جستجوی مقالات مرتبط با کلیدواژه « چسبندگی » در نشریات گروه « آب و خاک »

Due to the vulnerable nature of earthen dams , all factors affecting the stability of these dams should be studied. Consecutive wetting and drying of the earthen dam core is one of the important factors that can affect the physical and mechanical parameters of the dam core. These changes increase the subsequent risks such as leakage, piping and subsidence. This is especially happen in arid and semi-arid regions such as Iran. Various researches have been done in this field and some of these researches have provided suitable mathematical models for their data, but because the results of each research related to the studied soil are specific to the same study, these models can be unusable for other data. In the present study, after collecting 866 laboratory data from 23 researches, the effect of wetting and successive drying of clay dam cores on physical-mechanical parameters was investigated and multivariate mathematical relationships between physical-mechanical parameters and number of wetting and drying were investigated. This study showed that the effect of wetting and drying on mechanical parameters is very important and should be considered in the analysis of embankment dam structures.

One of the most significant environmental consequences of municipal solid waste is the generation of leachate at landfills. Leachate is a very hazardous liquid leading many difficulties including contamination of surface, groundwater, and soil. The mechanical parameters of the soil can be affected in contact with leachate and its changes depend upon the type of leachate and soil. The reactions between the soil system and the leachate cause changes in landfill soil mechanical properties that may affect the structural stability of the landfill structures. So that, the present study investigate the effects of natural leachate of Aq Qala landfill on silty-clay soil. For this purpose, the natural leachate samples and the untoched soil samples with leachate were collected from the Aq Qala landfill. Unconsolidated no drained (UU) triaxial test was performed on soil specimens containing 0, 5 and 15% leachate at three curing times; 7, 14, 28 days. In order to analyze the obtained results, the stress-strain curve was investigated in terms of leachate amount, curing period and cell pressure as the variables applied to the samples. The results indicate that the contamination of soil by leachate reduces the maximum deviator stress and the friction angle, while it increases the soil adhesion. In addition, the influence of leachate increases by leachate concentration in the soil and curing period.

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.

Soil surface shear strength is an important parameter for prediction of soil erosion, but its direct measurement is difficult, time-consuming and costly in the watershed scale. This study was done to predict soil surface shear strength using artificial neural networks (ANNs) and multiple linear regression (MLR) and to rank the most important soil and environmental attributes affecting the shear strength. A direct shear box was designed and constructed to measure in situ soil surface shear strength. The device can determine two soil shear strength parameters i.e. cohesion (c) and angle of internal friction (φ). The study area (3500 km2) was located in Semirom region, Isfahan province. Soil surface shear strength was determined using the shear box at 100 locations. Soil samples were also collected from 0-5 cm layer of the same 100 locations at which the surface shear strength was measured using the shear box. Particle size distribution, fine clay content, organic matter content (OM), carbonate content, bulk density and gravel content were determined on the collected soil samples. Normalized difference vegetation index (NDVI), the type of land use and geology were also determined. The MLR and ANNs were used to model/predict soil surface shear strength (c and φ). In order to compare the modeling methods, coefficient of determination and root mean square errors were used as efficacy indices. The results showed that ANN models were more feasible in predicting soil shear strength parameters than MLR models due to capability of ANN models in deriving nonlinear and complex relations between the parameters. Results of sensitivity analysis for ANN models indicated that NDVI, bulk density and fine clay content are more effective parameters in predicting c in the studied region. Also it was found that sand content, bulk density and NDVI were more effective parameters and OM/clay ratio and organic matter content were less effective parameters in predicting φ in the region.

Stickiness and pastiness after cooking is one of the basic problems of macaroni production technology. Investigation of the factors affecting stickiness and pastiness of Iranian Macaroni is essential. The purpose of this research was to study the effects of percentage of gluten in the flour as well as extruder and drying temperatures on the macaroni quality. The factors studied are as follows:1- Percentages of flour gluten at levels of 8.5, 10.5, 12.5 and 14.5 prepared by adding gluten to the macaroni flour purchased from the market.
2- Temperature of the dough discharged from the extruder (three levels: 48, 58 and 68 °C) obtained through changing the temperature of the water used in making the dough, circulation and noncirculation water in extruder jacket, and changing the rotational speed of extruder screw and increasing dough retention time.
3- Drying temperature (two levels: 50 and 62 °C) obtained through changing the number of burners in the heating system and using electrical heaters in the drying cabinet.
 The results of the e:xperiments and their evaluation are as follows: using flour with a gluten percentage of 12.5 or 14.5 (12.5% gluten is preferred for economic reasons) with an extruder temperature of 48 °C and a drying temperature of 62 °C will improve the macaroni quality. This treatment resulted in the production of macaroni with less stickiness, pastiness and cooking loss.