مجله مهندسی زیر ساخت های حمل و نقل
سال هفتم شماره 2 (پیاپی 26، تابستان 1400)

One of the main factors that cause distresses and cracks in asphalt pavement is ageing and it makes pavements deteriote over time. Previous studies about this phenomenon have shown that the use of "bioasphalt" has a positive effect on the ageing and it can act as an antioxidant and rejuvenating material. In this study, the possibility of using lignin and waste engine oil in bitumen to improve the chemical and ageing properties of bitumen was investigated. The lignin used in the study was extracted from black liquor. Waste engine oil was taken from a car repair shop. The samples are PG64-22 as control sample, samples containing 5 and 10% lignin, samples containing 4% waste engine oil, and samples containing both additives. FTIR analysis, ICP analysis, CHNS analysis and SEM analysis were performed on the samples to better investigate the effect of additives on aging. Also, three important aging indices were calculated using RV, DSR and FTIR tests. The results showed that the addition of lignin or WEO or a combination of both, can improve the chemical properties of bitumen. Also using waste materials in bitumen can be useful from an environmental and economic point of view. They are also effective for aging resistance and can be used as a rejuvenator.

Due to the problems and high cost of real-scale experimental studies and on the other hand, the ability of small-scale models in geotechnical centrifuges to establish physical similarity and take into account the real stresses in the model for a correct understanding of deformations and rupture mechanisms, major experimental studies on the phenomenon of surface faulting has been done using by geotechnical centrifuge. In this research, the concept of physical modeling with a geotechnical centrifuge, scale rules, constraints, and sources of error in simulating the interaction of dip‐slip fault with underground tunnels and shallow foundations are investigated. Finally, by minimizing modeling errors, the interaction of reverse fault with underground tunnels, as critical transport infrastructure, and the shallow foundation is simulated. The results showed that in reverse fault propagation in sandy soil when the rupture reaches the surface, its dip angle decreases, and at the ground surface, shear ruptures and tension cracks are created which can damage structures and infrastructures. The presence of the tunnel in the rupture path causes the fault rupture path to change and the fault rupture zone to increase at the ground surface, which can affect the performance of surface structures and buried structures adjacent to the tunnel. In the propagation of reverse fault rupture, the presence of the surface structure on fault outcrop, overburden pressure due to the structure, causes the rupture path to deviate to the right corner of the foundation and the structure to rotate. Besides, on the right side of the foundation, a fault scarp was observed, which was consistent with field observations in previous earthquakes with surface fault rupture.

Concrete is one of the most used materials in the world. Cracking in concrete is a common problem that occurs due to its relatively low tensile strength. The cracks created in concrete are the main reason for the reduced durability and useful life of concrete structures. Proper and timely repair of primary cracking is necessary in order to prevent its expansion in concrete and reduce the high cost of maintenance. For this purpose, self-healing methods have been developed. Adding microorganisms to concrete mixing and bio-concrete production is an intelligent and environmentally friendly strategy for the repair of concrete cracks. Bacterial species resistant to hard and rough concrete environment such as bacillus, with the production of calcium carbonate precipitation, can be repaired in a continuous hydration process by filling freshly formed fine cracks. The aim of this study was to identify the effective bacterial species and its effect on the strength properties of concrete as a restorative agent.The results show that the changes in the strength properties of bio-concrete by adding Bacillus subtelius at a concentration of 〖10〗^8 (Cells⁄ml), increase the compressive strength by 24.24% and also improve the durability of concrete by bacterial self-healing process.

Evaluating the safety of the railway network as the fundamental part of the economy development reflects the safety of the entire transportation network of a country. One of the challenges threatening the railway safety is the railway tunnel conditions in terms of safe operating during operation period and analyzing the consequences of its hazards. Today, Bayesian network are the most identified methods to graphically model the causes of accidents and their conditional probabilities. In order to develop a model that best matches the real condition of the railway tunnels risks, modeling process divided in to two sections; in the first section, the compromised causes that identified and concluded by the specialists scored according to their frequency of happening and the related network constructed. Second section joints the cause and consequence analysis of different scenarios offering remedial actions and concluding the final model based on severity degrees defined. Outcome of the model shows the high probability for water penetration in tunnels without permanent lining as the most important cause and the first degree of the accident severity according to the guideline as the most frequent consequence of the risks identified.

The growth of vehicle traffic in recent years in developing countries has led to an increase in the costs of road building and maintenance. Therefore, modification of bitumen properties is necessary due to the poor quality of bitumen. In this lab study, the relative performances of Gilsonite and FORTA fibers modifiers are evaluated. The bitumen tests conducted for this research are based on the addition of Gilsonite (0, 3, 6, 9, 12 and 15 % of made bitumen specimens), while the asphalt mixture tests are based on the addition of FORTA fibers (0, 0.3, 0.6, and 0.9% by weight of aggregate). The synergistic effect of adding both the additives as a composite additive on the relative performance of asphalt mixtures is also evaluated. The samples were tested for Marshall Stability and moisture sensitivity, while fatigue and dynamic creep tests were performed using the UTM machine. The results showed that only the use of Gilsonite as a modifier in bitumen significantly increases the Marshall Stability, fatigue resistance, the flow value resulted from dynamic creep tests and decrese moisture sensitivity of the asphalt mixtures compared to the use of FORTA fibers as a modifier in the mixture.

The safe movement of the rail rolling stock is not possible without train control systems. Train control systems ensure safety somehow and they play a vital role in increasing the speed and the capacity of the transport; So that, the failure of the whole or part of it can cause safety disruption, reduce productivity and increase line blockage. Due to the fact that all train control telecommunication services are based on optical transmission networks, the interruption of these networks will cause the interruption of all train control services and as a result, the line will be blocked. Therefore, evaluating and improving the sustainability of the optical transmission infrastructure is essential. In this research, in order to predict the number of the blockages due to the disruption of the transmission infrastructure, the rail transmission network is evaluated in two stages. In the first stage, the parameters of Availability, Reliability and Maintenance (RAM) of the railway transmission network are evaluated, and are simulated using the Monte Carlo method. In the second phase, the RAM mechanism is simulated again by implementing a network failure repair reduction model. In both stages, the probability of the shutdown of the railway telecommunication network, the numbers of blocked lines have been obtained. Predicting the number of network outages and rail line blockages due to the interruption of train control services has been conducted for the first time in research. The results of this study showed that a 10% reduction in network repair time led to a three-and-a-half-fold increase in RAM levels and a 70% reduction in line blockage. These results will be of great value in increasing system efficiency as well as the satisfaction of the users.

In order to mitigate the environmental impact of iron ore tailing (IOT) and also to reduce the use of natural aggregates, these materials can be used as road materials after stabilization with chemical additives. In this research, the feasibility of using Golgohar IOT, stabilized with 4, 6 and 8% of Portland cement as road base materials, has been investigated. To this end, modified Proctor compaction test, unconfined compressive strength (UCS) test and durability against freezing and thawing (F-T) cycles test were conducted on IOT samples stabilized with different percentages of Portland cement. Results of compaction testing on the samples showed that increasing the percentage of cement increases the optimum moisture content (OMC) and decreases the maximum dry density (MDD). In the next stage, IOT were stabilized using 4, 6 and 8% of Portland cement and UCS samples were fabricated with three different compaction moistures (dry side, optimum moisture content and wet side) and cured for 7, 28 and 56 days. The results showed that with increasing the percentage of cement from 4 to 8% for all curing times, the UCS increased between 1.45 to 2.15 times. Also, the 28-day UCS and 56-day UCS are about 1.73 times and 2.34 times the 7-day UCS, respectively. It was also found that the UCS increases with decreasing moisture content. The results of durability tests against (F-T) cycles on the samples showed that with increasing the percentage of cement, the durability of stabilized materials increases, so that in samples with higher percentage of cement, the lowest percentage of weight loss and volume reduction is observed. Finally, it was found that IOT stabilized with at least 4% of Portland cement provides the necessary strength and durability criteria for use as stabilized base layer.