Behavior of some clays on drying and wetting paths     

Assia Benchouk  Mounir Derfouf  Nabil Abou-Bekr  Said Taibi 《Arabian Journal of Geosciences》2013,6(12):4565-4573

This paper presents an experimental study carried out on some clayey soils of Tlemcen region situated in the North West of Algeria. The characterization of the volumetric behavior under the effect of suction is studied on drying–wetting paths which highlight the correspondence between void ratio, degree of saturation, and water content versus suction. The initial conditions of studied material are in slurry form and compacted at different initial water contents. For the slurry form, correlations are derived to predict parameters characterizing the drying path.  相似文献   

Observed Behaviour of Laterally Expanded Stone Column in Soft Soil   总被引：1，自引：0，他引：1  

Wissem Frikha  Mounir Bouassida  Jean Canou 《Geotechnical and Geological Engineering》2013,31(2):739-752

The paper describes the behavior of remolded kaolin clay reinforced by stone column as investigated in laboratory. The installation of stone column was simulated by performing lateral expansion at different rates within hollow cylindrical remolded kaolin specimens initially subjected to K0 consolidation path. These specimens were, then, subjected to classical consolidated undrained triaxial tests while recording excess pore pressure values. The objective of the experimental programme was to quantify the effects of consolidation stress and stone column on the undrained Young’s modulus and shear strength of kaolin clay. Obtained results showed a significant improvement in Young’s modulus when the cavity expansion ratio and the consolidation stress increase. It was also found that the increase in undrained shear strength of improved kaolin clay mainly occurred at lower consolidation stress. Another important finding of this study is that the ratio of undrained Young’s modulus to undrained shear stress increases when the consolidation stress decreases. Finally, the paper presents a model developed for the design of stone columns.  相似文献   

Laboratory Investigation into the Effects of Silty Fines on Liquefaction Susceptibility of Chlef (Algeria) Sandy Soils     

Hanifi Missoum  Mostefa Belkhatir  Karim Bendani  Mustapha Maliki 《Geotechnical and Geological Engineering》2013,31(1):279-296

In a number of recent case studies, the liquefaction of silty sands has been reported. To investigate the undrained shear and deformation behaviour of Chlef sand–silt mixtures, a series of monotonic and stress-controlled cyclic triaxial tests were conducted on sand encountered at the site. The aim of this laboratory investigation is to study the influence of silt contents, expressed by means of the equivalent void ratio on undrained residual shear strength of loose, medium dense and dense sand–silt mixtures under monotonic loading and liquefaction potential under cyclic loading. After an earthquake event, the prediction of the post-liquefaction strength is becoming a challenging task in order to ensure the stability of different types of earth structures. Thus, the choice of the appropriate undrained residual shear strength of silty sandy soils that are prone to liquefaction to be used in engineering practice design should be established. To achieve this, a series of undrained triaxial tests were conducted on reconstituted saturated silty sand samples with different fines contents ranging from 0 to 40 %. In all tests, the confining pressure was held constant at 100 kPa. From the experimental results obtained, it is clear that the global void ratio cannot be used as a state parameter and may not characterize the actual behaviour of the soil as well. The equivalent void ratio expressing the fine particles participation in soil strength is then introduced. A linear relationship between the undrained shear residual shear strength and the equivalent void ratio has been obtained for the studied range of the fines contents. Cyclic test results confirm that the increase in the equivalent void ratio and the fines content accelerates the liquefaction phenomenon for the studied stress ratio and the liquefaction resistance decreases with the increase in either the equivalent void ratio or the loading amplitude level. These cyclic tests results confirm the obtained monotonic tests results.  相似文献   

Modelling blue and green water resources availability in Iran   总被引：7，自引：0，他引：7  

Monireh Faramarzi  Karim C. Abbaspour  Rainer Schulin  Hong Yang 《水文研究》2009,23(3):486-501

Knowledge of the internal renewable water resources of a country is strategic information which is needed for long‐term planning of a nation's water and food security, among many other needs. New modelling tools allow this quantification with high spatial and temporal resolution. In this study we used the program Soil and Water Assessment Tool (SWAT) in combination with the Sequential Uncertainty Fitting program (SUFI‐2) to calibrate and validate a hydrologic model of Iran based on river discharges and wheat yield, taking into consideration dam operations and irrigation practices. Uncertainty analyses were also performed to assess the model performance. The results were quite satisfactory for most of the rivers across the country. We quantified all components of the water balance including blue water flow (water yield plus deep aquifer recharge), green water flow (actual and potential evapotranspiration) and green water storage (soil moisture) at sub‐basin level with monthly time‐steps. The spatially aggregated water resources and simulated yield compared well with the existing data. The study period was 1990–2002 for calibration and 1980–1989 for validation. The results show that irrigation practices have a significant impact on the water balances of the provinces with irrigated agriculture. Concerning the staple food crop in the country, 55% of irrigated wheat and 57% of rain‐fed wheat are produced every year in water‐scarce regions. The vulnerable situation of water resources availability has serious implications for the country's food security, and the looming impact of climate change could only worsen the situation. This study provides a strong basis for further studies concerning the water and food security and the water resources management strategies in the country and a unified approach for the analysis of blue and green water in other arid and semi‐arid countries. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Meshless Method for Analysis of Permeable Breakwaters in the Proximity of A Vertical Wall     

Chioukh  Nadji  Ouazzane  Karim  Yüksel  Yalçın  Hamoudi  Benameur  Çevik  Esin 《中国海洋工程》2019,33(2):148-159

In the present work, the improved version of the meshless singular boundary method(ISBM) is developed for analyzing the performance of bottom standing submerged permeable breakwaters in regular normally incident waves and in the proximity of a vertical wall. Both single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with appropriate mixed type boundary conditions, and solved numerically using the ISBM. To model the permeability of the breakwaters fully absorbing boundary conditions are assumed. Numerical results are presented in terms of hydrodynamic quantities of the reflection coefficients. These are firstly validated against the results of a multi-domain boundary element method(BEM) developed independently for a previous study. The agreement between the results of the two methods is excellent. The coefficients of reflection are then computed and discussed for a variety of structural conditions including the breakwaters height, width, spacing, and absorbing permeability. Effects of the proximity of the vertical plane wall are also investigated. The breakwater's width is found to have only marginal effects compared with its height. Permeability tends to decrease the minimum reflections. These coefficients show periodic variations with the spacing relative to the wavelength. Trapezoidal breakwaters are found to be more cost-effective than the rectangular breakwaters. Dual breakwater systems are confirmed to perform much better than single structures.  相似文献   

Analysis of size spectra off northwest Africa: a useful indicator in tropical areas?   总被引：1，自引：1，他引：1  

Stobberup  Kim A.; Inejih  Cheikh A.O.; Traore  Sory; Monteiro  Carlos; Amorim  Patricia; Erzini  Karim 《ICES Journal of Marine Science》2005,62(3):424-429

  相似文献   

Simulation of long‐term consolidation behavior of soft sensitive clay using an elasto‐viscoplastic constitutive model     

M.R. Karim  F. Oka  K. Krabbenhoft  S. Leroueil  S. Kimoto 《国际地质力学数值与分析法杂志》2013,37(16):2801-2824

The phenomenon of excess pore water pressure increase or stagnation and continuing large ground deformation in soft sensitive clay following the completion of construction of embankment is simulated for a case study at Saint Alban, Quebec, Canada. The present model employs an updated Lagrangian finite element framework and is combined with an automatic time increment selection scheme. The simulation based on an elasto‐viscoplastic constitutive model considers soil‐structure degradation effect. It is shown that without consideration for the microstructural degradation effect, it is not possible to reproduce the field responses of soft sensitive clay even during the construction of the embankment. When the soil‐structure degradation effect is considered, the present model can offer reasonably accurate prediction for the consolidation behavior of soft sensitive clay, including the so‐called anomalous pore water pressure generation and continuing large deformation even after the end of construction, which has been posing numerous uncertainties on the long‐term performance of earth structures. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

A new probabilistic approach to estimating marine gastropod densities from baited traps          下载免费PDF全文

Jennifer Coston‐Guarini  Jean‐Marc Guarini  Frederike Ricarda Boehm  Thomas R. H. Kerkhove  Frances C. Rivera  Karim Erzini  François Charles  Tim Deprez  Laurent Chauvaud 《Marine Ecology》2018,39(3)

A new probabilistic approach is proposed to assess muricid species population abundances at scales relevant to both Ancient and Modern coastal fisheries. Motivated by the long‐term goal of reconstructing the dynamics of exploited murex populations during Antiquity, the objective was to estimate the population density of the banded dye‐murex, Hexaplex trunculus (Linnaeus, 1758) from successive captures with baited traps, using a method similar to the technique employed in the Mediterranean purple dye industry. The stochastic model developed simulates cumulative captures while accounting for high variability. It was calibrated with data acquired during a field trapping experiment (Crete Island, Greece). Traps’ catchability and Effective Area of Attraction (EAA) were estimated using the individual speed and behavioural response towards bait from laboratory experiments. Average density of H. trunculus was estimated as 2.2 ± 1.4 SE individuals per square metre, with no significant differences between seagrass and rocky habitats. The clearing time of successive capture experiments averaged 84 ± 6 SE hr. Clearing ca. 0.4 ha of subtidal area would be necessary to produce ca. 1.0 g of pure Tyrian purple pigment. The method described is generalizable to making population abundance estimates for similar groups, such as whelks, in modern fisheries.  相似文献   

南海北部陆架和陆坡区小型底栖动物群落的比较研究   总被引：1，自引：0，他引：1  

周红  Saif MD Uddin  黄梦娇  刘晓收  王正茂  尹泳桐  姜钱钱  Rebeca Montero-Taboad  Karim MD Abdu 《海洋与湖沼》2020,51(3):555-563

为了解南海北部陆架与陆坡区小型底栖动物的群落特征,以及影响群落特征的环境因素,2015年6月对南海北部海域(19.3°—21.4°N, 112.4°—115.1°E)7个站位的小型底栖动物及环境因子进行了采样,并对陆架和陆坡区小型底栖动物群落的丰度、生物量、类群组成和群落结构进行比较。结果表明,在陆架站位,小型底栖动物由13个类群组成,平均丰度为(132±130)ind./10cm2,平均生物量为(169±79)μgdwt/10cm2;在陆坡站位由8个类群组成,平均丰度为(33±14)ind./10cm2,平均生物量为(56±35)μgdwt/10cm2。单因素方差分析结果表明,陆坡区小型底栖动物的总丰度和总生物量以及线虫和多毛类的丰度均显著低于陆架区,但优势类群的相对丰度组成没有显著不同,海洋线虫占总丰度的83%,其次为多毛类和桡足类,分别占7%和3%。环境因子的主成分分析(Principal ComponentsAnalysis,PCA)将陆架和陆坡站位沿第一主分量轴分开,小型底栖生物丰度和生物量与沉积物叶绿素a和脱镁叶绿酸含量以及底层水温呈最大正相关,与水深呈负相关;聚类(Cluster)和排序(non-metric Multidimensional Scaling, MDS),以相似性系数65%将7个站位划分为2组,与按照水深划分的陆架和陆坡组基本吻合;单因素相似性分析(one-way ANOSIM)显示陆架和陆坡区小型底栖动物群落结构差异显著;生物-环境分析(Biota-Environment,BIOENV)表明影响群落结构的最佳环境因子组合为叶绿素a和底层水温。综上可知,随水深增加的食物减少和底层水温的下降是限制南海北部研究海域小型底栖动物丰度和生物量及影响群落组成和结构的主要因素。  相似文献   

Temporal trends of hydro-climatic variables and their relevance in water resource management     

Karim Solaimani  Mahmoud Habaibnejad  Abdollah Pirnia 《国际泥沙研究》2021,36(1):63-75

Identification of temporal changes in hydrological regimes of river basins is an important topic in contemporary hydrology because of the potential impacts of climate change on river flow regimes.For this purpose,long-term historical records of rainfall(P),runoff(Q)and other climatic factors were used to investigate hydrological variability and trends in the Tajan River Basin over the period 1969e1998.Actual evaporation(E),rainfall variability index(d),evaporation ratio(CE)and runoff ratio(CQ)were estimated from the available hydroclimatological records.Mann-Kendall trend analysis and nonparametric Sen's slope estimates were performed on the respective time series variables to detect monotonic trend direction and magnitude of change over time.Rainfall variability index showed that 1973 was the wettest year(δ=+2.039)while 1985 was the driest(δ=-1.584).Also,decades 69e78 and 89e98 were recognized as the wettest and driest decades respectively.The gradient of variation of climatological parameters showed that during the study period,all three parameters of rainfall,evaporation and runoff have decreased and the variations of rainfall and evaporation were significant at the 95%level.Investigation of hydrological changes due of dam construction(1999)showed that the amount and annual distribution of discharge were completely different pre and post-dam construction.Discharge decreased in high water months and increased in low water months to meet water supply demands,especially for agriculture.The relationship between temperature and rainfall trends is compared for three stations in Mazandaran Province(Gorgan,Babolsar and Ramsar)from 1956 to 2003 and nine other stations with different statistical periods of 19e36 years,relating trends to northern hemisphere and global trends.Decreases in temperature were accompanied by decreases in rainfall,and vice versa.These trends were not observed in northern hemisphere and world scales,where temperature increases are accompanied by decreases in rainfall.These variations of hydroclimatological parameters show undesirable water resources situations during the statistical periods if the trend continues severe water resource crises.  相似文献