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21.
Leila Hazout Zein El-Abidine Zitouni Mostefa Belkhatir Tom Schanz 《Geotechnical and Geological Engineering》2017,35(5):2079-2105
Liquefaction of soils is a natural phenomenon associated with a dramatic loss of the soil shear strength in undrained conditions due to a development of excess pore water pressure. It usually causes extensive damages to buildings and infrastructures during earthquakes. Thus, it is important to evaluate extent of influential parameters on the liquefaction phenomenon of soils in order to clearly understand the different mechanisms leading to its triggering. The soil gradation is one of the most important parameters affecting the liquefaction phenomenon. In this context, a series of undrained compression triaxial tests were carried out on eighteen natural loose (Dr = 25%) sandy samples containing low plastic fines content of 2% (Ip = 5%) considering different extreme sizes (1.6 mm ≤ Dmax ≤ 4 mm and 0.001 mm ≤ Dmin ≤ 0.63 mm) and two mean grain size ranges (0.25 mm ≤ D50 ≤ 1.0 mm) and (1.0 mm ≤ D50 ≤ 2.5 mm). The initial confining pressure for all tests was kept constant (P′c = 100 kPa). The obtained test results indicate that the mean grain size (D50) and extreme grain sizes (Dmax and Dmin) have a significant influence on the undrained shear strength (known as liquefaction resistance) and appear as pertinent factors for the prediction of the undrained shear strength for the soil gradation under study. The undrained shear strength and the excess pore water pressure can be correlated to the extreme grain sizes (Dmax and Dmin) and the mean grain size (D50) of tested wet deposited samples. 相似文献
22.
Leila GHOLAMI Abdulavahed KHALEDI DARVISHAN Veliber SPALEVIC Artemi CERDà Ataollah KAVIAN 《山地科学学报》2021,(3):706-715
Raindrop size,rainfall intensity and runoff discharge affect the detachment and transportation of soil particles.Among these three factors,the rainfall intensity seems to be more important because it can change other two factors.Storm patterns can be determined by changing the rainfall intensity during the storm.Therefore,the objective of this research is to test the influence of storm pattern on runoff,soil erosion and sediment concentration on a rangeland soil slope under field rainfall simulation.Four storm rainfall intensity patterns were selected for examining the effects of variations in storm event characteristics on soil erosion processes.The selected storm patterns were:I(45,55 and 70 mm h-1);II(45,70 and 55 mm h-1);III:(70,55 and 45 mm h-1);and IV(55,45 and 70 mm h1).The last pattern is a new one instead of the uniform pattern which has been sufficiently studied in previous researches.The experiments were conducted in field plots(in Kojour watershed,Mazandaran Province,Iran)with an area of one square meter and an constant slope gradient of 18%,surrounded by galvanised sheets.Following the nonuniform prioritization of the storm patterns for the studied variables,time to runoff(I>II>IV>III),runoff volume(III>IV>II>I),sediment concentration(IV>III>I>II)and soil erosion(III>IV>II>I)),it can be generally inferred that each pattern has specific effect on soil erosion processes during a storm.The results of the general linear model(GLM)test indicated that the effects of storm pattern on time to runoff,total runoff volume,runoff coefficient and soil erosion were significant at a level of 99%.The Duncan test showed that the storm patterns can be divided into three groups of III,IV;II;I(for time to runoff),I,II;IV,III(for runoff coefficient),and I;II;IV,III(for runoff volume and soil erosion). 相似文献
23.
Leila M. Harris Danika Kleiber Lucy Rodina Sule Yaylaci Jacqueline Goldin Germaine Owen 《社会与自然资源》2018,31(1):89-105
We analyze the relationship between perceptions of domestic water access, and quality, in relation community engagement. While others have suggested linkages between material conditions of water access and engagement (e.g., that poor water access might spur engagement), to date there have been no studies those test these relationships using statistical methods. Based on a quantitative analysis of survey data from underserved sites in Accra, Ghana, and Cape Town, South Africa, our results show that water access and quality are both predictive of community engagement. The analysis also makes a strong case that there are different dimensions when considering the material conditions of water—in this case, water access and quality each condition engagement in opposite directions. Furthermore, consistent with other studies, our study also shows different demographics (notably gender) mediate these relationships in important ways. 相似文献
24.
Weak ion-acoustic (IA) solitary wave propagation is investigated in the presence of electron trapping and background nonextensivity. A physically meaningful distribution is outlined and a Schamel-like equation is derived. The role a background electron nonextensivity may play on the energy carried by the IA soliton is then examined. It is found that nonextensivity may cause a soliton energy depletion. An increase of the amount of electron trapping leads to a net shift towards higher values of the soliton energy. 相似文献
25.
Alicia Daniela Robles Paula Polizzi María Belén Romero Leila Natalia Chiodi Boudet Sandra Medici Agustín Costas Marcela Gerpe 《Environmental Earth Sciences》2016,75(23):1479
The presence of arsenic (As) in surface water constitutes an important environmental risk, where mobility and adsorption processes are responsible for its behavior in the sediment–water interface. Therefore, the assessment of adsorption, mobility and water availability of arsenic in freshwater sediments, with agricultural, livestock and urban soil uses was performed. Arsenic concentrations in sediments ranged from 5.4 to 15.9 mg kg?1 (total) and 2.8 to 6.5 mg kg?1 (labile), and those of iron and manganese were 11,563–23,500 and 140.6–662.1 mg kg?1, respectively. The As levels in water were significantly lower than those of sediments. Results would suggest that As co-precipitation and adsorption on Fe oxides are probably the major route of immobilization, determining its low lability. Manganese did not present an outstanding contribution to the retention, and cation-exchange capacity, pH and organic matter of sediments did not show an influence on the mobility of As. 相似文献
26.
Weak ion-acoustic double-layers (IA-DLs) in a two-component plasma are investigated in the context of the nonextensive statistics
proposed by Tsallis. Due to the entropic index q, our plasma model can admit compressive as well as rarefactive IA-DLs. It is shown that the values
\frac53 < q < 3\frac{5}{3}
q-parameters for the existence of small-DLs. As long as the Mach number M is less than ∼1.42, the only admissible q-values which may lead to IA-DLs are all positive. For −1<q<1 (1<q<5/3), the effect of increasing q is to lower (to shift towards higher values) the critical Mach number M cr above which only compressive IA-DL are admitted. Beyond q=3, only compressive small-amplitude ion-acoustic double layers are observed. Furthermore, due to the flexibility of the q-parameter, the obtained results bring a possibility to deal with small-DLs with relatively high Mach numbers. Our investigation may be of wide relevance to astronomers and space scientists working on interstellar plasmas. 相似文献
27.
Leila Djadia Djamel Machane Jean-Luc Chatelain Abdesslam Abtout Rabah Bensalem Mehdi Amine Guemache Bertrand Guillier Amar Boudella El-Hadi Oubaiche 《Environmental Earth Sciences》2010,59(5):1149-1158
Results from geophysical investigations (electrical resistivity, electromagnetic mapping and seismic refraction) on an excavated
cell of the Ouled Fayet (Algiers, Algeria) pilot landfill indicated the presence of an underground runoff and permeable soil
underneath the cell. These results contradict those obtained by a feasibility study, based, however, only on the analysis
of seventy-six 10-m drilling cores. The 1D boreholes information has been proven to be insufficient and to give biased results.
The presence of water at depth is evidenced by lower resistivity, high conductivity anomalies and increase of P-wave velocity.
Thus, to the contrary of what is claimed in the feasibility study, a threat of leachate pollution is real. This study shows
that landfill construction studies cannot give trustful results without geophysical investigations. More specifically, in
Algeria, it is imperative to elaborate a landfill construction code, which should include mandatory geophysical prospecting
and deeper drilling cores. 相似文献
28.
Although there is widespread concern over degrading marine environments, there is debate within the global marine conservation agenda about the nature of the problem and appropriate solutions. At the center of this debate lie questions about the appropriate scale at which to plan and implement marine resource management. In the late 1990s, Fiji became recognized as one of the most successful examples of community-based marine resource management in the world. Recently, there has been a move to manage human–environment interactions at larger “natural” scales. We draw from the political ecology and “politics of scale” literatures, and a critical realist understanding of nature and politics, to explain the emergence of large-scale management and conservation in Fiji. We contribute to a “political ecology of scale” by developing the concept of a scalar narrative to show how social and ecological scales are reworked in the development of an ecosystem-based approach to marine management in Fiji. In doing so, we consider implications of the struggle to define the appropriate scale of marine management, which is closely bound to debates about the role of science and local participation. Our findings suggest that the struggle to define the scale at which marine management should be planned and implemented is inseparable from the struggle over who should define, inform, and conduct the governance process. We aim to clarify marine policy debates as policy actors worldwide move forward to implement ecosystem-based management, increase marine protected area coverage, and pursue sustainable development. 相似文献
29.
Rahimi Leila Malekmohammadi Bahram Yavari Ahmad Reza 《Natural Resources Research》2020,29(6):3701-3718
Natural Resources Research - Understanding the spatial–temporal dynamics of wetland land cover (LC) changes and their impacts on ecosystem services (ESs) is essential for wetland conservation... 相似文献
30.
Mehdi A. Guemache Djamel Machane Hamoud Beldjoudi Sofiane Gharbi Leila Djadia Sihem Benahmed Hayet Ymmel 《Natural Hazards》2010,54(2):273-288
On March 20, 2006, an earthquake (M
w = 5.3; SED) struck the mountainous region of the Babors chain (Wilaya of Bejaia, northeast Algeria). The seismic epicenter
was located near the Kherrata village. This earthquake was felt on a large area of the northeastern part of Algeria. It reached
an intensity of VII (EMS scale) at the Laalam village, situated at about 20 km northeast of Kherrata. Here, many old and recent
houses were damaged or collapsed totally, four people died and 68 were injured. Field investigations revealed that these casualties
were caused by a landslide triggered by the earthquake. Many fissures were visible on ground throughout the site. They were
generated by both sliding and settling phenomena. The Laalam site is prone to landslide, as revealed by some evidences on
old instabilities. This is due to two main factors: local geomorphology and geology. These factors intervene synchronously
for reducing the slope instability at the Laalam village. The March 20, 2006 Kherrata earthquake was the trigger that released
the Laalam landslide. 相似文献