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21.
Samir Mefteh Mounir Medhioub Elhoucine Essefi Fakher Jamoussi 《Journal of the Geological Society of India》2014,83(2):198-210
This study aims to follow the effect of the diagenetic transformations on the clayey fraction and the organic matter of the Tunisian southern sub-surface. 61 samples from oil well named NWA-1 were recuperated for series of analyses. This study follows a comparative approach between the mineralogical, geochemical and petrographic studies. To discuss results from a statistical viewpoint, the Principal Component Analysis (PCA) was applied in order to find out any correlation between different components. The associated minerals quartz, feldspar, calcite, pyrite, anhydrite, gypsum, dolomite and olivine are also detected. These associated minerals remove by-products by the illitization reaction. The Index of Crystallinity (IC) of illite shows that, except some anomalies, the studied samples are between the epizone and the anchizone. Downward, samples show the effect of diagenetic processes and weak signs of low-grade metamorphism. As regards to the organic matter, values of Tmax range between 333°C and 463°C. On the other hand, potential hydrocarbon compounds (S2) show low values compared to those of (S1); but they maintain a similar variability from 0.63 to 21.12. SEM observations and X-ray microanalyses supported the formation of authigenic micro-quartz. The PCA of clay minerals, chemical components, and the depth shows three different populations. Feldspar, chlorite and quartz make up a population positively correlated with the depth. The second population seems to be indifferent to depth variation; it is made up of two sub-populations: the population of illite, gypsum and anhydrite, which is obtained by a counter clock rotation of depth population; and the population of pyrite, kaolinite, olivine phyllosilicate, which is obtained by an anticlockwise rotation of depth population. Third, the population of smectite, calcite and dolomite is inversely proportional to the depth variation. On the other hand, the PCA of TOC, Tmax, HI, S1, S2 and the depth make up a homogenous statistical population following the depth evolution. 相似文献
22.
Spatially Located Platform and Aerial Photography for Documentation of Grazing Impacts on Wheat 总被引：11，自引：0，他引：11
Abstract Goose populations that winter in Oregon's Lower Willamette Valley have increased from 25 000 to more than 250 000 birds in the last 25 years, resulting in heavy grazing of wheat and other crops. To map and document the extent and intensity of goose impacts on wheat fields, we combined rectified aerial photography with both globally positioned ground observations and vertical platform photographs. Aerial photos revealed areas of fields with sparse wheat cover while platform photos documented the cause. We estimated wheat cover in ground level photographs by ratioing red, green and blue digital numbers. From platform photographs we recorded occurrence of grazing (from grazed leaf tips), intensity of grazing (from residual plant cover and leaf length), and other indicators of goose use (footprints and droppings). Because the ground photographs were spatially positioned, we could use this information to verify the cause of “thin” wheat. Crop damage from grazing/trampling, water submergence, and other factors was evident. Our results illustrate practical ways to combine aerial and ground‐level image analysis, spectral observations, and global positioning systems to quantify field conditions in wheat. 相似文献
23.
Discussion on Tunis Soft Soil Sensitivity 总被引：1，自引：1，他引：0
Lamia Touiti Mounir Bouassida William Van Impe 《Geotechnical and Geological Engineering》2009,27(5):631-643
In Tunis City, the sensitivity of the marine deposits at shallow depth (z = 0–20 m) varies significantly. The influence of the process of the leaching out of Tunis soft soil on its geotechnical parameters
is a focal point in this research. This process leads finally to moderate levels of sensitivity for Tunis clays since it appears
to happen in a two steps with increasing sensitivity. The “hard water” leaching out and the dispersive action of organic matter
(humus) lead unexpectedly to higher but still moderate level of sensitivity as measured on many Tunis sites. These sensitivity
variations result from the combination of leaching out with hard ground water and high content of organic matter. This sensitivity
attracted our attention and remains of high interest for the study of the behaviour of the Tunis soft clay. 相似文献
24.
Wissem Frikha Habib Zargayouna Samia Boussetta Mounir Bouassida 《Geotechnical and Geological Engineering》2017,35(3):931-947
Tunis soft clay belongs to the category of problematic soils because of its weak strength characteristics, high compressibility and high content of organic matter (22%). Deep mixing column (DM) presents a well-developed technique to improve the properties of Tunis soft soils by increasing its bearing capacity and reducing settlements. This paper describes a laboratory experimental program performed to assess the effectiveness in improving the shear strength of Tunis soft clay. The two mains objectives of this research are to evaluate the effect of reinforcement by DM on the behaviour of the Tunis soft clay and to investigate parameters of influence on its strength characteristics. Five parameters are studied from the performed tests: (1) curing time: CT = 7, 14, 21 and 28 days; (2) injection pressure: IP = 50, 100 and 150 kPa; (3) water–cement ratio w/C = 0.7, 1 and 1.2; (4) rotation rate V = 15, 30 and 40 rpm and (5) consolidation pressure: б3 = 100, 150 and 200 kPa. 相似文献
25.
Benkhattab Fatima Zahra Hakkou Mounir Bagdanavičiūtė Ingrida Mrini Abdelmounim El Zagaoui Hafid Rhinane Hassan Maanan Mehdi 《Natural Hazards》2020,104(1):519-536
Natural Hazards - Analyzing and understanding coastline variability and dynamics are important for scientists and policy-makers. This study investigates the long-term process of shoreline change... 相似文献
26.
Muhammad Islam Abdul Razzaq Shamim Gul Sarfraz Ahmad Taj Muhammad Sawsan Hassan Barbara Rischkowsky M. N. M. Ibrahim Mounir Louhaichi 《山地科学学报》2018,15(4):685-694
Controlled grazing is considered a good management strategy to maintain or increase the live weight of livestock and to reduce vegetation degradation of rangelands. The present study investigated soil characteristics, aboveground vegetation biomass dynamics and controlled grazinginduced changes in the live weight of local ewes in the semi-arid rangeland of Ahmadun, Ziarat, Balochistan province of Pakistan. An area of 115 ha was protected from livestock grazing in April 2014. In June 2015, soil characteristics within 0-30 cm depth i.e. soil organic matter (SOM), mineral nitrogen, pH and texture in controlled and uncontrolled grazing sites were assessed. Aboveground vegetation biomass measured in early (June) and late summer (August) in 2015 and 2016. The nutritional value i.e. crude protein, phosphorus (P), neutral detergent fiber (NDF), acid detergent fiber (ADF), calcium (Ca), magnesium (Mg) and potassium (K) of dominant plant species were assessed at the beginning of experiment in 2015. Vegetation cover of controlled and uncontrolled grazing sites was also measured during the two years of the study period using the VegMeasure software. From June to November in 2015 and 2016, controlled and uncontrolled livestock grazing sites were grazed on a daily basis by local ewes with a stocking rate of 2 and 1 head ha-1 respectively. Results reveal that the organic matter contents of coarse-textured, slightly alkaline soil of the study site were in the range of 9.4 - 17.6 g kg-1 soil and showed a strong positive correlation with aboveground vegetation biomass. The biomass of plants was 56.5% and 33% greater at controlled than uncontrolled grazing site in 2015 and 2016 respectively and plant cover was also higher at controlled than uncontrolled grazing site in both years. The nutrient contents were significantly (P<0.05) lower in grasses than shrubs. In both years, the controlled grazing increased the weight gain of ewes about two folds compared to the uncontrolled grazing. The results indicate that controlled grazing improved the vegetation biomass production and small ruminant productivity. 相似文献
27.
The spatial variability of seismic ground motion is an important aspect for the earthquake resistant design of extended facilities. A modified response spectrum model, which addresses the problem of multiply supported structures subjected to imperfectly correlated seismic excitations, has already been developed (see References 1 and 2). The present paper proposes a modal combination rule for the case of non-uniform seismic input, which would be used together with the modified response spectrum model in order to compute physical responses. This rule, which accounts for modal cross-correlations, is an extension to an existing rule for the case of uniform seismic motions. It modifies the existing modal cross-correlation coefficients through a correction factor which depends on structural properties and on the characteristics of the wave propagation phenomenon. Finally, some practical considerations on the theoretical development are addressed. They aim at suggesting reasonable simplifications which render the modal combination rule more appealing for engineering purposes. The proposed practical combination rule is validated through a numerical experiment which also characterizes the effect of non-uniform seismic input on modal cross-correlation. 相似文献
28.
The influence of stochastic kinematic interaction (SKI) on structural response is investigated in this paper. The SKI is evaluated through a computational model based on the boundary element method (BEM) formulated in the frequency domain. The singular integrals required in the computation of BEM are evaluated in a closed form. It is assumed that the foundation input motion (FIM) is the result of the superposition of many plane, stationary, correlated stochastic SH‐, P‐ and SV‐waves travelling within a homogeneous viscoelastic soil at different angles. The results obtained indicate that the effect of SKI on the foundation response is qualitatively similar to that of wave passage. Both effects involve a reduction of translational components of the response at intermediate and high frequencies and creation of a rotational response component at intermediate frequencies, which decreases at high frequencies. While, it is found that the SKI decreases the maximum response of structures built on embedded rigid strip foundations excited by SH‐ and P‐waves, it increases the maximum response for SV‐waves, except when the natural frequency of the structure is less than 0.5 Hz and for short structures excited by shallowly incident SV‐waves. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
29.
Clay and Marl Formation Susceptibility in Mila Province,Algeria 总被引：2，自引：2，他引：0
Djamel Athmania Abdelkader Benaissa Achour Hammadi Mounir Bouassida 《Geotechnical and Geological Engineering》2010,28(6):805-813
In Mila Province, Algeria (a.k.a Mila Wilaya), sensitive clays presenting shrinkage-swelling phenomena are widespread, covering
large areas. Due to this, constructions and infrastructures sustainability built on such soils is questionable. Such clays
sensitivity is amplified by seasonal rainfall deficits which reaches extreme magnitudes. In order to develop disasters’ prevention
measures, we present in this work, areas mapping susceptible to shrinkage-swelling phenomenon by adopting a French method
developed by B R G M. This method takes into account three measurable characteristics: i.e. lithological, mineralogical and
geotechnical, of clayey formations identified in the studied sector. Based on these characteristics, three scores are attributed
for each formation. Then, the susceptibility index is the obtained score average for each clayey formation. The susceptibility
map is established on this index basis with three classes: low, medium, high. 相似文献
30.
A survey on the epiphytic microorganisms growing on Posidonia oceanica leaves was conducted along a depth transect along the coast of Eastern Tunisia (Mahdia). Samples were collected by SCUBA diving at depths of 3, 5, 10 and 12 m in July 2008 and January 2009. A total of 58 microepiphyte taxa were identified. Multivariate analyses revealed temporal and spatial variation of the abundance of epiphytic microalgae. Water motion, light availability, temperature and motility of species seem to be responsible of temporal and bathymetric variations of epiphytic microalgae. Unlike diatoms, dinoflagellates were more abundant in deep waters, suggesting that they are more vulnerable to hydrodynamics. The significant correlation between leaf area index and abundance of epiphytic species indicates that the phenological parameters of the host plant influence the abundance of the epiphytic microorganisms. Among the epiphytic dinoflagellates, our data showed a great number of potentially toxic species (Alexandrium minitum, Amphidinium carterae, Karenia selliformis, Coolia monatis, Karlodinium veneficum, Ostreopsis siamensis, Prorocentrum concavum, Prorocentrum minimum, Prorocentrum rathymum and Prorocentrum lima). These species were more abundant in the deep station under more sheltered conditions than found at inshore shallower stations, which are subjected to high water motion. 相似文献