AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2016 | Volume:47 | Issue:3|Papers Count:9

Various methods provided for reducing the seepage of water from the dam foundation and abutments that the most common techniques is Curtain Grouting. Quality and efficiency of Grouting operation depend on various factors such as absorption, grout properties and grouting Pressure. One of the most effective parameter is the grouting pressure, because of overpressure, causing hydraulic fracturing inrock mass and low Grouting pressure, causing partial stay of the operation and the site is not completely sealed. So far, different comments, equations, tables and charts have been provided to calculate the necessary pressure in grouting operation. In this paper, has been investigate the effect of grouting pressure in difference stag of Seymareh dam. For this purpose, the grouting pressure is Calculated based on the analytical equations and compared with the actual pressures and finaly the best Model is selected. The results show that Groundy and Zaruba equations (with horizontal joints) prepare more accurate estimates of the grouting pressure than others. Also, new Equation is developed to calculate of grouting pressure as a function of Lug eon number that is able to calculate the acceptable grout pressure.

This research was carried out in laboratory scale using dried leaves powder of Thuja and Populus assorbents to remove lead, copper and cadmium ions from aqueous solution. The effect of temperature on metal ions removal by sorbents was evaluated, the equilibrium data was fitted by Langmuir, Freundlich and Dubinin-radushkevich isotherms and thermodynamic constants were determined. For this purpose, solutions with different concentration of ionic metals were prepared. Sorbent amount equal to 10 gr/lit, pH=5 and detention time 60 minutes for all sorbents were adjusted. Studied temperatures were 20, 25, 35, 45 ºC. The results have shown that increasing the initial concentration, increases the adsorption capacity. The Langmuir model was found to best describe the data, although some adsorption processes were described with more than one model. This research indicated that the adsorption of metal ions byPopulus was endothermic and adsorption of them by Thuja was exothermic processes. Determination of the thermodynamic parameters, Gibbs free energy (DGº) and the mean adsorption free energy (Ea) showed that the adsorption of metal ions by two plants was physical.

Effects of DC stray current on concrete structures were studied concentrating on effect of concrete, instead of effects on corrosion of steel bars. Concrete samples prepared with different water/cement (w/c) ratio and silica fume content were submerged in distilled water for 30 days while subjected tothe application of a voltage of 50 VDC. The effects DC stray current on the properties of concrete were determined by resistivity, Electrochemical Impedance Spectroscopy, chloride diffusion depth and Rapid Chloride Penetration tests. The results showed DC stray current increased permeability of the concrete. The critical role of w/c ratio and silica fume additive on the degradation effects created by DC stray current was investigated. A mechanism based on the migration of calcium and hydroxyl ions out of thepore solution and the dissolution of Ca (OH) 2 precipitates from the hydrated phase was proposed for the explanation of DC potential on the degradation of concrete.

The use of heavy metals especially arsenic, lead, cadmium and mercury has led to extensive contamination of soils worldwide. Arsenic, however, is mostly noted because of its carcinogenic and mutagenic characteristics occurred due to the agricultural and industrial activities and the invasion of domestic and industrial wastewater into the soil environment. In this research, the removal efficiency of arsenic by useof soil washing process was assessed and diverse cleaning agents and also temperatures were applied. Water, Ethylene Diaminetetraacetic Acid (EDTA), Sodium Dodecyl Sulphate (SDS) and a mixture of EDTA and SDS were chosen as the agents to treat the contaminated samples. Regarding the analysis results, it could be observed that efficacy of water, EDTA, SDS, and the mixture solution of SDS and EDTA at 20˚C is 20.82, 45.21, 37.93, and 79.48%, respectively. These results were determined as 24.75, 52.34, 40.83, and 79.48% for treated samples at 50˚C, correspondingly. Consequently, the efficiency of soil washing solutions in the removal of arsenic (at 20˚C and 50˚C) is specified as: “Mixture of EDTAand SDS”>“EDTA”>“SDS”>“Water”. Additionally, the investigation of the results showed that by increasing the temperature, the effectiveness of soil washing process would be enhanced.

Due to special properties of clay, it has widely been used in geotechnical and geoenvironmentalprojects such as barriers in which very low seepage is required. With advances in nanotechnology, we are witnessing of nanomaterials application to modify material properties in different branchesof engineering such as geotechnical engineering. In this study, the hydraulic properties of Kaolinite extracted from Zenuz mine have been investigated experimentally by using nano clay as an additive. A series of tests, comprising Atterberg limits, standard compaction, one dimensional consolidation and cation exchange capacity test, were conducted on Kaolinite and modified Kaolinite with 1%, 2%, 4%, and 8% nanoclay. According to experimental results, adding 8% nano clay to Kaolinite increased plasticity index to 184%, and decreased the hydraulic conductivity 300 times when compared with raw Kaolinite. In addition, results of cation exchange capacity test showed that nano clay caused an in creasein cation exchange capacity from 12 to 21 meq/100 gr. This increase was related to a considerable increase in the amount of Na+.

Artificial Neural Network was used for predicting optimized conditions of column leaching on copper oxide ore. Optimization, control and analysis of heap leaching implicate an accurate, proper and comprehensive modeling. Providing such models need to identify all the effective parameters and their impact simultaneously on the output of the process. Important parameters such as height of column, particles size, acid flow rate and leaching time were studied and it was investigated their impacts on recovery of copper. Experiments were performed in three columns with the heights of 2, 4 and 6 meters and in the particle size distributions of 25.4 and 50.8 mm. The results showed that the copper recovery has an inverse relation with the column height and particle sizes. This relation is direct with leaching time and acid flow rate. The copper recovery obtained in the columns with heights of 2, 4 and 6 m were78.63%, 66.27%, and 52.89% respectively. According to the results, the Trained ANN modeling predicts the copper recovery based on operation conditions.

Two effective parameters in determining the length of reinforcements in the reinforced soil slopes are, the one, the length of reinforcement located in the active zone till to the location of failure surface and the second, the length of reinforcement located after the failure surface. Generally, the first one is calculated based on the angle of failure wedge by Rankin method. In this method the effect of reinforcement on the location of failure surface is ignored, while the presence of reinforcement is effective. In order to assess the location of the failure suface, the horizontal slice method based on Spencer assumption is used. In this method, slippery mass with the presence of reinforces is divided into a number of horizontal slices parallel to reinforcement direction. Inter-slice forces are computed by using Spencer basic rules. Earthquake load is affected on the center of each slice by horizontal and vertical pseudo-static coefficients. In the presented method, unlike the other existing methods, all of the critical slip surfaces are examined and are reinforced. In this paper, Genetic Algorithm (GA) optimization method is used to optimize the objective function for the produced non-circular slip surface of each horizontal for the safety factor of one. By comparing the results of Genetic Algorithm optimization approach introduced in this research with the results of the other investigators for the same geometry, material properties and loadings of the slopes it is indicated that the introduced and utilized method is more critical for the estimation of the length of reinforcements and the design of reinforcements with the proposed method is more reliable.

Two effective parameters in determining the length of reinforcements in the reinforced soil slopes are, the one, the length of reinforcement located in the active zone till to the location of failure surface and the second, the length of reinforcement located after the failure surface. Generally, the first one is calculated based on the angle of failure wedge by Rankin method. In this method the effect of reinforcement on the location of failure surface is ignored, while the presence of reinforcement is eff ective. In order to assess the location of the failure suface, the horizontal slice method based on Spencer assumption is used. Inthis method, slippery mass with the presence of reinforces is divided into a number of horizontal slices parallel to reinforcement direction. Inter-slice forces are computed by using Spencer basic rules. Earthquake load is affected on the center of each slice by horizontal and vertical pseudo-static coefficients. In the presented method, unlike the other existing methods, all of the critical slip surfaces are examined and are reinforced. In this paper, Genetic Algorithm (GA) optimization method is used to optimize the objective function for the produced non-circular slip surface of each horizontal for the safety factor of one. By comparing the results of Genetic Algorithm optimization approach introduced in this research with the results of the other investigators for the same geometry, material properties and loadings of the slopes it is indicated that the introduced and utilized method is more critical for the estimation of the length of reinforcements and the design of reinforcements with the proposed method is more reliable.