AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2019 | Volume:51 | Issue:2 |Papers Count:17

Appropriate ventilation in underground mines is one of the most important factors in deep mining. Mining engineers always pay attention to the design of the ventilation network during development and extraction of ore in underground mines. The ventilation network’ s efficiency depends on a variety of factors. The presence of barriers in mine ventilation networks is one of the important affecting factors. In this research, using the Monte Carlo technique, a probability distribution function is presented for the resistance of obstacles as the input to the model. For each simulated value, the ventilation network was analyzed and the air flow of all branches of the ventilation system of the NAKHLAK mine was determined. Reliability criteria were introduced. Results showed that branches 4, 6. 7, and 13 have been failed. Branch 7 will be able to find its initial performance by changing the flow direction. Branch 13 was completely failed during the simulation process.

The sustainable urban drainage systems approach or LID devices (low impact development) are designed to detain, store, infiltrate, or treat urban runoff, and so reduce the impact of urban development. The purpose of this research is to evaluate the application of detention tanks from low-impact structural methods in order to eliminate or reduce the rainfall flood in the collecting network and conveyance of surface drainage water in small part of the urban area in Babolsar city. By using the simulation of rainfall-runoff process at the catchment area and the runoff routing in the drainage networks with the SWMM, critical nods were identified. The results showed that some parts of system have high capacity and the others have low capacity which induces inundations. Several simulations were performed with considering detention tanks by different dimensions in the system and eventually the best option was selected. Considering a serial detention tank, no inundation occurred in 2 and 5 years return periods but for 10 year return period, inundation happened with 125 m3 flood volume. However, constructing parallel detention tank with same dimensions and place of serial type caused no inundations. Results showed that parallel detention tank has better function comparing with serial one. The results of this study emphasize the use of flood hydrodynamic simulation models to evaluate different scenarios of urban flood management.

Skewed beams may be utilized due to the architectural limitations. The use of skewed beam cause to initiation of torsional moment, in addition to flexural moment, at the connection face. In the beams with end plate connections, the torsional moment creates shear stress at the end plates which in combine with the shear stress due to connection shear force can lead to reduction in the connection frictional strength and the end plates slippage. This paper investigates the slippage of the end plates of skewed beam with rigid connection to columns with end-plates. 122 finite element non-linear models are used to study the end plate moment connections with skewed beams with 10, 20, 30 and 45 degree of deviation in the plan. The results showed that for the beams with low degree of deviation, the addition of one or two rows of bolts is a suitable method for reducing the loss of strength for skewed beams. For high deviation angle of 45 degree the friction strength loss is considerable and so large number of bolts may be required to be added to recover the friction strength loss, which may not be possible due to the geometric limitations of the connection and so it is recommended in the beams with 45 deviation angle other types of connections to be used.

Today, strengthening of reinforced concrete structures and especially flexural strengthening by fiber reinforced polymers (FRP) is used worldwide as an efficient way. In this study, the existing of a constant load during FRP flexural strengthening versus load removal before strengthening were experimentally investigated and compared. A preload with two different predetermined amounts, one to make the beam cracked elastically and the other to make beam deflected to plastic region, was applied before the strengthening of beam samples. All Externally Bonded Reinforcement In Groove (EBRIG) installed FRP sheets were ruptured during test and no de-bonding was observed. Pre-cracking of beams in unloaded strengthened beams caused a minor decrease in ultimate load capacity of strengthened beams. Also ductility and ultimate deformation was decreased. Flexural strengthened beams under constant load showed better ultimate strength (up to 8%) and also better ductility and energy dissipation ability. It can be concluded that FRP flexural strengthening of beams under constant load is more appropriate than load removal of beams during strengthening. The appropriate amount of load during strengthening must be studied in detail but excessive loading to plastic extents is not appropriate.

The superiority of the geosynthetic reinforced soil wall to another reinforced soil systems, is led to the increasing expansion. So far many studied have been conducted on geosynthetics reinforced soil walls, with assuming rigid bed. But the behavior of this system and mechanism of it components has less been considered when the bed is compressible or loose. The present study investigated the effect of effective parameters (i. e., facing inclination, connection type of geogrids to the facing, toe condition, length of reinforcement and vertical distance of reinforcements) on the behavior of reinforced soil wall seated on compressible bed, using finite element method. Also the behavior of the wall under conditions of end of construction and surcharge loading has been investigated. The results showed that the parameters that had the greatest effect on the behavior of the reinforced soil wall during the weakening of the bed, is facing inclination, vertical distance between reinforcements and toe condition. Decreasing vertical distance of reinforcements and increasing facing inclination, has led to significantly decrease in horizontal displacement of wall and maximum reinforcement load. Also according to the results, the bed with compressible soil, the type of connection of reinforcement and length of reinforcement did not show a significant effect on the improvement of the wall’ s behavior, except when the wall was placed on a loose bed.

With the increasing population growth and the importance of sustainable development, the need for wastewater treatment systems with less environmental load and therefore the economy is felt. The life cycle assessment method, is one of the methods of environmental assessment of products and services. in this study a comparison between two methods of sludge treatment systems, aerated lagoon (Ardabil wastewater treatment plant) and activated sludge (Khalkhal WWTP) were discussed. for this purpose, inputs (materials and energy) and outputs (related pollutants) of each system were determined. Based on the quality parameters data from the water and wastewater company in Ardabil province, the amount of CH4 and CO2 production gases in both systems were calculated, and analyzed with use of simapro 8. 2. 0 software and basic data of CML2001 and Eco-indicator 99. The results showed that, lagoon system had maximum effects in all impact categories and in contrast, activated sludge system had much less environmental impact than lagoon system. Thus, activated sludge system in the category of toxic effects for humans had the highest contribution (79 %) and in the global warming and photochemical oxidation impact categories had the lowest contribution (0. 72 %). So, the results of this research showed that activated sludge system had lowest environmental load and introduced as an alternative method of aerated lagoon system in the development of Ardabil wastewater treatment plant (WWTP).

Scouring is a natural phenomenon that arises from the erosive action of flow field in the alluvial streams. Local scour is a special type of scour. This type of scour is one of the reasons of bridge failures. One of methods of scour reduction is the use of collar and netting the collar makes it lighter. The position of collar plays an important role in reduce of scour bridge pier, therefore in this research effect of position of netted collar around of oblong bridge pier are investigated. The experiments have been in this direction on the flume with the length of 6 m, with of 73 cm and a depth of 60 cm with a slope near zero. In this research, simple collar and three netted collars(with opening parts equal to 30 percent, 50 oercent and 70 persent) in four levels including on the bed, 0. 1B under the bed(B: pier’ s width), 0. 5B and B above the bed. The results show that levels under the bed and on the bed were the best position to install the collars. On the bed, the simple collar had 100% sufficiency and the 70% netted collar had 92% efficiency in reducing the scour. In level under the bed simple collar and netted collars had the same performance and scour depth decreased by 88%.

Pavement condition assessment requires structural evaluation that can be achieved using Falling Weight Deflectometer (FWD). This paper focused attention to the FWD results. The main objective of this research is to present a new method to estimate the pavement layers elastic modulus and to investigate its precision considering the experimental test results. To this end, several sections in Shush-Andimeshk and Semnan-Damghan highways were evaluated by ground penetrating radar (GPR) for estimating the layer thickness and falling weight deflectometer test at different load levels for estimating the elastic moduli of pavement layers. At the same sections, some cores were extracted and tested to measure the elastic modulus using the indirect tensile and dynamic triaxial methods for bound and unbound layers, respectively. The FWD data were analyzed by ELMOD6. 0 software as a conventional back-calculation method. Furthermore, a new method was proposed by implementing a code using BASIC programming language and the obtained results were compared with those from ELMOD6. 0 and experimental results. Based on these investigations the proposed method could precisely estimate the experimental moduli. Some models were present to estimate laboratory modulus (assumed as real modulus) considering the back-calculated modulus. In addition to back-calculation based models, models were developed based on the independent variables such as surface curvature index (SCI) and base damage index (BDI). Using the latter models, the layer modulus can be estimated without using the complicated back-calculation analysis methods. The final part of this research related to the validation of developed models. Validation of these models showed that they were sufficiently reliable to predict the real elastic moduli.

Electro kinetic approach is a conventional method to improve soil characteristics. Dewatering, heavy metal remediation as well as injection stabilizers such as sodium silicate, colloidal silica and ionic solutions, especially in clayey and silty soil, which are sensitive to high pressure methods, are applicable via electro kinetic way. As a green product stabilizer, colloidal silica a dispersion of nano silica particles in water medium phase has been widely investigated by researchers. To quantify the effect of various factors such as solution electrochemical properties and electro kinetic injection conditions on stabilized soil and pore fluid, a suitable apparatus is necessary for laboratory tests. The apparatus should facilitate control and management of hydraulic and electro kinetic conditions. So, the main objective of the paper is to study the electro kinetic injection synced with hydraulic one into loose sand via appropriate instrument. An appropriate device has been designed and constructed and validated by feasibility tests. The trend of current intensity was compatible with previous works as well as uniaxial shear strength and shear wave velocity increase of soil. In conclusion, built apparatus could be useful for future studies.

by means of correlation of Weather Research and Forecasting (WRF) numerical model with air pollution dispersion model (CALPUFF) in this study, distribution of NOX air pollutant concentration from exhaust flues of Montazeri Power Plant at Isfahan was simulated in two intervals of 20 days during cold and warm seasons in 2014 and then the potential of the model was assessed in data simulation using statistical analysis. The results of statistical parameters used in this investigation, suggest good potential of California Meteorological (CALMET) model in simulation of 3-D meteorological field needed for CALPUFF model. Similarly, the results of statistical parameters indicate good agreement between simulated data by CALPUFF model and observed concentration data in pollution surveying stations so that the value of R-index for NO2 is placed within range (0. 706-0. 932) in cold year interval and in (0. 567-0. 804) during warm year interval. This shows high correlation between the observed data and simulated data. The value of FB index for NO2 is placed within ranges of (0. 051-0. 285) and (0. 040-0. 370) in cold and warm year intervals, respectively. The results of FB index indicate that the model given for the results of concentration of pollutants has generally forecast it below the actual level. Overall, the results of statistical assessments show good performance of CALPUFF model in forecasting of concentration for the given pollutants.

In mechanized tunneling with Tunnel Boring Machine (TBM), some parameters such as thrust force and penetration rate have an important role and they can be recorded and compared with values achieving from theoretical models. Karaj-Tehran water conveyance tunnel has been bored by hard rock TBM machine to supply the water for Tehran capital. This project is finished by two parts called Lot1 and Lot2. After investigating the tunnel face of each section in Lot2, ground characteristics and Geological Strength Index (GSI) were recorded respectively. After that, Uniaxial Compressive Strength (UCS) and Cerchar Abrasiveness Index (CAI) are measured by testing on rock samples. The boring thrust force of TBM was calculated by using above mentioned data and by using other common and applicable models. Beside, achieved data from TBM specially thrust force and penetration rate had been recorded at the same time. A comparison of measured and calculated thrust force by using TBM data showed that it is possible to analyze the differences between them at each section of tunnel. For this, some parameters such as database selection, sampling and tunnel face control have an important role on analysis. At the end, CSM model and tunnel face data are selected to evaluate the thrust force and their results are presented to describe the eight classes of rock mass.

One of the most essential works for sediment management in dam reservoirs is to identify the characteristics and effective parameters of deposition of sediments in the dam reservoir. In this research, the sedimentation process of fine sediments deposited into Karkheh dam reservoir was investigated in order to determine the required hydraulic conditions for desilting of the reservoir. Experiments were carried out in an annular flume located in Hydraulic Laboratory of Shahrekord University and sediment samples were taken from reservoir of Karkheh dam. Experiments were done at initial concentrations of 5, 10 and 20 g/l, and various shear stresses to determine the threshold shear stress for partial deposition and full deposition of suspended sediments. The obtained results showed that the shear stress of the initiation of sediment deposition was 0. 1 N/m2. It was also found that when the flow velocity to be exceed up to 0. 61 m/s, the sediments would be completely remained in term of suspension. Under these conditions, the shear stress and Froude number were obtained as 2. 55 N/m2 and 0. 43, respectively. Also, the results showed that in higher sediment concentrations, increasing of shear stress is more effective in the sediment deposition rate.

Preventing the penetration of leachate of landfill which contains heavy metal into the soil and aquifer layer is one of the most critical issues in the world. High capacity of Clay minerals to exchange cations with other metal onions, made it natural absorbent material. Previous studies show that interaction of clay and metal contaminations leads to variation of surface and micro-structure properties of clay which will results in the changing of geotechnical properties of clay. The aim of this study is to evaluate the settlement properties of sandy-clay kaolinite in the presence of heavy metal. Therefore after preparing samples some laboratory tests such as XRD, settling, absorbent, one dimensional consolidation and liquid limit determination done on the samples in the presence of lead and zinc. The results of XRD and settling show that the presence of lead and zinc change the structure of soil from disperse to flocculation. This phenomenon would intensify with the increase in contamination concentration. The change in structure of clay lead to decrease in void ratio and settlement properties. In addition the result of experiments show that, by increasing the concentration of lead heavy metal from 0 to 25 cmol/kg. soil the initial void ratio of sand-kaolinite with the ratio of 10, 25 and 40 would reduced 0. 17, 0. 20 and 0. 25 respectively. Also this reduction for similar samples in the presence of zinc is 0. 13, 0. 16 and 0. 18 respectively.

In this research, the effect of leachate on the shear strength parameters of fine soils was investigated in the laboratory conducting 14 consolidation, 42 large-scale direct shear test and SEM photography. Consolidation and shear tests conducted on specimens contaminated with different percentages of leachate ranging from 5% to 20% in short-term after 96 hours of contamination and long-term after 180 days of contamination. The results of these tests indicated that leachate contamination reduced the shear strength and compression index of clay. The peak shear strength of contaminated specimens achieved in lower deformations when compared to intact specimens. In the soil of CH and CL, with the increasing the leachate content up to 20% reduced the shear strength by about 30% in the short-term and by about 40% in the Long-term compared to intact specimens. In the soil of CH, with the increasing the leachate content up to 20%, reduced the compression index of soil by about 45% in compared to intact specimens. Results of this study showed that with the increasing the leachate content up to 20%, the peak shear strength of contaminated specimens achieved in lower deformations (36% lower deformations for CH and 32% lower deformations for CL) when compared to intact specimens.

The deterioration of concrete structures is a non-linear and complex phenomenon which is caused by different phenomena. Carbonation is known as one of the major reasons of concrete deterioration. Carbonation has two different effects on concrete structures. Carbonation may have a positive effect against corrosive materials because of its effect in reducing the concrete porosity by changing calcium hydroxide to calcium carbonate. On the other hand, carbonation may have a major role in improving corrosion by reducing the pH of concrete and omitting of passive layer. Although literatures on carbonation have been vast, there are so few studies in carbonation of concrete containing silica fume. In this research the effect of carbonation in reducing of the porosity of concretes containing silica fume was studied. For this reason, concrete specimens with different water to binder ratios (w/c = 0, 0. 35 and 0. 5) and silica fume percentage (S. F = 0%, 5% and 10%) were made and carbonated in different ages (28 and 90 days). The porosity of carbonated concretes compared with control specimens by different experiments. Finally, a mathematical model for concrete porosity reduction under carbonation phenomena was developed based on experimental results.

In this study, removal of ferrocyanide and ferricyanide ions from synthetic wastewater with activated red mud was studied. Two activation methods by ammonia (ABA) and cationic surfactant of cetyl trimethylammonium bromide (ABC) were used. In order to evaluate the process of cyanide ion adsorption and its effective parameters, 44 experiments were designed with seven variable factors using DX8 software by the response surface method. The results showed that the optimum conditions for achieving the highest adsorption capacity with ABC adsorbent were obtained as follows: pH=7. 1, adsorbent dosage of 0. 57 g, ferricyanide concentration of 126 ppm, contact time of 96. 66 min, agitated speed of 120 rpm and ion strength of 0. 24 M. In optimum conditions, the absorption capacity of 19. 5 mg/g and the absorption percentage of 99. 3% were obtained. The results showed that the use of ABC adsorbent has a higher efficiency in the removal of cyanide ions from the synthetic wastewater. Thermodynamic studies were carried out in optimal conditions. The results showed that the negative value of Δ G◦ parameters at different temperatures indicates the spontaneity of the cyanide complex adsorption process on adsorbents of ABA and ABC. The spontaneity of process increased with increasing the temperature.