Clear-water scour around semi-elliptical abutments with armored beds     

Jueyi SUI  Hossein AFZALIMEHR  Abdolreza Kabiri SAMANI  Mehrnoosh MAHERANI 《国际泥沙研究》2010,25(3):233-245

Experimental study has been carried out under a clear-water scour condition to explore the local scour around semi-elliptical model bridge abutments with armor-layer bed, compared with the local scour process around semi-circular abutment. Two types of model bridge abutments, namely semi-elliptical and semi-circular abutments have been used in this experimental study. The model abutments had a ratio of streamwise length of abutment to the length of abutment transverse to the flow of 2 for semi-circular abutments and 3 for semi-elliptical abutments. In total, 50 Experiments have been designed and conducted under different flow conditions such as bed shear velocities, flow depth, and dimensions of bridge abutment model, as well as grain size of the bed material. Based on these experiments, the scour process around bridge abutments has been assessed. The dependence of the equilibrium scour depth of the scour hole on hydraulic variables has been studied. Empirical equation describing the equilibrium scour depth of the scour hole around bridge abutments has been developed.  相似文献   

Reduction of local scour around bridge pier groups using collars     

Manouchehr HEIDARPOUR  Hossein AFZALIMEHR  Elham IZADINIA 《国际泥沙研究》2010,25(4):411-422

In this paper reduction of scour around group of two and three piers using circular collar has been carried out for the case of clear-water flow over uniform sediment. The efficiency of collars, with different sizes and spaces between piers is studied through experiments in group of two and three piers. The result reveals that collar has more influence in reduction of scour depth in rear piers than the first pier. Also, when the spacing between the piers increases the area without protection between the piers is washed away resulting deeper scour holes at the rear piers.  相似文献   

Cretaceous subduction-related volcanism in the northern Sanandaj-Sirjan Zone, Iran     

Hossein Azizi  Ahmad Jahangiri 《Journal of Geodynamics》2008,45(4-5):178-190

Cretaceous volcanic rocks (SCV) are widely developed in the northern part of the Sanandaj-Sirjan Zone, northwest Iran. Based on the mineralogy, texture and geochemical composition these rocks are divided in two main groups, the first and main one situated in the central part of the study area and the second one in the northeast. The former is dominantly basalts, andesitic basalts, and andesites and the latter comprises andesite, trachy-andesite to acidic variants, with porphyritic to microlithic porphyry and vitrophyric textures. Beside the differences between these two groups, the chemical compositions all of these rocks show a calc-alkaline affinity and enrichment in LIL elements (Rb, Ba, Th, U, and Pb) and depletion in Nb, Ti, and Zr, as evident in spider diagrams normalized to primitive mantle. The rocks are particularly enriched in Rb and depleted in Nb and Ti, as well as displaying high Rb/Sr and Rb/Ba ratios and low ratios of incompatible elements such as Nb/U (<10; range, 0.6–9), Th/U (<2), and Ba/Rb (<20). The significant U enrichment relative to neighbouring Nb and Th in the mantle-normalized variation diagram is mainly a result of source enrichment by slab-derived fluids. Significantly lower Nb/U ratios are observed in arc volcanics. These low values are generally ascribed to the strong capacity of LILE and the inability to transfer significant amounts of HFSE via slab-derived hydrous fluid. The results of geochemical modelling suggest a mantle lithospheric source that was metasomatized by fluids derived from a Neo-Tethyan subducted slab during the Middle to Late Cretaceous in the northern part Sanandaj-Sirjan Zone.  相似文献   

On the structural age of the Rhoscolyn antiform,Anglesey, North Wales     

Hossein Hassani  Stephen J. Covey‐Crump  Ernest H. Rutter 《Geological Journal》2004,39(2):141-156

In the Rhoscolyn area of Anglesey, the late Precambrian interbedded psammites and pelites of the Monian Supergroup are folded into a kilometre‐scale antiform, plunging about 25°NE and with an axial surface dipping about 40°NW. Numerous folds of up to a few tens of metres in wavelength are present on both limbs of this antiform. These smaller‐scale folds also plunge about 25°NE but clearly belong to two separate episodes of folding, and it has become a matter of longstanding controversy as to whether the larger antiform belongs to the first or second of these episodes. Close examination of the cleavage/bedding asymmetries from all the lithologies, however, shows that the large antiform is a second‐generation structure, and that on the gently dipping northwest limb, the sense of cleavage/bedding asymmetry of the earlier cleavage in the psammitic units has been almost uniformly and homogeneously reversed (so that it appears to be axial planar to the antiform), while in the pelitic units the sense of cleavage/bedding asymmetry of the earlier cleavage has been preserved. Many of the small‐scale complexities of the observed cleavage/bedding relationships may be explained by appealing to differences in the timing of the formation of buckling instabilities relative to this reorientation of the early cleavage in the psammites during the second deformation. A first‐order analysis of the finite strains from around the large‐scale antiform shows that the orientation of the first cleavage prior to the second deformation was steeply dipping to the southeast. The second deformation correlates with the southeast‐verging Caledonian deformation affecting the Monian and Ordovician units elsewhere in northwest Anglesey, while the northwest‐verging first deformation event, which is not present in the Ordovician rocks, must have occurred before they were deposited. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Simulating winter wheat production potential under near-future climate change in arid regions of northeast Iran     

Saberali  Seyed Farhad  Shirmohammadi-Aliakbarkhani  Zahra  Nastari Nasrabadi  Hossein 《Theoretical and Applied Climatology》2022,148(3-4):1217-1238

Theoretical and Applied Climatology - Water scarcity is the key challenge in arid regions, which exacerbates under climate change (CC) and must be considered to assess the impacts of CC on cropping...  相似文献   

Applicability of generalized additive model in groundwater potential modelling and comparison its performance by bivariate statistical methods   总被引：3，自引：0，他引：3  

Fatemeh Falah  Samira Ghorbani Nejad  Omid Rahmati  Mania Daneshfar  Hossein Zeinivand 《国际地球制图》2017,32(10):1069-1089

Groundwater is the most valuable natural resource in arid areas. Therefore, any attempt to investigate potential zones of groundwater for further management of water supply is necessary. Hence, many researchers have worked on this subject all around the world. On the other hand, the Generalized Additive Model (GAM) has been applied to environmental and ecological modelling, but its applicability to other kinds of predictive modelling such as groundwater potential mapping has not yet been investigated. Therefore, the main purpose of this study is to evaluate the performance of GAM model and then its comparison with three popular GIS-based bivariate statistical methods, namely Frequency Ratio (FR), Statistical Index (SI) and Weight-of-Evidence (WOE) for producing groundwater spring potential map (GSPM) in Lorestan Province Iran. To achieve this, out of 6439 existed springs, 4291 spring locations were selected for training phase and the remaining 2147 springs for model evaluation. Next, the thematic layers of 12 effective spring parameters including altitude, plan curvature, slope angle, slope aspect, drainage density, distance from rivers, topographic wetness index, fault density, distance from fault, lithology, soil and land use/land cover were mapped and integrated using the ArcGIS 10.2 software to generate a groundwater prospect map using mentioned approaches. The produced GSPMs were then classified into four distinct groundwater potential zones, namely low, moderate, high and very high classes. The results of the analysis were finally validated using the receiver operating characteristic (ROC) curve technique. The results indicated that out of four models, SI is superior (prediction accuracy of 85.4%) following by FR, GAM and WOE, respectively (prediction accuracy of 83.7, 77 and 76.3%). The result of groundwater spring potential map is helpful as a guide for engineers in water resources management and land use planning in order to select suitable areas to implement development schemes and also government entities.  相似文献   

Practical Investigations on Use of Weighted Joint Density to Decrease the Limitations of RQD Measurements     

Mohammad Haftani  Hossein A. Chehreh  Abolfazl Mehinrad  Kheirollah Binazadeh 《Rock Mechanics and Rock Engineering》2016,49(4):1551-1558

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Design of a support vector machine with different kernel functions to predict scour depth around bridge piers     

Hassan Sharafi  Isa Ebtehaj  Hossein Bonakdari  Amir Hossein Zaji 《Natural Hazards》2016,84(3):2145-2162

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A Simple Limit Equilibrium Approach for Calculation of Ultimate Bearing Capacity of Shallow Foundations on Two-Layered Granular Soils     

Mahmoud Ghazavi  Amir Hossein Eghbali 《Geotechnical and Geological Engineering》2008,26(5):535-542

The bearing capacity of shallow foundations in a non-homogeneous soil profile has been a challenging task in geotechnical engineering. In this paper, a limit equilibrium method is used for calculating bearing capacity factors of shallow foundations constructed on a two-layered granular soil profile. The main objective has been to determine the ultimate bearing capacity computed from equivalent bearing capacity factors N_q and N_γ and comparing that with numerical analysis using finite element methods. It will be shown that the data obtained form the developed method are well comparable with those obtained from FE approach, specially when the difference between shear strength parameters of layers is low which is a practical case for sedimentary soil profiles and also for artificially compacted soils. A computer program has been developed to investigate the influence of various parameters on bearing capacity factors.  相似文献   

Modelling thermal comfort of visitors at urban squares in hot and arid climate using NN-ARX soft computing method     

Shahab Kariminia  Shervin Motamedi  Shahaboddin Shamshirband  Jamshid Piri  Kasra Mohammadi  Roslan Hashim  Chandrabhushan Roy  Dalibor Petković  Hossein Bonakdari 《Theoretical and Applied Climatology》2016,124(3-4):991-1004

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