سهیل قره

Today, the use of pits in construction projects is increasing due to the maximum use of land and also the high price of land. The use of methods to maintain stability, security, time and cost has always been a concern of employers and those involved in excavation projects. Value engineering is a way to achieve the optimal state in carrying out construction projects, which is effective in reducing project time by eliminating additional costs as well as ineffective activities without affecting the process and operation of the project. Due to the importance of two issues in this research, an attempt has been made to investigate the factors affecting excavation projects by adopting a value engineering approach. In this research, the staticity of the pits based on truss, concrete pile, nailing and anchor methods as well as the use of soil rupture wedge as an innovative method for stabilizing shallow, semi-deep and deep pits have been investigated. The results are evaluated in terms of cost, time, pit security and occupied space and are evaluated and weighted using Analytic Hierarchy Process (AHP). The results show that the use of wedge rupture method in shallow excavations can be a good option in terms of value engineering. Also, using concrete pile method for semi-deep pits and using anchorage method for deep pits according to the results are considered suitable options.

In the present paper, results of a study on the use of Bacillus pasteurii to reduce wind and water erosion in alkaline silty soils are presented (Kim et al., 2014). The treated soil specimens were prepared in different periods and different concentrations and amounts of bacteria on different surfaces and were exposed to a wind tunnel constructed and calibrated for the present study and their surface erosion was measured. For further analysis of the samples, melting and freezing tests, cone penetration, electrical conductivity, pH and SEM, XRD, and EDS analyzes were also performed on the treated and untreated specimens. The results of this study showed that the use of MICP as a surface crust is an effective and environmentally friendly process to control dust caused by wind erosion in the Meighan Wetland. 

2.1. Experimental study The treated soil specimens were prepared in different periods and different concentrations and amounts of bacteria on different surfaces and were exposed to a wind tunnel constructed and calibrated for the present study and their surface erosion was measured. For further analysis of the samples, water erosion test (Gao et al., 2020), freeze and thawing test (Qi et al., 2006), cone penetration, electrical conductivity, pH and SEM, XRD, and EDS analyzes were also performed on the treated and untreated specimens. To compare the stabilization method with bacteria and conventional stabilizers, surface stabilized samples were prepared by spray method (Ivanov & Stabnikov, 2016) of cement and lime and exposed to wind tunnels and surface erosion was measured. 

3.1. Effect of bacteria on reducing wind erosion The results of this study showed that the use of MICP as a surface crust is an effective and environmentally friendly process to control dust caused by wind erosion in the Meighan Wetland. With this method, the surface resistance of 28-day-old samples can be increased up to 95% and the rate of wind erosion can be reduced to 89.8%. 3.2. Effect of bacteria on water erosion The formation of biological crust in a scouring cycle by 98.59% has reduced the surface scouring, which can indicate the stability of this crust against water erosion in the study area. 3.3. Effect of bacteria on freeze and thawing cycles Freeze and thawing cycles do not cause surface crust loss and increase wind erosion in bacterial-modified soil samples. 

The use of bacteria to improve the soil and create a biological crust by spraying has shown a significant effect on the rate of erosion of samples exposed to wind and this method can be used in fine-grained soils of Meighan area and soils with similar conditions to prevent surface erosion. This method increases the surface resistance of the soil against melting and freezing, scouring, and penetration of the cone. Soil bacterial stabilization in the study area is more suitable than cement and lime stabilizers in terms of reducing erosion and reducing pollution.

In this paper, the effects of rail vibrations transferred from the ground to the building in the vicinity of the rail are studied. The additional forces mostly produced in the contact area of the wheel and structure’s rail influence on the building in the vicinity through the soil underneath. The building is a concrete chamber located between 2 high speed railroadand in 2 meters distance from them. The Ansys software was used which can model the train forces, soil, rail and building’s components. One of the ISO 14837-1 curves was used as a raw curve of train vibrations’ effect and was made ready to enter in the software by mathematical transformations. The results of the software model have been studied in case the vibration frequency received by the building is equal to one of the effective natural frequencies of the building, which leads to damage to the joinery of the building (if the building is old or historical, it will overturn). By using damping layers in the building, the effect of train vibrations on the building adjacent to the rails is greatly reduced, and with this solution, damage is not caused even in the joinery of the building. The damping layers are made of rubber and polyurethane, which is produced by the German company "BSW". Another way to reduce the resonant effect is to increase the damping of the structure in different ways.

Today, the vulnerability of cities, especially old and dilapidated structures to earthquakes, is a global issue facing experts in various fields. This situation has become more acute in countries with endangered natural structures, including Iran, in recent decades. Dilapidated urban structures as the main boiling point of a city reflect the identity of that city, are unstable and vulnerable to natural disasters and phenomena, especially earthquakes. The aim of this study was to develop a model for reducing the risk of seismic damage in urban environments by considering the uncertainties. The present research is applied in terms of purpose and descriptive-analytical in terms of method. The statistical population of the present study consisted of urban specialists and experts. The estimated sample size was 60 people. The results of this study showed that natural factors, housing quality, distance from special uses and demographic and economic factors have a positive and significant effect on reducing the risk of seismic damage in urban environments. Among the mentioned factors, the housing quality factor with an impact factor of 0.458 had the most impact and the demographic and economic factor with an impact factor of 0.131 had the least impact.

Usually the vibrations caused by the movement of the train on the line are divided into two categories: ground and air. Ground vibrations propagate around the line, inside the ground, and vibrate in any object they reach. These vibrations in the body are converted to other types of vibrations and displacements or heat, or changes in the environment. In some areas, there are buildings near the line, where the vibrations cause secondary vibrations, structural problems, and annoying noise. Several factors affect the transmission of vibrations due to the movement of the train to the surrounding buildings. One of these factors is the length of the transmission path, which is inversely proportional to the level of vibration created in the body. In order to reduce ground vibrations caused by the movement of trains in buildings, first, the background of the technical literature on the subject has been studied. In the following, some solutions have been developed in the path of vibration transmission and then these solutions have been expanded by the brainstorming method and new solutions have been presented. There are suggestions for construction that are mentioned in the results for the most critical situation, namely the construction of a high-speed railway station with an iron wheel on an iron railway.

According to the expansion of cities, the necessity of high-rise buildings construction and the need to retrofitting the old buildings is inevitable, particularly in metropolises such as Mashhad with expanded urban areas and neighbor areas of Imam Reza shrine built on the fine-grained deposits, the necessity of improvement and reinforcement of soil is evident. Nanotechnology can be significantly efficient as one of the most useful modern technologies in the recent century to meet the needs of the construction industry. The technology has a significant effect on the improvement of strength and mechanical parameters of soil because of a considerable increase in particle surface. In this regard, this study has investigated the effect of adding clay nanoparticles of type Montmorillonite and Silica of type "S" on the strength and mechanical parameters of silty-clay soils adjacent to Imam Reza's Shrine using laboratory studies. The results showed a significant increase in shear and compressive strength parameters and a decrease in settlement of soil in the Nanosilica-improved samples compared to nanoclay-improved ones. In this way, adding 1% nanosilica and 2.5% nanoclay could cause a 620 and 134% increase in bearing capacity of silty-clay soil, respectively.

Today explosion in urban centers and residential areas, there is a danger that threatens all buildings. Explosions inside or near a building can cause sudden damage to building frames. Analysis and design of structures under explosive loads requires a precise understanding of the dynamic response of members and systems of structures under this load.In this research, the behavior of three types of flexural joints of reduced type, end plate and reinforced with top and bottom plate in the phenomenon of explosion and progressive failure has been studied and to perform these studies and numerical simulation of ABAQUS finite element software And Etabs (V.NL13) were used.In determining the type of explosion, two parameters are usually decisive: the size of the weapon, which is equivalent to the weight of TNT, and the distance, which indicates the distance from the center of the explosive to the desired volume. In steel structures, there are two types of lateral load-bearing systems: flexural frame system and simple frame system with bracing. In the meantime, the bending joints of the beam to the column are the bridge of this partnership, and if it is destroyed, the structure can suffer a lot of damage. Due to the above explanations and the importance of flexural joints under lateral loads, in this research, flexural joints have been investigated.

Deep foundation are used to transfer loads of large and high rise building to subsurface layers that have sufficient strength. Piles are one of the most common deep foundations which are installed in the form of driven an bored for many years, the high noise and variation by the driving and the hardness and the limitations of the performance of the bored piles caused to use a new type of pile which installed to the soil using torque and a small amount of axial compressive load, Helical pile can be considered as such piles. Drilled displacement piles are another type of this piles. Due to the increasing use of these piles, there are still limit studies on them and there is a need to study their behaviour in different soils and conditions. Three models of piles in the laboratory section were implemented and loaded in FCV-AUT and compared with studies in the field. Compressive and tensile static load were performed according to ASTM D1143 and ASTM D3689 standard and rapid loading test.Drilled displacement pile in tensile and compressive performance was better than other torque driven pile. Because of concrete is cheaper than steel, these piles can be a good alternative for driven and bored pile in urban areas.

Lack of accurate knowledge of pavement behavior under moving loads is the one of the most important disadvantages in calculation of Equivalent Axle Load Factor (EALF) in roads pavement. Among the many researches, the most comprehensive method is based on the AASHTO road test. As the main weakness of this method, the results are limited to the experimented axles, which makes it impossible to determine the EALF for all existing axles, hence reducing the accuracy of the results, causing premature failure, and leading to higher maintenance costs. Today, although numerous software packages are available for EALF calculation, they require various parameters, are time-consuming, and can only simulate one section at a time . On the other hand, artificial neural networks, as an artificial intelligence subcategory, have many advantages such as reduced input data, increased modeling process speed, ability of parallel modeling of several pavements with different conditions, etc. In this paper, after verifying the simulation of flexible pavements in ABAQUS, a model based on Artificial Neural Network (ANN) was presented to calculate EALF using the back-propagation architecture. Finally, from among the reviewed ANN configurations, the network with the 7-13-1 architecture incorporating the sigmoid function was selected as the optimum network.

The existence of problematic soils due to their geotechnical properties, such as low strength and stability, high compressibility, and swelling, is one of the most important issues and challenges that geotechnical and civil engineers are faced in urban environments, especially in metropolises. Various methods are used to stabilize and to improve the behavior of problematical soils such as compaction, consolidation, stone columns, jet grouting, biological procedures, and additive materials including nanomaterials. Because of their high specific surface, the use of nanoparticles is very effective to increase the shear and mechanical strength parameters of soil. Mashhad city is located on alluvial deposits of Mashhad Plain. A wide area of this city, especially the central and eastern areas where the Imam Reza holy shrine is located, has been built on weak and fine-grained deposits. Considering constructing high-rise buildings such as hotels and commercial complexes in these areas, as well as the need for restructuring the urban decay, the soil improvement will be inevitable. Given the significant application of these nanoparticles, the purpose of this study is to investigate the effects of nanoclay and nanosilica on each other and to find their optimal composition as a suitable alternative for traditional materials to improve the weak and problematic soils. This not only increases the bearing capacity and strength properties but also reduces the cost and time of project implementation.

To achieve a hybrid with maximum strength and bearing capacity in executable projects, laboratory tests were performed on the soil picked up from the vicinity around Razavi holy shrine in Mashhad mixed with nanoclay and nanosilica. The type of soil is classified as CL-ML based on sieve and hydrometer tests. The nanoclay used in this research is the type of montmorillonite- K10, and the nanosilica is as a powdered shape with 99% purity.At first, nanoclay and nanosilica were mixed independently with soil in six different weight ratios (0%, 0.1%, 0.5%, 1%, 2.5%, & 5%) and (0%, 0.1%, 0.25%, 0.5%, 0.75%, & 1%). Soil mechanical and strength properties, including compressive and shear strength, settlement, plasticity index, and swelling, were studied by standard laboratory tests on all specimens. After determining the optimum ratio of each nanoparticle, four hybrids consisting of nanosilica and nanoclay were made in four different combinations and then the effects of these four hybrids were investigated on the soil in the laboratory scale (Table 1). Table 1. Composition of hybrids made with different percentages of nanomaterials

The results of the Atterberg limit test on improved and pure soil indicate that the addition of nanoclay and nanosilica and the optimized ratios of these nanoparticles hybrid to increase the soil resistance parameters did not change the soil swelling index.Evaluation of shear strength test results showed a significant synergistic effect of these nanoparticles on increasing the shear strength parameters. The nanoparticles hybrid of 2.5% nanosilica and 1% nanosilica increased the cohesion up to 106% and also hybrids of 5% nanosilica and 1% nanosilica increased the internal friction angle of soil up to 32%. Examination of unconfined compressive strength tests presented a 134% increase in the compressive strength of the specimen improved with 2.5% nanoclay and a 620% increase in soil improved with 1% nanosilica. The optimum hybrid compositions of 5% nanoclay and 1% nanosilica increased significantly the compressive strength of the studied soil up to 785% and reduced the settlement of the soil by 60% compared to pure soil Laboratory studies of electron microscopy examination on ​​pure and improved soil samples with nanoparticle hybrid revealed the presence of these particles in pores of the improved soil. On the other hand, the high specific surface area of ​​the nanoparticles increased the interaction of the soil particles, and the effect of adding these nanoparticles on the refining process is observed in compressive strength increase. As the nanoclay, nanosilica, and hybrid of nanoparticles are the results of soil processing, these particles are very effective to solve the environmental problems because of good compatibility with soil environments. In addition, low volumes of nanoclay, nanosilica, and hybrid in these nanoparticles are necessary to increase the compressive strength and decrease the settlement of soil. Therefore, using these nanoparticles at the project site reduces significantly the cost and execution time of the project.

Today, the vulnerability of cities, especially the old and worn-out tissues to earthquakes, has become a global issue for experts in various fields. This situation has become more acute in countries with dangerous natural structures, including Iran, in recent decades. Exhausted urban tissues, as the main boiling point of a city, reflect the identity of that city, and are vulnerable to natural disasters, especially unstable earthquakes. This study was conducted with the aim of identifying and prioritizing the factors affecting the increase of earthquake risk in worn-out urban areas. The present study is applied in terms of purpose and in terms of analytical method based on multi-criteria approach. Library and field methods were used to gather information. The statistical population of the study consisted of experts and specialists in the field of urban planning, and the sample size was estimated at 30 people. In order to achieve the goals considered in this study, fuzzy Delphi technique and BMW model were used. The results of fuzzy Delphi technique confirmed the identified factors and subscales. The results of the BMW model indicated that among the identified factors, natural factors with a final score of 0.321 were in the first place, housing quality factor with a final score of 0.287 in the second place, distance from special uses with a final score of 255. 0.0 is in the third place and the demographic and economic factor with the final score of 0.137 is in the fourth place.

The study of earth dams behavior during the construction, completion and also the first impoundment as one of the most critical times during the life time of the dam because of the stress and water pure pressure in the core and also water level in this period has special importance. For this purpose, the behavior of the Chahchahe dam was studied by using of obtained results from monitoring recorded data and back analysis was done by GeoStudio finite element software. This dam is an earth dam with core clay and its maximum height is 47 meters from the natural bed of river. Chahchahe dam which has been constructed on Chahchahe river is located in the Kalat basin watershed, in 95 kilometers northeast of Mashhad. In order to consider the parameters in design process and simulate as real conditions of dam construction, back analysis was done base on the results of monitoring to can be predict the behavior of dam. In this study, the comparison of numerical model and monitoring results show acceptable and suitable accordance, so that the amount of settlement in the clay core was obtained 65 cm from monitoring result and evaluated 66 cm by numerical model. Also, the maximum stress at the 530 meter level in the core was read 820 kPa, which was calculated 950 kPa based on the numerical model at the same level, and in all of cases, the obtained values from numerical models are as confidence.

Considering the necessity of developing the road network, bridges as infrastructures, play a key role in helping and sustaining vital activities in the recovery phase after natural disasters and events. So, In Khorasan Razavi province, with regard to climatic conditions on the one hand, and the presence of corrosive agents in the soil profile of many areas, as well as seasonal rivers with high water salinity, on the other hand, many concrete structures of roads such as bridges, culverts and concrete foundations are subject to corrosion and degradation. Therefore, the present study aimed to prioritize the restoration and reconstruction of important concrete bridges in the main roads of Khorasan Razavi province. This prioritization provides the possibility of allocating the annual budget necessary for the maintenance and utilization of concrete bridges of the roads in this province. In this research, 52 concrete bridges with a length of more than 15 meters were studied under precision field observations after geotechnical studies, review of design procedure and as-built maps and after weighing the failure criteria according to the expert opinion, concrete bridges that requiring repair and Rehabilitation were prioritized using Analytical Hierarchy Process with Expert Choice software and finally 10 bridges with the highest priority were identified. Results show that the most important and influential criterion in prioritizing the restoration and reconstruction of concrete bridges is the general characteristics of the bridge site with a priority index of 0.115 and the least effective criterion in this field is creating green area which leads to deterioration of foundation materials near footing, with priority index of 0.014. Results of the sensitivity analysis based on performance for prioritization criteria of the bridges needed restoration and reconstruction showed that the bridge importance criterion has the most sensitivity in prioritizing the restoration and reconstruction of large concrete bridges.

Dams have an essential role in development of economic and water supply in Iran. In addition, due to annual decline in rainfall and hydropower production requirement, water resources management is one of the most important issues. It is worth noting the construction of dam, not only supply the required water of farmers, but also prevents the occurrence of floods devastating and incidence of drought in low rainfall season. After the destruction of the Teton Dam in 1976, which lead to deaths of several people and losses of several hundred million dollars, it was proposed to be placed instruments in body of dams to identify and warn behavior such as seepage or settlement. By studying the results of instrumentations and evaluate the changes of reading data during the time, it’s possible to identify the phenomena that lead to erosion or destruction of dam and prevent from happening of these events or minimize the potential damages (Beiranvand et al., 2013). Currently, numerical modeling and geotechnical software are used to analyzed and designing geotechnical structures which their results can be compared with information are recorded by instrumentations. Recent studies indicate this technique is one of the most suitable methods to estimate soil dams behaviors, as lots of numerical models provide an acceptable estimation of displacement and stress values in embankment dams.

People have paid attention to the use of supportive elements in retrofitting and soil improvement since a long time ego. Nowadays, the capability of reinforcement soil applications has been showed in different civil engineering projects. In order to increase of bearing soil capacity and reduce the settlement of structure, Geosynthetic Cellular System (GCS) has been invented. GCS consists of frame, geosynthetic fabric and soil. In this research, experimental and analytical behavior of small scale geosynthetic cellular systems has been analyzed. Our test case is a cylindrical specimen filled of sand from the beach of Khazar Sea. These cylinders are 10.5 cm in high and theirs base circle diameter are 10 cm in unreinforcement and reinforcement condition. Experimental studies were done with Teri axial test without back pressure and analytical studies were done with finite element soft ware (ABAQUS 6.7). Also in this research, the effect of vertical and horizontal reinforcement, the number of reinforcement, and their arrangement effect in the increase of bearing capacity, the decrease of settlement and lateral deformation of the instance have been presented. The experimental results and analytical studies are completely comparable and analytical results cover the experimental results. Also the results show that the reinforcement elements extremely cause to increase the bearing capacity and decrease settlement and lateral deformation. But, the horizontal reinforcement facilities in construct make it better than vertical reinforcement.

Evaluation of soil bearing capacity coefficients of has been the focus of a significant amount of studies by various researchers. In all conducted studies and analyses, by considering different forms of earthquake load with pseudo-static performance, different results have been obtained. In this research, evaluation of soil bearing capacity coefficients under earthquake load has been carried out using finite elements software Plaxis and the obtained results have been compared with those from other published studies. Moreover, the effect of the inertia of the underpinning soil on the soil bearing capacity coefficients was modeled in the pseudo- static mode and the results indicated that bearing capacity coefficients obtained from pseudo-static gave good agreement with other methods. However, comparison of these two results revealed that the results obtained from numerical modeling are more conservative and are on the safety side. Finally, since the pseudo –static load is not characterized as an appropriate alternative for the earthquake load; the effect of underpinning soil on the manner of transferring the earthquake waves until reaching the foundation bed has been also investigated.Evaluation of soil bearing capacity coefficients of has been the focus of a significant amount of studies by various researchers. In all conducted studies and analyses, by considering different forms of earthquake load with pseudo-static performance, different results have been obtained. In this research, evaluation of soil bearing capacity coefficients under earthquake load has been carried out using finite elements software Plaxis and the obtained results have been compared with those from other published studies.