The aging of asphalt pavements leads to less flexible asphalt mixtures that are prone to cracking and spalling. In this study, the relationship between lab and field aging was evaluated based on both theoretical asphalt aging models and practical asphalt and asphalt mixture performance tests. The results show that the corresponding field aging duration calculated using the mixture testing, especially the cracking test, is more conservative than the traditional aging models or binder rheological measurements. 5 and 12 days appear to simulate 16 and 38 years of field aging (in New Hampshire) for the top 12.5 mm pavement, respectively, based on the asphalt binder test results. In contrast, the theoretical aging model considers climatic conditions and suggests that 5 and 12 days simulate in-field aging of 6.2 and 15.0 years, respectively. The asphalt mixture test results indicate that the laboratory aging conditions simulate minimal field aging durations. This is because the damage to the asphalt pavement structure caused by climatic conditions and traffic loads is fully considered. This could be very useful for designing a more reliable and durable pavement incorporating intricate field conditions.

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To address the safety management issues of oil depots in case of earthquakes, firstly, seismic resilience is defined as the ability of oil depots to maintain their storage functions in terms of resisting earthquake damage, mitigating secondary disasters, adapting to environments after earthquakes, and quickly recovering after earthquakes. Moreover, an assessment model for the seismic resilience of Oil depot is proposed by quantifying the four types of abilities. Secondly, a quantitative assessment of the seismic resilience of the oil depot is realized through a dynamic Monte Carlo method, considering the uncertainty of the resistance and mitigation stages, thereby obtaining the seismic resilience value. Finally, the performance of the proposed model is validated against the oil depot in an earthquake area. The results indicate that the uncertainty of the resilience ability of the oil depot results in a significant fluctuation in resilience values, and the domino effect has a significant influence on the oil depot's resilience and cannot be ignored. Moreover, the farther the earthquake source distance and the lower the fault slip rate lead to higher seismic resilience. The seismic resilience can be improved by staying away from active faults, predicting earthquake hazards, and reducing emergency response time.@en

Drinking water biosafety has become an increasing concern for public health. Chlorination is widely used as the main disinfection strategy worldwide but has clear and well-known byproduct issues. The Netherlands has successfully demonstrated unchlorinated approach for almost 20 years but has not been widely adopted by other countries. To chlorine or not chlorine is becoming a critical question in front of all the water utilities. This review aims to provide a good overview of current biosafety management strategies, their disadvantages, as well as the latest developments and future trends. Firstly, the advantages and deficiencies of conventional disinfection and non-disinfection were discussed. Secondly, the commonly used and promising methods for biostability assessment are described. Finally, critical views on the strategy selection for ensuring drinking water biosafety were discussed. It is recommended to achieve both biological and chemical balance by removing pathogens while minimizing the organic matter and dosing a minimum level of disinfectants, which would represent the compromise choice between the current chlorine-based disinfection and chlorine-free strategy. It's worth noting that the complexity of ensuring biosafety lies in the variations among different regions, the selection of suitable methods should be tailored to specific situations on a case-by-case basis.

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Retrogressive failures occur in slopes consisting of sensitive materials such as snow or quick clay. They can be triggered by a small disturbance at the slope toe, but can cause propagated failure spreading miles away. Understanding the physical mechanism and predicting the retrogressive failure process are particularly important. Previous studies have discussed the failure criteria, the soil properties or the method of numerical modeling of retrogressive slope failure. However, little attention has been paid to the microscopic failure mechanism, especially relating to various possible failure patterns. In this study, multiscale modeling is incorporated to study the physical mechanism of different retrogressive failure patterns, including earth flow, flowslide and spread failure, within a unified framework. Utilizing multiscale analysis, we found that earth flow failure is related to the shear failure of granular materials. In contrast, the development of macroscopic shear bands is accompanied by tensile failure. As shear and tension failures are typical failure mechanisms of frictional and cohesive materials, it is deduced that friction and cohesion effects play key roles in different retrogressive failure patterns. Therefore, the distributions of attractive and repulsive contact forces are explored and a novel parameter η is proposed to quantify the interplay between friction and cohesion. Further analysis proves that η can capture the effect of friction and cohesion and distinguish different retrogressive failure patterns. Finally, a spectrum of retrogressive failures for a granular slope is established, in which the failure mechanism is explained by the changeable dominant effect, that is, frictional or cohesive in soil.

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Aiming at modelling the mechanical behaviour of soil-rock mixtures accurately and efficiently, a coupled MPM-DEM formulation combining the material point method (MPM) and the discrete element method (DEM) is proposed. It is solved concurrently via the contact force linking the two individual methods. Specifically, the soil is modelled with MPM as continuums to avoid handling the contacts between fine particles. The rocks are modelled by DEM to capture the contact characteristics of rocks. This method is validated with ball impacting and block sliding tests first for the contact between material points and DEM particles. Its capability in describing the mechanics of soil-rock mixtures is thereafter proved by comparing the simulation results with pure DEM simulations of binary mixtures and laboratory tests of soil-rock mixtures. It is demonstrated that MPM-DEM can reproduce the stress–strain response of soil-rock mixtures and capture the influence of rock contents and rock sizes. In addition, a coarse-graining modelling scheme is implemented, i.e., representing the soil particles with fewer material points, which significantly increases the efficiency compared with pure DEM. Our proposed method provides a novel way to model soil-rock mixtures with reasonable computational efforts, which sheds light on simulating large-scale soil-rock mixtures in nature or engineering.

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RILEM TC-279 WMR task group TG 1 studied the performance of waste Polyethylene (PE) in bituminous binders and bituminous mixtures. Several laboratories participated in this study following a common protocol. Locally sources aggregates and bituminous binder and same source of waste PE were utilized. The binder experiments showed that at high temperatures, using MSCR tests, PE modified blends had better resistance to permanent deformation in comparison to the non modified binder. Whereas at intermediate temperatures, using the LAS tests, fatigue performance of the PE blends could withstand more loading cycles under low strains; however, it could sustain less loading cycles under high strains due to the increase in brittleness. Dry process was used for the mixture experiments in order to bypass the stability and inhomogeneity experience that was observed at the binder scale. The PE modified mixtures showed improved workability and increased strength. The higher the PE dosage, the higher the ITS increase with respect to the values measured for the control materials (i.e., without any plastic waste) thanks to the improved cohesion of the plastic modified mastic. The stiffness experiments tended to show an improved performance with a lower time dependence and a higher elasticity when plastic was added. The cyclic compression tests demonstrated a reduced creep rate along with a higher creep modulus thanks to the addition of PE; similar conclusions can be drawn from the experimental findings coming from wheel tracking test. Furthermore, acceptable and often improved moisture resistance was observed for PE modified materials.

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Inter-laboratory experiments were designed to evaluate the impact of plastic waste blended directly in bitumen and to assess the properties, using conventional and advanced bituminous binder testing. The blends targeted 5% of plastic waste in 95% bitumen, using two types of polyethylene (PE) primary (pellets) and secondary (shreds) waste. The experiments showed that the addition of PE waste to bitumen does not alter the chemistry of the bitumen, the blending is physical. The DSR results indicate a strong dependency on the testing temperature as at low temperatures the composite material bitumen and PE behave both elastically whereas, at higher temperatures, the bitumen becomes viscoelastic. The MSCR tests indicated that the neat binder is more sensitive to permanent deformation compared to the blends with PE. The fatigue performance using the Linear Amplitude Sweep test showed a better performance in terms of stress and fatigue life for the PE blends.

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Rubberized asphaltic materials have been frequently combined with warm-mix asphalt technologies to tackle the issues of high energy consumptions and emissions during construction. Effective and accurate characterization of binder properties is conducive to the improvement of long-term pavement performance. The current study aims to quantify the effects of rubber content and warm-mix additives on rutting and thermal cracking performance of crumb rubber-modified bitumen (CRMB), and explore the rubber and additives modification mechanisms and their impacts on the binder performance. CRMBs containing different rubber contents and warm-mix additives after long-term aging were subject to multiple stress creep and recovery (MSCR) tests and low-temperature frequency sweep tests using a dynamic shear rheometer (DSR) with 4-mm loading plate to investigate the high- and low-temperature performance, respectively. Rheological tests were also conducted on the bitumen and rubber phases of CRMB to understand the rubber modification mechanism. Results show that CRMB binders have superior rutting and thermal cracking resistance due to rubber modification. The improvement of high- or low-temperature performance is more prominent at higher rubber concentrations. The effects of warm-mix additives on the rutting and thermal cracking performance are different. Generally, the wax-based additive improves the rutting resistance but negatively affects the low-temperature performance. In contrast, the chemical-based additive has an opposite effect except for the high-temperature performance of neat bitumen. The stiffening of the bitumen phase and the contribution of swollen rubber particles in the bitumen matrix together contribute to the peculiar viscoelastic response of CRMB, i.e., stiffer/softer and more elastic at high/low temperatures. This modification mechanism explains the superior rutting and thermal cracking performance of CRMB.

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Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.

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The energy separation and the increase of heating effect and the decrease of cooling effect in the vortex tube with various gases, such as R41, R32, R23, R290, R134a, R1234yf, was studied in the numerically simulated. The pressure field and temperature field and velocity field of the vortex tube were analyzed with R41. The results show that the R41 in the vortex tube, the cold and hot performance will best, the maximum temperature difference what be between cool area and hot area is 5.2 K. The numerical results show that flow motion inside the vortex tube presents extraordinary complicated behavior; The flow inside the vortex tube exist an outer region of quasi-free vortex flow and an inner region of quasi-forced vortex flow; there are the parallel flow, reverse flow and secondary flow in the vortex tube, The interface between parallel flow and reverse flow is that the energy separation place in the vortex tube.

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