جستجوی مقالات مرتبط با کلیدواژه « Soil compaction » در نشریات گروه « منابع طبیعی »

Agricultural soils improvement and amendment has an inevitable importance. The implementation of new tillage methods and using some additives such as superabsorbent, in order to optimally use of water in rainfed farms to increase the yield of crops, has particular importance in this relation. Superabsorbent polymers are organic compounds that are able to absorb water several times of their own volume or weight without changing their physical structure. The purpose of this research is to investigate pre-compaction stress as a measure of resistance of soil compaction in the presence of superabsorbent polymers. In this research, the pre-compaction stress was determined using the confined compression test (CCT). The factorial experiment was carried out in the form of a completely random design with three replications on the samples with humidity of 15% and 10% and density of 1.4, 1.5 and 1.6 at five levels of 0, 1, 2, 3 and 4 grams of polymer per kilogram of soil. The results of the tests showed that with the increase in the amount of superabsorbent, pre-compaction stress and compaction index increased. The maximum effective amount of superabsorbent is three percent by weight, which creates moisture suitable for agricultural products. In both humidity of 10 and 15%, the highest pre-compaction stress was equal to 2.8.

The mechanical parameters of soil have been used in several different perspectives to describe the mechanical behaviors of the soil-dynamic loads interaction, and Becker's equation is one of the most common methods. In this study, the effect of the speed of soil deformation and the load on wheel on the three parameters of the soil deformation equation as well as the deformation energy for soil deformation have been investigated. The tests were performed in the soil bin environment using a single-wheel tester and a Bevameter. Forward speeds of 0.5, 1, and 1.5 km/h as well as three vertical load levels of 2, 2.5, and 3 kN on the wheel for two different sizes of rectangular pressure plates, were selected. Each test was repeated three times. A same exponential behavior was observed for pressure-sinkage changes in all combinations of load and speed, which progress almost parallel to each other. Based on the research observations, among the three parameters n, Kc and Kφ, both the forward velocity and the load on the wheel have a significant effect at 1% level on the two parameters kc and Kφ. While, the changes of the n parameter are independent of different levels of load and forward velocity. On the other hand, the load-velocity interaction effect was not significant. With the increase of vertical load, resulted in soil compaction, an increasing trend was observed for the energy of penetration of plates into the soil. The speed of penetration of plates showed a direct relationship with the amount of deformation energy. Velocity at 5% level has a significant impact on the soil deformation energy.

Soil compaction increase is one of the main threats to agricultural soil structure, which may even lead to soil decomposition. In order to prevent the phenomenon of soil compaction, knowing the mechanical properties of soil is important in the determination of the allowable stress limits. Pre-compaction stress, as the maximum stress that soil can withstand without increasing its compaction, is one of the most important mechanical properties of soil. The plate sinkage test is a suitable method for determining the soil pre-compaction stress. In this research, the experimental test of plate deposition on a sample of arable soil (loamy sandy loam) at the moisture content of 15% d.b. with density of 1500 kg.m3 was performed and the soil mechanical properties were determined. Then, the plate sitting test was performed in twodimensional and symmetrical methods by finite element method and Drucker Prager model in Abaqus software and precompression stress was predicted by this method. Stress distribution and displacement in the soil depth layers were also analyzed. The results showed that the Drucker-Prager model with a 99% explanation coefficient was in good agreement with the data obtained from the experiments. Examination of compressive stress and displacement in different layers in the soil depth showed that the amount of stress and displacement in the layers close to the load surface was higher than that for the lower layers.

Animal logging with proper designation and management was being used from many years ago as harvesting system with low undesirable effects. Therefore, we studied the effect of animal logging on forest soil, in district 9 of Shafaroud. Two type of soil samples were used to estimated soil compaction caused by animal logging: depth 0-10 cm and 10-20 cm from soil surface. These samples were collected by standard steel cylinders along tree 100 m distance by 50, 80 and 120 m3 out put volumes. Result showed that compaction has no significant difference with those three distance with different output volume .therefore, we can found that , soil compaction caused by animal logging occur in primary trips, and compaction was slightly increased by increment of output volume (in consequence, increscent, of animal trips) depth 0-10 cm was mast effected by compaction.