جستجوی مقالات مرتبط با کلیدواژه « bulk density » در نشریات گروه « توقف انتشار »

In the current study، the effects of both hysteresis and soil compaction on the calibration curve of a gypsum block were investigated. For this، block calibration curve for a heavy soil (silty clay) with three bulk densities (normal as in the field and plus or minus 10%) during two cycles of wetting and drying conditions were obtained. The results showed that block calibration curves varied between wetting and drying cycles under different soil compactions. By reducing soil compaction، hysteresis and its effect on the shape of block calibration curve was increased، probably because of a reduction in soil fine pores and more non-uniformity of pore distribution. The effect of soil compaction on block calibration curve was different with drying and wetting conditions، where at specific soil moisture، the block electric resistance increased with drying cycle but reduced with wetting cycle when soil compaction increased. During drying and wetting events، increasing soil compaction resulted in 16% increase and 3% decrease in soil field capacity، respectively. Thus، it is recommended that the soil compaction level of the specified location for block installation should be equal to that of the surrounding soil when using gypsum block.

Agricultural soils are continuously under wetting and drying cycles during flood irrigation. Large air-dry disturbed soil specimens with dry bulk density (BD) of 1. 2 g cm-3 were prepared and the effect of wetting and drying cycles on compactibility of fine and coarse textured soils was studied. The large soil specimens with/without wetting and drying cycles were compressed under three preloads (0، 100 or 200 kPa) and then the small soil samples for water content and bulk density measurements were removed. The results showed that the wetting and drying process resulted in increase in an BD for both soils without applying any compacting load. This process resulted in soil susceptibility to compaction for coarse textured soils، whereas it increased the resistance to soil compaction for fine textured soils. Therefore، in fields with coarse-textured soils and under flood irrigation، are more sensitive to soil compaction at harvest traffic at both soil conditions as compared with the fine-textured soils. Therefore، with reducing contact pressure and axal loads the soil compaction could be prevented.