Assessment of contaminants in Dubai coastal region, United Arab Emirates

Coastal uses and other human activities have inevitably impinged on the Gulf environment; therefore, these regions require continuous monitoring. The investigated area covered the maximum fragments of Dubai coastal region in the Arabian Gulf. The determination of major oxides and trace metal concentrations in Dubai sediments revealed three heavily and moderately contaminated regions. One is in the far northeastern part at Al-Hamriya Sts 1–3 and contaminated by Fe, Cu, Pb, and Zn; the second is in the mid-northeastern part at Dry Docks and contaminated by Cu, Ni, Pb, and Zn; and finally, the third is in the near southwestern part at Dubal and contaminated by Fe, Mg, Cr, Ni, and Zn. Al-Hamriya St 3 represented the highest values of Cu, Pb, and Zn, whereas Dubal exhibited the maximum values of Fe, Mg, Ba, Cr, Mn, Ni, and V. The anthropogenic discharge and natural deposits are the main sources of contamination. In general, all trace and major elements showed the minimal levels at Jebel Ali Sanctuary (Sts 11, 12, 13) except for Sr and Ca, which showed their maximum values. The highest concentrations of Ca and Sr are mainly attributed to carbonate gravel sands and sands, which cover most stations. Each of V and Ni showed negative correlation with TPH, which may be indicated that the source of oil contamination in the region is not related to crude oil but mostly attributable to anthropogenic sources. The significant positive correlation, which was found between trace metals and TOC indicates that organic matter plays an important role in the accumulation of trace metals in case of Cu, Zn, and Pb.     

New approaches to determine the ultimate bearing capacity of shallow foundations based on artificial neural networks and ant colony optimization

In this study, two different approaches are proposed to determine the ultimate bearing capacity of shallow foundations on granular soil. Firstly, an artificial neural network (ANN) model is proposed to predict the ultimate bearing capacity. The performance of the proposed neural model is compared with results of the Adaptive Neuro Fuzzy Inference System, Fuzzy Inference System and ANN, which are taken in literature. It is clearly seen that the performance of the ANN model in our study is better than that of the other prediction methods. Secondly, an improved Meyerhof formula is proposed for the computation of the ultimate bearing capacity by using a parallel ant colony optimization algorithm. The results achieved from the proposed formula are compared with those obtained from the Meyerhof, Hansen and Vesic computation formulas. Simulation results showed that the improved Meyerhof formula gave more accurate results than the other theoretical computation formulas. In conclusion, the improved Meyerhof formula could be successfully used for calculating the ultimate bearing capacity of shallow foundations.     

Application of statistical learning algorithms to ultimate bearing capacity of shallow foundation on cohesionless soil

This study employs two statistical learning algorithms (Support Vector Machine (SVM) and Relevance Vector Machine (RVM)) for the determination of ultimate bearing capacity (q_u) of shallow foundation on cohesionless soil. SVM is firmly based on the theory of statistical learning, uses regression technique by introducing varepsilon‐insensitive loss function. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. It also gives variance of predicted data. The inputs of models are width of footing (B), depth of footing (D), footing geometry (L/B), unit weight of sand (γ) and angle of shearing resistance (?). Equations have been developed for the determination of q_u of shallow foundation on cohesionless soil based on the SVM and RVM models. Sensitivity analysis has also been carried out to determine the effect of each input parameter. This study shows that the developed SVM and RVM are robust models for the prediction of q_u of shallow foundation on cohesionless soil. Copyright © 2010 John Wiley & Sons, Ltd.     

Scenarios of Seismic Risk in the United Arab Emirates,an Approximate Estimate

We estimate the losses due to 10 scenario earthquakes in 150 settlements of the United Arab Emirates (UAE). For southern Iran, we use four source zones and the maximum magnitudes in them as determined by GSHAP (7.2 M 8.1). For six local scenario earthquakes, we use the range 5.5 M 6.5, place the sources mainly on mapped faults and vary the distance to major cities from 10 to 60 km. In the test case of the Masafi earthquake (M5, 11 March 2002), the method and data bank we use yield the correct results, suggesting that our approach to the problem is valid for the UAE. The sources in Iran are expected to cause only minor damage, except for an M8.1 earthquake in the Makran region. For such an event we expect some deaths, several hundred injured and a loss of 3–6% of the value to the building stock in the northeastern UAE, including Oman. The losses for local scenarios with epicenters in the unpopulated areas of the UAE and for scenarios with M < 5.8 are estimated to be minor. Because the two major mapped faults run through several of the large cities, scenarios with short epicentral distances from cities have to be considered. Scenarios with M6 near cities lead to estimates of about 1000 ± 500 deaths, and several thousand injured. Most buildings are expected to be damaged to a moderate degree and the loss to buildings is estimated around 1/4of their value. If the magnitude should reach 6.5, the losses to humans and to building value could be staggering. These estimates are approximate because: (1) there exists no local seismograph network that could map active faults by locating microseismicity; (2) there exist no historically old buildings that could serve as tests for effects due to strong ground motion in the past; (3) there exist no microzonation of the subsurface properties in this region of unconsolidated building ground; (4) there exist no detailed inventory of building fragility. Nevertheless, our conclusion that there exists a substantial seismic risk in the UAE is reliable, because our method yields accurate results in the cases of earthquakes with known losses during the last several decades in the Middle East.     

小波分析和RBF神经网络在地基沉降预测中的应用研究

地基沉降是一种危害很大的环境灾害。地基沉降的监测数据经常受降雨及工程施工等诸多外界因素的干扰,故而在沉降曲线中存在许多数据突变点。为此,提出基于小波分析与RBF神经网络相结合的新的地基沉降预测方法,首先采用小波分析对对原始监测数据进行数据去噪处理,进而得到反映实际变化的地基沉降曲线,然后采用径向基函数（RBF）神经网络方法对其进行预测,为工程设计提供依据。最后结合工程实例分析,通过多种小波去噪与预测结果的对比研究,表明3次B样条小波的去噪及预测效果最好,与实测值能较好地吻合,具有较好的工程应用前景。     

Assessment of organic pollutants in the offshore sediments of Dubai, United Arab Emirates

Fifteen stations (st) were selected along Dubai coastal region to delineate the distribution and the source of total petroleum hydrocarbon (TPH), total organic carbon (TOC), total Kjeldhal nitrogen (TKN), polycyclic aromatic hydrocarbon (PAHs) and polychlorinated biphenyls. The concentrations of TPH fluctuated between 2 μg g ⁻¹ and 48018 μg g ⁻¹ and the values of TOC were in the range of 0.16–5.9 wt%, while TPAHs ranged from 0.09 μg g ⁻¹ to 161.72 μg g ⁻¹. On the other hand, TPCBs showed values between 0.8 μg kg⁻¹ and 93.3 μg kg⁻¹ and TKN values varied from 218 μg g⁻¹ to 2457 μg g ⁻¹. Distribution of oil and organic compounds in Dubai sediments are safe compared with previous studies except for limited areas at the northeastern offshore. These readings are probably due to: (1) presence of commercial or industrial ports, dry docks and fishing harbours and (2) population centers mainly concentrated at the northern part of the study area. Results indicate that TOC can be used as indicator of oil pollution only in heavily oiled sediments. The highest values of TOC, TPH, TPAHs and TPCBs corresponded to the stations covered with fine sand, due to adsorption properties and larger surface area. The evaporation of low boiling point compounds from surface layers led to enrichment of sediments with the thick residual. Al-Hamriya St 3 exhibited the highest values of TPH, TOC, TPAHs and TPCBs and the second highest value of TKN.     

Source parameters of March 10 and September 13, 2007, United Arab Emirates earthquakes

On March 10 and September 13, 2007 two earthquakes with moment magnitudes 3.66 and 3.94, respectively, occurred in the eastern part of the United Arab Emirates (UAE). The two events were widely felt in the northern Emirates and Oman and were accompanied by a few aftershocks. Ground motions from these events were well recorded by the broadband stations of Dubai (UAE) and Oman seismological networks and provide an excellent opportunity to study the tectonic process and present day stress field acting in this area. In this study, we report the focal mechanisms of the two main shocks by two methods: first motion polarities and regional waveform moment tensor inversion. Our results indicate nearly pure normal faulting mechanisms with a slight strike slip component. We associated the fault plane trending NNE–SSW with a suggested fault along the extension of the faults bounded Bani Hamid area. The seismicity distribution between two earthquake sequences reveals a noticeable gap that may be a site of a future event. The source parameters (seismic moment, moment magnitude, fault radius, stress drop and displacement across the fault) were also estimated from displacement spectra. The moment magnitudes were very consistent with waveform inversion. The recent deployment of seismic networks in Dubai and Oman reveals tectonic activity in the northern Oman Mountains that was previously unknown. Continued observation and analysis will allow for characterization of seismicity and assessment of seismic hazard in the region.     

桩承载力时效对桩土相互作用及沉降的影响分析

对软土中两根47 m长灌注桩分别在成桩28 d和1 750 d后进行了承载力试验，其极限承载力提高幅度达到30％左右。分析了单桩承载力随时间提高(称为时效)的机理，提出了单桩承载力时效对桩筏基础桩土相互作用影响的分析方法，并结合工程实例进行了分析。     

高压旋喷桩复合地基承载力与沉降计算方法分析

以具体工程为背景,以准确翔实的承载力与沉降量实测资料为依据,以高压旋喷桩复合地基的承载力、沉降量实测值与计算机值进行了对比与分析。结果表明，旋喷复合地基载荷试验时承压板下桩数不同，测得的复全地基承载力也不同，承压板下桩数越多，所得的承载力标准值越低；高压旋喷桩的加固深度与承台宽度的比值I/B对复合地基沉降量的计算机有较大影响；用分层总和法计算机复合土层的沉降量时，复合压缩模量的不同计算方法，会使计算结果出现较大差异。     

An evaluation model of artificial neural network to predict stable width in gravel bed rivers

Regime width of alluvial channels is a vital problem in river morphology and channel design. Many equations are available in the literature to predict regime width of alluvial rivers. In general, there are many approaches to estimate regime width; however, none of them is widely accepted at present. This is due to the fact that most hypotheses have many constrains which may lead to simplify governing conditions and also lack of knowledge of some physical processes associated with channel formation and maintenance. Intelligent models are a new approach to describe complex problems one of which is artificial neural networks. In this research, initially, gravel bed rivers database was used in bankfull discharge condition to train various dimensional and non-dimensional neural-network schemes with three and four variables as input data, respectively. Then, the same database was applied to fit regression analysis to estimate regime width; this led to drive dimensional and non-dimensional equations. Finally, dimensional and non-dimensional neural-network models and regression equations were compared together based on 50% error bands with other dataset. Results show that neural network can adequately estimate the regime width in gravel bed rivers and multilayer perceptron network with one hidden layer and eight hidden neurons based on dimensional data set was selected as optimum network to predict regime width. A sensitivity analysis also shows that bankfull discharge has a greater influence on regime width of gravel bed channels than the other independent parameters in dimensional scheme of neural network.     

Triassic stratigraphy,facies and evolution of the Arabian shelf in the northern United Arab Emirates

This study provides a reconstruction of the Late Permian and Triassic depositional history of the Arabian shelf in the northern United Arab Emirates based on facies analysis and foraminiferal biostratigraphy. The presented data show that sedimentation occurred in three major sequences. From the Late Permian to Olenekian carbonates and evaporites were deposited in restricted lagoons and tidal flats. After a hiatus, sedimentation resumed and continued until the Late Ladinian/Carnian, leading to the deposition of a carbonate platform dominated by peritidal dolostones. A period of shelf exposure and erosion, spanning from the Carnian to Norian, was followed by the third major sequence with sedimentation into the Early Jurassic. During this third depositional sequence sedimentation changed from pure carbonate into mixed carbonate–siliciclastic deposits. This transition reflects the global regression of the sea in the Late Triassic (Triasina hantkeni Zone) and the increased erosion of large parts of the Arabian hinterland. A comparison of the evolution of the Arabian shelf in the study area with chronostratigraphic reference schemes for the Arabian Plate reveals remarkable differences in the distribution of Middle and Upper Triassic sequences. These are most likely the result of poor biostratigraphic control on previously studied formations in the region.     

A facies and palaeogeography-based approach for analysis of petroleum systems in United Arab Emirates

The United Arab Emirates(UAE) is the 8 th largest oil producing country and is rich in oil and gas resources. By the end of 2015, 68 oil and 23 gas fields had been discovered. The initial proved and probable(2 P) oil, gas and condensate reserves amount to 81,135.9 MMb(million barrels), 192.09 Tcf(trillion cubic feet),and 6496.58 MMb respectively, which are mostly reservoired in the Jurassic and Cretaceous carbonates. With the latest field data, this study attempts to document the salient features of petroleum systems in UAE. Based on depositional facies of source rock intervals, pods of source rocks were delineated. On the basis of an oiland gas-source correlation, five known petroleum systems were identified and they are Lower Silurian-Upper Permian Khuff gas, northeast foreland Upper Jurassic-Lower Cretaceous gas, Upper Jurassic-Jurassic petroleum, Upper Jurassic/Lower Cretaceous-Lower Cretaceous composite petroleum, and Middle Cretaceous-Middle to Upper Cretaceous/Cenozoic petroleum systems. Of them, the Upper Jurassic/Lower Cretaceous-Lower Cretaceous composite petroleum system contains 73.2% of the total 2 P reserves and thus it is the focus of this study. The Upper Jurassic and Lower Cretaceous source rocks consist of argillaceous limestone, mudstone and shale, which were deposited as intrashelf basin facies. The distribution of oil and gas in this system is controlled by the source kitchens and the regional evaporite seal.     

Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates

The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42 ^°N, 54.61 ^°E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012–July 2015), at Abu Dhabi located at the south-west coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurement site indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March–May) and summer (June–September), to the abundance of fine/accumulation mode aerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October–November) and winter (December–February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from ?13.2 Wm^?2 (～?0.96 Wm^?2) in November to ?39.4 Wm^?2 (?11.4 Wm^?2) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from + 12.2 Wm^?2 (November) to 28.2 Wm^?2 (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surface are observed in spring (?85.0 ± 4.1 W m^?2 τ ^?1) followed closely by winter (?79.2 ± 7.1 W m^?2 τ ^?1) and the lowest values during autumn season (?54 ± 4.3 W m^?2 τ ^?1). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day ^?1) and the lowest in November (0.17 K day ^?1) and the temporal variability of this parameter is linearly associated with the aerosol absorption index.     

Undrained lateral load capacity of piles in clay using artificial neural network

This paper describes the application of the artificial neural network model to predict the lateral load capacity of piles in clay. Three criteria were selected to compare the ANN model with the available empirical models: the best fit line for predicted lateral load capacity (Q_p) and measured lateral load capacity (Q_m), the mean and standard deviation of the ratio Q_p/Q_m and the cumulative probability for Q_p/Q_m. Different sensitivity analysis to identify the most important input parameters is discussed. A neural interpretation diagram is presented showing the effects of input parameters. A model equation is presented based on neural network parameters.     

Estimation of compressional seismic wave attenuation of carbonate rocks in Abu Dhabi,United Arab Emirates

The subsurface geology of Abu Dhabi in the United Arab Emirates is primarily composed of carbonate rocks. Such media are known to be highly heterogeneous. Very few studies have attempted to estimate attenuation in carbonate rocks. In Abu Dhabi no attenuation profile has been published. This study provides the first seismic wave attenuation profiles in Abu Dhabi using dense array of VSP data. We estimated three attenuation profiles: the apparent, the scattering, and the intrinsic attenuations. The apparent attenuation profile was computed using amplitude decay and spectral-ratio methods. The scattering attenuation profile was estimated using a generalized reflection–transmission matrix forward model. It is usually estimated from the sonic log, but to be more consistent with the apparent attenuation, we succeeded in this paper to estimate it from the VSP data. We subtracted the scattering attenuation from the apparent attenuation to deduce the intrinsic attenuation. The results of the study indicate that the scattering attenuation is significant compared to the published studies that are mainly based on clastic rocks. The high scattering attenuation can reach up to 0.02. It can be explained by the strong heterogeneity of the carbonate rocks. This study demonstrates that the Simsima and Rus Formations have considerable scattering and intrinsic attenuations. These formations are considered aquifers in Abu Dhabi; we therefore interpreted this high intrinsic attenuation zones to be due to the heterogeneity and to the fluids contained in these formations. The Umm-Er-Radhuma Formation is a more homogenous formation with limited aquifer potential. Hence, scattering and intrinsic attenuations of the Umm-Er-Radhuma Formation are low.     

Rate of deposition and quality of sedimentation dust in Al Ain and Ras Al Khaimah, United Arab Emirates

This study presents data on the mineralogy and the metal content of dust deposited in Al Ain and Ras Al Khaimah, United Arab Emirates. The mineralogical compositions of the dust were determined using X-ray diffraction, and the results revealed that quartz is the dominant mineral, whereas calcite, dolomite, plagioclase, and serpentine were minor minerals. Two sampling sites were chosen from both Al Ain and Ras Al Khaimah. The concentrations of Fe, Zn, Cu, Cr, Pb, Cd, Ni, and Co in the sedimentation dusts samples of these sites were determined using inductively coupled plasma. The levels of most of heavy metal were generally below those determined in the other cities in the Middle East. The air enrichment factors for all the samples were analyzed, and the results indicated that Cd, Zn, Co, and Ni were highly enriched relative to their crustal ratios (to Fe) and correspond to substantial contribution of anthropogenic source of these metals. These metals mainly originate from the traffic emissions and industrial activities with contribution from natural sources. The average rates of deposition in Al Ain and Ras Al Khaimah were 193 and 972 mg m^?2 day^?1, respectively. These rates were higher than those of other regions.     

Late Quaternary chronology of major dune ridge development in the northeast Rub' al-Khali, United Arab Emirates

The northeastern sector of the Rub' al-Khali desert in the eastern United Arab Emirates (UAE) is dominated by large NE-SW trending dune ridges orientated perpendicular to the currently prevailing northwesterly wind regime. In this study, extensive use has been made of artificially exposed sections through these major dune ridges that reveal internal sedimentary structures and allow an intensive, high-resolution sampling programme to be carried out. Here, we present the optical dating results for samples from 7 sections. The results indicate that dune activity and preservation occurred within the periods 7-3 ka, 16-10 ka and 22-20 ka with evidence of earlier preservation during marine oxygen isotope stages MIS 3 and 5, with net accumulation rates in the range 2.2-25 m.ka^− 1. In several instances, hiatuses in the preserved record of dune accumulation coincide with stratigraphic bounding surfaces visible in the exposed section profiles with associated truncation of internal sedimentary structures. Caution must be exercised when interpreting such gaps in the recorded accumulation chronologies of these dunes since these may simply constitute phases of low preservation potential rather than phases of low aeolian activity. Other factors such as sediment supply and availability in relation to sea-level dynamics may be significant and are also considered.     

Solute and isotope constraint of groundwater recharge simulation in an arid environment,Abu Dhabi Emirate,United Arab Emirates

A simple, well-constrained simulation of solute increases in a downgradient direction was used in the shallow unconfined aquifer of eastern Abu Dhabi Emirate (United Arab Emirates). The simulation indicates that the observed exponential increase in solute concentrations results from a combination of upward transport of solutes from underlying mudstones and evaporites, and groundwater losses by evaporation. Groundwater recharge and discharge flux in unconfined regional aquifers in arid regions commonly are difficult to estimate because there are few constraints on the flux of water lost or gained from the system. Total dissolved solids (TDS) and deuterium isotopes (δ²H) in groundwater are used to constrain estimated fluxes to the shallow aquifer of eastern Abu Dhabi Emirate. Vertical upward transport of solutes from underlying mudstones and evaporites accounts for solute increases along approximately the first 80 km of the simulated flow path, but a combination of upward solute transport and evaporation is necessary to explain observed solute concentrations beyond 80 km. Mobilization and transport of solutes in the unsaturated zone by recharging precipitation is not a significant factor.

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Résumé Une simulation simple et bien contrainte de l’augmentation des solutés dans la direction de l’écoulement a été réalisée sur l’aquifère phréatique et libre de l’Est de l’émirat d’Abu Dhabi (émirats Arabes Unis). La simulation indique que l’augmentation observée de solutés, de forme exponentielle, est le produit de la combinaison du transport ascendant de solutés provenant des mudstones et des évaporites sous-jacents, et de l’évaporation des eaux souterraines. La recharge des eaux souterraines et les flux de vidange dans les aquifères régionaux libres des régions arides sont habituellement difficiles à estimer du fait du peu de contraintes agissant sur la perte ou le gain d’eau dans le système. La charge dissoute totale (TDS, en anglais) et les isotopes deutérium (δ²H) des eaux souterraines sont utilisés pour contraindre l’estimation des flux en direction de l’aquifère phréatique de l’Est de l’émirat d’Abu Dhabi. Le transport vertical ascendant des solutés à partir des mudstones et des évaporites fait parti des processus qui concentrent les solutés approximativement le long des 80 premiers kilomètres du trajet des écoulements simulés, mais une combinaison du transport ascendant des solutés et de l’évaporation est nécessaire pour expliquer les concentrations observées en soluté au delà des 80 km. La mobilisation et le transport des solutés par les précipitations efficaces dans la zone non saturée ne représentent pas des facteurs significatifs.

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Resumen Se utilizó una simulación simple y muy restringida, de incrementos de soluto en la dirección del flujo, en el acuífero libre poco profundo del Emirato oriental de Abu Dhabi, (Emiratos árabes Unidos). La simulación indica que el aumento exponencial observado en las concentraciones del soluto, resulta de una combinación de transporte ascendente de solutos desde las evaporitas y lodolitas subyacentes, y por pérdidas del agua subterránea por evaporación. Los flujos de recarga y descarga de agua subterránea, en los acuíferos libres regionales en regiones áridas, normalmente son difíciles estimar, porque hay algunas restricciones en el flujo de agua perdido o ganado por el sistema. Los sólidos disueltos totales (TDS) y los isótopos de deuterio (δ²H) en el agua subterránea, se usan para forzar los flujos estimados hacia el acuífero poco profundo del Emirato oriental de Abu Dhabi. El transporte ascendente vertical de solutos desde las lodolitas y evaporitas subyacentes, involucra los aumentos del soluto a lo largo de aproximadamente los primeros 80 Km. de la dirección de flujo simulada, pero es necesaria una combinación de transporte ascendente del soluto y la evaporación para explicar las concentraciones del soluto observadas más allá de 80 Km. La movilización y transporte de solutos en la zona no saturada, por recarga debida a precipitación, no es un factor significante.