Undrained Shear Characteristics of Tropical Peat Reinforced with Cement Stabilized Soil Column     

Sina Kazemian  Bujang B. K. Huat  Hossein Moayedi 《Geotechnical and Geological Engineering》2012,30(4):753-759

Peat commonly occurs as extremely soft, wet, unconsolidated surface deposits that are integral parts of wetland systems. Cement is widely used for the stabilization of peat by deep mixing method. This paper presents the results of the shear strength parameters of study models (fibrous, hemic and sapric peats stabilized with columns formed by dry mixing method). The columns were formed of peat treated with cement in different proportions. Triaxial test was performed after curing the samples for 28?days to evaluate the shear strength parameters. The results showed that the shear strength of peats can be improved significantly by the installation of cement stabilized soil columns. The amount of cement used to form the column and its diameter were observed to influence the strain–stress graph of peat reinforced. Furthermore, the result showed that the effect of cement was the highest on sapric peat due to its physico-chemical properties.  相似文献   

Investigation of groundwater level fluctuations in the north of Iran   总被引：3，自引：1，他引：2  

Hossein Tabari  Jaefar Nikbakht  B. Shifteh Some’e 《Environmental Earth Sciences》2012,66(1):231-243

Groundwater is the main source of water supply for drinking and agriculture uses in Mazandaran province. In recent years, the rapid growth of population and the increased need for water and food has put its land and water resources under severe stress. The main objective of this study was to investigate the temporal trends in annual, seasonal and monthly groundwater level using the Mann–Kendall test and the Sen’s slope estimator in the area during 1985–2007. The results indicated a mix of negative and positive trends in the groundwater level series. However, the positive trends were much more than negative ones. The statistical tests detected a significant increasing trend in more than 28% of the wells. The stronger increasing trends were identified in the series in summer and spring compared with those in autumn and winter. Moreover, the highest numbers of wells with significant positive trends occurred in August and July, respectively. The results of spatial analysis showed that the significant positive trends were concentrated in the central parts of Mazandaran province where paddy fields are the major water demanders. Analysis of climatic parameters revealed that decreasing trend of relative humidity and increasing trends of minimum and maximum air temperature can be attributed to groundwater level fluctuations in the study region. The research will be helpful for planners and policy makers to allocate groundwater resources in different sectors including agriculture, drinking and industry.  相似文献   

Robust attenuation relations for peak time-domain parameters of strong ground motions     

Ali Kafaei Mohammadnejad  Seyyed Mohammad Mousavi  Mohammad Torabi  Mehdi Mousavi  Amir Hossein Alavi 《Environmental Earth Sciences》2012,67(1):53-70

This study presents new attenuation models for the estimation of peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) using a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The PGA, PGV, and PGD were formulated in terms of earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms. A worldwide database of strong ground motions released by Pacific Earthquake Engineering Research Center (PEER) was employed to establish the models. A traditional genetic programming analysis was performed to benchmark the proposed models. For more validity verification, the GP/SA models were employed to predict the ground-motion parameters of the Iranian plateau earthquakes. Sensitivity and parametric analyses were carried out and discussed. The results show that the GP/SA attenuation models can offer precise and efficient solutions for the prediction of estimates of the peak time-domain characteristics of strong ground motions. The performance of the proposed models is better than or comparable with the attenuation relationships found in the literature.  相似文献   

Computation of the structure of a magnetized strange quark star     

Gholam Hossein Bordbar  Ali Reza Peivand 《中国天文和天体物理学报》2011,(7)

We have calculated some properties of spin polarized strange quark matter(SQM) in a strong magnetic field at zero temperature using the MIT bag model.We showed that the equation of state of spin polarized SQM is stiffer than that for unpolarized cases.We have also computed the structural properties of a spin polarized strange quark star(SQS) and found that the presence of a magnetic field leads to a more stable SQS when compared to the structural properties of an unpolarized SQS.  相似文献   

Peaty Soil Improvement by Using Cationic Reagent Grout and Electrokintic Method   总被引：2，自引：1，他引：1  

Hossein Moayedi  Mansour Mosallanezhad  Ramli Nazir  Sina Kazemian  Bujang Kim Huat 《Geotechnical and Geological Engineering》2014,32(4):933-947

Peat is known as soft soil with low shear strength and high compressibility. Electrokinetic injection technique is being used by applying a direct electrical potential across the soil specimens to improve physicochemical characteristics of the peat. Such applications cause electrochemical effects on the soil, leading to changes in the soil’s chemical, physical, and mechanical properties. This paper presents the results of the undrained shear strength, pH, water content across the electrokinetic box after injecting the cationic grouts. Four cationic grouts namely; calcium chloride, calcium oxide, Aluminum hydroxide, and sodium silicates were selected as grout. The microstructures of the stabilized peats were investigated by scanning electron microscopy and energy dispersive X-ray spectrometer analysis. The result showed that the cationic stabilizer injected by the electrokinetic technique could significantly increase the peat soil’s shear strength. Furthermore, the result showed that the effect of calcium oxide was the highest on the shear strength of peat due to its physico-chemical properties. The shear strength, pH and moisture content of peats across the electrokinetic box also altered depending on the used electrolytes and time.  相似文献   

Numerical and intelligent modeling of triaxial strength of anisotropic jointed rock specimens     

Mojtaba Asadi  Mohammad Hossein Bagheripour 《Earth Science Informatics》2014,7(3):165-172

The strength of anisotropic rock masses can be evaluated through either theoretical or experimental methods. The latter is more precise but also more expensive and time-consuming especially due to difficulties of preparing high-quality samples. Numerical methods, such as finite element method (FEM), finite difference method (FDM), distinct element method (DEM), etc. have been regarded as precise and low-cost theoretical approaches in different fields of rock engineering. On the other hand, applicability of intelligent approaches such as fuzzy systems, neural networks and decision trees in rock mechanics problems has been recognized through numerous published papers. In current study, it is aimed to theoretically evaluate the strength of anisotropic rocks with through-going discontinuity using numerical and intelligent methods. In order to do this, first, strength data of such rocks are collected from the literature. Then FlAC, a commercially well-known software for FDM analysis, is applied to simulate the situation of triaxial test on anisotropic jointed specimens. Reliability of this simulation in predicting the strength of jointed specimens has been verified by previous researches. Therefore, the few gaps of the experimental data are filled by numerical simulation to prevent unexpected learning errors. Furthermore, a sensitivity analysis is carried out based on the numerical process applied herein. Finally, two intelligent methods namely feed forward neural network and a newly developed fuzzy modeling approach are utilized to predict the strength of above-mentioned specimens. Comparison of the results with experimental data demonstrates that the intelligent models result in desirable prediction accuracy.  相似文献   

Improvement of soft clay using installation of geosynthetic-encased stone columns: numerical study     

Asskar Janalizadeh Choobbasti  Hossein Pichka 《Arabian Journal of Geosciences》2014,7(2):597-607

The use of geosynthetic-encased stone columns as a method for soft soil treatment is extensively used to increase the bearing capacity and reduce the settlement of raft foundations and the foundation of structures like embankments. Pre-strain is an effect occurring in the encasement during stone column installation due to the compaction of the stone material. The present study uses the finite element program Plaxis to perform a numerical analysis of the soft clay bed reinforced by geosynthetic-encased stone columns. An idealization is proposed for simulation of installation of geosynthetic-encased stone columns in soft clay based on the unit-cell concept. In the analyses, initially, the validity of the analysis of the single column-reinforced soil in the unit-cell model was performed through comparison with the group columns. Then, by considering a unit-cell model, the finite element analyses were carried out to evaluate the stiffness of the reinforced ground to estimate the settlement. The results of the analyses show that the improved stiffness of the encased stone column is not only due to the confining pressure offered by the geosynthetic after loading, but the initial strain of the geosynthetic that occurred during installation also contributes to the enhancement of the stiffness of the stone column and the reduction of the settlement.  相似文献   

Metal Concentrations in the Coastal Fauna of the Caspian Sea     

Mirzajani  Alireza  Hamidian  Amir Hossein  Hassan  Jalal 《Ocean Science Journal》2021,56(3):256-265

Ocean Science Journal - Metal concentrations were measured in predominant coastal fauna of the Caspian Sea including six macro-invertebrates (Mnemiposis leidyi, Balanus improvisus, Pontogammarus...  相似文献   

Streamflow drought severity analysis by percent of normal index (PNI) in northwest Iran   总被引：1，自引：0，他引：1  

Jaefar Nikbakht  Hossein Tabari  P. Hosseinzadeh Talaee 《Theoretical and Applied Climatology》2013,112(3-4):565-573

The streamflow drought is the most important type of drought due to the high dependence of many activities on surface water resources. The streamflow drought severity was identified by the percent of normal index (PNI) in the western basins of the Lake Urmia located in northwest Iran. The streamflow records were obtained from 14 hydrometric stations for the period October 1975–September 2009. The temporal trends of the streamflow drought severity were detected by the parametric Student’s t test and the nonparametric Mann–Kendall and Sen’s tests. The worst streamflow droughts at almost all the stations occurred in 1999–2000 and 2000–2001. The streamflow drought severity based on the PNI increased during the last 34 years. The results also indicated that the temporal dependency of time series had a dominant role in detecting trend by the parametric Student’s t test.  相似文献   

Spatiotemporal trends of aridity index in arid and semi-arid regions of Iran   总被引：2，自引：2，他引：0  

B. Shifteh Some’e  Azadeh Ezani  Hossein Tabari 《Theoretical and Applied Climatology》2013,111(1-2):149-160

The spatiotemporal trends of aridity index in the arid and semi-arid regions of Iran in 1966–2005 were investigated using the Mann–Kendall test and Theil–Sen’s slope estimator. The results of the analysis showed negative trends in annual aridity index at 55 % of the stations, while just one site had a statistically significant (α?=?0.1) negative trend. Furthermore, the positive trends in the annual aridity index series were significant at the 95 % confidence level at Bushehr and Isfahan stations. The significant negative trend in the annual aridity index was obtained over Mashhad at the rate of ?0.004. In the seasonal series, the negative trends in the spring and winter aridity index were larger compared with those in the other seasonal series. A noticeable decrease in the winter aridity index series was observed mostly in the southeast of the study area. In the summer and autumn aridity index, two significant positive trends were found.  相似文献