JWSS - Journal of Water and Soil Science

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Sedimentation and consolidation of cohesive sediments near the dam body can cause many problems such as clogging the bottom outlets and entering the sediments into the hydropower intakes. Flushing of these sediments through the bottom outlet will be successful only if the hydraulic conditions are designed according to the physical and mechanical properties of consolidated sediments. During the past decades many researches have been conducted on the distribution of non cohesive sediments in the reservoir, yet little information is available for cohesive sediments. Therefore the main purpose of this study is to conduct a physical model study to investigate the process of sedimentation and consolidation of cohesive sediments in the dam reservoir. The experimental tests were conducted in a settling column test with a height of 3.8 m and diameter of 0.3m. The sediment samples were collected from the Dez dam reservoir since it is predicted that in less than 5 years the sediment will reach to such an elevation that can enter into the hydropower intakes. The obtained results show that there is a an algorithmic relationship between the time and changing of the sediment concentration during the sedimentation and self-weight consolidation processes. This process can be divided into four separate phases. It is also of note that in this paper the effective stress-void ratio and coefficient of permeability – void ratio relationship were obtained as a power relationship, which are in agreement with the results obtained by other investigators. These relationships can be used as primary data in the mathematical model of sedimentation and consolidation.

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The purpose of this study was to assess characteristics of and reasons for farmers’ disagreement on implementation of land consolidation projects. Part of needed information was collected through questionnaire and interviewing 75 farmers in 6 unsuccessful villages in Kermanshah and Lenjanat region and also visiting some performed and ongoing projects. Other part of information was obtained by questionnaire and interviewing 44 experts involved with performing the project in Jahad Agricultural offices. Fragmentation of properties were measured by Januszewski fragmentation coefficient. Correlation coefficient and comparison of mean were used to analyzed the information. The results showed that disagreement of farmers is the most important obstacle for progress on land consolidatin projects, which accounted for farmers. In Lanjanat, these farmers have a better land structures in respect to size and fragmentation of parcels. In both rejoin reasons for farmer’s disagreement are divided in three groups: logical-justified reasons, logical-unjustified and illogical. Mediation, preference and legislative force are the three interactive methods to satisfy these farmers. To decrease disagreements and promote land consolidation in the two regions, following suggestions are offered: education and extension, correcting the technical and adminestrative methods of land consolidation and legal and judicial supports to implement the projects.

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  The purpose of this research was to study factors on farmer’s request to land consolidation projects and also consolidation’ adventages in utilization units. The data of this study was collected through completing questionnaires and interviewing 34 experts connected with administrating of land consolidation projects in agricultural offices and service centers in Kermanshah township and Lenjanat region in Isfahan. Data was also collected through visiting some performed and performing projects. The results showed that in Kermanshah land consolidation improves the technology, farm management and land more than other production factors. In Lenjanat it improves technology and farm management in comparison with other factors. In both regions the aplicant villages of the projects have a larger ownership and more fragmentaed parcels than other villages. Moreover they have younger exploiters, more educated and less in number. It is also notworthy that these regions obtain more extention education, are nearer to agricultural offices, and have closer relation with extention agents.

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Land and its size are important as the most basic factors of production in agriculture .Fragmentation is one of the main problems that rice producers of Mazandaran province are confronted with. Non-efficiency in farm management, inability in effective using of agriculture technology and machinery, and low range productivity of production are all related to land fragmentation. In order to overcome the problems and consequences originating from land fragmentation, specialists recommend the logical solution of land consolidation process, which is a basic strategy for changing the farm size. The purpose of this research was to identify and determine effective factors in land consolidation adoption by rice producers in Mazandaran province by using Logit Regression model. In this study, 150 rice producers from 5 villages have been investigated since 2007. Results show that variables of education, land quality, fragment distance and extension effort (learning programs) are the most important factors in land consolidation adoption by rice producers in this province (Sig=1%) . Also, number of the household and credit support are the next factors affecting in land consolidation adoption (Sig= 5%). I t must be noted that other variable such as age, farmer’s income, children education, experience of rice producers, cultivation area, membership in cooperatives, land situation, number of pieces and technical supports were not significantly involved.

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Expansive soils swell and shrink periodically when subjected to seasonal water content changes. As a result, they are a constant source of problem in the design and construction of foundations. In this study, the behaviour of an expansive soil was studied through a number of experiments involving cycles of wetting and drying using three different water qualities. Laboratory tests were performed on statically-compacted samples of an expansive soil in a modified Oedometer under constant surcharge pressure of 10 kPa. Vertical deformation of the soil sample was recorded continuously, and during the test, void ratio and water content of the sample were determined at different stages. The results indicated that the equilibrium condition was reached after about six wetting-drying cycles. It is shown that the swelling potential changes with changes in water quality the saline water reduced the swelling potential of the soil compared to the distilled water during wetting and drying cycles. Furthermore, the results showed that the variations of water content-void ratio paths during wetting-drying were the same (no hysteresis) when the equilibrium condition was achieved

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Excess pore water pressure in clay core dams during construction and primary filling reservoir (first impounding) causes initiation and progression of hydraulic fracture. In this research, the instrumentation data during construction and first filling reservoir (first impounding) was analyzed. It measured internal deformations, pore water pressures and total vertical stresses and compared with the analysis results in Masjed-e-Soleiman dam. To do this analysis, GEOSTUDIO 2004 V. 6.02 software was used. The staged construction of the dam was the model in the form of 2D coupled consolidation. The Non-linear elastic model for the core material and Linear Elastic model for other zones were incorporated into the models. For exact assessment and to obtain correct parameters of the constitutive model, the triaxial tests were performed on the core material of Masjed-e-Soleiman Dam and acceptable results were obtained.

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Transporting borrow materials for proper infrastructure of water channels to bear the load of such structures is important in the development plans. Therefore, in this research clay nanocomposite material with a weight ratio of %1 was added to the soil. Soil sample was taken from the bed of the C25 canal (distributary of GanjAfrooz diversion dam within Alborz project area) at various intervals and the depth of 1 meter. Unconfined compression strength and consolidation tests were performed on the selected soil. The results showed that the addition of nanoclay to the soil increased the rate of shear resistance, cohesion property and compressibility of soil, respectively, equal to 14.13, 14.13and 82.76 percent. Also, angle of failure and ultimate void ratio decreased. As a result, the addition of nanoclay to the soil makes soil strength and stability greater and there are no problems caused by bed erosion and transporting of borrow material for infrastructure of channel.

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Today, modern irrigation systems are constructed at a very high cost to operate for optimal use of water and soil. Lack of appropriate technical, social and economic studies, caused high maintenance costs of these facilities during operation. Water resources have been polluted due to industrial development, increasing human population and non-compliance with environmental standards. Most of hydraulic structures are built in areas with poor water quality. Furthermore, engineering properties of fine-grained soils, especially the clay soils, depend on factors such as salinity of solute in the pore water. So that any change in salinity of solute leads to change in the physical and mechanical properties of soils, and consequently make damage to hydraulic structure. This study investigated the effect of water salinity on engineering properties of fine-grained soils. For this purpose, NaCl, with 5 different levels (0, 0.1, 0.2, 0.41 and 0.72 mol/L) was added to the soil and the mechanical properties of soil including compaction, shear parameters, Atterberg limits and consolidation parameters were investigated. The results showed that the addition of NaCl had made no significant changes to the maximum dry unit weight and optimum moisture content of the soil, but it reduced cohesion of soil and increased the internal friction angle .Also, Limit Liquid (LL) are decreased, but it had little effect on the Plastic Limit(PL) of soil.