Piles in fully liquefied soils with lateral spread     

Mohamed Ashour  Hamed Ardalan 《Computers and Geotechnics》2011

The paper provides a new analysis procedure for the assessment of the lateral response of isolated piles/drilled shafts in saturated sands as liquefaction and lateral soil spread develop in response to dynamic loading such as that generated by the earthquake shaking. The presented method accounts for: (1) the development of full liquefaction in the free-field soil that could trigger the lateral spread of the overlying crust layer; (2) the driving force exerted by the crust layer based on the interaction between the pile and the upper non-liquefied soil (crust) layer; and (3) the variation of the excess pore water pressure (i.e. post-liquefaction soil strength) in the near-field soil with the progressive pile deflection under lateral soil spread driving force. A constitutive model for fully liquefied sands under monotonic loading and undrained conditions is developed in order to predict the zone of post-liquefaction zero-strength of liquefied sand before it rebounds with the increasing soil strain in the near-field. The analytical and empirical concepts employed in the Strain Wedge (SW) model allow the modeling of such a sophisticated phenomenon of lateral soil spread that could accompany or follow the occurrence of seismic events without using modifying parameters or shape corrections to account for soil liquefaction.  相似文献   

Geochemical Record of the Cenomanian–Turonian Anoxic Event in Tunisia: Is it Correlative and Isochronous to the Biotic Signal?     

Mohamed SOUA  Dalila ZAGHBIB-TURKI  Hela BEN JEMIA  Jalel SMAOUI  Amel BOUKADI 《《地质学报》英文版》2011,85(6):1310-1335

In Tunisia, five Bahloul spaced sections, Bargou, Jerisa, Guern Halfaya, Kherij and Gafsa were analyzed for biostratigraphy (foraminifera and radiolarians) and major and trace elements. This high-resolution biostratigraphic and chemostratigraphic integrated analyses for the Late Cenomanian–Early Turonian Bahloul Formation provide new insight into the palaeoceanographic evolution of the southern Tethyan margin. Relative low abundance of related terrigenous Ti/Al and K/Al ratios and enrichment of some productivity proxies such as Ba, Cu, and Ni (organic matter related trace elements) suggests that the Bahloul, deposited during a relatively short period (0.5 Ma), was of relatively elevated primary productivity and minimal detrital input. While higher D* values concurrent with lower Ti/Al ratios are interpreted as caused by enhanced fluvial material contribution, due to more humid climate during the OAE-2. Enhanced humidity triggered probably fluvial influxes, resulted in a sluggish water circulation and consequent anoxic/euxinic conditions favoring the preservation of organic matter at the bottom. Enrichments in redox-sensitive trace metals U, V, and Mo in the Bahloul Formation deposits and redox indices, such as V/(V+Ni), U/Th, V/Cr, and Ni/Co, indicate that oxygen-restricted conditions prevailed during the Late Cenomanian to earliest Turonian times and correlate well with relative abundances of some foraminiferal and radiolarian paleo-environmental relevant indicators. High Baxs values and Uauth may indicate anoxic conditions at least at the water–sediment interface during the Bahloul Formation deposition and provide information about low to moderate sulfate-reduction reactions.  相似文献   

Petrographic modelling of Egyptian limestones for quicklime manufacture     

Abdel Monem Mohamed Soltan 《Arabian Journal of Geosciences》2011,4(5-6):803-815

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Environmental impact assessment inside and around Mahd Adh Dhahab gold mine, Saudi Arabia     

Abdallah S. Al-Hobaib  K Q. Al-Jaseem  Hassan M. Baioumy  Ahmed H Ahmed 《Arabian Journal of Geosciences》2011,5(5):985-997

Environmental impact of the mining activities in the Mahd Adh Dahab gold mine was examined through detailed chemical analyses of a number of samples represent the gold-bearing rocks, soils, dust, and plants from inside and outside the mine area and within the Mahd City as well as the surrounding areas. The obtained data were compared with the standard values of heavy metals concentrations in order to evaluate the pollution levels of these activities on the different systems around the mine area. The data of rock samples shows relatively high concentrations of Cu (up to 11.9%), Pb (up to 4.1%), and Zn (up to 14.2%), which attributed to the outcropping of the sulfide-bearing veins on the surface of the mine area. Soil samples inside the mine area show high concentrations of Zn, Cu, Cd, Pb, and As compared to those from outside the mine indicating pollution impact of the mine activities on soils from inside the mine with these elements. Dust samples collected from inside the mine have considerably high concentrations of Cd, Zn, and Pb compared to those from outside the mine. Values of heavy metals in the collected dust from outside the mine are comparable with those from many big cities including Riyadh City, Saudi Arabia, indicating contaminations with heavy metals to the dust from inside the mine at Mahd Adh Dahab City. Heavy metals concentrations in the stems and leaves samples of the various types of plants inside and outside Mahd Adh Dahab gold mine area show that they have relatively higher concentrations of Cu and Zn compared to other metals. Stem samples show relatively higher concentrations of Zn, Cu, Cr, and V compared to the leaves samples. Although values of most heavy metals in the plants, both stems and leaves, are comparable with those of the typical levels of heavy metals in plants, Co and Cr show relatively higher concentrations suggesting a pollution impact of the mine activities in plants with Co and Cr. As a conclusion, results indicated that the contamination effect of Mahd Adh Dahab gold mine activities are clear in soils and dusts inside the mine area with some metals such Zn, Cu, Cd, and Pb due to their relatively enrichment in mineralization. Therefore, careful treatments of the waste dump materials inside the mine area are recommended to protect soils and air contaminations and to prevent the extension of pollution outside the mine in the future.  相似文献   

Spatio-temporal characterization of the Pliocene aquifer conditions in Wadi El-Natrun area,Egypt   总被引：3，自引：1，他引：2  

Alaa A. Masoud  Mohamed G. Atwia 《Environmental Earth Sciences》2011,62(7):1361-1374

Wadi El-Natrun area has recently undergone extensive urban and agricultural expansion. Due to the absence of natural surface irrigation supplies, the only source of water in the area is the Pliocene groundwater aquifer. As a result, secondary salinization from increased abstractions is the major threat to the groundwater aquifer. There is a dire need for efficient strategies to ensure long-term sustainability of the area’s productive agriculture. These strategies should be based on scientific spatio-temporal monitoring and analysis of the groundwater conditions that is also lacking. To capture the spatio-temporal variability in groundwater conditions, field measurements of total dissolved solids, electrical conductivity, pH, temperature, and water level as well as lab-based ionic composition were performed on 47 groundwater samples collected during 2006 and 2007. Determinations of the hydrochemical characteristics, water types, salt assemblages, and the sodium adsorption ratio were carried out on the samples. Reference data sets recorded in 1973 and 1997 were available for the area and were used to monitor the changes occurred in these periods. Geographic information system (GIS) was appraised for mapping and for integrated analysis of the different layers. Remotely sensed change detection techniques were applied to the Landsat TM and the ETM + imageries and used to highlight the extensive reclamation and urbanization and to find key trends for the alterations in the groundwater conditions and their spatial association with land covers. Results revealed a topographic depression-induced flow pattern, predominance of leaching and dissolution processes, the presence of saline lakes, over-pumping from the Pliocene aquifer, and temporal changes in land uses are the main factors combined to control the spatio-temporal variability in the groundwater. Results also clarified the presence of two: northwestern and southeastern zones that varied distinctively in their hydrodynamic and hydrochemical characteristics. The northwestern zone showed an average water level decline of 15 m, the water of which is brackish (av. 2,037 mg/l) with dominant Na⁺, Cl⁻ and SO₄ ²⁻ ions. The groundwater of this zone is characterized by high to very high salinity hazard and high to very high alkali hazard and is not recommended for irrigation on soils with poor drainage and without proper management for salinity control. The southeastern zone showed water level decline less than 2 m, the water of which is fresh (av. 424 mg/l) with major Na⁺, HCO₃ ⁻, Cl⁻, and SO₄ ²⁻ ions, and quality suitable for irrigation with medium to high salinity and low to medium alkali hazards. The article represents the first step towards an integrated management of Wadi El-Natrun groundwater resources within a GIS framework.  相似文献   

Understanding the origin of salinization of the Plio-quaternary eastern coastal aquifer of Cap Bon (Tunisia) using geochemical and isotope investigations   总被引：3，自引：1，他引：2  

Mohamed Fethi Ben Hamouda  Jamila Tarhouni  Christian Leduc  Kamel Zouari 《Environmental Earth Sciences》2011,63(5):889-901

As in many other semi-arid regions, the Plio-quaternary aquifer of the eastern coast of Cap Bon peninsula (NE Tunisia) shows a parallel increase in overexploitation and mineralization of groundwater resources and so the water quality is deteriorating. Different methods using geochemistry (ions Na⁺, Cl⁻, Ca²⁺, Mg²⁺, Br⁻) and stable isotopes (¹⁸O, ²H) are compared with the hydrodynamic information for identifying the main processes involved in the increase of salinization. Along the coast, intrusion of seawater resulting from groundwater overexploitation is identified, but is not the only cause of qualitative degradation: the development of irrigation that induces soil leaching and transfer of fertilizers to groundwater over the whole aquifer extent is another major reason for the increase in salinization. A total of 48 groundwater wells were sampled to obtain additional information on the hydrochemical characteristics of the groundwater defined in previous studies.  相似文献   

Potentiality of land and water resources in African Sahara: a case study of south Egypt     

A. H. El Nahry  E. S. Mohamed 《Environmental Earth Sciences》2011,63(6):1263-1275

The investigated area is located south Egypt, between latitudes 22°00′N and 24°15′N, and longitudes 28°00′E and 30°00′E. It covers a total area of about 95,000.17 km². The area was remotely sensed to identify landscape and its land and water resources. A reconnaissance survey followed by detailed one was done to verify the information resulted from satellite images. The prevailing deposits of the area could be expressed as (1) the Nubian sandstone, (2) the Quaternary sediments, and (3) the sand dunes belt. Fourteen main and sub-main landforms were recognized, i.e., sand sheets (high, moderately high, moderate, and low), depressions (high, moderately high, moderate, and low), dry valleys, peniplains, footslopes, barchans, tablelands, and scattered hills. Associated soils were distinguished and classified as Typic Torripsamments, Typic Haplocalcids, Typic Torrifluvents, and Typic Haplodurids. Spatial variability of soil and water characteristics was identified through using ordinary Kriging interpolation method. Land surface temperatures in both summer and winter seasons were derived from thermal band, and soil temperature regimes were defined digitally as hyperthermic. Water potentiality was identified and classified according to salinity and sodicity hazards to C2-S1 and C3-S1. Using GIS techniques, soil potentiality spatial model (SPSM) was designed to get potentiality classes, i.e., high, moderately high, moderate, low, and very low.  相似文献   

The Cenomanian/Turonian oceanic anoxic event in the Razzak Field, north Western Desert, Egypt: Source rock potential and paleoenvironmental association     

Mohamed K. Zobaa  Francisca E. Oboh-IkuenobeMohamed I. Ibrahim 《Marine and Petroleum Geology》2011,28(8):1475-1482

The Western Desert of Egypt is one of the world’s most prolific Jurassic and Cretaceous hydrocarbon provinces. It is one of many basins that experienced organic-rich sedimentation during the late Cenomanian/early Turonian referred to as oceanic anoxic event 2 (OAE2). The Razzak #7 oil well in the Razzak Field in the northern part of the Western Desert encountered the Upper Cretaceous Abu Roash Formation. This study analyzed 23 samples from the upper “G”, “F”, and lower “E” members of the Abu Roash Formation for palynomorphs, particulate organic matter, total organic carbon (TOC) and δ¹³C_org in order to identify the OAE2, determine hydrocarbon source rock potential, and interpret the depositional environment. The studied samples are generally poor in palynomorphs, but show a marked biofacies change between the lower “E” member and the rest of the studied samples. Palynofacies analysis (kerogen quality and quantity) indicates the presence of oil- and gas-prone materials (kerogen types I and II/III, respectively), and implies reducing marine paleoenvironmental conditions. Detailed carbon stable isotopic and organic carbon analyses indicate that fluctuations in the δ¹³C_org profile across the Abu Roash upper “G”, “F”, and lower “E” members correspond well with changes in TOC values. A positive δ¹³C_org excursion (∼2.01‰) believed to mark the short-term global OAE2 was identified within the organic-rich shaly limestone in the basal part of the Abu Roash “F” member. This excursion also coincides with the peak TOC measurement (24.61 wt.%) in the samples.  相似文献   

Seismic velocity and Poisson’s ratio tomography of the crust beneath East Anatolia     

Mohamed K. Salah  Şakir Şahin  Ufuk Aydin 《Journal of Asian Earth Sciences》2011,40(3):746-761

Eastern Anatolia is a region in the early stages of continent–continent collision and so provides a unique opportunity to study the early development of continental plateau. Located within the Alpine–Himalayan fold-thrust fault belt, the Anatolian plateau is geologically very complex, with over half of the surface area covered with late Cenozoic volcanics of diverse composition. The plateau is also seismically active and is dissected by numerous seismogenic faults predominantly of strike-slip motion. In this study, we determine 3-D tomographic images of the crust beneath eastern Anatolia by inverting a large number of arrival time data of P- and S-waves. From the obtained P- and S-wave velocity models, we estimated the Poisson’s ratio structures for a more reliable interpretation of the obtained velocity anomalies. Our tomographic results are generally consistent with the major tectonic features of the region. High P- and S-wave velocity anomalies are recognized near the surface, while at deeper crustal layers, low seismic wave velocities are widely distributed. Poisson’s ratio exhibits significant structural heterogeneities compared to the imaged velocity structure. The seismic activity is intense along highly heterogeneous zones and is closely associated with pre-existing faults in the central and western parts of the study area. Results of the checkerboard resolution test indicate that the imaged anomalies are reliable features down to a depth of about 40 km. The low-velocity/high Poisson’s ratio zones in the middle to lower crust are consistent with many geophysical observations such as strong Sn attenuation, low Pn and Sn velocity, and the absence of mantle lid, implying the presence of partial melt in the uppermost mantle.  相似文献   

Hydrogeochemical characterization and isotope investigations of a carbonate aquifer of the northern part of the United Arab Emirates     

Ahmed A. Murad  Hassan Garamoon  Saber Hussein  Hind S. Al-Nuaimi 《Journal of Asian Earth Sciences》2011,40(1):213-225

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