JOURNAL OF TRANSPORTATION RESEARCH
Year:2015 | Volume:12 | Issue:2 (43)|Papers Count:8

Realizing influencing factors in reducing tunneling-induced settlement, especially in urban and industrial environment, is important to underground construction because excessive ground displacements could trigger potential damage to existing structures. In this research, the impacts of different NATM patterns on the magnitude of induced surface settlements due to excavation of shallow twin-tunnel (such as urban metro tunnels) are investigated. To this aim, finite element method using ABAQUS commercial application was implemented to simulate NATM excavation famous patterns including top heading (TH), central diaphragm wall (CDW) and side wall drift (SWD). The effects of further parameters like excavation lagging, pillar width (horizontal distance between the tunnels) and various loading patterns on the lining stability and surface settlements were also investigated. Comparison of the results show that in the same conditions of loading and using SWD pattern, the deformations is decreased and the threshold of load-bearing can be increased up to two times. On the other hand, the response of ground-tunnel system and the interaction between tunnels are significantly affected by the status and amount of surcharge. In addition, the finite element analysis confirmed that the reduction of the pillar width tends to increase the ground settlements and cause more subsurface deformations due to increasing the tunnels interaction, regardless of surcharge condition. It is demonstrated that although the increase of excavation lagging does not have considerable influence on the surface settlements, it decreases the lining stability. Generally, it can be concluded that by using SWD pattern with zero step lag of excavation and when the pillar width is higher than three times the radii of the tunnel, the unfavorable impacts resulting from the construction of shallow twin tunnel in soft ground would be limited. Accuracy in the prediction of such tunnels behavior is strictly a function of the proper modeling of surface loading conditions.

Environmental pollution caused by noise is one of the most adverse consequences of railways operation. In spite of the vast amount of studies on railway noise, little attention has been paid to the effect of rail corrugation on rolling noise. Corrugation on the wheel tread and the railhead causes vibrations within the vehicle and the track, causing different ranges of noise. There is a need for a thorough investigation into rail corrugation effect on rolling noise. In response to this need, present research concentrates on rolling noise and investigates rail corrugation effects on rolling noise. For this purpose, a thorough field investigation into the noise and corrugation measurements was carried out in this research. Measurements of the noises generated in the track by the passage of railway vehicles in a tangent track and a curve with small radius, were recorded by field tests. Rail corrugation measurement was performed in an indirect method by EM50 track recording car. Results obtained from the field tests were analyzed leading to new findings in rail corrugation effect on rolling noise. The effects of rail corrugation types on rolling noise were indicated. According to the research findings, the formation and occurrence of rail corrugation in curves is much more than that in tangent tracks. Rolling noise is so sensitive to the short-pitch rail corrugation in the tangent track. Moreover, it was noticed that the short-pitch rail corrugation in the tangent track is the most controlling factor because of having higher rate of rolling noise in the test site which leads to dissatisfaction of train passengers and residents of nearby residential areas. However, the lowest effect of rolling contact fatigue corrugation on rolling noise was observed for the curve.

In recent years, the economy and sustainability are considered together in construction projects. One measure that can be done in this regard is partial or full replacement of construction materials by recycled waste materials. A large volume of waste materials are produced annually from construction and demolition of civil projects. On the other hand, the construction projects consume a large amount of natural resources. Replacing the virgin materials by recycled materials, while the properties is maintained or improved, is an eco-sustainable measure. In this research, the viability of using two types of recycled construction and demolition waste materials, namely glass and brick, as powder in asphalt concrete has been evaluated. The natural filler, as control, has been replaced in different percentages (25, 50, 75 and 100%), with the recycled materials, and the mixtures have been evaluated in terms of, marshal stability, flow, indirect tensile strength, moisture damage and volumetric characteristics. The results show that, the marshal stability increases, and the flow decreases by replacing the natural filler with brick powder. However, except for 100% of replacement, replacing the natural filler with glass powder, results in a higher Marshal quotient, indicating a better strength against deformation. Also, the results show that, at both25 and 40oC, the indirect tensile strength of asphalt concrete increases with increasing the replacement by brick powder. However, although the indirect tensile strength is improved at 25oC, by 25% of replacing the natural filler with the glass powder; however, at 40oC, the indirect tensile strength decreases with increasing the replacement with glass powder. The tensile strength ratio, which is an indicator for moisture damage, is increased with increasing the brick powder content, and increased until 50% of replacement with glass powder, beyond which starts to decrease. It is also found that, the brick powder does not influence the air voids in mixture, and the voids in mineral aggregates. However, the air voids content increases, and the voids in mineral aggregates decreases with increasing glass powder content.

Soil slopes are structures that apply in many cases such as roads, rail ways and many others. these structures need to be reinforced in the case of low-resistance ground, loading on a slope or geometric properties such as very steep or high slope.one of the methods for analyzing the behavior and providing appropriate model for designing the slopes is the Schmertmann method. In this method, the influence of reinforcement in the vicinity of sliding surface is considered so that the vertical component of reinforcement force increase the vertical forces on the slip surface, thus increasing the shear strength. but pulling out the reinforcement during mass movement and interaction between soil and geotextile and the vertical component of resultant shear stress between them can decrease the resistance forces perpendicular to the slip surface and so the safety factor of the slope.in order to verify the accuracy of the problem, this study is performed using ABAQUS software based on the finite element method. seen as a result that interaction between soil and geotextile has little effect on reducing the resisting force and the factor of safety of slope.

The rapid growth of traffic, especially heavy vehicles passing by repeated loading, poor quality asphalt mix and not reaching different the required density of asphalt pavement can cause asphalt damage. One of the most important types of flexible pavement failures, is permanent deformation, which are known by the name rutting. Rutting is done by aggregation of Permanent deformation and irreversible through the pavement layers under traffic loading repeated. Through the all different layers involved in rutting, permanent deformation in the surface layer of pavement is allocated to the main contribution of rutting, thus Provide an appropriate mix design, attention to the potential risk of permanent deformation asphalt mixtures that weakness indication shear resistance in the asphalt is essential to be considered. On the other hand the specified flow number is beginning marker for Shear deformation in asphalt mixtures is known as a marker for evaluation of asphalt mixtures rutting. In this study, we have tried to build the asphalt samples with Marshall method, that including range of the aggregates, asphalt, aggregate, filer and bitumen percentage with the development of a relationship between obtained flow number from the dynamic creep test, tensile strength from indirect tensile test and the parameters of the Marshall mix design while providency administrative costs, predicted the mixture rutting status, without spending extra time. The accuracy of this model was confirmed by the artificial neural network, makes it possible to prevented produce concrete with low shear resistance in the laboratory and before factory manufacture. Thus, considerable savings in future time and costs there would be in mix design.

The cracks resulted from fatigue are one of the main types of failures in flexible pavements. The bitumen aging is one of the major factors of creating fatigue cracks. The bitumen used in asphalt mixture is exposed to hardening and aging during making the mixture as well as on the pavement. The aging mainly occurs due to bitumen oxidation with the oxygen existing in the air. This process in high temperature such as the mixing temperature of asphalt occurs more quickly when the bitumen covers the surface of aggregates with a thin film. The mixture of bitumen with aggregates in mixing temperature of asphalts can be considered as a stage in which the most sever oxidation and hardening of bitumen during production and making asphalt occurs. Therefore, the mixing temperature of aggregates and bitumen in asphalt factory is one of the most important factors of aging and the resulted fatigue of asphalt mixture. This is the reason why warm mix asphalts were used for reducing the mixing and compacting temperature. The objective of the present research paper is studying the influence of reducing mixing temperature on fatigue life of the asphalt mixture. In this study, the asphalt mixture has been made in three temperatures of 100, 120 and 145oC in order to study the influence of mixing temperature. Sasobit and Asphamin have been used for reducing the mixing temperature. The results of testing show that the fatigue life of warm mix asphalt is higher than hot mix asphalt. The samples produced in 120oC have a higher fatigue life without any consideration to the type of additives and the samples containing Sasobit have a fatigue life higher than the samples with Asphamin.

Motorcycle accidents have a high proportion of the total traffic accidents. On the base of available statistics, motorcycle accidents in the Bushehr Province are high. Because of many negative consequences that these accidents cause for motorcyclists and generally for society, it is important to identify the factors affecting such an accidents and provide some guidelines in order to removing or reducing those factors. In this study, the effective factors on motorcycle accidents and its consequences in the roads of Bushehr province are evaluated for three years (2009-2011). For this, we have analyzed a sample of 140 motorcycle accidents in these three years. In order to analyzing the data, first we have described the effective factors causing such an accidents (road and climate related factors, vehicle related factors, human related factors and complete reasons) by use of descriptive statistical tools such as graphs and tables, and then, we have presented the model of the most effective factors regarding each group. In the next section, we have tested the research hypothesizes by using of binominal test. All computations have done in the spss18 software. The research hypotheses are about the effect of the most important factors related to road and climate, vehicle, human and complete reasons groups. In addition, we test three hypothesizes about the percentages obtained from the samples of three groups (road and climate related factors, vehicle related factors and human related factors) in order to generalize them to Statistical population. In general, 22 hypothesizes are considered in this study for all of which the binominal test has been used. The results showed that in the selected level of significant, all hypothesizes were confirmed.