Analysis of the Circulation System of a Slurry Shield and the Muck Carrying Ability of a Dredging Pipe北大核心CSCD

The circulation system of a slurry shield is composed of a transportation system and a processing system.For shield construction, correct selection of the circulation system for the slurry shield is directly related to construc-tion speed. Using the Nanjing Yangtze tunnel as an example, the material balance calculation of the circulation sys-tem, sieving effect analysis, and analysis of the muck carrying ability of the dredging pipe are conducted for various strata. The practical results show that above mentioned calculations and analysis method provide a good reference for the proper selection of a slurry separation system and dredge pipe. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Analysis of the Circulation System of a Slurry Shield and the Muck Carrying Ability of a Dredging Pipe北大核心CSCD

The circulation system of a slurry shield is composed of a transportation system and a processing system.For shield construction, correct selection of the circulation system for the slurry shield is directly related to construc-tion speed. Using the Nanjing Yangtze tunnel as an example, the material balance calculation of the circulation sys-tem, sieving effect analysis, and analysis of the muck carrying ability of the dredging pipe are conducted for various strata. The practical results show that above mentioned calculations and analysis method provide a good reference for the proper selection of a slurry separation system and dredge pipe. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Modelling of vehicular exhausts – a review

A review of the air pollution studies carried out to study the dispersion of vehicular exhaust emissions (VEEs) has been made. The review includes the modelling studies in the domain, primarily, of analytical modelling – deterministic mathematical models and numerical models, and statistical models. Various model performance evaluation and comparative assessment studies have also been discussed. Further, the studies conducted to model VEEs at the urban road intersection and urban street canyons have also been reviewed.     

The Value of a Statistical Life in a Road Safety Context — A Review of the Current Literature

Abstract

This paper summarizes the state-of-the-art for assessing the value of a statistical life (VSL) as a component of the costs of road accidents. It focuses on the most popular approaches for assessing the VSL, with respect to its theoretical foundations, current state-of-research and empirical evidence. Our paper also provides a first (to our knowledge) compendium of results for the VSL based on Stated Choice (SC) methods. Among the analysed alternatives, the willingness-to-pay (WTP) appears to be the leading approach for assessing the VSL and the SC methods represent the current state-of-the-art for determining the WTP for non-market goods. We conclude that the SC approach overcomes some of the most important shortcomings of the alternative approaches and offers a significant flexibility that can be used to address its own limitations. We also identify a significant need for research, as a gap between the methods employed in research (SC methods) and the state-of-the-practice (other methods) has emerged.     

Effect of Explosion in a Gas Pipeline Compartment of a Utility Tunnel on Neighboring Metro Tunnels北大核心CSCD

In this paper the numerical simulation analysis of the effect of explosion in the gas pipeline compartment of a utility tunnel on neighboring metro tunnels was conducted using the software AUTODYN. The results show that the TNT equivalent in a fireproof partition with length of 200 m is 41.6 kg when the gas concentration in the gas pipeline compartment reaches 10%; the blast wave has much effect on the crown and arch waist of the round metro tunnel and it’s necessary to take some protective measures in both areas; when the surrounding soil is sand, the utili- ty tunnel is above the round metro tunnel and their alignments are in the same direction, the greater the vertical spacing between the utility tunnel and the metro tunnel, the smaller the effect of the blast wave on the metro tunnel; when the vertical spacing is 7.2 m, the maximum dynamic tensile stress is 1.86 MPa (including the static stress value of 1 MPa in the tunnel segment) and it is slightly smaller than the designed tensile strength of metro tunnel (about 1.89 MPa). The maximum vibration velocity and the maximum displacement meet the structural stability require- ments, so it is suggested the vertical spacing between the utility tunnel and metro tunnel shall not be less than 7.2 m. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Dynamic Evaluation of Reliability and Stability of the Primary Support of a Tunnel北大核心CSCD

The evaluation of the stability of a tunnel’s primary support is a crucial component of ensuring the safety of subsequent construction. In light of the measured clearance displacements of the Wushishan Tunnel, the reliabili-ty of the primary support is evaluated dynamically and the design of the support structure is optimized. The research results show that full displacement and ultimate displacement are two main parameters for tunnel reliability analy-sis: the former can be obtained by positive and negative analysis, and the latter can be acquired by simulating a field measurement of displacement. It is not sufficient to apply the data specified in the code for railway tunnel design re-liability regarding determination of the reliability of a road tunnel structure using reliability theory, and it is neces-sary to use reliability theory to amend the standard of allowable empirical displacement in the Code of Road Tunnel Design. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Addendum to “a comparison of heuristics for a school bus scheduling problem”

Given a group of one or more schools, each with a specific arrival time window, and the bus routes serving these schools, the problem is to create an optimum set of combinations of routes to be served by a single bus, where optimality is defined in terms of fleet size and deadhead travel distance. We present the results of a computational study comparing ten heuristics, adapted from procedures which have appeared in the literature, on a set of 30 test problems derived from actual school data. This study is a follow on to that reported in Graham and Nuttle (1986).     

Users of a regional telephone-based traveler information system – a study of TravInfo™ users in the San Francisco Bay Area

This paper reports the results of a 1998 survey carried out among a small sample of people who had called the TravInfo Travel Advisory Telephone System (TATS) in April 1997 looking for current information about traffic conditions in the San Francisco Bay Area. The survey employed a series of tradeoff questions designed to identify the specific attributes of the information that the respondents felt to be most important, and to estimate the relative values that these users had for various possible information improvements. Despite the small size of the sample, it proved feasible to investigate how the implicit valuations placed on each attribute of the service (update frequency, extent of road coverage, and level of customization) varied among different user segments. For the most part, respondents appeared to value basic enhancements – those that establish an initial quality differential above the baseline set by free broadcast traffic information – more than they value further subsequent improvements. Overall, more frequent information updates are the highest priority among the range of possible enhancements explored in the survey, followed by an extension of coverage to include major arterials in addition to freeways. However, the evidence suggests relatively little value in door-to-door coverage – that is, coverage of streets beyond the freeway and major arterial networks. This research produced some estimates of the average monetary values ("willingness to pay") that the sample of current users attached to information improvements of various kinds. While these values varied among subgroups in ways that fit a priori expectations, it is not clear whether they provide an unbiased picture of the users' absolute levels of willingness to pay, such that they could be used reliably to inform (for example) information pricing decisions. The value of this research lies more clearly in the light it sheds on the relative structure of user preferences, and on the variations in preferences between information attributes and market segments. Overall, the authors conclude that the prospects for self-sustaining ATIS services are unclear. In response to a direct question, a majority of users (perhaps influenced by a strategic bias) indicated that they were unwilling to pay for ATIS services; some of these same people, however, indicated later that they might indeed be willing to buy a particular enhanced ATIS package, in direct competition with free broadcast services.     

Application of BIM Technology in the Construction Management of a Metro Station北大核心CSCD

For the restricted construction site of a Beijing metro station surrounded by many important buildings and characterized by complex staggered underground pipelines, many construction difficulties and a high level of re-quired management, settlement monitoring is necessary for the sake of construction safety. A 3D model of the metro,a model of the specially shaped structure and models of many details of the metro were established using the BIM technique, allowing for: creation of a 3D presentation, extraction of construction quantities, construction conse-quence optimization, guidance of construction endeavors, simulation of the construction process, 4D dynamic con-struction management and 4D dynamic settlement monitoring. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

A merging–giveway interaction model of cars in a merging section: a game theoretic analysis

In many past studies dealing with traffic phenomena in merging or weaving sections, only the influence of through traffic on the behavior of a merging car is considered in the analysis. It is, however, often seen that a through car, which runs on the most outside lane, takes a cooperative motion for the merging car called “giving way” by moving to the adjacent lane. That is, both the merging car and the through car affect one another. Because their influence is not independent from one another, it should be jointly treated in the analysis as “interaction”. This behavior is typical in merging sections, and is a dominant factor forming the traffic phenomena in a section of this type. This study develops a game theoretical model to describe the traffic behavior of a pair of merging and through cars, while explicitly considering the interaction between them. Both the merging and through cars attempt to take the best actions for themselves by forecasting the other’s action, respectively. Such a behavior is modeled as a two-person non-zero-sum non-cooperative game. Through a case study with data analysis of videotaped observation, the proposed model can be used to obtain an understanding of traffic behavior at on-ramp merging sections. ©     

Parking Benefit Districts – The transferability of a measure to reduce car dependency to a European context

Parking Benefit Districts (PBDs) are a parking measure where revenues from on-street parking charges are returned to the area where they are charged, and stakeholders in the area participate in prioritizing how the revenues are to be spent. The purpose of this article is to analyse whether and how a PBD programme can be transferred to a European context, and whether it can contribute to reduced car dependency. The first part of the article provides an overview of some salient features of PBD programmes in the USA through a literature survey. This is followed by results from interviews and from a focus group with civil servants and a deputy mayor in Stockholm. The results are used to analyse the conditions for implementing a PBD programme in Stockholm, as well as for analysing how such a programme can be designed to reduce car dependency. A main conclusion is that there are no legal barriers that render a PBD programme impossible in Stockholm, even though there are some legal restrictions. We also conclude that a PBD programme might contribute to reduced car dependency in two different ways, either by increasing acceptance for parking charges or by improving the alternatives to private cars. There seem to be several aspects in a PBD programme that can contribute to increased acceptance for parking charges. However, there is no tradition of working with these principles in Sweden and the programme’s redistributional effects need to be taken into account when designing the programme.     

Mechanism of Tunnel Water Inflow Caused by Bending Failure of a Waterproof Dike Based on a Circular Thin Plate Mechanical Model北大核心CSCD

Water bursts during tunnel construction endanger construction, and it is therefore necessary to reserve a waterproof dike with the required thickness to avoid water bursts and to take reinforcement of the dike and treatment of the structure liable to trigger a water burst. Using the water burst at K5+398 of the Mingyueshan tunnel of the Shanghai-Chengdu expressway as an example, and considering the type of tunnel section and the upright mudstone of the dike, the waterproof dike at the work face is simplified as a round thin plate. A formula for the calculation of a minimum safety thickness for the critical waterproof dike is deduced by analyzing the force applied on the water-proof dike, and the minimum safety thickness for the water burst section at K5+398 of the Mingyueshan tunnel is cal-culated. The numerical simulation analysis demonstrates the critical thickness of waterproof dike at K5+398 of the Mingyueshan tunnel is 1.4-1.55 m, and the calculated water inflow and water burst basically agree with the actual condition. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Evaluating a concept design of a crowd-sourced ‘mashup’ providing ease-of-access information for people with limited mobility

This study investigates the impact of using a concept map-based ‘mashup’ (www.accessadvisr.net) to provide volunteered (i.e. user contributed) ease of access information to travellers with limited mobility. A scenario-based user trial, centred around journey planning, was undertaken with 20 participants, divided equally between (1) those who have physical restrictions on their mobility, due to disability, illness or injury, and (2) those with practical mobility constraints due to being parents with young children who have to use a child’s pushchair when using public transport. Both user groups found the concept useful, but its potential impact was less for the pushchair user group. There were mixed views in relation to the ability of the mashup to convey the trustworthiness, credibility and reliability of information necessary for journey planning. The study identified a number of key information-related user requirements which help enable effective design of user contributed web-based resources for travellers with mobility-related issues.     

Modelling travellers’ risky choice in a revealed preference context: a comparison of EUT and non-EUT approaches

Recent work on risky choice modelling has sought to address the shortcomings of expected utility theory (EUT) by using non-expected utility theoretic (non-EUT) approaches. However, to date these approaches have been merely tested on stated choice data which is flexible and cheap. In this study, we empirically investigate the feasibility and validity of non-EUT approaches in a revealed preference (RP) context in which travel time distribution is extracted from observed historical travel time data, and subsequently present systematic comparisons between EUT, weighted utility theory, rank-dependent expected utility theory, and prospect theory (PT). The empirical evidence indicates that each non-EUT model has important behavioural insights to offer, moreover, EUT as well as non-EUT models can be applied to the RP context. However, the EUT and non-EUT model fits are generally similar with only PT providing a marginally improved model fit over EUT. The key findings presented in this study reinforce the importance of exploring non-EUT models within a revealed preference context before they can be applied reliably to modelling risky choices in the real world.     

Strategic flexibility in shipping: an examination of a sector of the short‐sea ferry market

In the generally more dynamic modern business environment new modes of strategic planning have emerged, in which a premium is attached to the maintenance of flexibility in resource deployment. This paper discusses the principles involved, and considers the capacity of a segment of the sea ferry industry to exploit strategic flexibility as a means of coping with a rapidly changing environment. Potential sources of flexibility are examined in the paper and possible constraints identified. For the sector in question, it appears that strategic flexibility has been unduly limited by the nature of the resources employed, by prevailing corporate values, and by a tendency to respond to environmental uncertainty by short‐term reactions rather than long‐term measures. The general conclusion of the paper is that the sector examined, and possibly the industry as a whole, is strategically weak.     

Axial Response of a Compression Pile to Nearby Excavation北大核心CSCD

One of the major concern in the excavation in soft soil areas is the effect of soil movement on adjacent pile foundations. In this paper, three-dimensional finite element models are established to study the axial response of the adjacent pile foundations close to an excavation in soft soil. The results show that, due to the nearby excavation, the axial bearing capacity of a single pile under compression decreases about 13.6%, and considerable additional settlements of a single pile subjected to the working compression load are generated. Therefore, the characteristics of load transfer mechanism between pile shaft and around soil, as well as the tip soil reaction are investigated extensively, which demonstrates that, as expected, the nearby excavation leads to a reduction of ultimate soil friction resistance. Furtherly, the widely employed load transfer method for pile foundation is modified to consider the effects of nearby excavation, which can be employed to predict the axial response of an axially loaded pile foundation beside an excavation. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Structural Optimization and Strength Analysis of the Lifting Arm of a Wet Shotcrete Spraying Unit北大核心CSCD

Wet shotcrete spraying units are widely used in underground engineering, for railways, highways, water conservancy and hydropower stations, municipal works, mining and military and other industries. Structural analysis and mechanical behavior optimization are conducted regarding the lifting arm of a TKJ series shotcrete spraying unit, and optimization of the hinge point position and working scope of the lifting arm is realized. The optimal layout scheme for the hinge force is given based on the Monte Carlo method, the hinge force of the lifting arm is improved for the mean and maximum values, and the maximum and average hinge force of the lifting cylinder decrease by 23.14% and 7.70%, respectively, compared with that of the original scheme. The static strength is checked using Ansys-Workbench for the optimized scheme, and the results show that the optimized scheme has a larger safety re-serve and that the structural design is more reasonable than the original scheme. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Do new sources of traffic data make the application of Chaos Theory to traffic management a realistic possibility?

Current signal systems for managing road traffic in many urban areas around the world lack a coordinated approach to detecting the spatial and temporal evolution of congestion across control regions within city networks. This severely inhibits these systems’ ability to detect reliably, on a strategic level, the onset of congestion and implement effective preventative action. As traffic is a time-dependent and non-linear system, Chaos Theory is a prime candidate for application to Urban Traffic Control (UTC) to improve congestion and pollution management. Previous applications have been restricted to relatively uncomplicated motorway and inter-urban networks, arguably where the associated problems of congestion and vehicle emissions are less severe, due to a general unavailability of high-resolution temporal and spatial data that preserve the variability in short-term traffic patterns required for Chaos Theory to work to its full potential. This paper argues that this restriction can now be overcome due to the emergence of new sources of high-resolution data and large data storage capabilities. Consequently, this opens up the real possibility for a new generation of UTC systems that are better able to detect the dynamic states of traffic and therefore more effectively prevent the onset of traffic congestion in urban areas worldwide.     

The effects of a compressed working week on commuters’ daily activity patterns

This study was based on 220 randomly selected government employees of the University of the Philippines in Los Baños, and was carried out after the Philippine government implemented an experimental two-month compressed working week scheme. The study aimed to examine compressed working week-related lifestyle pattern changes, especially changes in activity–time patterns. The moderating effects of compressed working week to the commuters were also explored. Survey results showed that two-hour increases in the compressed working week workday substantially impacted activity–travel patterns. Commuters reduced household activities by about one hour, sleeping time by about 20 minutes, and pre-work preparation time by about 30 minutes. Commuting times also significantly declined during the compressed working week. This study also identified factors that moderated the compressed working week plan’s effects on activity–travel patterns.     

Effects of providing total cost of ownership information on consumers’ intent to purchase a hybrid or plug-in electric vehicle

Energy-saving technologies have a difficult time being widely accepted in the marketplace when they have a high initial purchase price and deferred financial benefits. Consumers might not realize that, in the long-run, the financial benefits from reduced energy consumption offset much or all of the initial price premium. One strategy to address consumer misconception of this advantage is to supply information on the “total cost of ownership”, a metric which accounts for the purchase price, the cost of the fuel, and other costs over the ownership period. In this article, we investigate how providing information on five-year fuel cost savings and total cost of ownership affects the stated preferences of consumers to purchase a gasoline, conventional hybrid, plug-in hybrid, or battery electric vehicle. Through an online survey with an embedded experimental design using distinct labels, we find that respondent rankings of vehicles are unaffected by information on five-year fuel cost savings. However, adding information about total cost of ownership increases the probability that small/mid-sized car consumers express a preference to acquire a conventional hybrid, plug-in hybrid, or a battery-electric vehicle. No such effect is found for consumers of small sport utility vehicles. Our results are consistent with other findings in the behavioral economics literature and suggest that further evaluation of the effects of providing consumers with information on the total cost of vehicle ownership is warranted.