metal concentrations in ores and their structural analysis allowed determining that the structure of the ore body at the Rubtsovsk massive-sulfide copper-lead-zinc deposit is heterogeneous, both in vertical section and along its strike. Application of a prospecting circle of at least 50 m diameter when recalculating the reserves is recommended.  相似文献   

Dead Sea influence on the chemical and mineralogical characteristics of the dry deposition fallen over the eastern highland of central Jordan     

Tayel El-Hasan  Kamal Momani  Jafar Al-Nawayseh  Khaled Al-Nawayseh 《Environmental Geology》2008,54(1):103-110

The Dead Sea as a unique geological and geographical phenomenon has an effect on its adjacent areas. Therefore, 17 sampling sites at the eastern highlands facing the Dead Sea; beside three blank sites were collectedlocated during summer (2005). The aim was to investigate such influence on the chemical and mineralogical composition of dry deposition, and to measure the settling rate. The investigations showed that the depositional rate at the studied sites was much lower than other areas at central and southern Jordan. The average heavy metal contents are almost similar in all sampling sites and the blanks, and they exhibit similar enrichment series, whereas, the meaningful difference between sampling sites and blank was in cation and anion content, which caused different enrichment series between the two sites. The index of pollution (IP) confirms that mainly cations and anions have IP > 1.0 and they dominate the southern and the closest sampling sites to the Dead Sea. The XRD results reveals that the studied samples have minor phases such as halite, gypsum, and dolomite. Meanwhile, these mineral phases are not found in blank samples. All these results indicates the influence of the Dead Sea, as it is a highly saline large water mass, which accompanied with by high evaporation rates causing causes the atmosphere over the Sea to be enriched with these cations, anions, elements and minerals, which eventually are adsorbed in air particulate or carried out as dry deposition and transported by the NW–SE prevailing winds, and fall over the eastern highlands.  相似文献   

Evaluating distribution pattern of petrophysical properties and their monitoring under a hybrid intelligent based method in southwest oil field of Iran     

Aynur Nasseri  Mohammad Jafar Mohammadzadeh 《Arabian Journal of Geosciences》2017,10(1):9

This study deals with reservoir characterization based on well log data using an unsupervised self-organizing map (SOM) and supervised neural network algorithms with the aim of clustering log responses into reservoir facies of an oil field located in southwest of Iran. In order to promote and justify the quality control and quantify spatial relationships for petrophysical properties, some of neural network-based approaches were introduced such as the SOMs as the intelligent clustering method compared with other hybrid methods, principal component analysis networks (PCANs) and multilayer perceptron (MLP) and statistical clustering (CA) methods. The results obtained from all the abovementioned methods are compared to each other, and the best option is selected based on accuracy and capabilities of clustering and estimation of the petrophysical data, concluding that for predicting any characteristic of the reservoirs, the appropriate network should be chosen and a unique network cannot be convenient for all of them. Accordingly, the SOM clustering technique was employed to classify the reservoir rocks. Based on the SOM visualization, the reservoir rocks were classified into six facies associated with specific petrophysical properties; among them, F6 expressed the best reservoir quality which is characterized by the low amount of density, highest DT, high amount of neutron porosity (NPHI), and lowest GR response. Ultimately, the performance of all the methods was compared to estimate the porosity and permeability within each facies. The results revealed the preference and reliability of PCAN in predicting porosity and confirmed the capability of MLP in permeability prediction. This study also indicates that neuro-prediction of formation properties using well log data is a feasible methodology for optimization of exploration programs and reduction of expenditure by delineating potentially oil-bearing strata with higher accuracy and lower expenses. The resulting neural net-based model can be used as a powerful and distributive system to reduce the high impact of risk in similar fields.  相似文献   

Seasonal variation of the double diffusion processes at the Strait of Hormuz     

AZIZPOUR Jafar  CHEGINI Vahi  SIADATMOUSAVI Seyed Mostafa 《海洋学报(英文版)》2017,36(1):26-34

Profiles of salinity and temperature were measured in the strait of Hormuz (SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion (DD) processes, Turner (TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering (SF), diffusive convection (DC) and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses (the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part, water column was stable in summer and DC happened in most part of water column in winter.  相似文献