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51.
Pile groups are frequently used to support bridge decks. Scour in the vicinity of piles is the main cause for the bridges failure. In this research, to address the effects of uniform and nonuniform pile spacing on the equilibrium scour depth, laboratory experiments were carried out under steady clear-water conditions. For this purpose, scour depth produced by pile group with various pile spacing and arrangement was investigated using a laboratory flume. Flume bed was covered by uniform sediments with a median size of 0.9?mm and 0.2?m thickness. Flow discharge and velocity as well as scour depth were recorded in each experiment and the data were analyzed. The results showed that the pile spacing influences the local scour depth and with increase in uniform and transverse (perpendicular to the flow) spacing, the maximum scour depth was reduced. The pile spacing variation in line with the flow has a minor effect on scour depth. In addition, the pile spacing perpendicular to the flow was with the most influences on scour depth. The results of this research can be used by engineers to optimize the design of bridges. 相似文献
52.
Natural Resources Research - Prediction of biochemical oxygen demand (BOD) as the main pollution indicators of organic pollution in freshwater resources is necessary. In the present work, a hybrid... 相似文献
53.
Over the past decade, land development activities on hillsides in northern Utah have resulted in a significant increase in
landslide activity throughout the region. The majority of recent landslides are shallow and they occurred on cut gentle slopes
especially during spring and early summer due to snowmelt induced elevated groundwater tables. The geologic material documented
at numerous landslide sites is a soft gray-green completely decomposed Norwood Tuff. The present study addresses the mechanism
of a shallow landslide in completely decomposed Norwood Tuff based on field, laboratory and numerical investigations. Detailed
slope surface geometry obtained from laser-scan surveys together with strength and stress–strain parameters derived from laboratory
triaxial tests on undisturbed samples of completely decomposed Norwood Tuff collected from the landslide site are employed
with finite-element modeling to examine the effects of ground surface deformation patterns on the yielding behavior of the
slide mass. The numerical results indicate a gradual retreat of the yield zone with progressive landslide deformation, which
eventually becomes concentrated within the accumulation zone of the landslide, compared to a well-developed yield zone within
the entire slide mass at the onset of landslide movement. Limit equilibrium stability analyses along potential sliding surfaces
of extent limited within the yield zone of the displaced slide mass produce lower safety factors than an analysis based on
the original sliding surface comprising the entire slide mass. 相似文献
54.
Mahdi Jafarzadeh Reza Moussavi Harami Abdolhossein Amini Asadollah Mahboubi Farzin Farzaneh 《Arabian Journal of Geosciences》2014,7(10):4245-4263
In this study, the whole-rock geochemistry of 35 Oligocene–Miocene sandstone and shale samples from the Zivah Formation, Moghan area (NW Iran) were collected and analyzed for evaluation of their provenance, tectonic setting and the intensity of paleo-weathering. Low to moderate values of the chemical index of alteration (mean CIA?=?53/68 for sandstones/shales) and relatively high values of index of compositional variability (mean ICV?=?1.23/1.08 for sandstones/shales) suggest weak chemical weathering and an immature source. These results support for the semi-arid and semi-humid paleoclimate conditions in the source area. The geochemistry results reveal that the sediments were deposited in a basin related to the island arc and active continental margin tectonic settings, probably indicating the time of initial collision between Arabia and Eurasia. The enrichment of Cr, Ni and V in the sandstone and shales are consistent with mafic input from the source area. However, La/Th vs. Hf and La/Sc vs. Co/Th plots reveal mixed source of felsic and intermediate volcanic rocks. The data indicate that the sediments most likely originated from a mixture of mafic, intermediate and felsic igneous source areas, possibly as the erosional products of localized topography of the Talysh and the Lesser Caucasus mountains (south to southwest), created by compression in the Moghan region during the syn-collisional development of the Caucasus. 相似文献
55.
Lin Li Yi Pan Farshad Amini Kuang Cuiping Jean-Louis Briaud 《Geotechnical and Geological Engineering》2014,32(4):847-857
Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and land-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. This study addresses erosion resistance performance of a levee strengthening technique—high performance turf reinforcement mat under combined wave and surge overtopping conditions using full-scale flume tests as well as erosion function apparatus (EFA) tests. Based on the results of full-scale flume tests, an “upper limit” of soil loss is observed for certain flow conditions. Erosion rate was presented as a function of velocity and freeboard. The effect of duration of overtopping on the erosion depth is also determined. The results of EFA tests indicate that the presence of grass roots substantially improve the critical velocity and soil erodibility. 相似文献
56.
Natural Hazards - Hurricanes Irma and Maria caused widespread destruction in Puerto Rico in 2017. In the absence of government recovery support and denial of assistance based on ownership, many... 相似文献
57.
Sfidari EBRAHIM Amini ABDOLHOSSIEN Kadkhodaie ALI Sayedali MOHSEN Zamanzadeh SEYED MOHAMMAD 《《地质学报》英文版》2018,92(4):1523-1543
The Kimmeridgian‐Tithonian aged Arab Formation, as the main reservoir of the Jurassic succession in the Balal oilfield, located in the offshore region of the Iranian sector of the Persian Gulf, is investigated in this study. The formation is composed of dolomites and limestones with anhydrite interbeds. Based on detailed petrographic studies, six microfacies are recognized, which are classified in four sub‐environments including supratidal, intertidal, lagoonal and the high energy shoal of a homoclinal carbonate ramp. The main diagenetic features of the studied succession include dolomitization, anhydritization, cementation, micritization, fracturing and compaction. Based on stable isotope data, dolomitization of the upper Arab carbonates is related to sabkha settings (i.e. evaporative type). In terms of sequence stratigraphy, three shallowing‐upward sequences are recognized, based on core and wireline log data from four wells of the studied field. Considering depositional and diagenetic effects on the reservoir quality, the studied facies are classified into eight reservoir rock types (RRT) with distinct reservoir qualities. Dolomitization has played a major role in reservoir quality enhancement, whereas anhydritization, carbonate cementation, and compaction have damaged the pore throat network. Distribution of the recognized RRTs in time and space are discussed within the context of a sequence stratigraphic framework. 相似文献
58.
S. Akbarnezhad A. Amini A. Soltani Goharrizi T. Rainey L. Morawska 《International Journal of Environmental Science and Technology》2018,15(5):1039-1048
Two proposed quartz fibrous filters with dissimilar solid volume fractions and thicknesses are investigated for their efficiency in removing soot aerosol particles from air. Soot particles are sourced from a candle burning in a chamber, and the tests involve 1.5 h of continuous loading of particles at three different flow rates: 4.5, 8.15 and 9.55 l/min. The fractional efficiency, morphology and pressure drop of both clean and loaded filters are studied using a scanning mobility particle sizer, scanning electron microscope and differential pressure gauge. Both filters have relatively similar levels of efficiency 93% for particle size (100–400 nm) at the lowest flow rate. At higher flow rates, the re-entrainment process effects the filtration efficiency of both filters. At the higher flow rate of 8.15 l/min, the filter with a higher solid volume fraction and thickness shows a higher pressure drop and an efficiency level of 95%. Increasing the flow rate to 9.55 l/min helps to pass the particles with diameters larger than 100 nm through two filters. This phenomenon decreases the fractional efficiency of both filters during the loading time. 相似文献
59.
The Upper Red Formation (URF) comprises over 1–5 km of late Miocene siliciclastic sediments in the Central Iran Basin. The formation is dominated by volcaniclastic conglomerates and arenites. The prevailing arid conditions during most of the basin's history resulted in deposition of predominantly organic‐poor, red sediments with gypsum and zeolites. This investigation concentrates on the mineralogy and geochemistry of the URF in the southern and northern margins of the basin where the formation was buried to depths of 2.4 and 6.6 km, respectively. Fine fraction mineral separates from the southern margin consist of nearly pure smectite and zeolites at a depth of 400 m and smectite with minor quartz and calcite at 1800 m. Shallow samples (1350 m) from the northern section are rich in smectite, illite/smectite with some discrete illite and chlorite. This assemblage is progressively replaced by discrete illite and chlorite with increasing burial depth so that only these two minerals are found at depths greater than 4300 m. The initial alteration process involved replacement of glass and volcanic lithics by smectite and zeolites in both margins of the basin. Increased depth of burial in the northern margin resulted in the progressive isochemical alteration of smectite to discrete illite and chlorite. Diagenesis of clay assemblages occurred essentially in a closed system. Solute products of glass hydrolysis reactions were retained in highly alkaline, saline ground waters from which zeolites, carbonates and oxides precipitated as cements. It is unlikely that these sediments were ever significantly leached by meteoric waters or by organic acids generated during burial diagenesis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
60.
Tao Pei Stanislav Sobolevsky Carlo Ratti Alexander Amini Chenghu Zhou 《Transactions in GIS》2014,18(Z1):126-142
The aggregated mobile phone network (AMPN) (i.e. the calling time or numbers are aggregated at every vertex), which records the call volume between different places over time, has been studied extensively to reveal the mobility patterns of residents, etc. Nevertheless, most previous works were implemented based on the non‐directionality of the network model. This simplification may overlook some important characteristics of AMPN. To explore the AMPN as a directional network model, we introduce the concept of directional heterogeneity in the study of AMPN data. The heterogeneity is twofold: (1) the imbalance of vertex (difference between outgoing and incoming calls of the vertex); and (2) the reciprocity of each edge (difference between the directed weights of the same edge). Taking the data of Singapore as an example, we systematically analyze the directional heterogeneity of AMPN. Our findings include three aspects. First, the AMPN shows as more unbalanced in the night‐time than in the daytime, and its imbalance decreases as vertex granularity increases. Second, the directional heterogeneity varied with locations. Specifically, the residential area is dominated by deficits and others by surpluses. Third, the trajectories of incoming and outgoing calls follow a similar geographical pattern (i.e. southeast‐north‐south‐north‐southeast), indicating the calling behavior and routine mobility of users over time and space. 相似文献