جستجوی مقالات مرتبط با کلیدواژه "improvement" در نشریات گروه "آب و خاک"

In this research, the improvement of a clay soil contaminated with MTBE using GGBS activated by magnesium oxide and slaked lime was studied. Contaminated soil with MTBE was artificially prepared in the laboratory with a concentration of 2.25 g (MTBE)/kg (soil) and activated GGBS with slaked lime was added to it with different percentages. Experiments including Atterberg limit, compaction, uniaxial strength and SEM were conducted on samples of natural soil, contaminated and those which were mixed with the mentioned additives. The results showed that the used additives increase the strength of natural and contaminated soil and this improvement is a function of  percentage of the used materials and the curing time. In general, adding the used additives increases the strength by 14-22% by increasing the mixing percentage and curing time. In addition, the strength of natural soil with a same percentage of additives and the same processing time is about 3 to 7% higher than contaminated soil. Comparison of the effect of two additives clarified that lime has a greater effect in improving than activated GGBS. The SEM results also clarified that the hydration of the additives cause producing the cementitious materials which improves the mechanical behavior of the soil.

Soil contamination through petrochemical activities and leakage of organic hydrocarbon is not just an environmental problem and also can be considered as an important geotechnical issue. Adding amendment material is one of the most suitable and economical solutions to improve the geotechnical parameters of contaminated soil. In this study, the effect of Portland cement content (3, 6 and 9%) and lime content (10, 20 and 30%) on kaolinite clay contaminated with glycerol content (3, 6 and 9%) was investigated through an experimental program. For this purpose, the samples were prepared as mixtures of clean or glycerol-contaminated clay with different Portland cement and lime contents for 7 days curing time. Then, unconfined compressive strength (UCS) tests were conducted on the samples. The results showed a reduction of the strength of glycerol-contaminated kaolinite clay. The strength reduction increased with increase in degree of contamination. Based on the scanning electron microscopy (SEM) analysis, it was found that the presence of glycerol prevents the interaction between soil-cement particles. However, adding Portland cement and lime to uncontaminated and contaminated soil increased the strength. The rate of increase in UCS increased with Portland cement and lime content. Also, the results of soil improvement showed that the strength of soil-cement mixture containing 9% Portland cement is approximately equal to that of the soil mixed with 10% lime. In other contents, the degree of improvement was dependent to the applied cement content. The main reasons were polar behavior of glycerol and its dielectric constant. The results were also analyzed and proved using the images taken by SEM.

Leakage of hydrocarbon organic fluids into the soil usually causes a reduction in its bearing capacity and performance. Cementation is one of the most effective and suitable solutions to improve the geotechnical parameters of contaminated clays. In this study, the effect of Portland cement (3, 6 and 9%) and lime (10, 20 and 30%) on improvement of kaolinite clay contaminated with anthracene (0.06, 0.09 and 0.12%) was investigated by performing an experimental study. For this purpose, the samples were prepared as mixtures of clean or anthracene-contaminated clay with different cement and lime contents for a curing time of 7 days. Then, unconfined compressive strength (UCS) tests were conducted on the samples. The results showed the strength reduction of anthracene-contaminated kaolinite clay compared to the clean soil. The reduction in the unconfined strength was about 46% with an increase in degree of contamination up to 0.12%. Adding Portland cement and lime to the clean and contaminated soil increased the compressive strength. As, the addition of 3% Portland cement or 10% lime to clay contaminated with 0.12% anthracene increased UCS up to 4 times. Thus, according to the results of soil improvement, the strength of soil-cement mixture containing 3% Portland cement is approximately equal to that of soil-lime containing 10% lime. Both the Portland cement and lime were capable of improving the strength of anthracene-contaminated soil. However, the rate of improvement by cement was more than that of lime. The main reason was due to the reduction of double layer thickness which causes flocculation of particles and tendency of clay structure to behave like granular soils.

Precipitation is an important component of the hydrological cycle which links atmospheric and surficial process. Therefore, accurate modeling and estimation of parameter are needed for water resources management, irrigation scheduling, agricultural management and water allocation. SARIMA model is the most popular model for monthly precipitation simulation. The weakness of model is to ignore the inter-monthly variation within each year. Therefore, the aim of paper is the improvement of SARIMA model which takes into account the interannual, inter-monthly variation and comparison the performance of improved model with SARIMA model in Ardabil station. Ward's method for clustering of monthly precipitation time series and linear regression model for determination the relation between statistical characteristic of each cluster and monthly precipitation have been applied. 24.05%, 17.24% and 28.48% decreasing of RRMSE, RMSE and MAE from SARIMA to improved SARIMA model indicated the acceptable performance of improved model. The comparison of observed and simulated values showed the overestimation of improved model simulation. 51.16% RRMSE decreasing in seasonal precipitation simulation was expressive of accuracy increasing of improved model basis on the clustering analysis. The correlation coefficient between simulated of improved SARIMA model and observed precipitation data was increased and reached to the significant level. Therefore, the clustering analysis and improvement of SARIMA model, increased the accuracy of model.

Wind erosion is one of the main causes of soil and environmental degradation, the transfer of suspended particles and its sediment in irrigation and drainage networks. Due to the monsoon winds of the region, the erosion of the agricultural lands will attack the agricultural lands of the East and West Azarbaijan provinces and will have devastating effects on environmental resources and economic facilities. The high cost of using mulch and its destructive effects on the environment has led to the use of new and more environmentally-friendly materials. In this research, the effect of SBR resin polymeric material and Bacillus pasteurii microorganism on the control of wind erosion and dust storms in Jabal Kandi region have been evaluated. To simulate soil erosion, a wind tunnel with a velosity range of 0 to 15 m/s at a height of 15 cm from the bottom of the tunnel has been used. According to the results, in samples, with increasing wind speed, the amount of soil erosion increases exponentially, so that in the control sample, up to 7 m/s, the amount of soil erosion is negligible, but the velocity rate of soil erosion from 5.51 to 240 Kg/m2/hr has increased from about 7 m/s to about 15 m/s. Also, the trend of increasing the amount of soil erosion in a sample stabilized by microorganisms is very slow and at a speed of 15 m/s, it is equal to 1.1 kg/m2/hr and in the polymer- stabilized sample is almost zero. To test the surface resistance of stabilizaed soil samples, an penetration resistance test was used which according to the results, the mean value of the penetration resistance in the samples treated with microorganism and polymer was 58 and 76 kPa, respectively, while the penetration resistance of the control sample is 15 kPa.

Reservoirs as traditional structures in water resources management system in MAZANDARAN province play a major role in supplying irrigation water for paddy fields. Dredging and improvement of such structures can result in getting more benefits from the surface runoff. In current research¡ using satellite images and ArcGIS software¡ land use over the case study area of GATAB¡ BABOL¡ Iran¡ was determined. Then the potential of the surface runoff in the area was estimated by SCS method. Also¡ irrigation costs for paddies¡ irrigated by groundwater well (four groundwater wells) and reservoir water (four Reservoirs)¡ were estimated. The effect of dredging and improvement of reservoirs on the reduction of groundwater withdrawal and irrigation costs were evaluated. The potential of runoff in the area was estimated to be 31 MCM (million cubic meters). Dredging of all Reservoirs by 1 to 2 meters would result in the exploitation of 1.68 to 3.37 MCM from the surface runoff. A fall in irrigation cost¡ estimated to be 991 to 1982 million Rials per Hectare¡ is a consequent of more proper utilization of surface runoff. According to the results¡ the increase in the storage capacity of reservoirs will result in saving part of groundwater storage in the case study area.