深层搅拌桩复合地基加固实施分析

正道路建设呈带状分布,在穿越不同地区时常常会遇到软土地基,软土地基的变形大,容易产生局部或整体的剪切破坏。为确保建成的道路安全正常使用,通常需要在建设过程中对软弱地基进行特殊处理。目前,处理软土地基的方法多样,其中深层搅拌桩处理软土地基的方法是一种较为理想的处理方法,它具有施工速度快、成本低、不易受外界环境影响等特点,能够适应不同地层及施工环境。深层搅拌桩技术现状深层搅拌桩是利用机械搅拌软土,同时注入胶凝材     

CFG桩复合地基在高速深厚软基处理中的应用

本文在概述CFG桩复合地基施工技术原理的基础上,以YH高速公路为例分析了CFG桩施工的关键技术,并采用抗压强度试验、钻孔取芯检验、静载试验等方式试验检测了深厚软基加固处理后的CFG桩施工质量。     

软土基处理方法及基层优化设计

<正>高速公路施工中,不但要求路堤的稳定性强,而且要尽量避免后期的沉降产生。桥梁一般采用桩基础,投运后沉降量极小,但是建在软土基上的桥头就很容易产生差异性沉降,导致桥头跳车问题的产生。当不均匀沉降达到20mm至40mm时,如不及时采取补救措施,可能会导致严重的交通事故。常规处理沉降的方法是堆载预压处理,但这种方法工期较长,且填筑路堤的稳定性难以保障。目前,提升软基道路承载力的最优方法就是加装碎石桩、CFG桩、PHC管桩,并配合褥垫层形成复合地基。其中,     

公路路基加宽施工中的土工格栅加筋优化技术应用

为了研究公路路基加宽施工中土工格栅加筋优化技术,本文针对土工格栅加筋弹性模量进行了研究,确定了格栅最佳弹性模量。通过优化土工格栅加筋施工技术,提出了一套成熟的路基加宽施工工艺流程,针对路基沉降量、压实度等质量指标对加宽路基施工质量进行评价。结果表明:土工格栅加筋优化技术的应用,可有效提高路基施工质量,降低新老路基沉降量。     

水泥搅拌桩软基处理质量控制

在软基处理中，利用水泥搅拌桩进行处理的方法已被广泛采用，特别是在桥涵两端软土地基以及高填方地段，往往会有更加明显的效果。本文从水泥搅拌桩处理软基的机理出发，结合水泥搅拌桩复合地基的承载特点．以及在水泥搅拌桩处理软基旋工中的实践体会，探讨了水泥搅拌桩处理软基质量控制应注意的几个问题。     

专家答疑

安徽郑先生：灰土挤密桩在软基处理中的应用范围比较广泛，请问在成孔过程中，监理主要应该控制哪些细节？ 答：灰土挤密桩常用于处理软弱地基，以石灰粉作为加固剂的深层搅拌桩在软土地基处理中应用得较多。目前，干振式复合桩作为一种新桩体，在软土地基处理中已开始广泛应用。     

高速公路路基加宽土工格栅加筋优化技术分析

正改扩建工程缓解了当今交通量猛增所带来的交通运输压力,并大幅度提高了原有道路的服务水平,但改扩建工程的新旧路基拼接常会使路基结合面产生滑动现象,从而导致不均匀沉降的产生。高速公路路基加宽土工格栅加筋优化技术能够有效控制差异沉降的产生,本文研究了高速公路路基加宽土工格栅加筋优化技术,首先介绍路基差异沉降的产生机理、土工合成材料的功能效果与加筋机理,并基于某公路实际改扩建工程进行应用研究,对土工格栅施工质量提出施工控制要点,观测了采     

深层水泥搅拌桩施工质量监理

深层水泥搅拌桩是利用水泥作为固化剂的主剂，通过特制的深层搅拌机械在地基深部就地将软土和固化剂强制拌合，使软土硬化而提高地基强度。这种方法适用于处理软土，效果显著，处理后可很快投入使用。如何有效控制深层水泥搅拌桩的成桩质量．确保软基处理的效果是监理工作的关键。     

盐渍化软弱土地基砾石桩处理效果检测与评定方法

以新疆盐渍化软弱土地基处理为例,在符合规范、标准要求的基础上,详解介绍了砾石桩地基处理效果的检测方法、评定标准和补救措施。     

碎石桩处治砂土液化地基效果评价

本文综合运用标准贯入法、静力触探法这两种评价方法,对碎石桩处治前后的砂土地基液化点进行了判别。研究结果表明:无论采用哪种方法,都可以有效检测出砂土地基液化点,但二者检测到的液化点数目和位置可能不一致,实际检测时建议综合使用这两种方法进行判定;碎石桩可有效消除砂土地基液化病害,因此可以在滨海相砂土地基中推广应用。     

A multi-time scale management structure for airport ground handling automation

The sustainability of air travel relies on proper and timely aircraft ground handling at airports. This research proposes a ground handling management structure which allows the automation of operations to face the growing demand for this service. It is shown how at operations level, information exchange with the airport collaborative decision-making system turns possible on-line fleet assignment to ground handling tasks. This is done by designing different heuristics for assignment of fully automated or semi-automated vehicles to ground handling tasks. Numerical results for an actual airport are presented to illustrate the potential performance of automated ground handling operations.     

Optimal route decision with a geometric ground-airborne hybrid model under weather uncertainty

Adverse weather is the dominant cause of delays in the National Airspace System (NAS). Since the future weather condition is only predictable with a certain degree of accuracy, managing traffic in the weather-affected airspace is a challenging task. In this paper, we propose a geometric model to generate an optimal combination of ground delay and route choice to hedge against weather risk. The geometric recourse model (GRM) is a strategic Probabilistic Air Traffic Management (PATM) model that generates optimal route choice, incorporating route hedging and en-route recourse to respond to weather change: hedged routes are routes other than the nominal or the detour one, and recourse occurs when the weather restricted airspace becomes flyable and aircraft are re-routed to fly direct to the destination. Among several variations of the GRM, we focus on the hybrid Dual Recourse Model (DRM), which allows ground delay as well as route hedging and recourses, when the weather clearance time follows a uniform distribution. The formulation of the hybrid DRM involves two decision variables - ground delay and route choice - and four parameters: storm location, storm size, maximum storm duration time, and ground-airborne cost ratio. The objective function has two components: expected total ground delay cost and expected total airborne cost. We propose a solution algorithm that guarantees to find the global optimum of the hybrid-DRM. Based on the numerical analysis, we find that ground-holding is effective only when combined with the nominal route. Otherwise, it is optimal to fly on the route determined by the DRM without ground delay. We also find the formula of the threshold ground-airborne cost ratio, which we call the Critical Cost Ratio (CCR), that determines the efficacy of ground delay: the higher the CCR, the more effective the strategies involving ground delay. We conclude that both ground delay and route hedging should be considered together to produce the best ATM decisions.     

Surface movement ground control by means of a GPS–GIS system

Despite the traffic increases at the World's airports, little works have been done on methodologies to improve vehicles and airplanes ground control. This may be leading to reduced safety. Here an integrated system is developed to help guarantee suitable separations of land vehicles and airplanes moving on the airport ground area It can also addressed issues of the optimal use of taxi and runways. The system is composed of global positioning systems hardware, checks on the position of land vehicles and airplanes on the ground in real time, and special-purpose geographical information systems software for the tracking of land vehicles and airplanes within different planning operations.     

Integrating node-place and trip end models to explore drivers of rail ridership in Flanders,Belgium

The node-place model is an analytical framework that was devised to identify spatial development opportunities for railway stations and their surroundings at the regional scale. Today, the model is predominantly invoked and applied in the context of ‘transit-oriented development’ planning debates. As a corollary, these model applications share the pursuit of supporting a transition towards increased rail ridership (and walking and cycling), and therefore assumingly a transition to more sustainable travel behavior. Surprisingly, analyses of the importance of node and place interventions in explaining rail ridership remain thin on the ground. Against this backdrop, this paper aims to integrate the node-place model approach with current insights that derive from the trip end modeling literature. To this end, we apply a series of regression analyses in order to appraise the most important explanatory factors that impact rail ridership in Flanders, Belgium, today. This appraisal is based on both geographical and temporal data segmentations, in order to test for different types of railway stations and for different periods of the day. Additionally, we explore spatial nonstationarity by calibrating geographically weighted regression models, and this for different time windows. The models developed should allow policy and planning professionals to investigate the possible demand impacts of changes to existing stations and the walkable area surrounding them.     

Airline choice by passengers from Taiwan and China: A case study of outgoing passengers from Kaohsiung International Airport

Understanding what factors passengers consider when selecting an airline is critical, as airlines can utilize this information in market segmentation and marketing strategies. However, few studies have explored how passenger demographics and the nationality/type of carrier (full service or low-cost; regional or international) affect the choice factors of passengers when selecting airlines. The main objective of this study was to explore the airline choice factors considered by passengers, compare the choices of passengers with different demographics, and analyze which factors are emphasized by passengers from Taiwan and China when selecting airlines. We conducted a questionnaire survey of outgoing passengers at Kaohsiung International Airport in relation to 22 factors underlying their choice of airline. Using factor analysis, we identified the five factors: ground services, convenience, in-flight services, price, and travel availability. We then utilized cluster analysis to identify four groups, each concerned with price, comfort, convenience, and ground services, respectively. Nationality, age, income, flying frequency, and purpose of travel lead to differences in deciding which factors were considered by cross-strait passengers. Passengers of different nationalities concerned with different factors when selecting airlines. Our findings can add to the completeness of existing research as well as provide airlines with reference in developing marketing strategies for different customer groups.     

A heuristic approach for solving an integrated gate reassignment and taxi scheduling problem

Capacity limitation of airport ground operation is one of the major limiting factors in air traffic operation. The congestion on the gate and taxiway causes severe delay and propagate effect on the flight schedule. This paper considers the problem of integrated gate reassignment and taxiway scheduling, in which complex constraints related to runway restriction, gate allocation and taxiway conflict are all incorporated when determining the schedule. To solve this problem, we propose a novel heuristic approach. First, all possible aircraft schedules are enumerated by disretizing the waiting time along the path. Then, the cost is evaluated for each schedule and the conflict detection is conducted to generate constraint sets. Finally, we propose a set partition model, in which each decision variable denotes a candidate schedule that takes into account the possible constraints when generated. This method is compared with a sequential method that solves gate reassignment and taxiway scheduling problem separately. Computational results highlight the strength of our method.     

Challenges for ground operations arising from aircraft concepts using alternative energy

Current research in the field of future aircraft concepts aims at accommodating ambitious reduction goals set by national and international regulators. These concepts should be investigated not only with regard to aircraft efficiency, but also in terms of their compatibility with airline operations, existing ground handling procedures and airport infrastructure requirements, as these influence the overall performance of a future aircraft concept. This paper addresses this aspect, focusing on case studies concerning hybrid-electric and universally-electric aircraft concepts, analyzing implications for current ground handling operations at the airport. Current bottlenecks, such as capacity shortages, and potential areas of improvement are identified based on a state-of-the-art reference ground handling process. To this end, requirements of different stakeholders, including airports, airlines and ground handling providers, are outlined. In the next step, insights are contrasted with operational requirements of the future aircraft concepts under consideration. The paper stresses the anticipated challenges involved in aligning future aircraft requirements with current procedures, discusses the necessary adaptions to operational processes. The results highlight changes that need to be made to the current system before an aircraft can enter service, and provide an initial basis for the strategic planning of the stakeholders involved.     

Data-driven reduction targets for a highway safety plan

A safety plan or policy should have traffic safety targets. Setting the targets is challenging but is possible through data-driven approach. This paper describes a study that forecast fatalities and injuries under three scenarios, examined the probabilities of meeting different reduction targets, and proposed realistic targets for Virginia’s safety plan. The study combined statistical forecasting approach, inputs from safety experts, and reported effects of safety improvement measures to come up with ambitious yet achievable targets. Realistic targets for the safety plan in Virginia by 2010 are a 10% reduction in fatalities and a 5% reduction in injuries. These targets assume enactment of a primary safety belt law and deployment of crash countermeasures comparable to 20–30% engineering treatments.     

Investigating the impact of recession on transportation cost capitalization: a spatial analysis

The unprecedented economic crisis experienced by Greece is fertile ground for research at myriad levels. In this paper, the authors aim to investigate the effects of the crisis on real estate prices by measuring the impact of transportation infrastructure location. For the purposes of this research, on-line real estate data collected in 2011, when the consequences of the crisis were still uncertain, and in 2013, when a significant decline had been observed, are combined.The analysis is based on various spatial statistical methods. In order to identify potential common price patterns, G spatial clustering is first performed. Spatial error models (SEM) are then developed to parameterize the real estate prices. The results show that, overall, purchase prices have been reduced by 18.2% and rents by 15.2%. More specifically, the positive impact of metro station locations (<500 m) has declined 42.5% for purchase prices and 62.5% for rents. Moreover, dwellings located in the Inner Ring are still more expensive than others; however, the impact of the crisis has been reduced by 30.3% for purchases and 50.7% for rents. On the other hand, the negative impact of ISAP station locations (<500 m) has declined by 53.5% for purchase prices.The findings of this paper could be of great interest to the transportation policy research community and could be used to better predict the benefits and costs of public transport investment under extremely uncertain conditions, such as a long-lasting recession.     

The reflection of the fear of falls and risk of falling in walking activity spaces of older adults in various urban environments

Participation of older adults in daily activities has a major positive impact on health and contributes to a sense of accomplishment, satisfaction, self-efficacy, and well-being. Walking is considered to be one of the most influential activities promoting health and active living. Older adults are particularly vulnerable to their immediate local environment where age- related declined capabilities combined with barriers in the home neighborhood pose a risk of falling and fear of falls. Most research focusing on the built environment role in incidents of older adults' outdoor falls and fear of falls is focused on identifying the environmental features' risk factors. Effort is made to develop audit checklist tools to assess out-door falls risk. In contrast, this study focuses on the manifestation of fear of falls in older adults' walking activity spaces. We identify spatial walking patterns of outdoor daily activities in public urban spaces and examine the relations between fear of falls, risk of falling status, previous occurrence of fall incidents and number of medical diagnoses and walking activity spaces among older adults in different urban environments.The analysis included 271 older adults (age 60+ with 70% females and 30% males), and 483 walking routes in three cities. A psychological measure related to mobility self-efficacy was evaluated by the Falls Efficacy Scale examining the fear of falling through a functional perspective. Motor evaluation was conducted by functional mobility evaluation through the Timed Up and Go (TUG) screening test which assesses the level of risk of falling. GIS analysis was conducted for mapping and identifying walking activity spaces. The analysis shows different walking activity spaces of people with high risk of falling and fear of falls in comparison to those with no risk and no fear of falling across gender and age groups (60–65, 66–74, and 75+). In this approach we show the outcome reflection of barriers and enablers and their revealed cumulative effect through walking activity spaces among older adults.