Clay is the main construction material for clay cores of earth-fill dams. Clay minerals swell when they become wet and shrink when they dry out; cracks develop as they lose moisture. If precautions are not taken to prevent seepage through these cracks, dam failures may result. In this study, sand was added to montmorillonite-dominant clay soils to investigate the effect of sand-inclusion rates on the engineering characteristics of clay soils used in the construction of clay cores of earth-fill dams. Changes in the consistency limits, compaction characteristics, permeability, stress-strain relationships and swelling characteristics with increasing sand inclusion rates were evaluated. Based on the results from experimental trials, a 30% sand inclusion rate appears to be the optimum proportion; most of the swelling occurred in the voids of grains and led to permeability levels below the allowable limits for earth-fill dams.
Efforts to increase the amount of irrigation schemes transferred to irrigation associations (IAs) in Turkey have been motivated by the poor performance -in terms of cost recovery, equity, efficiency in operation and maintenance (O&M) and repairs -of many large irrigation schemes by government agencies, namely the State Hydraulic Works (DSI). The objective of this study is to assess the irrigation system performance of transferred irrigation schemes in the DSI Fifth Regional Directorate service area mainly for the year 2003 with benchmarking indicators.According to the findings of the study, relative water supply was recorded as 1.5-8.4 respectively. The financial performance indicators including cost recovery ratio, maintenance expenditure to revenue ratio, operating cost per unit area, total cost per person employed on water delivery, revenue collection performance and service area per personnel were found to be 1.0-10.6%, 0.7-12.5%, US$6.5-53.3 ha À1 , US$636.0-7045.9 per person, 78-95%, 67-13 000 ha per person, respectively. As regards productive performance, output per unit command area, output per unit irrigated area, output per unit irrigation supply and output per unit water consumed were determined as US$325.2-2745.1, US$1028.03-5070.9 ha À1 , US$0.2-0.7 m À3 and US$0.2-2.6 m À3 respectively. Water quality classes were found to be C 3 S 1 in all schemes. The results of the case study show that following the transfer of irrigation schemes to the user organizations, significant improvements are recorded in irrigation water fee collection rates and financial cost reduction in the systems operated by the IAs. Mixed results are observed in terms of irrigation ratios. While there are improvements in two irrigation schemes, there are evident increases in the water supply ratio in six other irrigation schemes. Management, operation and maintenance (MOM) costs in general and the maintenance costs per se have increased compared to the collected water fees in the case-study irrigation schemes. Copyright # 2008 John Wiley & Sons, Ltd.key words: Turkey; irrigation associations; water delivery performance; financial performance; productive performance de maintenance sur recettes 0.7-12.5%, les coûts d'exploitation par unité de surface 6.5-53.3 US$ ha À1 , le coût total par personne employée pour la distribution de l'eau 636.0-7045.9 US$/personne, le recouvrement des recettes de fonctionnements 78-95%, la surface de service par personne 67-13 000 ha/personne. En ce qui concerne la performance de production, ont été déterminés: la production par ha dominé 325.2-2745.1 US$ ha À1 , la production par ha irrigué 1028.0-5070.9 US$ ha À1 , la production par m 3 livré 0.2-0.7 US$ m À3 et la production par m 3 consommé 0.2-2.6 US$ m À3 . La classe de qualité de l'eau a été trouvé en C3S1 dans tous les périmètres. Les résultats de l'étude de cas montrent qu'à la suite du transfert aux associations d'irrigants, des améliorations significatives sont enregistrées dans les taux de recouvrement des redevances d'irrigation et d...
The present study was conducted to investigate the effects of different soil compaction levels (non-compacted control, low compaction, high compaction), irrigation management practices (conventional furrow and alternate furrow) and nitrogenous fertilizer levels (60, 90, 120 kg ha<sup>–1</sup>) on vegetative characteristics (dry biomass production, plant height, number of branch and number of pod per plant, height of the first pod, leaf area index, stem diameter), physiological characteristics (leaf relative water content, leaf chlorophyll content and leaf temperature) and root development through 0 -80 cm soil profile of soybean grown in Harran Plain of Turkey. Experiments were conducted in Sanliurfa Province of Turkey in split-split plots experimental design with 3 replications during the years of 2006 and 2007. Irrigation program was created by using KanSched simulation model. The amount of applied irrigation water in conventional and alternate furrow systems in 2006 and 2007 were measured as 435.61 and 291.59 mm, and 429.51 and 271.72 mm, respectively. While the highest yield (947.8 kg ha<sup>–1</sup>) was observed in control treatment of the year 2006, conventional furrow system had the highest yield (2099.3 kg ha<sup>–1</sup>) in the year 2007. Soil compaction, irrigation and nitrogenous fertilization in general had significant effects on entire vegetative characteristics investigated in the present study. Increasing compaction levels yielded decreasing plant height, stem diameter and leaf area indexes. Biomass production increased with increasing nitrogen doses. Results indicated that negative impacts of soil compaction in agricultural fields due to traffic and various other reasons could be eliminated with proper irrigation and fertilization implementations.
Bentonite mixed with varying quantities of sand is currently of widespread interest as engineering liners for water containment and waste disposal. However, the alternative use of pumice, widespread in many volcanic regions, has been less studied and requires further characterization of geotechnical properties and performance prior to its extensive use. The objective of this study was to determine and compare the compaction and swelling characteristics of sandbentonite and pumice-bentonite mixtures using available geo-materials from Turkey. Standard Proctor compaction tests and constant volume swell tests were carried out using mixtures with four different bentonite contents (15, 20, 25, 30%) and three different sand and pumice grain size ranges (2.00–1.00; 1.00–0.50; 0.50–0.25 mm). The results indicate that pumice-bentonite mixtures have lower maximum dry unit weights, higher optimum moisture contents and greater swelling potentials than equivalent sand-bentonite mixtures. Important differences occur in the swelling potentials of the sand and pumice mixtures with respect to grain size whereby sand-bentonite mixtures show increased swelling with coarsening grain size, in contrast to the pumice–bentonite mixtures which showed a decrease. These differences are attributed to the amount of grain-size-dependent connected pore space that can be filled during bentonite expansion and the presence of dissolvable salts in the pumice. It is concluded that locally available pumice material could be used to replace sand in engineering bentonite seals, despite some differences in their geotechnical properties.
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