Use of remote sensing and GIS to determine recharge potential zones: the case of Occidental Lebanon

Water recharge from land surfaces into subsurface media is an essential element in the hydrologic cycle. For a small-scale assessment, experimental approaches are usually followed, however, on a regional scale, this assessment needs to be made into a comprehensive picture where spatial data of the different contributing factors are treated. The case of Occidental Lebanon, with an area of around 5,000 km², was studied by the integration of all factors influencing this hydrologic process. Contributing factors are: lineaments and drainage frequency density, lithologic character, karstic domains and land cover/land use. The determination of these factors was carried out mainly by the application of remote sensing. Satellite images (Landsat 7 ETM &; SPOT) and aerial photos were subjected to several treatment processes using a miscellany of software, mainly ERDAS Imagine and ESRI’s Arc View software. Furthermore, exogenetic data, such as topographic and geologic maps, were utilized. The extracted information for these factors was plotted on maps. The integration of the maps in a GIS allowed deciding their interactive effects. However, each factor had its own degree of effect, i.e., weight, which was also determined in this study. This study is an approach to better estimate and provide qualitative assessments of recharge potential (RP). The resultant map shows the highest recharge potentials towards the elevated regions where karstification is well development. It was found that around 57% of the study area is terrain with very high to high recharge rate values, which a considerable amount of precipitated water is allowed to percolate into subsurface rocks.     

The Cambrian Araba Formation in northeastern Egypt: Facies and depositional environments

The Cambrian Araba Formation exposed in Gabal El Zeit and in the Sinai Peninsula unconformably overlies Precambrian basement rocks, and is in turn overlain unconformably by the Ordovician Naqus formation. The Araba Formation has been subdivided into three informal lithologic units: lower, middle and upper, from field observations. Seven sedimentary facies assignable to three facies associations (fluvial, tidal and coastal to open marine) are recognized within the Araba Formation. The lower unit comprises two main facies: matrix-supported conglomerate (facies-A) in the south (Gabal Araba and Wadi Feiran) and interbeds of granulestone and sandstone (facies-B) in the north (Gabal Dhalal and Taba) deposited in fluvial conditions. The middle unit includes four facies: cross-bedded sandstone (facies-C), thin laminated sandstone (facies-D), burrowed-massive sandstone (facies-E) and rhythmically bedded sandstone–mudstone (facies-F) deposited mainly under tidal conditions in the coastal zone. The upper unit consists mainly of interbeds of burrowed mudstone-siltstone, with Skolithos, probably deposited in open marine environment. The sequence records the southward transgression of the Tethys Ocean over a horst and graben system developed in the late Precambrian on the northern margin of the Arabo-Nubian continent.     

Impacts of the dumping site on the environment: Case of the Henchir El Yahoudia Site, Tunis, Tunisia

The Henchir El Yahoudia landfill is one among many uncontrolled dumping sites in Tunisia with no bottom liner. It is located at the southeastern edge of Sijoumi Sebkha. The site has been exploited since 1963 until 1994. It constitutes a peculiar case because of its situation, its exploitation mode and the nature of buried wastes. Leachate analysis shows that they are strongly charged with nitrogen (especially ammoniacal and kadjedahl), organic compounds with a high biodegradability and a charge of metallic elements exceeding the Tunisian norm NT 106-002. Sediment analyses show that the highest rate of heavy metals and organic matter coincides with clay-richest layers, characterized by the highest specific-surface values. The percolation of these pollutants until the groundwater between 0.5 and 5 m has provoked a pollution characterized by high rates of organic matter (BOD, COD and nitrogen) and heavy metals. To cite this article: A. Marzougui, A. Ben Mammou, C. R. Geoscience 338 (2006).     

Current motion and short-term deformations in the Suez–Sinai area from GPS observations

We analyze observations from eight GPS campaigns carried out between 1997 and 2005 on a network of 13 sites in the Suez–Sinai area, where separation between the African and the Arabian plates takes place. This is the key area to understand if and in which way Sinai behaves like a sub-plate of the African plate and the role played by seismic and geodetic (long-term) deformation release.Our analysis shows that, on average, the Suez–Sinai area motion, in terms of ITRF00 velocities, matches the African plate motion defined by the NNR-NUVEL-1A model.The horizontal principal strain rate axes estimated separately in the Gulf of Suez area and in the northern Sinai vary from compression across the Gulf (−2.2 ± 1.2) × 10⁻⁸ year⁻¹ to NE extension (1.0 ± 1.5) × 10⁻⁸ year⁻¹ in the North, showing the presence of two distinct domains, so that in our opinion Sinai cannot be considered simply a unique rigid block.The analysis of GPS baseline length variations shows short-term deformations across the Gulf of Suez, reaching up a maximum value of more than 1 cm in 8 years.Since current geodynamical models do not predict significant tectonic deformation in this area, we work under the hypothesis that a contribute may be expected by post-seismic relaxation effects. Under this hypothesis, we compare the baselines length variations with the post-seismic relaxation field associated with five major local earthquakes occurred in the area, testing two different viscoelastic models. Our results show that the detected short-term deformations are better modeled for viscosity values of 10¹⁸ Pa s in the lower crust and 10²⁰ Pa s in the asthenosphere. However, since the modeled post-seismic effect results modest and a certain amount of the detected deformation is not accounted for, we think that an improved modeling should take into account the lateral heterogeneities of crust and upper mantle structures.     

Two-dimensional development of the dynamic coupled consolidation scaled boundary finite-element method for fully saturated soils

The scaled boundary finite-element method is a powerful tool used to analyse far-field boundary soil–structure interaction problems. In this paper, the method is extended to include Biot's coupled consolidation in order to deal with fully saturated soil as a two-phase medium. The advantages of this method are explained in this paper. The detailed formulation considers the general two-dimensional (2D) analysis case, accounting for body forces and surface tractions in both bounded and unbounded media.     

Benthic foraminiferal turnover across the Paleocene–Eocene Thermal Maximum (PETM) event in Eastern Desert,Egypt

Benthic foraminiferal fauna are analyzed quantitatively and qualitatively at three stratigraphic sections in Eastern Desert of Egypt (Serai, Duwi, and Um El Huetat). These sections embrace the Paleocene–Eocene Thermal Maximum (PETM) interval which is represented by the occurrence of five distinctive beds. These beds constitute the Dababiya Quarry Member at the lower part of Esna Formation. The occurrence of them indicates an expanded and relatively continuous record across the P/E boundary. The organic-rich clay layer (bed no. 1 of the Dababiya Quarry Member) marks the start of the PETM event. This bed is characterized by the extinction of all benthic foraminiferal fauna except for the occurrence of rare agglutinated foraminiferal species. The presence of these species indicates an oceanic anoxic event at the sea floor. High concentration of phosphatic contents including fish remains occurred in the middle part of the PETM (bed nos. 2 and 3 of the Dababiya Quarry Member) with the continuous absence of benthic foraminiferal fauna except for few specimens at the top of bed 3. Bed nos. 4 and 5 of the Dababiya Quarry Member represent the upper part of the PETM and the initial stage of sea floor recovery. Low diversity and abundance of benthic foraminiferal taxa occurred within these beds, represented by Valvulineria scrobiculata, Lenticulina midwayensis, Loxostomoides appliane, and Siphogenerinoides eleganta. This phenomenon continues upward during the post-PETM event. The Paleocene velasco-type benthic foraminifera Angulogavelinella avnimelechi and Coryphostoma midwayensis species are extinct within the advent of the PETM event. The benthic foraminiferal assemblages at the studied sections are dominated by midway-type fauna with little representative of velasco-type fauna. The velasco-type species are represented with high abundance at Serai section and with low densities at Um El Huetat section, while at Duwi section, they rarely occurred. This suggests outer neritic-upper bathyal (150–400 m) setting at Serai section and mostly middle-outer neritic (50–150 m) setting at Um El Huetat and Duwi sections.     

Developing artificial neural network models to predict allowable bearing capacity and elastic settlement of shallow foundation in Sharjah,United Arab Emirates

This research proposes the use of artificial neural network to predict the allowable bearing capacity and elastic settlement of shallow foundation on granular soils in Sharjah, United Arab Emirates. Data obtained from existing soil reports of 600 boreholes were used to train and validate the model. Three parameters (footing width, effective unit weight, and SPT blow count) are considered to have the most significant impact on the magnitude of allowable bearing capacity and elastic settlement of shallow foundations, and thus were used as the model inputs. Throughout the study, depth of footing was limited to 1.5 m below existing ground level and water table depth taken at the level of the footing. Performance comparison of the developed models (in terms of coefficient of determination, root mean square error, and mean absolute error) revealed that the developed artificial neural network models could be effectively used for predicting the allowable bearing capacity and elastic settlement. As such, the developed models can be used at the preliminary stage of estimating the allowable bearing capacity and settlements of shallow foundations on granular soils, instead of the conventional methods.     

Secondary dispersion of trace elements in bottom sediments of the High Dam Lake,South Egypt and North Sudan

Thirty-four chemical elements, pH, total nitrogen, and total organic carbon were determined in 49 bottom sediment samples from the whole High Dam Lake in order to improve our understanding of geochemical characteristics of these sediments and geochemical patterns of trace elements and related feeding sources. The present study revealed that the lake were clearly discriminated into three portions in accordance with the sediment geochemistry and geographic position. Likewise, the analyzed elements in the entire lake sediments were classified into six geochemical association patterns that are indicative of the contributing geogenic and anthropogenic sources. As has been noted here, mineralogy, anthropogenic inputs, pH, and organic matter had significant roles in controlling the behavior, concentration, dispersion, and geochemical patterns of the trace elements in the lake sediments. Consequently, the elevated concentration of Bi, Cd, Co, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Sc, V, Y, and Zn posed moderate contamination level in the sediments. At the same time, the enhancement of Ag, Se, and Te levels caused contamination up to very high levels. Admittedly, the contamination levels were generated by natural and human activities that are coming from the Nile basin countries. Despite progressive deterioration of these sediments, they still have economic applications.     

Hydrogeochemical characterization and groundwater quality assessment in Al-Hasa,Saudi Arabia

Fifty groundwater samples were collected from Al-Hasa to analyze the pH, electrical conductivity (EC, dS m^?1), total dissolved solids (TDS), major anions (HCO₃^?, CO₃^2?, Cl^?, SO₄^2?, and NO₃^?), major cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), and total hardness. The analyzed data plotted in the Piper, Gibbs, and Durov diagrams, and water quality index (WQI) were calculated to evaluate the groundwater geochemistry and its water quality. The results reveal that most of the investigated samples are Ca²⁺, Mg²⁺, SO₄^2?, Cl^? and Na⁺, and HCO₃^? water types using the Piper diagram. Na⁺?>?Ca²⁺?>?Mg²⁺ are the dominant cations, while Cl^??>?HCO₃^??>?SO₄^2??>?CO₃^2? are the dominant anions. Sodium adsorption ratio (SAR) values varied from 0.79 to 10; however, the Kelly ratio (KR) ranged between 0.1 and 2.2. The permeability index (PI) showed that well water is suitable for irrigation purposes with 75% or more of maximum permeability. The US salinity diagram revealed that the water quality classes of studied waters were CIII-SI, CIII-SII, and CIV-SII, representing height hazards of salinity and medium- to low-sodium hazard. The water quality index (WQI) results indicated that total dissolved solids are out of the drinking water standard limits in Saudi Arabia. The WQI revealed that 38% of the studied wells were considered as poor water (class III), 52% are found as very poor water class (IV), and 10% are unsuitable water for drinking class (V).     

Statistical Evaluation of CPT and CPTu Based Methods for Prediction of Axial Bearing Capacity of Piles

Piles are structural members made of steel, concrete, or wood installed into the ground to transfer superstructure loads to the soil. Nowadays, many structures are built on poor lands, and therefore piles have crucial roles in such structures. Performing in-situ tests such as cone penetration (CPT) and piezocone penetration tests (CPTu) have always been of great importance in designing piles. These tests have a brilliant consistency with reality, and as a result, the outcome data can be used in order to achieve reliable pile designing models and reduce uncertainty in this regard. In this paper, the capability of various CPT and CPTu based methods developed from 1961 to 2016 has been investigated using four statistical methods. Such CPT and CPTu based methods are adopted for direct prediction of axial bearing capacity of piles using CPT and CPTu field data. For this purpose, 61 sets of field data prepared from CPT and CPTu have been collected. The data sets were utilized in order to calculate the axial bearing capacity of piles (Q_E) through 25 different methods. In addition, the measured axial pile capacities (Q_M) have been collected, recorded and prepared from field static load tests, respectively. Then, four different statistical approaches have been applied to assess the accuracy of these methods. Finally, the most reliable and accurate methods are presented.