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Showing 6 results for Tunnel
Experimental Evaluation of Relative Efficiency of MWAC, MDCO, CDSC, and CDS Aeolian Dust Traps
S. Abdoli, B. Khalili Moghadam, M. Rahnama,
Volume 19, Issue 71 (6-2015)
Abstract

Quantitative measurement of aeolian dust may help properly monitor and control the wind erosion. The aim of this study was to evaluate the efficiencies of four aeolian dust samplers including the modified Wilson and Cooke sampler (MWAC), cyclone dust sampler with cone (CDSC), cyclone dust sampler (CDS), and marble dust collector (MDCO) in comparison with the big spring number eight sampler (BSNE) in different velocity rates and particles sizes. For this purpose, MWAC, MDCO, BSNE were simulated and CDSC and CDS were designed and constructed. The relative efficiencies of the CDSC, CDS, MWAC, and MDCO were evaluated for the 80, 137, 260 micron diameter particle sizes (D50) in 2-7 ms-1 velocity by wind tunnel. The results showed that relative efficiency of CDSC is higher than CDS, MWAC, and MDCO as a consequence of the wind speed. CDSC and CDS relative efficiencies varied in relation to wind velocity, but MWAC, MDCO relative efficiencies remained constant. Also, CDSC, CDS, MWAC, MDCO relative efficiencies varied from 0.8, 0.48, 2.18, 0.58 times by increasing the particle size diameters from 80 to 260 micrometers, respectively.


Effective Factors in Fine-Grained Soil Stabilization to Prevent Dust Generation
A. Jafarishalkoohy, M. Vafaeian, M. A. Rowshanzamir, M. Mirmohammadsadeghi3,
Volume 19, Issue 73 (11-2015)
Abstract

A laboratory research program was arranged to study the effect of different factors influencing the stability of fine soils against wind action. For this purpose, a laboratory wind tunnel was stabilized and several soil samples were examined by putting the sample trays inside the wind tunnel for different rates of wind velocities. The tray for soil samples was 20´30 cm2 with the depth of 5 cm, and the fine soil samples were chosen with different sizes of particle and porosity. Because the main aim of this research was to investigate the effect of some polymer additives to the soil, many samples were made of the soils improved by different additives in different percentages. Furthermore, the effect of infiltration of the liquid additives was also examined, which could show different infiltration heights as functions of soil type, additive type and the height of pouring. Some of the results were examined by using software. The lab results in this research were compared with some proposed theoretical ones. It was found that as the average diameter of particles increases, erodibility under the same wind velocity decreases, and the applied polymer emulsions decrease the erodibility up to 90% compared to the initial condition. Impacts of dust emission due to the suspended dispersion of fine particles and creeping movements of coarse particles are mitigated as a result of treatment with these emulsions. Variations in erosion of soils at various wind velocities depend on the value of threshold friction velocity with the result that the soil erosion values in case of coarser soils after the increase in velocity would be higher than those of threshold friction velocity. Finally, a relationship is proposed for estimation of soil erosion in terms of wind velocity. The results are consistent with the transport rate relationships proposed by different scholars.


Evaluation of the Ecological Risk for the Tunnel Drilling Waste of Tehran-Shomal Highway on Chaloos River
Z. Ghorbanpour, O. Abessi, F. Kardel,
Volume 24, Issue 4 (2-2021)
Abstract
Drilling material from the tunnel of the Tehran-Shomal highway was estimated to be about 2.5 Million Cubic Meters by the project authorities. Sadly, from the beginning, the drilling materials had been deposited on the open space in the floodplain of the Chaloos river with slightest environmental considerations. During the previous years, weathering and leaching from the drilled materials besides the discharge of drain water from the tunnel had led to seriouse contaminations and the deterioration of the water quality of the Chaloos river. In this paper, the ecological risk of nonorganic pollutants due to drilled materials was investigated. The sampling was done from the excavated materials and river sediment in five different locations throughout a complete year. From the many pollutants, Nickel, Cadmium and Copper were chosen to be investigated. The results showed that almost 15 percent of the samples had a high degree of pollution, while 60 percent of them were clean and the other 25 percent included the highly contaminated ones. All samples were also estimated to have a low to high ecological risk.

Investigating the Effect of Microbial Induced Carbonate Precipitation on Reducing Wind Erodibility of Soils in Segzi Desert Area, Isfahan
A.r Modares Nia, M. Mirmohamad Sadeghi, A. Jalalian,
Volume 25, Issue 4 (3-2022)
Abstract
Desertification has become one of the main problems of human societies living in the vicinity of desert areas in recent years. One of the methods that have been considered in recent years and are rapidly expanding in the field of soil mechanics is the Microbial Induced Carbonate Precipitation (MICP). In this method, urea-positive organisms that are naturally present in the soil can stabilize the soil and improve its engineering parameters by using urea and calcium chloride. Recently, attempts have been made to use this method to create a crustal layer on the soil to prevent wind erosion. In the present study, the effect of environmental conditions in deserts such as temperature and sand bombardment on microbial soil treatment has been investigated using this new method. The soil of the Segzi region as one of the main centers of dust in the Isfahan region was studied in this research. Therefore, the improved samples are subjected to regional temperatures which increased the surface layer resistance with increasing temperature. Also, the sandstorm conditions of the region were simulated using three different grain sizes of sand inside the wind tunnel. The results of these experiments showed that stabilized soil could withstand the conditions at wind speeds of 7 and 11 m/s. However, by increasing the wind speed to 14 m/s and the grain size, the crustal layer destroys and increases the wind erosion of the soil. Also, the resistance of the surface layer increased by increasing temperature in the tested samples. This increase in resistance continued up to 24 degrees with a high slope, but from 24 degrees onwards, this slope decreases. Based on the results of this research, it can be said that the microbial improvement method can be used as an alternative method in the future to stabilize desert soils.

Investigation of Wind Erosion Threshold in Different Land Cover and the Effect of Soil Properties on It (Case Study: Niatak Region of Sistan)
A.r. Nourafar, A. Pahlavanravi, M. Nohtani, V. Rahdari,
Volume 26, Issue 1 (5-2022)
Abstract
Wind erosion is one of the most important natural processes in arid and semi-arid regions. Sistan plain has a hyper-arid climate and is one of the windy regions of the country. Due to the soil characteristics of the Sistan plain, wind erosion is very intense in this region. In this study, the relationships between some soil's physical and chemical properties and wind erosion were investigated in different land cover in a part of the central region of Sistan in 2018. A map of land cover in five classes was prepared using the results of field studies and the classification of satellite images. Fifty soil samples at a depth of 10 cm were collected to investigate the physical and chemical soil properties and the wind erosion threshold was determined at each location using a portable wind tunnel device. Also, the relationship between physical and chemical soil properties including soil texture, soil moisture, specific apparent weight, EC, SAR, ESP, Na+, k+, with the speed of wind erosion threshold was investigated. According to the results, the highest and the lowest threshold speed were 8.2 and 3.8 m s-1 and occurred in agricultural lands and hilly lands, respectively. The results of this study indicated that the velocity of wind erosion threshold in different lands adjacent to sandy areas is less than the average of that cover. Also, the soil texture, EC, and SAR have the most significant effect on soil wind erodibility at P <0.05 in the study area.

Investigation of the Surface and Tunnel Runoff and Sediment Production in Saline-Sodic Soil under Different Slopes
S. Esmailian, M. Pajouhesh, N. Gharahi, Kh. Abdollahi,
Volume 27, Issue 3 (12-2023)
Abstract
Awareness of the number of changes in runoff and sediment on different slopes can be useful in modeling the production of runoff and sediment. Therefore, this study was conducted to investigate the production of surface and tunnel runoff and sediment in saline and sodic soils on different slopes. Saline-sodic soil was collected and transported to the laboratory. Laboratory experiments were performed on a soil bed in a rectangular flume at three different slopes (5%, 10%, and 15%) under simulated rain (30 mm/h) for one hour. An analysis of variance was used to investigate the effect of slope on runoff and sediment production, and the means were compared using Duncan's test at the five percent level using SPSS version 26 software. The results showed that there was a significant difference between the slopes of the runoff (P<0.001) and sediment (P<0.001). In the first minute of the experiments, due to the lack of moisture in the soil, the amount of runoff was low, but over time, the amount of runoff increased. It is because the pores are blocked by the dispersion of soil particles owing to the presence of sodium ions, which ultimately leads to a decrease in permeability. Similarly, in the last few minutes, outflow from the tunnel was observed, and this flow occurred only on slopes of 10% and 15%. The amount of sediment was also low in the first few minutes, which could be related to the low amount of runoff and the lack of sediment particle removal. Nonetheless, after the lapse of time, its amount increased, and the primary reasons were reduced permeability, increased runoff, and removal of fine particles from the soil surface.

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