فصلنامه جاده
سال نوزدهم شماره 3 (پیاپی 69، زمستان 1390)

Skid resistance is a very important parameter of road surfaces, and many research studies have shown it has a considerable bearing on the incidence of accidents in Iran. The rationale for this research study is that improvement of skid resistance and reduction of accidents will have a positive social and financial outcome for the country. There are a number of existing methods for restoring the skid resistance of a pavement surface as an alternative to resurfacing; most of which focus on removing excess binder from the surface. Only one of these methods is capable of restoring both the microtexture and the macrotexture of the polished surface. Preliminary investigations of both laboratory samples and field trial sections have determined that ultra-high pressure water cutting can restore the microtexture of polished aggregate to a level close to that of freshly crushed aggregate. The monitoring of the treatments in this paper includes skid resistance, texture depth, performance and safety. This paper discusses the technical and environmental aspects of the treatments that make them sustainable and the implications for the road authorities and contractors. The future of sustainable treatments for roads in Iran is also discussed.

Rock slopes may be natural or human-made structure; with the latter taking the form of civil engineering projects such as embankments, road cuts and landfill sites. In areas where human-made rock slopes are used, safety is clearly of paramount importance, as catastrophic failure of such a structure could have serious implications for human health, the success of the project and financial considerations. In rock slopes with one set of discontinuities, if the inclination of the slope is more than the dip of the discontinuities, the entire rock mass may be subject to catastrophic bending and buckling failures. Although the geometric conditions of the failures are the same; there may be different prevailing mechanisms. The aim of this research study is to mitigate against such failures by way of numerical analysis. In this research study, rock slopes have been assessed against the buckling failure criteria in both static and dynamic conditions. The second phase was to analyze the bending failures using differential equations of beam-column deflection. To process the results, the stability of rock slopes with one set of discontinuities was checked against the simultaneous failures, and then the critical mode of failure was determined for each.

In this paper, a method has been developed from a combination of quality and quantity trends for classification of cities in order apply to the establishment of an airport. In this method, firstly a Data Envelopment Analysis-Like (DEA-like) model is solved for each output from the options, without consideration of other outputs. After calculation of the efficiency percentage for each output by means of the obtained results, a pair-wise comparisons matrix is produced, and full ranking is performed by applying the one surface hierarchical process. The pair-wise comparisons matrix is completed based on solving the Envelopment Analysis-Like (DEA-like) model for each option by considering an output. This method is based on quantity, but the final ranking is performed by means of quality trends. This combinational method has some benefits. Firstly, it removes inconsistencies obtained from applying subjective judgment in the pair-wise comparisons matrix and hierarchical process. Another important benefit is that it removes the limitation of agencies against inputs and outputs. When considering the Data Envelopment Analysis-Like (DEA-like) model, if the number of agencies against inputs and outputs are low, then many of agencies will have an efficiency grade equal to one, which causes difficulty in their ranking. By designing and applying the Data Envelopment Analysis-Like (DEA-like) model, and considering its combination with hierarchical analysis, this problem will be removed completely. Finally, a numerical example has been presented with real data, in order to describe the method and intuitional unstinting from the designed problem.

The Marshall Compaction Method has been used to prepare asphalt mixture samples in laboratories for many years, despite its technical disadvantages. It has since been replaced by the Gyratory Compacting Machine, which came about when the SuperPave mix design method was introduced. Shaft reaction to a specimen with a vertical pressure equal to 600 kPa under a determined angle-applied load is determined, and the specimen is compacted by vertical pressure and mould shear pressure simultaneously. One of the benefits of this new method is that the specimen height is measurable during the compaction procedure in this machine. Since the weight and height are known in the compaction procedure, the specimen density and air void fractions can be determined during the test. During this research study, equilibrium equations were used, and the specimen forces were presented to determine the shear stress in the Gyratory Compacting Machine. The results showed that there is a direct relationship between the shear stress and the mixture rutting resistance. Therefore, by determining the specimen shear stress during mixture preparation, the rutting potential can be measured simultaneously.These results offer the potential for cost and time saving in laboratory experiments, and allow an insight and extra degree of confidence in the experimental methods.

It is clear that road accidents have a significant impact on the social and financial health of a country. Prior research has shown there are many affecting parameters on road accidents, but little focus on which are the most important when pedestrians are involved. Pedestrian accidents, including both fatalities and injuries, have accounted for a major proportion of driving accidents in recent years. In Iran, more than 30 percent of accidents are pedestrian related, and in addition, 23 percent of road fatalities are involving pedestrians. In this research study, an attempt has been made to analyze the available pedestrian accident data and identify the major factors affecting those accidents. Based on the preliminary investigations, it has been found that several parameters, such as driver sobriety, color of the pedestrian clothes, geometric characteristics, vehicle speeds, hours of driving, vehicle dimensions, and the level of the drivers’ education, are the most important affecting factors in pedestrian accidents. Based on this data and findings, some recommendations have been presented in this paper in order to improve the safety of pedestrians and reduce the incidence of pedestrian accidents. It is hoped this data will be used to inform road safety and improve and reduce fatalities and injuries in pedestrians in Iran.

Aggregates constitute the largest proportion of material in pavement projects, which includes concrete pavements or asphalt pavements (about 70 to 80 % by weight of concrete, and 90 to 95% by weight of asphalt mixes).Therefore, the quality of aggregates in the mixes is crucial for forming the behavior and the performance of pavement, and studies have shown it has the most influence on pavement properties. In addition, at present the most important issue for a pavement is its durability. Pavement durability is affected by various factors, such as type of aggregate, mix design method, environmental conditions and its implementation techniques. The use of aggregates of suitable quality and high durability can reduce most of the common pavement failures. Therefore, the durability and quality of aggregate materials should be tested before they are used in pavements. This paper reviews and investigates a variety of available experimental methods for determining the durability of aggregates. It also specifies the advantages and disadvantages of each of these methods. Finally, the most appropriate method is presented with regards to the limitations and availability of laboratory equipment in Iran.

With regards to the various uses of piles in road construction, recognition of their behaviour and properties of the soil around them is an important issue. One of the possible uses of piles is as the foundations of a bridge pier. In most bridges, for which their pier is in the river or exposed to the path of the water, piles are used to increase the pier strength. Therefore, this research intended to determine an appropriate method to control the behaviour of piles in specific conditions, and to cost-effectively improve and optimise the piles’ behaviour. This method is called Electro-Osmosis, which has many applications in pile engineering and in the analysis of the soil around them. This author can determine the name bearing capacity and negative skin friction in piles from the external conditions, which are the prevalent phenomena in bridge pier piers. In this article, two experiments are described separately. In the first phase, a model of the experimental pile takes the role of the anode in the Electro-Osmosis method, with some cathodes set around it. After treatment by the Electro-Osmosis method, the bearing capacity increases considerably. In the second step, the model of the experimental pile has the role of the cathode, and the surrounding experimental apparatus has the role of the anode in Electro-Osmosis. In this research study, by exerting consolidation phenomena, the negative friction force or down drag force that occurs in the pile has been reduced by the Electro-Osmosis method.