جستجوی مقالات مرتبط با کلیدواژه « ماسه بادی » در نشریات گروه « عمران »

The present study has investigated the effect of vinyl acrylic polymer emulsion (VA) on the shear strength of aeolian sands in the Khuzestan plain. For this purpose, after sampling the aeolian sands of the mentioned area, a standard compaction test was performed and the optimum water content and maximum dry density of the aeolian sand were determined. Then, solutions with percentages of 10, 20 and 30% of polymer material were made and added to the aeolian sand in such a way that it reached the optimum water content. The prepared soil with maximum dry density was placed in square metal molds kept in the laboratory for 1, 7, 14 and 21 days and then subjected to direct shear test. The results of the direct shear test on the stabilized samples showed that by increasing the curing time and the concentration of the polymer solution, cohesion and the shear strength increase and the angle of internal friction decreases. So the polymer solution with a concentration of 30% has caused a 146% increase in shear strength aeolian sand. Electron microscope images (SEM) show the creation of bridges between sand grains in the stabilized samples, which is the reason for the increased cohesion and shear strength of the samples.

The existences of loose soils such as soft sands have always created concerns for bearing the load. Their inability to withstand pressure and weak shear resistance have forced engineers to move the project site or accept expensive methods such as pile driving as solutions to overcome them. Today, many additives such as polymers, lime, cement, etc. have been introduced to improve soil properties and land improvement; however, each of them, having their strengths and weaknesses, has created problems for their use. Cement factory furnace ash, which is one of the by-products in the cement production process; at the outlet, the gases released from the furnace are collected by fabric filters or electrostatic precipitators. Due to its similarity with the compounds found in cement, the compounds of this material have some of the positive properties and characteristics of cement and can be used to stabilize weak soils due to its cheapness. In this research, the effect of cement furnace ash on the engineering properties of unsuitable and weak sand-blasted soil has been investigated, in such a way that cement furnace ash with proportions of 5, 10, 15 and 20% with sand-blasted soil in the periods of 7, 14 and 28 days processing of the combination and direct cutting test have been done on them. Also, in order to create ideal conditions, the standard Proctor compaction test was used to obtain the maximum dry weight of the soil and the optimum humidity for each sample. The results of this research show that the samples with 10% cement furnace ash compared to other samples create a more ideal composition and the shear strength is more than 7 times compared to samples without cement furnace ash.

Stabilizing weak and poorly graded soils in engineering projects is commonly achieved using lime and cement. However, the cement production process requires significant energy and generates a substantial volume of carbon dioxide, which presents considerable environmental risks. As an alternative to cement and lime, alkali-activated aluminosilicates have gained recognition due to their cost-effectiveness and environmental compatibility. This study aims to investigate the feasibility of utilizing metakaolin as a stabilizing agent for sandy soil, with Calcium carbide residue (CCR) serving as an alkaline activator. To this end, factors such as the concentration of alkaline activator, metakaolin content, curing time, and temperature of treated soil samples were examined through unconfined compressive strength (UCS) and California Bearing Ratio (CBR) tests. The results were then compared to those of sand stabilized with Portland cement. Furthermore, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the microstructures formed during the soil stabilization process. The findings indicate a significant increase in the stabilized soil samples' compressive strength and ductile behavior. Moreover, the analysis of the developed microstructures in the stabilized soil samples demonstrates a noticeable bond between the binding gel and sand particles and the filling of intergranular space with alkali-activated binding gel. Overall, the findings of the present study suggest that the introduced binding gel has the potential to be an environmentally compatible stabilizing agent for stabilizing sandy soils.

Since one of the major problems is these sands, its low resistance to natural moisture and saturation conditions, a laboratory study was conducted to investigate the effect of adding polyvinyl alcohol polymer to improve the mechanical and geotechnical properties of dune sands. The results revealed that the addition of this polymer up to 0.2 weight percent increases the maximum dry weight and does not significantly change optimal moisture. The experiments also showed that by increasing the polymer content, the CBR resistance of the samples increased significantly, so in samples made with 0.5 % of the polymer, the CBR value reached 185; this amount is more than 7.5 times the CBR for neat soil. Experiments showed that by adding 2% cement to the mixture, the resistance of the samples was increased, and their resistance to scouring increased. The direct shear test results indicated that the addition of polymer also significantly increased the shear strength of the samples. Tire fibers were used to prevent this condition and made the samples more ductile. The optimum amount of fiber needed was 0.6% in this case. The results of single-axial tests also showed that adding polyvinyl alcohol increases the soil's compressive strength and shear strength considerably. For example, in a combination of 0.4% polyvinyl alcohol, 1% cement, and 0.6% tire fiber with sand, the compressive strength reached approximately 15 kg/cm2, while the compressive strength for 1% sand cement was about 0.29 kg/cm2.

In road projects, a suitable base for project execution is essential. Many of the soil types, such as wind sand, are not suitable for road building, and there is a need to carry out operations to prepare these soils for the base. In many cases, there is a need to switch to bed soil, but it is costly and will prolong the execution time of the project. Since it is challenging to reach ideal soil for road construction projects, soil improvement is being carried out. This is done in different ways, one of which is adding different materials to the soil. In this study, this method is used to stabilize the wind sand of Yazd. Two different types of glass fibers (type E and AR) have been used in this study. In order to perform the compressive test, the soil with both types of glass fibers was mixed in different percentages of 0.25, 0.5, 0.75, and 1 percent. The results showed that the percentage of optimum moisture increased by increasing the percentage of glass fibers. It should be noted that glass fibers did not affect the maximum dry soil weight. The direct shear test was done with the same percentages used in the compressive experiment. In this experiment, adding 0.75 and 0.5 percent of the type of AR and E to soil was selected as optimal for internal friction angle and cohesion, respectively. Also, using glass fibers of type AR in the studied soil had better results.

Construction wastes can be found easily and are increasing by the developing of cities. Lack of sufficient knowledge and facilities for recycling these materials causes deposition of these materials and unfavorable scenes in suburban regions. Settlement of these materials makes some troubles for building constructions on them. Prevalence of disease, growing of vermin and also the low potential of these materials for raising plants are some of the problems which are the motivation for many scientific researches about recycling of these materials. In this study first brick, gypsum and cement contained wastes were collected and then 200 samples with 3, 6 and 12 percent of cement in 4 groups with different mixture of wastes were made. Compressive and indirect tensile strength tests and the test of durability against freezing and thawing were conducted to evaluate these materials to be used in stabilized base and subgrade layers. The results show that many mixtures of these materials have sufficient compressive strength and durability to be used in base and subgrade layers according to highway construction codes.

Nowadays, the Iran country with considering huge reserves of building stone, is one of the important countries in world. But, unfortunately when building stones are processed in factories, significant part of material changed to waste. In final of processing, simultaneous national treasures are spoiled and environment is damaged too. Therefore, propose new methodologies and reuse of waste materials due to building stone is necessary. In this research, main idea is study of mudstone due to travertine and granite on geotechnical properties of dune sand. In present research, some factors such as optimum water content, dry density, bearing capacity, internal friction angle and cohesive by using laboratory tests including compaction, California Bearing Ratio (CBR) and direct shear tests were evaluated.

Problematic soils are those that make the construction of foundations extremely difficult. Some problematic soils loss their strength, at saturated conditions. As silty soil and quicksands have low strength at saturated condition, it seems that stabilizing of these soils is necessary. In literature, stabilizing these soils by cement is more effective. On the other hand, by developments in nanotechnology within last three decades, researchers discovered a material with unique properties, named as carbon nanotube. The carbon nanotubes has very high strength even higher than steel, high elastic module and toughness and other unique properties. Within last three decades, many studies are concerned about applying this material in cement composites, but only we can find a few works related to use this material in soil stabilization. Since carbon nanotube attract each other, we should separate nanotube particles. In this study, different values of ultrasonic energy and polycarboxilate based super plasticizer solution was used to overcome carbon nanotubes agglomeration problem. As it is not possible to use carbon nanotubes in dry state, to investigating the effect of carbon nanotubes on the soils, the aqueous solution of carbon nanotube was added to the soil, using wet mix method. The samples were cured in water for 7 days. After performing direct shear test the shear strength and its parameters were evaluated.

Utilizing considerablepetroleum products، increasing soil contamination and need to its clean-up is one of serious environmental issues. Soil vapor extraction is a common and very wide used method for soil remediation because of its Easy operation، low cost and high efficiency. In this paper، influence of soil type and heating، as two important parameters in efficiency of soil vapor extraction method is examined. The used soil is blown sand، which is mixed with different percentages ofkaolinite clay. Establishing pilot and running experiments، the result of soilsremediationout of aliphatic hydrocarbons in gas-oil is reported. The results indicate thatenhancement of clay percentage leads to great reductioninclean-up efficiency. After 24 hours test running،removal efficiencyreached to 78. 4%for the soil with 20% clay content، while this efficiency fell down to 23. 75% for the soil with 40%of clay content. Having no clay within the soil، soil-heated vapor extractionmethod did not causenoticeable increasing in clean-up efficiency. However، heating has the most influence and increases clean-up efficiency for 20. 6%with presence of 20% clay within the soil، while presence of %40 clay decreasesthe efficiency to 12. 57%.

Sand and clay soils are the most usually common soils that constitute the subgrade of roads in northern parts of Iran. The clay soil has high plasticity index. Also they have high strength in dry condition, in saturated state; they lose most of strength and during this time, sustain much swelling which is dangerous for pavement. Sandy soils in coastal zones are termed Beach sand and have considerable strength in confined state. However In unconfined state, because of their uniform gradation and lack of cohesion,
they will be washed out by water flow. In this research, the effects of Waterproof cement on engineering properties of these soils compared to Type 2 cement and Lime have been considered. In order to investigate the effects of the above materials on improving soil properties, Atterberg limit, Unconfined Compressive Strength and CBR tests have been carried out. It was found that the Waterproof cement has superior effect on strength properties of soils compared to the two other additives. The tests have also shown the average effect of this additive on the Plastic properties of soils.