The hydrogeochemical characteristics of shallow groundwater in the Grombalia region, northeastern Tunisia, were investigated to evaluate suitability for irrigation and other uses and to determine the main processes that control its chemical composition. A total of 21 groundwater samples were collected from existing wells in January–February 2015 and were analyzed for the major cations and anions concentrations. Conductivity, pH, T°, O2 and salinity were also measured. Interrelationships between chemical parameters were determined by using the scatter matrix method. The suitability of groundwater for irrigation and other uses was assessed by determining the sodium adsorption ratio, soluble-sodium percentage, total dissolved solids, total hardness, Kelly’s index and permeability index values of water samples. The spatial distribution of key parameters was assessed using a GIS-based spatial gridding technique. This analysis indicated that the chemical composition of groundwater in the study area is of Cl–SO4–Na–Ca mixed facies with concentrations of many chemical constituents exceeding known guideline values for irrigation. The salinity of groundwater is controlled by most dominant cation and anion (Na–Cl). A correlation analysis shows that Na+ is the dominant cation and that reverse ion exchange is a dominant process that controls the hydrogeochemical evolution of groundwater in the area. Geospatial mapping of hydrochemical parameters and indices analyzed with the USSL and Wilcox diagrams show distinctive areas of irrigation suitability. In contrast, 76.2% of samples fall in the highly doubtful to unsuitable category and indicate that the central and north-eastern parts of the study area are unsuitable for irrigation due to a high salinity and alkalinity. 相似文献
The provenance of the Upper Cretaceous Nubia sandstones from four vertical sections along Qena-Safaga and Qena-Quseir roads in central Eastern Desert of Egypt was investigated based on their modal composition and geochemical data. The Nubia sandstone samples are abundant in quartz content with low feldspar and lithic fragments. Their average modal composition (Q94.2F1.3R4.5) classifies them as quartz arenites with subordinate quartz wackes which is consistent with geochemistry data. The average CIA, CIW, PIA, and Th/U ratio values revealed that the intensity of weathering in the studied areas was similar, varying from moderate to intensive weathering, and may reflect low-relief and warm humid climatic conditions in the source area. The ICV (<?1) and SiO2/Al2O3 ratio (>?5) indicate that the Nubia sandstones are texturally and mineralogically mature. The petrographical and geochemical analyses suggest that the Nubia sandstones were mainly derived from felsic (granitic) and/or recycled sand sources. The major element-based multidimensional tectonic discrimination diagrams suggested the Nubia sandstones were deposited in a passive continental margin of a syn-rift basin. This result agreed with the general geology of central Eastern Desert of Egypt during the Upper Cretaceous. 相似文献
One of the most important problems during tunneling in soft rock is deformation and fracturing of the rock during tunneling. The problem was successfully explored by using a transparent rock surrogate to simulate the behavior of soft rock, which permitted visualizing conditions within the rock. Synthetic soft rock was made using consolidated fused quartz saturated with a blend of two mineral oils that have the same refractive index as the quartz. The tunnel was simulated using a smooth aluminum tube and two tunneling methods representing machining and blasting were considered. Two observation planes made of seeding particles were pre-placed within the model and used to track soil movements and crack propagation. Images of both planes were captured simultaneously using two orthogonal cameras. Rock deformations were concentrated in the vicinity of the tunnel face, and deformation rates behind the tunnel face were significantly greater than those ahead of the face. However, deformation rates and patterns varied considerably depending on the excavation method/rate. Fracturing mechanisms exhibited similar differences, for machining deformations occurred higher above the crown and propagated toward the tunnel face. Conversely for blasting deformations sprang from the crown upwards. These observations can assist with numerical simulations and in planning tunnel support systems.
In this study, thermal groundwater from arid area in southeastern Tunisia was assessed for irrigation use. For this purpose, thirty-one water samples were collected and physiochemical parameters (EC, pH, TDS, major ions) were measured and analyzed. A fuzzy logic model was developed in which six parameters were integrated: electrical conductivity, sodium adsorption ratio, sodium percentage, Kelly ratio, permeability index and temperature. The membership functions for a fuzzy logic model were developed using linguistic terms and trapezoidal shapes. The fuzzy logic model developed was validated with a dataset of chemical analyses from groundwater sampled in the study area. The assessment indicated that 26% of the samples were in the “good” class, 10% in the “good to permissible” class, 55% are in the “permissible” class, 6% are in the “permissible to harmful” class and 3% were considered to be harmful and therefore unsuitable for use in irrigation. The effectiveness, simplicity and robustness of the fuzzy model assessment make this approach a more consistent and reliable way of assessing water quality than conventional methods of assessing water quality data. 相似文献
Geotechnical and Geological Engineering - Reliable prediction of surface and subsurface settlements induced by shallow tunnels is important to minimize the adverse effects which may take... 相似文献
Substantial progress has been recently achieved in the development of a clean alternative to mercury intrusion porosimetry (MIP) based on single-phase flow measurements in porous samples using yield stress fluids. However, no study to date has examined the scale of the pore length actually provided by the yield stress fluids porosimetry method (YSM) in consolidated porous media. Indeed, while the results of YSM were compared to those provided by MIP in the past, the relationships between the characterized pore size distribution (PSD) and the actual pore geometry have still not been addressed for this type of porous media. This issue is of special interest to geoscientists involved in seeking relevant information from core characterization operations. With this aim in mind, the objective of the present paper is to evaluate the agreement between the PSDs characterized by YSM, the pore-opening size distributions provided by MIP tests, and the pore-throat and pore-body size distributions obtained from X-ray computed microtomography. For this purpose, a set of artificial and natural porous samples with permeability values extending over two magnitudes were characterized by using both YSM and MIP laboratory tests. Then, the results were matched to the model pore geometries extracted from digital images of the real microstructure. This analysis led to the main conclusion that YSM can be reliably used as an adequate substitute for MIP in the case of the investigated consolidated media, given the general agreement observed between these methods.
This paper aims to prepare purified Na-bentonite with improved properties for its use in the pharmaceutical industry. Calcium bentonite from the Sohag region of Egypt was activated with various proportions of sodium carbonate (2, 3, 5 and 8 wt.%). Additionally, bentonite was purified by sedimentation to eliminate impurities, especially quartz. The results of X-ray diffraction (XRD) and swelling volume data confirmed that raw bentonite was converted to sodium bentonite using 5% Na2CO3. The sodium bentonite (M5) obtained by activation met the chemical and microbiological requirements set by the pharmacopoeias regarding toxic trace elemental contents (As, Pb and Cd), the absence of E. coli, the total contents of aerobic microbes and physicochemical properties such as swelling volume, pH and sedimentation volume. Therefore, (M5) bentonite can be designated as being potentially appropriate for pharmaceutical applications. The cation exchange capacity (CEC), surface area, porosity, pH, gel formation and swelling volume data indicated that M5 bentonite could be used to formulate oral suspensions and in topical application. 相似文献
On August 21st and 22nd 1856, two strong earthquakes occurred off the seaport of Djidjelli, a small city of 1000 inhabitants, located 300 km east of Algiers (capital of Algeria). In relation to these two earthquakes, an important tsunami (at least one) affected the western Mediterranean region and the eastern Algerian coastline between Algiers and La Calle (Algero-Tunisian border). Based on historical information as well as on data recently collected during the Maradja 2 survey conducted in 2005 over the Algerian margin, we show that the tsunami could have been generated by the simultaneous rupture of a set of three en echelon faults evidenced off Djidjelli. From synthetic models, we point out that the area affected along the Algerian coast extended from Bejaia to Annaba. The maximum height of waves reached 1.5 m near the harbor of Djidjelli. 相似文献
This study aims to quantify the effect of heating and freezing temperatures on the pore size distribution of saturated clays. Three kaolinite clay specimens were subjected to different temperatures: 20, 70, and ? 10 °C. Upon achieving the desired temperature for each specimen, the specimens were flash frozen in liquid nitrogen to preserve their microstructure. Each specimen was, then, freeze-dried for 24 h after which consecutive two-dimensional (2-D) SEM images were taken using a dual focused ion beam/scanning electron microscope. The produced 2-D images of each specimen were used to reconstruct three-dimensional tomographies of the specimens, which were analyzed to determine the pore size distribution at each temperature. Compared to the specimen at room temperature, the pores in the specimen subjected to ? 10 °C were larger; this is believed to be due to the formation of ice lenses inside the pores upon freezing and potential merging between initial pores to form larger pores. On the other hand, the heated specimen showed an increase in the volume of the smaller pores and a decrease in the volume of the larger pores compared to the specimen at room temperature. This opposite behavior between the small and large pores in the heated specimen is justified considering (1) the easier flow of water out of the larger pores compared to that in the smaller pores and (2) the anisotropic nature of the thermal expansion of the clay particles. 相似文献
Sustainable management and exploitation policies as well as suitable conservation and mitigation strategies are mandatory to preserve cultural heritage and to reduce threats, weathering phenomena, and human actions that may produce significant deterioration and alteration of cultural heritage and “its environment”. In this context, remote sensing technologies can offer useful data to timely update information and documentation and set up reliable tools for systematic monitoring of cultural properties. In this study, multi-temporal and multi-sensor satellite data from Corona, Landsat, Spot, Quickbird, and Sentinel-2A have been exploited along with spatial analysis to investigate the area of the Theban temples at west Luxor (Egypt), severely threatened by uncontrolled urban sprawl. The results from our analyses showed that the urban expansion continuously occurred during the whole investigated period causing an increasing in urban areas around (1) 1.316 km2 from 1967 to 1984, (2) 1.705 km2 from 1984 to 2000, (3) 0.978 km2 from 2000 to 2003, (4) 2.314 km2 from 2003 to 2011, and (5) 1.377 km2 from 2011 to 2017. The random urban expansion caused bad sewage networks and high groundwater depth which in turn affected the archaeological areas directly (as evident on a landscape view) and indirectly by causing changes (growing) in the level of ground water depth and increasing and accelerating weathering phenomena. The quantification and mapping of urban sprawl enabled us not only to quantify and spatially characterize urban sprawl but also to create a model to mitigate the impact and provide some operational recommendations to protect the archaeological site. Outcomes from our analysis pointed out that today the tremendous availability of advanced remote sensing data has opened new prospectives unthinkable several years ago. 相似文献
