جستجوی مقالات مرتبط با کلیدواژه « Atterberg limits » در نشریات گروه « جنگلداری »

Fine-grained soils often have problems such as low load ability and shear resistance, difficulty in compaction and settlement. Therefore, the stabilization of fine-grained soils with additives has always been the focus of road construction engineers. On the other hand, today, the use of waste materials in soil stabilization has become common due to its economic nature. In this study, stone powder, which is the waste of stone-cutting workshops, was used to stabilize fine-grained soils.

Clay samples with low pastiness (CL) were mixed with different amounts of 0, 3, 5, 10, 15, and 20 percent of stone-cut soil compared to dry soil. 7, 28 and 90 days were taken into account for the processing time of soil and stone. In the next step, geotechnical characteristics including grain size, Atterberg limits and compressive strength or CBR were investigated. The characteristics of granulation were investigated using the sieve method, Atterberg limits using the Cassagrande and paste wick method, and compressive strength using the California loading test.

The results showed that with the addition of stone powder, the contribution of coarse soil fraction increased. So that by adding 20% of stone powder and after 28 days, more than 60% of the weight of each sample belonged to particles with a diameter greater than 0.1 mm. There was no significant difference between the processing times of 28 days and 90 days in terms of mental limit, mental index and loading capacity. However, the values of the mentioned variables were significantly different from the figures recorded in the processing time of 7 days. Adding rock powder to the soil samples decreased the flow limit and the paste index. By adding 20% of stone powder, the soil samples were transformed from pasty state (pasty index = 25) to medium pasty state (pasty index = 8). In addition, the highest amount of CBR or soil loading capacity (19%) was obtained by adding 20% of rock powder.

After 28 days, the soil samples showed the results of all the positive or negative interactions caused by the addition of stone powder, and the passage of more time has no tangible effect on the mechanical properties of the soil. Besides, in the present research, the desired changes in the mechanical properties of the soil were obtained by adding 20% of stone powder.

In order to strengthen and stabilize the soil masses in the range of soil till optimum, it should be used appropriate stabilization methods. The purpose of this study was to evaluate the effect of excess ash as an additive to soil and improve soil properties. To do this, 15 soil samples from the forest road fill slope were randomly selected combined with 3, 6, 9 and 12 weight percent logging residual ash. In order to investigate the effect of addition of stabilizing agents on the chemical and mechanical parameters of soil in the studied area, the experiments Atterberg limits, California bearing ratio, moisture as well as acidity, electrical conductivity, phosphorus, nitrogen, organic matter and carbon were carried out on control and treated soil samples. Data were analyzed using one-way ANOVA and Tukey tests were used to compare the averages. The results of the experiment show that the addition of logging residual ash increased plastic limit and California bearing ratio and reduced liquid limit and plasticity index. Also, the results of one-way ANOVA showed that the mean difference in moisture, acidity and nitrogen were not significant (P>5%) while electrical conductivity, phosphorus, potassium, organic matter and carbon showed significant differences.

In this study, Nano-polymer CBR PLUS is sued for soil stabilization in forest roads. Tests were carried out to identify the texture, Atterberg limits, compaction and CBR on the control and treated soil samples with different percentage of 0.25%, 0.50%, 0.75% and 1%. In order to study the mechanical characteristics of upper layer, five plots including one control plot (untreated) and four sample plots were carried out on forest road. The results showed that the Nano-polymer reduced liquid and plastic limits. By increasing the percentage of CBR PLUS, the soil fine particles decreased in control and treated samples, in which that 1% treatment has the minimum content in weight percent of soil fine particles and maximum content in coarse particles compare to other treatments. Also soil treated with CBR PLUS, reduces the optimum moisture content and increases maximum dry density and California Bearing Capacity (CBR). Investigation of chemical properties showed that the amount of Calcium, Magnesium and Potassium increased in runoff. It was concluded that 1% of Nano-polymer CBR PLUS acted better in comparison with other treatments.

  Swelling soil such as clay soil is known as unsuitable material for forest transportation due to the high volume change and mechanical defects. So, it is necessary to improve the mechanical properties of clay soil by silica content biologic stabilizers such as ash. The aim of this study was to investigate the capability of corncob ash for enhancing the mechanical strength of soil in recommended forest roads of district two in Bahramnia forestry plan in Golestan province. In this study the waste of corncob plant was collected from farmlands of province. The nodes of stem which have higher content of Silica were separated and then grind and heated in furnace at 580°C for 2 hours. Produced ash didn’t have plastic properties and most of the particles had the size of smaller than 0.075 mm. In addition the swelling soil samples were brought from the recommended roads to the soil mechanic laboratory. Samples were treated by 5%, 10%, 15% and 20% corncob ash and in curing times of 7, 14 and 28 days the tests of Atterberg limits (Plastic and liquid limits), standard proctor or maximum dry density and unconfined compressive strength were done with three replications. Findings showed that plastic index decreased by increasing of corncob ash. With increasing the amount of ash content in the mixture, the maximum dry density of the mixture decreased and optimum moisture content increased. Proctor curves of the treatments of 10% and 5% were similar from curing time of 14 days and had significant distance from the curves of the treatments of 15% and 20%. This issue shows that the use of ash more than 10% couldn’t change the dry density and optimum moisture content. Unconfined compressive strength of the mixture increased until adding 10% of ash, and then the trend didn’t change significantly. Increasing the curing time causes that the maximum dry density and unconfined compressive strength to increase, whereas plastic index of soil decreased. In most of cases there wasn’t significant difference between the curing times of 14 and 28 days, in terms of unconfined compressive strength, maximum dry density and optimum moisture content. Findings indicated that because of the pozzolonic properties of corncob ash, it is enough to use the optimum amount of 5% and curing time of 14 days for improving the mechanical properties of swelling clay soil of forest road bed

Knowledge on physical and mechanical properties of soil is necessary for forest road construction and in turn for optimal forest management. Avoiding a mixture of organic matter with soil is considered as being principal in constructing forest roads which is, however, often neglected. Therefore, quantifying the consequences of such mixture can help optimizing the high economic and environmental costs associated with road constructions. The aim of this study was to assess if and how the level of organic matter affects the physical and mechanical properties of soil on forest roads. To this aim, soil samples were collected by profile excavation. Organic matter was collected from residual and litter layer of forest floor. Different mixtures of organic matter with soil were tested (0%, 5%, 10% and 15% of weight), followed by Atterberg limits and CBR tests conducted on the samples. Results showed that increasing organic matter content would increase plastic and liquid limits, which in turn increases the CBR values. Results also showed a significant negative effect of organic matter on soil engineering properties. Therefore, it necessitates a separation between the organic matter and soil during forest road construction.

One of the most important principles that forest managers should consider is the kind and methods of logging and transportation of forest products. Assessment of mechanical properties of forest soils is an important criterion in selecting and using suitable machines، because the forest floor bears the pressures of machines. On the other hand proportion of machines with soil properties plays important role in sustainable yield of forests. In order to obtain these objectives، mechanical properties of forest soil such as Atterberg limits، liquidity index، plasticity index، consistency index، grain size distribution and soil classification base on Unified Soil Classification System were assessed in Kheyroud Forest. The results showed that soils are fine grained and the percentage of clay in all samples is more than 5% so the soil is sensitive to freezing. The liquidity index for most of samples is less than to 0. 5 and so wheeled skidders can be used in most of the region except samples with liquidity index more than 0. 5 which crawler skidders should be used. All samples had a liquid limit greater than 30; therefore soil is sticky and should be considered when using machines. With regard to plasticity index، the soil showed high tendency in water absorption and will be dried slowly، so the machines should be scheduled and used in dry weather. Soil can not be used for road construction without physical and mechanical improvement. The elevation range of study area is up to 900 meters above sea level so risk of freezing is rareness; therefore sensitiveness of CL and CH soils to freezing is not very important in this region.