Soil Body Deformation Caused by Construction of a Double-Line Shield Tunnel with Multiple Factors北大核心CSCD

Considering the influence of many factors (soil loss, frontal additional thrust, the friction force of the shield shell and the additional grouting force), a method for improving the uniform soil body movement model is pro-posed, and a mechanical calculation model is established to study the calculation method for soil body deformation caused by double-line parallel shield driving. Based on the Mindlin solutions of elastic mechanics, the theoretical solutions for soil body deformations caused by the last three factors are calculated; considering the uniform soil body movement model, the theoretical solutions for soil body deformations caused by soil loss are calculated, then the to-tal theoretical solutions for soil body deformations under multiple factors are obtained by means of superposition. The vertical surface settlement, vertical horizontal displacement, and vertical displacements of the soil body at different depths of Hangzhou Metro Line 1 are calculated to analyze the variation laws. Meanwhile the influential factors for horizontal displacement variation are studied. The research shows that with a change of depth, the settlement of the soil body changes within the scope of 10 to 13 m in the horizontal direction near where the maximum settlement occurs;the direction of the horizontal displacement of the soil body changes with a change of the positional relationship be-tween the calculation points and the tunnel; and with an increase of interval J for the two tunnels, the horizontal dis-placement of the soil body of a deep double-line tunnel decreases while the displacement near the surface changes slightly. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Adapting without Retreating: Responses to Shoreline Change on an Inlet-Associated Coastal Beach

Coastal barrier systems around the world are experiencing higher rates of flooding and shoreline erosion. Property owners on barriers have made significant financial investments in physical protections that shield their nearby properties from these hazards, constituting a type of adaptation to shoreline change. Factors that contribute to adaptation on Plum Island, a developed beach and dune system on the North Shore of Massachusetts, are investigated here. Plum Island experiences patterns of shoreline change that may be representative of many inlet-associated beaches, encompassing an equivocal and dynamically shifting mix of erosion and accretion. In the face of episodic floods and fleeting erosive events, and driven by a combination of strong northeast storms and cycles of erosion and accretion, the value of the average Plum Island residence increases by 34% for properties on the oceanfront where protection comprises a publicly constructed soft structure. Even in the face of state policies that ostensibly discourage physical protection as a means of adaptation, coastal communities face significant political and financial pressures to maintain existing protective structures or to allow contiguous groups of property owners to build new ones through collective action. These factors mitigate against adapting to shoreline change by retreating from the coast, thereby potentially increasing the adverse effects of coastal hazards.     

A continuous network design model in stochastic user equilibrium based on sensitivity analysis

The continuous network design problem (CNDP) is known to be difficult to solve due to the intrinsic properties of non‐convexity and nonlinearity. Such kinds of CNDP can be formulated as a bi‐level programme, in which the upper level represents the designer's decisions and the lower level the travellers' responses. Formulations of this kind can be classified as either Stackelberg approaches or Nash ones according to the relationship between the upper level and the lower level parts. This paper formulates the CNDP for road expansion based on Stackelberg game where leader and follower exist, and allows for variety of travellers' behaviour in choosing their routes. In order to solve the problem by the Stackelberg approach, we need a relation between link flows and design parameters. For this purpose, we use a logit route choice model, which provides this in an explicit closed‐form function. This model is applied to two example road networks to test and briefly compare the results between the Stackelberg and Nash approaches to explore the differences between them.     

Mathematical model for optimising the sequence for clearing snow from the manoeuvring area during winter operations

This article considers the optimisation of the sequence for clearing snow from stretches of the manoeuvring area of an airport. This issue involves the optimisation of limited resources to remove snow from taxiways and runways thereby leaving them in an acceptable condition for operating aircraft. The airfield is divided into subsets of significant stretches for the purpose of operations and target times are established during which these are open to aircraft traffic. The document contains several mathematical models each with different functions, such as the end time of the process, the sum of the end times of each stretch and gap between the estimated and the real end times. During this process, we introduce different operating restrictions on partial fulfilment of the operational targets as applied to zones of special interest, or relating to the operation of the snow‐clearing machines. The problem is solved by optimisation based on linear programming. The article gives the results of the computational tests carried out on five distinct models of the manoeuvring area, which cover increasingly complex situations and larger areas. The mathematical model is particularised for the case of the manoeuvring area of Adolfo Suarez Madrid—Barajas Airport. Copyright © 2016 John Wiley & Sons, Ltd.

Highlights
• Optimal sequence for clearing snow from the manoeuvring area of an airport.
• Contains optimising algorithms solved using CPLEX LP‐based tree search.
• Restrictions on partial fulfilment of operational targets applied to subsets of significant stretches, used for planning the operation of snow‐clearing machines.
• Model applied to the case of the manoeuvring area of Adolfo Suárez Madrid Barajas Airport.
• Conclusions are given on the results of the computational tests carried out. There are five models of the manoeuvring area which cover increasingly complex situations and larger areas.

     

Introduction: Habitual travel choice

In this introduction to the special issue on habitual travel choice, we provide a brief account of the role of habit in travel behaviour, discuss more generally what habitual choice is, and briefly review the issues addressed in the solicited papers. These issues include how habitual travel behaviour should be measured, how to model the learning process that makes travel choice habitual, and how to break and replace car-use habits.     

Subsidy and public transit performance: A factor analytic approach

The need to measure and evaluate transit system performance has led to the development of numerous performance indicators. However, depending upon the indicator, we oftentimes reach different conclusions regarding transit system performance. The research reported in this paper uses factor analytic methods to generate a set of underlying attributes (factors) that capture the performance of public transit systems in Indiana. Similar to what is reported in the literature, this study finds three attributes that best describe transit system performance: efficiency, effectiveness, and overall performance. Based upon systemsÕ factor scores, the study finds that systems scoring highly on one attribute generally perform well on the remaining attributes. Further, there is an inverse relationship between system performance and subsidies, a finding that supports performance based subsidy allocations.     

A frequency-based maritime container assignment model

This paper transfers the classic frequency-based transit assignment method of Spiess and Florian to containers demonstrating its promise as the basis for a global maritime container assignment model. In this model, containers are carried by shipping lines operating strings (or port rotations) with given service frequencies. An origin–destination matrix of full containers is assigned to these strings to minimize sailing time plus container dwell time at the origin port and any intermediate transhipment ports. This necessitated two significant model extensions. The first involves the repositioning of empty containers so that a net outflow of full containers from any port is balanced by a net inflow of empty containers, and vice versa. As with full containers, empty containers are repositioned to minimize the sum of sailing and dwell time, with a facility to discount the dwell time of empty containers in recognition of the absence of inventory. The second involves the inclusion of an upper limit to the maximum number of container moves per unit time at any port. The dual variable for this constraint provides a shadow price, or surcharge, for loading or unloading a container at a congested port. Insight into the interpretation of the dual variables is given by proposition and proof. Model behaviour is illustrated by a simple numerical example. The paper concludes by considering the next steps toward realising a container assignment model that can, amongst other things, support the assessment of supply chain vulnerability to maritime disruptions.     

Design and evaluation of an integrated inventory and transportation system

This paper proposes the adoption of an integrated inventory and transportation system (IITS) to minimize the total costs of inventory and transportation. A non-linear programing is developed by analyzing transportation and inventory costs with one supplier and many retailers in the distribution environment. The paper compares the proposed model with the traditional approach in computing total costs with numerical data. The results indicate that the total costs can be optimized by adopting integrated programing rather than the traditional approach, along with achieving improved customer service levels. In particular, sensitivity analysis is applied to determine the performance of the IITS under various transportation costs, holding costs and shortage costs. It shows that the transportation cost per unit is most sensitive in the proposed model. In this situation, the IITS is more effective for cost saving when set-up cost, holding and shortage costs are high, but is less effective for situations involving high per-unit transportation costs.     

Evaluation of general aviation management at Denver Stapleton airport

The potential benefits of general aviation management at a major airport is examined in this paper. The three general aviation management techniques investigated are volume reduction, runway segregation and time restriction.

First, a methodology for analyzing these techniques is discussed. The various effects on each user group are quantified for economic comparison between each management technique attempted. A computer simulation model was used to measure the delay effects. Then, these techniques are applied to Denver Stapleton Airport to measure their effects in present and future scenarios.

The results show that the best general aviation management technique is volume restriction. The use of peak‐hour pricing mechanism provided better results than random rejection, particularly if only a small degree of diversion is desired. The construction of a new general aviation runway provided equivalent results to the best technique tested.