نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و هفتم شماره 1 (پیاپی 86، بهار 1396)

Cement treatment produces bonding strength between soils particles that makes their behavior different from the behavior of reconstructed soils without structure. Soft cemented soils show a great change in their void ratio after virgin yielding as the result of destruction of their cemented structure. In this paper the compressibility of soft cemented soils was investigated in the laboratory. In order to obtain highly compressible cemented soil specimens, an artificially soil was produced mixing clay, silt and sand with cement and polystyrene granules with water content more than liquid limit. All the tests carried out on oven dried specimens at similar conditions such as temperature, stress level and loading rate in oedometer apparatus. Based on the experimental results a pressure-void ratio relationship was proposed for cement treated soft soils. The proposed model employs a variable slope for compression curve in ln(e)-ln(p’) space. The performance of the proposed model was also verified for compression of naturally cemented soils using the data available in the literature.

Flow in river bends is three-dimensional, the combination of secondary flow and longitudinal flow in rivers leads to the formation of helical flow which is the main cause of erosion in the outer bend and sedimentation in the inner bend. So far, many numerical models regarding flow patterns in rivers have been introduced and available to river engineering scholars. Moges et al. (2010) simulated the hydraulic and sediment flow in Meander Rivers using SRH-2D two-dimensional model and eventually determined the best equation for predicting the water surface profile and bed level changes in sediment situations. Naji Abhari et al. (2010) studied the flow pattern in a 90 degree bend. The results of their study results showed that from the beginning of the bend till the 30 degrees angle the maximum velocity is close to the inner wall and from the 30 degree angle till the end of the bend the maximum velocity is diverted to the outer bend. Maghrebi (2012) studied the turbulent flow pattern in a longitudinal range of Karoon river, containing two 180 degree steep bends using MIKE21FM and CCHE2D models, the results showed that that both models simulate the flow pattern accurately. The aim of the present study is simulation of the flow pattern in a 90 degree mild bend using CCHE2D and SRH2D models.

Clouds and aerosols discrimination and also its monitoring always is a big part of human concerns including the modeling of climate systems. Issues related to air pollution and aerosols are one of the major problems of the environment for the residents of the world and the Middle East in recent years. Specific geographical and political conditions which are prevailed in the Middle East, being neighbored with dry and desert countries, also being located in the dust belt path (Liu, Vaughan et al. 2009), increases the necessity of monitoring and discrimination of clouds and aerosols for countries in this region, especially Iran. Aerosols are clearly and explicitly can have an impact on global emission rate and significantly limits the human’s understanding of climate systems and its potential for global climate change which is caused by the absorption, scattering and of course in the sunlight passes through the atmosphere features to the Earth's surface.

Tensegrity systems are innovative systems in the spatial structures field and refer to a special type of tensile structures that can offer an alternative to traditional space structures. These systems are defined as any given set of cables connected to a set of struts in which cables connectivity must be able to stabilize the configuration (Skeltton and Oliviera, 2009). The self- stresses contribute to the system’s rigidity and stability. In tensegrity systems, a number of members are critical, with the loss of any of them likely to produce serious strength reductions. In practice, members of a tensegrity system may be lost due to a poor member node connections or geometric imperfections, e.g. lack of fit. In fact, having one or more faulty connections in a structure, containing hundreds of connections, is a realistic possibility. In such a case, it can be argued that this member has in effect been lost.

Currently, concrete based on Portland cement (PC) is the most used construction material. However, Portland cement is not without problems. Manufacturing of Portland cement consumes 10-11 EJ of energy annually, approximately 2-3% of global primary energy use. Furthermore, Portland cement production results in approximately 0.87 of carbon dioxide for every tons of cement produced (roy, 1999; Damtoft et al., 2008). Recent researches on construction industry show an increasing interest in partial replacement of cement by pozzolans and minerals. Production and use of these materials can be accompanied by economic, environmental and technical advantages such as saving energy, reducing heat of hydration, environmental protection or improvement of the durability against chemical attacks (Kargol et al., 2013; Madlool et al., 2013). Wollastonite is a natural mineral that has been recently proposed as an alternative part of cement in concrete (Ransinchung and Kumar, 2010). There is little information about the effect of this material on mechanical properties and durability of concrete. In this study the effect of different replacement percentages of wollastonite and silica fume with cement on concrete properties was evaluated.

Analyzing stop and go traffic that observes unexpected reasons on freeways is important for modeling generation and growth oscillation and estimate congestion effects on traffic flow. Numerous theories on traffic have been developed as traffic congestion gains to model congestion traffic, many traffic theorists have adopted theories from other fields such as fluid mechanics and thermodynamics. However, these theories cannot explain the complicated driving behavior patterns from the fluid mechanics’ perspective. In these paper, because stop and go traffic identify at a microscopic level and based on asymmetric theory and trajectory data of NGSIM, traffic flow state can be classified into five phases according to speed and movement of the vehicle: Free flow, acceleration, deceleration, stationary and coasting phases and also, traffic flow departs between boundaries of acceleration and deceleration phases. Based on asymmetric theory can analyze driver’s behavior responses: maneuvering errors and anticipation, and also life cycle of stop-and-go Traffic can demonstrate three cases: Generation, Growth, Dissipation.

Spur dikes are one of the best and most economical methods for bank protection in river bends and they are used in most parts of the world. The scour around the spur dike may lead to the destruction of the spur dike. Therefore Most of the previous investigators have published experimental data on the various aspects of the local scour around impermeable spur dikes. Less attention has been paid to permeable groins which can be used to minimize the occurrence of deeper erosion around the groins and reduce the flow velocity near the bank adjusting the permeability of the structure and consequently reducing the bank erosion. Bandal-like structure is a low cost alternative. It is usually used to maintain the navigation conditions in alluvial rivers at Indian Sub-Continents. The bandal-like structure is a combination of a permeable and impermeable groin. The effects of the bandal-like structures on river morphology have been verified through few studies including field investigations and laboratory experiments. Such as Rahman et al. (2004, 2005), Zhang et al. (2010) and Teraguchi et al. (5010, 2011) the results of these investigations showed that bandal-like structures have less erosion around the structure compared to impermeable groins and have more deposition near the bank and form a deeper main channel compared to permeable groins. All of the previous investigations on bandal-like structures were in straight channels and there have been very few investigations regarding bandal-like structures in submerged conditions therefore in this study the effect of three different types of spur dikes (permeable, impermeable and bandal-like) on the bed topography in a 90 degree bend, under four different Froude numbers (0.21, 0.23, 0.26, 0.29) and in submerged condition is examined and compared.

With increasing demand for large scale and complex structural models, optimum design has become a challenging and important issue in structural engineering and meta-heuristic algorithms have become powerful tools for optimal design of structures. Charged System Search (CSS) is one of the meta-heuristics, inspired by the governing laws of electrical physics and the Newtonian mechanics, Kaveh and Talatahari (2010). CSS based optimum design of structures needs adjustments for variable based and problem based constraints. The first adjustment guarantees to select from predefined cross sections and as a result, all specifications of sections will be ready to run the analysis and the second one helps to find the optimum design in fewer steps.

Studies about effects of blast in the reservoir on dynamic behavior of concrete dams is accelerated with began of Second World War and the necessity of finding the persevering ways of this structures against of blast loading (Cole, 1948). In the present paper the effect of explosion in the reservoir on dynamic response of concrete gravity dam is study using ABAQUS commercial software. In the present research two different gravity dam model are considered and the effect of geometrical and material properties on dynamic response of gravity dam are studied. In the first model the linear behavior of material and in the second model the linear and nonlinear behavior of material are considered in the analysis (Sprague and Geers, 2006).

Nowadays, air pollution is one of the most concerning environmental problems in major cities all over the world. Surface ozone (O3) as one of the most important pollutants in troposphere is one of the major components of smog and is formed through a series of photochemical reactions in the presence of volatile organic compounds (VOCs) and nitrogen oxides (NOx). High oxidizing potential of ozone can lead to respiratory problems. Breathing ground-level ozone can trigger variety of health problems such as chest pain, throat and eye irritation, asthma attacks, bronchitis, emphysema and headaches. Also, high ozone concentrations deeply affect plants and cells, and impact worldwide crop and forest. In the last decade, a number of studies have been done in the case of O3 concentration in urban areas. These studies indicate that O3 concentration has increasing trend in major cities (Mohammadi et al., 2016; USEPA, 2013; Im et al., 2013).