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31.
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
32.
The accuracy of conventional global navigation satellite systems (GNSS) positioning in dense urban areas is severely degraded due to blockage and reflection of the signals by the surrounding buildings. By using 3D mapping of the buildings to aid GNSS positioning, the accuracy can be substantially improved. However, positioning performance must be balanced against computational load. Here, a likelihood-based 3D-mapping-aided (3DMA) GNSS ranging algorithm is demonstrated that enables signals predicted to be non-line-of-sight (NLOS) to contribute to the position solution without explicitly computing the additional path delay due to NLOS reception, which is computationally expensive. Likelihoods for an array of candidate positions are computed based on the difference between the measured and predicted pseudoranges. However, a skewed distribution is assumed for those signals predicted to be NLOS on the basis that the ensuing ranging errors are always positive. An overall position solution is then extracted from the likelihood surface. GNSS measurement data have been collected at several locations in both traditional and modern dense urban environments. Horizontal root-mean-square single-epoch position accuracies of 4.7, 5.6 and 6.5 m are obtained using, respectively, a Leica Viva geodetic receiver, a u-blox EVK M8T consumer-grade receiver and a Nexus 9 tablet incorporating a smartphone GNSS antenna and a GNSS chipset that outputs pseudoranges. The corresponding accuracies using single-epoch conventional GNSS positioning are 20.5, 23.0 and 28.4 m, about a factor of four larger. The 3DMA GNSS algorithms have also been implemented in real time on a Raspberry Pi 3 at a 1-Hz update rate.
相似文献33.
This paper presents the results of an experimental investigation carried out on disturbed clay samples to analyze their creep behavior. The experimental program included compression triaxial tests with varied degree of saturation of the samples and stress level. Triaxial tests were performed at imposed strain rate varied from 0.005 to 0.10%/min. Various stress paths have also been tested including isotropic consolidation and deviatoric stress. The obtained results showed that shear deformation increases with the initial degree of saturation and stress level of clay samples. At fixed stress level and for both isotropic and deviatoric stress paths, the initial degree of saturation and the second invariant of the strain tensor varied with a similar trend. The variation of axial creep strain is correlated with time in a semi-logarithmic function. 相似文献
34.
Mounir Karim Mehdi Maanan Mohamed Maanan Hassan Rhinane Henri Rueff Lahssen Baidder 《国际泥沙研究》2019,34(1):65-72
Coastal lagoons have significant biodiversity and ecologic and socio-economic interest. Several resident and migratory birds live in coastal lagoons as well as fish and other aquatic biota. Over the years, lagoons worldwide have been subject to considerable sediment deposition coming especially from soil erosion due of agricultural activities, and the lagoon's inflows have resulted in an accelerated sedimentation which can drastically affect the aquatic ecosystem balance. A new, fast, and cost-effective approach was developed, using water surface change as a proxy, to evaluate the sediment deposition rate. In the current research, this methodology was applied in the Moulay Bousselham Lagoon in Morocco, and a combination of Landsat 8 and Landsat 5 imagery acquired at four points in time over 30 years(1985-2015) was used. Following geometric correction and enhancement, the interpretation of the acquired images provided important insight on the current conditions of the water surface change using the Normalized Difference Water Index(NDWI). Several iterations were done to determine a suitable threshold for effective water surface detection. In order to validate the automatically extracted water surface features, many band combinations of Landsat and Sentinel 2 were used as references to run the accuracy assessment. The results show that the Moulay Bousselham Lagoon lost 17.60%(106 ha) of its water surface area, and 530,000 m^3 to 1,060,000 m^3 of its water volume during the last three decades.Converting water surface loss into sedimentation returned a rate of 0.58 cm/yr. These results have been confirmed by previous field work using sedimentological approaches. Proper management should be applied to sustain the vitality of this lagoon environment. 相似文献
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36.
An important aspect of earthquake loads exerted on extended structures, or structures founded on several foundations, is the spatial variability of the seismic motion. Hence, a rigorous earthquake resistant design of lifeline structures should account for the spatial character of the seismic input, at least in an approximate way. A procedure is proposed which enables addressing the problem of multiply supported structures, subjected to imperfectly correlated seismic excitations, by means of an extension to the response spectrum method. A modified response spectrum model is developed for the design of extended facilities subjected to single and multicomponent ground motion. The modification procedure is based on adjusting each spectral value of the given design response spectrum by means of a correction factor, which depends on the structural properties and on the characteristics of the wave propagation phenomenon. Finally, the theoretical model is validated through digital simulation of seismic ground motion, whereby model predictions are found to be in good agreement with exact results. 相似文献
37.
Ali?Ben Dhiab Mehdi?Ben Mimoun Jose?OterosEmail author Herminia?Garcia-Mozo Eugenio?Domínguez-Vilches Carmen?Galán Mounir?Abichou Monji?Msallem 《Theoretical and Applied Climatology》2017,128(3-4):541-549
Tunisia is the world’s second largest olive oil-producing region after the European Union. This paper reports on the use of models to forecast local olive crops, using data for Tunisia’s five main olive-producing areas: Mornag, Jemmel, Menzel Mhiri, Chaal, and Zarzis. Airborne pollen counts were monitored over the period 1993–2011 using a Cour trap. Forecasting models were constructed using agricultural data (harvest size in tonnes of fruit/year) and data for several weather-related and phenoclimatic variables (rainfall, humidity, temperature, Growing Degree Days, and Chilling). Analysis of these data revealed that the amount of airborne pollen emitted over the pollen season as a whole (i.e., the Pollen Index) was the variable most influencing harvest size. Findings for all local models also indicated that the amount, timing, and distribution of rainfall (except during blooming) had a positive impact on final olive harvests. Air temperature also influenced final crop yield in three study provinces (Menzel Mhiri, Chaal, and Zarzis), but with varying consequences: in the model constructed for Chaal, cumulative maximum temperature from budbreak to start of flowering contributed positively to yield; in the Menzel Mhiri model, cumulative average temperatures during fruit development had a positive impact on output; in Zarzis, by contrast, cumulative maximum temperature during the period prior to flowering negatively influenced final crop yield. Data for agricultural and phenoclimatic variables can be used to construct valid models to predict annual variability in local olive-crop yields; here, models displayed an accuracy of 98, 93, 92, 91, and 88 % for Zarzis, Mornag, Jemmel, Chaal, and Menzel Mhiri, respectively. 相似文献
38.
Vulnerability assessment of reinforced concrete bridge structures in Algiers using scenario earthquakes 总被引：1，自引：1，他引：0
Abderrahmane Kibboua Hakim Bechtoula Youcef Mehani Mounir Naili 《Bulletin of Earthquake Engineering》2014,12(2):807-827
Algeria has an inheritance of more than 11,000 bridges, with approximately 5,000 road bridges of which more than 30 % have a high probability to be exposed to major earthquakes and serious damages in the future. Therefore, it is of great importance to retrofit the existing bridges and assess their seismic vulnerability and set a permanent monitoring survey to follow the change of their dynamic characteristics such as natural frequency and modal damping. The assessment of the seismic vulnerability of existing RC bridges was carried out based on the consistent and complete post earthquake survey after the Boumerdes earthquake. The information on the damaged existing RC bridges was investigated and evaluated by the authors. This paper presents a simple and efficient inspection method for the preliminary evaluation of the seismic vulnerability of existing bridge structures. To assess the seismic damage of 148 existing bridges, two seismic scenarios were carried out using “Khair al Din” and the “Zemmouri” faults that are capable to generate earthquakes with a maximum acceleration of 0.8g. The main findings of this study are summarized in this paper. 相似文献