Construction Processes Paradigm and Reinforcement Alternatives for Tailings Dam Soil

In the last decade, Brazil was the scene of two of the world’s biggest disasters related to mining tailings dams. The collapse of the Mariana and Brumadinho dams was catastrophic event that brought to light major environmental and humanitarian crises. Facts like this incite debate on the safety of dam construction methods and highlight the need for a broad discussion of dam safety legislation in the country. From the above, this paper promotes a review of various forms of construction of tailings dams and their associated problems, as well as discusses the techniques for soil reinforcement and their construction methods. The work also brings an overview of the Brazilian dams from April to July 2019, tracing the context of the Brazilian tailings dams months after the tragedy of Brumadinho. The methodology includes a robust literature review and discourse analysis. In Brazil, the number of ruptured dams is alarming, especially in the state of Minas Gerais, in which more than 7 have broken in the last two decades. Among the damages, the deaths impact society abruptly and were cataloged 455 deaths, of which 216 correspond to the rupture of the dam of the Córrego do Feijão mine in Brumadinho. To evaluate and diagnose a dam, one should consider ordinance N ° 70,389, 2017 revoked by Resolution ANM n ° 95, of February 7, 2022. In this context, in March 2019, we experienced several disturbing situations regarding dam instability in the state of Minas Gerais, being categorized as risky structures. To exemplify, one can cite dams classified as level 2 risk that became level 3. Due to the above facts, several studies are being conducted to improve soil aspects. For example, we highlight the increase in soil resistance that can be done using commercial and alternative materials available in the environment.

Experimental Characterization of Rutting Performance of HMA Designed with Aggregate Gradations According to Superpave and Marshall Methods

The permanent deformation (rutting) of pavement is a major distress in flexible pavement. It is related to vehicles properties and/or pavement materials and conditions. This article presents an extensive experimental investigation in order to compare between the aggregate gradation according to Superpave and Marshall methods of asphalt concrete mix design on pavement rutting and to examine the sensitivity of rutting resistance to aggregate gradation. A wheel truck machine has been used for measurement of pavement rutting (permanent deformation). The tests were carried out at two controlled different air temperature 55℃ and 25℃. The results obtained showed that the adopting of aggregate gradation procedure of Superpave method of pavement mix design for Marshall method of asphalt concrete mix design can reduce the pavement rutting by about 50%. This achievement may be related to missing of three sieves in aggregate gradation procedure of Marshall method which controls rounded and finer aggregate particles. These sieves provide more continuity for aggregate gradation to ensure filling unnecessary gaps and produce more contact points between the aggregates in Hot Mix Asphalt (HMA). The outputs of the research support modifying Marshall method of asphalt concrete mix design by adopting aggregate gradation proposed in Superpave method. The results of study also showed that the coarser aggregate provided more resistance to pavement rutting.

Influence of Selective Edge Removal and Refractory Period in a Self-Organized Critical Neuron Model

A simple model for a set of integrate-and-fire neurons based on the weighted network is introduced.By considering the neurobiological phenomenon in brain development and the difference of the synaptic strength,weconstruct weighted networks develop with link additions and followed by selective edge removal.The network exhibitsthe small-world and scale-free properties with high network effficiency.The model displays an avalanche activity ona power-law distribution.We investigate the effect of selective edge removal and the neuron refractory period on theself-organized criticality of the system.

Study of Wave and Tide Influence on Slope Stability of the Navigation Channel of Tianjin Port

The Tianjin Port is the largest man-made port in China. Since the navigation channel of the Tianjin Port is constructed by dredging, a very important problem, as many people concerned, is the submarine slope stability. As the environment on land is different from that in submarine, it is necessary to evaluate the influence of the environmental loading, such as wave and tide, on the stability of navigation channel slope. In the present study, based on the observed results, the characteristics of the navigation channel slope are summarized, and the causes of creating the special slope shape are analyzed. The ioles of waves and tides are evaluated, and failure mechanics are discussed to helq us predict what will happen in the future.

Accessibility of a Destination-Based Transportation System: A Large Airport Study

The accessibility of a destination-based transportation system is defined to quantify the performance of transportation systems which access a distinct destination. The access cost is used to reflect the utility of the transportation system including the fatigue and inconvenience in the total cost. The cost is quan- tified by two coefficients which represent the different characteristics of various people. The average cost and the income-relative accessibility are used to describe various aspects of the accessibility and to evaluate the accessibility of a destination-based system. A case study uses data from the Kunming transportation system to evaluate the accessibility of the present city airport. The calibrated coefficients are then used to evaluate the transportation system to the new Kunming international airport. The results show that this transportation accessibility evaluation can be combined with transportation planning to study transportation sub-systems.

Road Resources Distribution and Evolution Analysis Using a Species Competition Model for Improving Road Equity

The paper analyzes the equity of road resources distribution in urban areas by modeling the competitive relationship among different road users. A logistic model is used to describe the development of different traffic modes in the transportation network. The system is similar to the species competition model, so a two-species model is used to analyze the relationship between users based on the stability of the equilibrium points. The Lotka-Volterra model is then used to describe the multi-species cases with numerical examples, showing that this model can describe the effects of the road space distribution on the competitive user relationships. Policy makers must ensure the equity of road resources distribution so that each urban transportation mode is properly developed for sustainable social development.

Mechanical Response of Single Plant Cells to Cell Poking:A Numerical Simulation Model

Cell poking is an experimental technique that is widely used to study the mechanical properties of plant cells. A full understanding of the mechanical responses of plant cells to poking force Is helpful for experimental work. The aim of this study was to numerically investigate the stress distribution of the cell wall, cell turgor, and deformation of plant cells in response to applied poking force. Furthermore, the locations damaged during poking were analyzed. The model simulates cell poking, with the cell treated as a spherical, homogeneous, isotropic elastic membrane, filled with incompressible, highly viscous liquid. Equilibrium equations for the contact region and the non-contact regions were determined by using membrane theory. The boundary conditions and continuity conditions for the solution of the problem were found. The forcedeformation curve, turgor pressure and tension of the cell wall under cell poking conditions were obtained. The tension of the cell wall circumference was larger than that of the meridian. In general, maximal stress occurred at the equator around. When cell deformation increased to a certain level, the tension at the poker tip exceeded that of the equator. Breakage of the cell wall may start from the equator or the poker tip, depending on the deformation. A nonlinear model is suitable for estimating turgor, stress, and stiffness, and numerical simulation is a powerful method for determining plant cell mechanical properties.

Optimizing Work Zones for Two-Lane Urban Road Maintenance Projects

Road maintenance work brings costs to the government and delays to users. The setting up of work zones often leads to severe congestion during peak hours, especially in busy urban areas. A road maintenance delay model is presented here that includes consideration of excessive traffic flow and non-motorists. Atrial-and-error method is used to find the optimal work zone length and the best work starting time to minimize the total cost of maintenance and delays. A numerical example with a sensitivity analysis is also given. The results show that optimal starting time is not sensitive to the flow speed and the increase of work zone speeds sharply reduces the total cost when the road is congested.

Prediction Method for Regional Logistics

Currently applied prediction methods of regional freight traffic and freight ton-kilometer forecasting were analyzed using typical Chinese regional goods transportation characteristics. The review of prediction methods showes that practical planning experts tend to apply the traditional methods which are easier to implement. The comparison also demonstrates that a combination of traditional methods is more effective than the simple models for practical planning. Research using the statistical data for the Yangtze Delta, Pearl River Delta, and Bohai Rim areas shows that ignoring differences between transport modes impacts the prediction accuracy. The four main transport modes suit different methods. The results show that the power model is better for railways, and the linear model is better for highways and waterways. Thus a combined model gives better results for all modes. The results for regional systems can be generalized to national transportation systems.

The Meso-inhomogeneous Deformation of Pure Copper under Tension-Compression Cyclic Strain Loading

The investigation based on experiments and crystal plasticity simulation is carried out to undertake research on mesodeformation inhomogeneity of metals under cyclic loading at grain level.Symmetrical tension-compression cycle tests are performed on pure copper specimens to observe the inhomogeneous distribution of slip deformation and its evolution with cycle number.Cyclic hardening process and stable hysteretic behavior of pure copper under cyclic loading are simulated by applying a crystal plasticity constitutive model including nonlinear kinematic hardening associated with the polycrystalline representative volume element(RVE)constructed by Voronoi tessellation.Inhomogeneous deformation processes of materials under six different strain amplitudes are simulated by 1600 cycles,respectively.We discuss the variation law of the inhomogeneous meso-deformation distribution of material with the increase in cycle number,and research the rationality of characterizing the inhomogeneous deformation distribution and variation with the statistical standard deviation of the micro-longitudinal strain or the statistical average of the first principal strain based on the statistical analysis of the inhomogeneous deformation of the polycrystalline RVE model during the cycling process.It is found that these two parameters are related to and approximately inversely proportional to the length of measuring gauge.

Effects of odd-even traffic restriction on travel speed and traffic volume:Evidence from Beijing Olympic Games

This paper reports the effects of using an ＂odd and even＂ traffic restriction policy in Beijing during the 2008 Olympic Games. Based on data from 529 traffic detectors on the expressway network and some main arterials in Beijing, China, a comparative analysis has been carried out on the following parameters： the total traffic volume within the expressway network, the total traffic volume on different ring expressways, the traffic volume and speed of a freeway segment, and an arterial street before and after the implementation of the traffic restriction policy. The results show that during the traffic restriction period, although more than 50% of vehicles were forbidden to travel in Beijing, the traffic volume was only reduced by 20%-40% while the travel speed had been increased by 10%-20%. This suggests that such traffic restriction policy may be an effective shortterm management measure in dealing with increased transportation demand and congestion during major events, such as the Olympic Games. Results also indicate that vehicle travel demand does not decrease with the same proportion as the total vehicles forbidden, at least for the expressway and main arterials in a city.

Injury severities from heavy vehicle accidents:An exploratory empirical analysis

Despite the importance of heavy vehicles in Australia’s transportation system,little is known on the factors influencing injury severity from accidents involving a single heavy vehicle.Heavy vehicular crashes have been one of the main causes of fatal injuries in Australia,and this raises safety concerns for transport authorities,insurance companies,and emergency services.Although there have been several potential attempts to identify the factors contributing to heavy vehicle crashes and injury severity,it is still necessary to reduce the number of traffic crashes and lower the fatality rate involving heavy vehicles.The aims of this study were investigating the effects of heavy trucks’presence in accidents on the injury severity level sustained by the vehicle driver and detecting the contributing factors that lead to specific injury severity levels.Fixed-and random-parameter ordered probit and logit models were applied for predicting the likelihood of three injury severity categories severe,moderate,and no injury based on data from crashes caused by heavy trucks in Victoria,Australia in 2012-2017.The results showed that the random-parameter ordered probit model performed better than the other models did.Twenty variables(i.e.,factors)were found to be significant,and 12 of them were found to have random parameters that were normally distributed.Since some of the investigated factors had different effects on the type of injury severity in Australia,this paper does not recommend generalizing the findings from other case studies.Based on the findings,Victoria state authorities can have insight and enhanced understanding of the specific factors that lead to various types of injury severity involving heavy trucks.Consequently,the safety of all road users,including heavy vehicle drivers,can be enhanced.

Driver injury severity analysis of crashes in a western China’s rural mountainous county:Taking crash compatibility difference into consideration

China’s traffic safety attracts increasing research interest.Official data show that crashes in the western region of China are more severe than those in the eastern region.However,research on crash severity in western China is scarce.This study applied a hierarchical Bayesian logistic model to examine the significant factors related to crash and vehicle/driver levels and their heterogeneous impacts on the severity of drivers’ injury.Crash data were collected from Lintao,a rural mountainous county in western China.A variable was proposed to measure the relative difference between the crashworthiness of one vehicle and the aggressivity of the other vehicle in the mixed traffic flow.Results indicated that the majority of the total variance was induced by between-crash variance,showing the suitability of the utilized hierarchical modeling approach.One crash-level variable and six vehicle/driver-level variables,namely,road type,compatibility difference,age,vehicle type,drunk driving,driving unregistered vehicle,and driving years,significantly affected modeling drivers’ injury severities.Among these variables,road type(national and provincial),age(young and senior drivers),driving unregistered vehicle,and drunk driving tended to increase the odds of crash-related mortality.Driving years(new drivers with less than six years of driving experience) and vehicle type(heavy vehicle) were likely to decrease the probability of fatal outcomes.Compatibility difference was relatively significant,and the possibilities of mortality in single vehicle crashes were higher than those inmultivehicle and pedestrian-involved crashes.The developed methodology and estimation results provided insights into the internal mechanism of rural crashes and effective countermeasures to prevent rural crashes.

Influencing factors analysis of helmet wearing for electric bicycle riders based on ordinal multinomial logistic model

The helmet of riders of electric bicycles plays an important role in reducing injuries and deaths in traffic accidents.This paper conducts a questionnaire survey,data analysis and modelling to investigate the influencing factors of electric bicycle helmet wearing.First,living area,gender,age,marital status and education level are selected as independent variables for data analysis.The factor analysis divides the sentiments of electric bicyclists for wearing helmets into four aspects:safety perception,practical sensation,satisfaction perception and emergency perception,and ordinal multiple logistic models are built to analyse the influencing factors.The result shows that people aged 18−25,26−35,36−45 and 46−55 are 1.3,1.8,2.0 and 2.3 times more likely,respectively,to have at least a grade higher safety perception than those aged 56 and over;men are 0.77 times more likely than women to feel at least one grade higher about the practical perception and 1.48 times more than women about the satisfaction perception;people with primary school,junior high school,senior high school,junior college and bachelor’s degree education are 1.64,2.44,1.50,1.70 and 1.55 times more likely,respectively,than people with a master’s degree to feel at least one grade higher about the satisfaction perception.