جستجوی مقالات مرتبط با کلیدواژه "nanoclay" در نشریات گروه "آب و خاک"

Soil improvement in loess soils, due to susceptibility to erosion, can increase strength, resistance and change or modify their mechanical properties. The purpose of this study was to investigate the changes in soil moisture curve parameters and some mechanical indices of loamy sand soils containing montmorillonite nanoclay. Thus, soil water retention was investigated by applying 1 and 5% of nanoclay and water holding capacity in soil was investigate by VanGenukhten and Brooks-Corey models. Then mechanical properties of soil was investigated by measuring Atterberg limits and how they change. Both experiments were re-evaluated over time. Nanoclay had a significant effect on water retention in various moisture suction systems and increased volumetric moisture content, especially in low suction. It also increased the fine porosity at the air entry value, indicating a decrease in the rate of water drainage from soil and increased its storage capacity in losses soil. Increasing the amount of nanoclay led to increase in Θs, but the change in Θr was not significant. As nanoclay increased, α and n parameters decreased, respectively. Predicting the parameters of the moisture curve equation using VanGenukhten model showed better results. Liquid and plasticity limits of the soil also increased. However, the increase in the amount of liquid limit was higher and the soil plasticity index increased. The increase in the surface area and the ability to maintain water by the clays and their shear strength can be due to this fact. Monitoring of atterberg and moisture curve parameters over time indicated their persistence.

Hydraulic structures situated as an obstacle in front of water flow that changed the flow pattern in their vicinity and causing the local scour around the structure. The scour around the bridge pier is one of the most important phenomena in sediment hydraulics, which creates a hole around the pier and undermines its stability. Different methods have been proposed to prevent or reduce the local scour. In this study, the effects of collars, nanoclay materials and angle of piers have been studied in pier group. The results show that for the pier with the angle of 15 degree was observed the greatest decrease in the depth of the scour hole. Studies show that in the group pier with inclination angle of 15 degrees, there was 14 percent scour hole reduction and with presence of a collar the reduction of scour hole was 86 percent. Also, by using nanoclay materials, the depth of the scour hole in the without collar condition was reduced by 18.5%.

Recently, due to improvements and progresses in nanotechnology, application of Nano particles in different sciences especially geotechnical engineering have been widely considered. In this research, the effect of different amounts of Nano clay on dispersivity potential of two clayey soils with low and high plasticity has been studied. For this purpose, first identification tests were implemented on clayey soils and Nano clay and then pinhole tests conducted on specimens of soils with different amounts of Nano clay particles including ; 0, 0.25, 0.5, 1, 2 and 4 percent by weight for evaluation of their dispersivity potential. The specimens were cured for 1, 3 and 7 days. The results indicated that that the addition of Nano clay particles could reduce dispersive potential of clayey soil considerably. It is also found that the effect of Nano particles on two clayey soils with different plasticity is the same and the plasticity characteristics have no important role in chemical reaction between Nano clay particles and clay minerals. Furthermore, curing time was found to be as a main factor in stabilization of clayey soils with Nano particles.

To deal with the destructive effects of swelling soils, different methods have been proposed by researchers. Chemical stabilization of expansive soils is one of the effective methods that are low-cost and efficient economically and technically. Recently, with the improvements of nano science in nanomaterials production and application, using this type of materials has been considered in different sciences especially geotechnical engineering. In this research, the effect of adding different amounts of nanoclay on swelling behavior modification of two types of clayey soils with low plasticity and high plasticity has been studied. For this purpose, first, identification tests were implemented on two types of clayey soils and nanoclay. Then, swelling potential tests were conducted on samples of soils with different amounts of nanoclay including (0, 0.25, 0.5, 1 and 2 weight percent) considering curing ages of 3 and 10 days. The results showed that the effect of adding nanoclay to the high plastic soils swelling potential is more than adding it to that of low plastic soils. So, adding 0.25 to 0.5 weight percent of nanoclay reduces the swelling potential of high plastic soils about 67 percent, and that of low plastic solis about 3 percent. Furtheremore, the maximum reduction in swelling potential increases by adding up to 0.5 percent nanoclay; and decreases for adding amounts more than 0.5 percent.

Water and organic contaminant transport in soil porous media, particularly in light textured soils due to high transmission capacity and create a secondary sources of pollution is very important. The aim of this study was kerosene and water transport in a light texture soil system containing different treatments of montmorillonite nanoclay. For this purpose, treatments including 0, 2, 4 and 6 wt% of nano clay- sandy soil in a funnel containing filter paper based system was applied. Then kerosene and water (4 pore volumes alternatively) were passed into soils. The breakthrough curves showed that the water passes through soils was slower and gentler slope, so the volume output was lower compared to kerosene. It seems that water molecules with a diameter of less than 3.0 nm fitted well in the small spaces between the layer of nanoclay, which are held with strong hydrogen bonds. Kerosene, with a density equals 0.78, only attract surface places, therefore, pass from porous soil surface well due to having molecules with 11 to 15 carbon atoms, which are larger than the density of water. In both fluids, the more percentage of nanoclay there is, the more retention of kerosene and water would be expected. The results of X-ray showed that the distance of nanoclay increased from 14.4 to 24.77 Å with addition of water.

Transporting borrow materials for proper infrastructure of water channels to bear the load of such structures is important in the development plans. Therefore, in this research clay nanocomposite material with a weight ratio of %1 was added to the soil. Soil sample was taken from the bed of the C25 canal (distributary of GanjAfrooz diversion dam within Alborz project area) at various intervals and the depth of 1 meter. Unconfined compression strength and consolidation tests were performed on the selected soil. The results showed that the addition of nanoclay to the soil increased the rate of shear resistance, cohesion property and compressibility of soil, respectively, equal to 14.13, 14.13and 82.76 percent. Also, angle of failure and ultimate void ratio decreased. As a result, the addition of nanoclay to the soil makes soil strength and stability greater and there are no problems caused by bed erosion and transporting of borrow material for infrastructure of channel.