مجله مهندسی زیر ساخت های حمل و نقل
سال هفتم شماره 3 (پیاپی 27، پاییز 1400)

Stone matrix asphalt (SMA) is a gap-graded mixture that contains high percentages of coarse aggregates, bitumen, and filler. In the SMA mixture, due to the high amount of bitumen and the necessity to prevent it from draining down during asphalt transportation, bitumen adsorbent material is needed, which also has a stabilizing role. In this research, date palm fibers, cigarette butts, and Topcel (common cellulose fibers) were used. To reduce costs and protect the environment, reclaimed asphalt pavement (RAP) was used to produce SMA mixtures. This study aimed to investigate the effect of date palm fibers as natural waste fibers and cigarette butts as environmental pollutants and different percentages (w/w) of RAP in the SMA mixture. For this purpose, the draindown characteristics, moisture sensitivity, and rutting of SMA mixtures prepared with these materials were investigated using draindown basket, indirect tensile strength, and Hamburg wheel track tests. Results showed that in the draindown test, asphalt mixtures containing cigarette butts showed better performance than mixtures containing the other two fibers. Results of indirect tensile and rutting tests showed that by increasing the percentage of RAP, the indirect tensile strength increased and the rut depth decreased. Moisture sensitivity of samples containing 15% RAP and palm fiber was lower than the other mixtures. Although samples containing Topcel fibers performed better in rutting, the performance of samples containing date palm and cigarette butts fibers was also acceptable. Results showed that the date palm and cigarette butts with the application of RAP materials could contribute to the performance properties of SMA mixtures. These fibers can be suitable replacements for expensive fibers such as Topcel, and in addition to using RAP in the mix, they can provide a resistant and durable mixture.

The use of industrial waste, such as steel slag, in the road construction industry, to reduce the use of stone materials and also the environmental benefits of reusing these materials is very important. Research on the use of steel slag as an alternative to stone materials in asphalt pavements has been carried out for many years due to the improvement of some of the main properties of these mixtures. In these researches, slag in general (including fine-grained and coarse-grained with the same percentage) or coarse-grained has replaced the stone materials. However, since some properties of asphalt mixtures show different effects by changing the fine-grained materials or a different combination of fine-grained and coarse-grained to the simultaneous and equal replacement of fine-grained and coarse-grained, in this research, optimum percentage of using slag materials in fine-grained and coarse-grained size has been investigated using the response surface method. In this regard, different mixing schemes of this substitution have been investigated using modulus of resistance, Marshall resistance, indirect tension and moisture sensitivity tests. Results of the performed experiments and their analysis has determined the type of fine-grained and coarse-grained behavior in asphalt mixtures, and finally, for each experiment, the proposed model has been determined based on the research conditions.

In this study, for comparison of the results of dynamic shear rheometer (DSR) and multiple stress creep and recovery (MSCR) tests, based on rutting performance of asphalt binders modified with mesoporous silica, four different asphalt binders were produced using a mixture of 2%, 4%, 6% and 8% (w/w) of this additive and neat bitumen. After a 20-minute vibration, the produced mixtures were mechanically mixed for 30 minutes, in a high-shear homogenizer mixer. Then, the modified binders and neat bitumen were subjected to DSR and MSCR tests, after the aging process in RTFO test. The comparison between outputs indicated that the results of DSR and MSCR tests have been consistent, as the variation trends of R and G*⁄sin δ have been the same at different temperature levels. On the other hand, the variation trend of Jnr has been the opposite, and in both tests, maximum value of R and G*⁄sin δ and minimum value of Jnr have occurred in the 4% bitumen modifier. This suggests that the greatest potential resistance to rutting has been observed in the binder containing 4% (w/w) mesoporous silica. Furthermore, at both DSR and MSCR tests, asphalt binders at high temperatures revealed a more viscous behavior like Newtonian fluids. The difference between the results of the two experiments was that in the MSCR test, the highest resistance to increasing the stress level was assigned to the binder containing 6% mesoporous silica.

In the last few years, several studies have focused their attention on production methods of bitumen emulsion to enhance the cold asphalt properties. Accodrdinly, because of improving some characteristics like temperature susceptibility, ductility and rutting resistance, polymer- modified bitumen emulsion (PMBE) is more sutiable for cold asphalt mixure. Generally, the formulation of PMBE depends on addition methods of the latex. In this study, PMBE is produced based on two types of emulsifier and various manufacturing techniques including soap pre-batching, co-milling, and post-blending. Results showed that soap pre-batching method of type 2 emulsifier and co-milling method of type 1 emulsifier had best performance in physical properties including Saybolt-Furol Viscosity (SFV), softening point and penetration and also rheological properties containing complex modulus (G*), phase angle (δ), rutting parameter (G*/sin δ) and surface performance grade (SPG). Thus, type of emulsifier has an important role in selection of PMBE manufacturing method. So, the design procedure to optimize manufacturing of PMBE is different for each type of emulsifier.

Nowadays, maintenance and health monitoring of structures and infrastructures of the country are the top priority of engineers. Therefore, acceleration sensors, which are installed on the bridge are used to extract the bridge's modal response, and even the latest studies have shown that sensors that have been attached to the car's chassis can record the bridge's response to vibration. Thus, it is important to use an accurate method, which is based on the output-only, to measure frequency, damping ratio, and mode shape. As a result, practical modal analysis is used for that purpose. In this paper, a new method of blind source separation, called complexity pursuit (CP), is investigated which is able to measure and extract dynamic characteristics in the time domain. Complexity pursuit is a well-known method, that is able to recover hidden sources (independent responses of every degree of freedom) and it can calculate the mixing matrix from measured mixed output data only. Some various conditions are considered in this paper to verify complexity pursuit (3 degrees of freedom mass-spring with various damping ratios, in white Gaussian noise conditions, in non-diagonal damping matrix, close modes, and for 12 degrees of freedom mass-spring system). Comparison of the CP results and modal analysis under all the conditions showed that the proposed method is able to detect, measure and extract the modal characteristics with an error of less than 3% and in most cases less than 1%.

Remote sensing has wide applications in many scientific and research fields, including road engineering and transportation, the most important of which is extraction of road network and preparation of a schematic map of road network. Extraction of road network from satellite images is a complementary technology for accessing information, which simplifies the interpretation and analysis of image and improves the quality, which is one of the most important goals of planners. The main purpose of this study was to automatically extract road network on Shahroud-Miami route so that the resulting road network map can be used as the input of pavement management system (PMS). The proposed method in this study is based on the technique of merging and combining images of Sentinel-1 and Sentinel-2 satellites with the majority voting method in order to make maximum use of spectral and spatial information of multiple images (detail increase) instead of single image using texture features. Then, for the monitored classification, three classifications of artificial neural network (ANN), support vector machine (SVM) and maximum likelihood of similarity (ML) were used in two general classes of road and non-road. Random and homogeneous experimental samples and evaluation samples from the existing images and maps of the region were used to assess the accuracy of classification. Results of this study showed that integration of the results of classifications with the majority voting method improved the accuracy by 4% for Sentinel-1 satellite and 6% for Sentinel-2 satellite in identifying the route and the road network. Also, the kappa coefficient in the majority voting method has increased by about 0.11 for Sentinel-1 satellite and by about 0.06, compared to ANN (the best effective classification performance).

Horizontal alignments are one of the most important parts of road infrastructure. Safety and driving comfort in these areas has always been the focus of researchers. Due to the geometric nature and especially the change in the curvature of the road and the existence of superelevation, horizontal alignments are more prone to accidents than other parts of the highways. Superelevation attaining based on current methods has linear form. Spiral transition curves as one of the most practical options for connecting between a circular alignment and a straight path, in the absence of a circular part (due to geometric constraints or designer's initial choice) can be considered as a spiral-spiral combination. In this case, linear increase in path edge elevation from start to top (connection point of the two spirals) and then a sudden linear descent to the end of the second spiral can cause problems for safety and comfort of the vehicle passengers. In this study, in order to solve this problem, the use of nonlinear superelevation attaining at the junction of the two spiral alignments has been investigated. For this purpose, the quarter car suspension model was used to study the vertical acceleration. According to the research results, by applying linear superelevation attaining in the spiral-spiral alignments, at the starting point of the spiral or at the junction of the two spirals, vertical acceleration above the ride comfort threshold (0.8 m/s2), based on vehicle speed, will be very probable (even three times the mentioned limit). On the other hand, by using non-linear methods as combined parabolic and cubic equations, the mentioned vertical acceleration will be reduced to less than 0.8 m/s2. As an example, for design speed of 100 km/hr, and using linear method, the vertical acceleration will be 2.5 m/s2, while with nonlinear method it reduces to 0.8 m/s2.