Investigation of monitoring system for high-speed railway subgrade frost heave

This paper presents methods for monitoring frost heave, device requirements, testing principals, and data analysis requirements, such as manual leveling observation, automatic monitoring (frost heave, frost depth, and moisture), track dynamic detection, and track status detection. We focused on the requirements of subgrade frost heave monitoring for high speed railways, and the relationship of different monitoring methods during different phases of the railway. The comprehensive monitoring system of high speed railway subgrade frost heave provided the technical support for dynamic design during construction and safe operation of the rail system.     

Dangerous deformations of subgrade and methods of their calculation

The main reasons for a breach of trouble-free operation of the subgrade are the different kinds of deformation, such as train load impact on subgrade surface, loss of stability to subgrade slope, weight of embankment on the base, and partial or complete failure of the railway track due to frost heaving. This paper gives a summary of deformation analysis methods being developed in Russia to estimate the operating conditions of the railway subgrade.     

Structural analysis and design of frost resistance function for subgrade of high-speed railway ballasted track in cold regions

According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action of biaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value (high-cycle long-term dynamic strength) under the circumstance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K₃₀ were deduced, based on the characteristics of cumulative deformation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uniaxial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced subgrade bed in the double-layer subgrade mode along with the change of K₃₀ at the subgrade bed bottom. The double-layer structure mode of "closure on the upper layer and drainage on the lower layer" was proposed in order to meet the waterproofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10^-4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10^-2 cm/s is adopted on the lower layer.     

高速铁路对中国城市市场潜力的影响——基于铁路客运可达性的分析

近10年来中国高速铁路快速发展,对城市发展的影响正逐步显现.本文从市场潜力角度研究这一影响,根据《全国铁路旅客列车时刻表2012.07》统计获得的城市之间平均旅行时间和发车频次数据重新定义市场潜力函数,对比中国地级及以上城市普通铁路和叠加高速铁路之后的市场潜力特征,探讨高铁对城市市场潜力的提升作用,并从中分离出时间压缩效应和频次效应.研究发现:①普通铁路市场潜力呈现“多中心—廊道”结构,市场潜力高的城市主要分布在长三角、珠三角、京津冀城镇群内,以及京广、京沪、京哈等重要铁路线沿线;②叠加高速铁路之后城市市场潜力整体上仍呈现“多中心—廊道”结构,且多中心结构更为突出;③京沪、沪杭铁路沿线城市和东南沿海宁波—厦门段客运专线沿线城市的高铁效应最大;④高铁连接的109个城市时间压缩效应的平均值为31.3％,频次效应的平均值为68.7％,频次效应是高铁效应的主要形式.     

Numerical analysis of applying special pavements to solve the frost heave diseases of high-speed railway roadbedsin seasonally frozen ground regions

The Haerbin-Dalian Passenger Dedicated Line is the first high-speed railway constructed in the seasonally frozen ground regions of northeastern China. Frost heave diseases occurred in the first winter of its operation(between October 2012 and January 2013), and frost heave was observed mainly in the roadbed fills that were considered not susceptible to frost heave. This paper proposes applying two special pavements — black pavement and insulation-black pavement — to improve the thermal regime of the roadbed. Three numerical models of the roadbed temperature field were built based on the field conditions of the Changchun section(D3K692+840 to D3K692+860). The results show that:(1) Compared with cement pavement, black pavement and insulation-black pavement could reduce the freezing index at the roadbed surface by 37% and 64%, respectively, which could influence the maximum frozen depth;(2) the maximum frozen depths under the black pavement and insulation-black pavement were respectively 1.3–1.4 m and 1 m. Compared with cement pavement, they could reduce the maximum frozen depth by 0.4 m and 0.7–0.8 m, respectively, which would reduce the permitted amount of frost heave by 4 mm and 7–8 mm, which would meet the deformation limit established by the Code for Design on Special Subgrade of Railway;(3) the freezing periods of the black pavement and the insulation-black pavement were, respectively, approximately four months and two months. Compared with cement pavement, they could reduce the freezing period by approximately 19 days and 40 days, respectively, and delay the initial freezing time by 9 days and 18 days; and(4) compared with cement pavement, black pavement and black-insulation pavement could reduce the frozen areas of roadbeds in the cold season, which suggests that these two special pavements could provide better thermal stability for roadbeds.     

高铁影响下的中国区域创新时空演化与效应分解

探究高速铁路对区域创新的影响机制将深远影响我国区域经济发展。运用ESDA、SDM和求偏微分等方法,测算了由高铁开通带来的时空压缩对区域创新产出产生的直接效应和间接效应,并通过分地区回归对异质性进行了深入分析。结果表明：我国创新产出具有显著的空间相关性,且集聚程度不断增强,“核心-外围”区域基本形成,创新活动具有一定的锁定特征;其中,R&D人员投入、FDI、政府财政科技支出和居民消费支出是影响区域创新产出的重要因素;高铁开通对创新的影响存在空间异质性,R&D人员全时当量对东部地区的影响最大,东北和中部地区则同时依赖于R&D人员和R&D资本投入,西部地区并未受到极化影响,反而因时空压缩产生了正向溢出效应。     

Analysis of temperature field characteristics based on subgrade site measurements of Harbin-Qiqihar High-speed Railway in a deep seasonal frozen soil region

Recent years have seen a large number of high-speed railways built and will be built in seasonal frozen soil regions of China. Although high-speed railways are characterized by being fast, comfortable and safe, higher standards for deformation of the railways' frozen subgrade are required. Meanwhile, changes in subgrade soil temperatures are the main factors affecting the deformation of frozen subgrade. Therefore, this paper selected typical test subgrade sections of the Harbin–Qiqihar Line, a special line for passenger transport built in the deep seasonal frozen soil regions of China, to monitor field temperatures. Also, the temperature changing laws of railways' subgrade in this region was analyzed by using testing data, the aim of which is to provide a technical support for future design and construction of buildings and structures in a deep seasonal frozen soil region.     

Propagation of vibrations in thawing deep seasonally frozen soils in railway subgrade

In this study, in-situ testing results are given, and the analytical relationship of the vibrations' amplitudes inside an embankment by the thawing of the subgrade surface of seasonably deep frozen soils is provided. The peculiarities of the vibration waves' propagation during the springtime thawing of soils compared to those during the summertime period and the correlation of the vibrations with the under-rail basement modulus of elasticity are defined.     

高速铁路和城市蔓延对雾霾污染的异质性影响

为了探寻高铁开通能否抑制雾霾污染以及这种抑制作用在不同城市空间形态下是否存在异质性,本文首先分析了高铁和城市蔓延对雾霾污染的作用机制,在利用LandScan数据测算2003-2016年中国281个地级市城市蔓延指标的基础上,采用动态空间面板模型检验了城市蔓延与雾霾污染的空间动态关系.借助双重差分(DID)模型验证了高铁...     

高铁新时代下中国铁路交通可达性分布格局及其均衡程度的研究

基于交通可达性指数对2009—2016年期间中国主要城市的交通可达性及其区域差异进行了比较分析,整体上所有主要城市的交通可达性均得到了大幅提升。从范围上来看,无论时间可达性还是经济可达性,东部城市都高于中部和西部城市。高铁建设导致经济活动向区域中心城市的集聚,经济可达性的分布呈现出显著的以各区域中心城市为核心的“中心-外围”结构。但集聚外溢效应同样存在,这种外溢效应主要集中在中心城市的近邻地区,向周边中等规模以上城市扩展。这些现象说明我国区域间交通成本仅仅出现了中等程度的下降,由此导致区域经济集聚程度的提高,尚处在交通成本与区域经济差距之间“倒U字曲线”的中前期阶段。     

Determination of allowable subgrade frost heave with the pavement roughness index in numerical analysis

Frost heave is an upward swelling of soil during cryogenic conditions in cold regions. It is caused by the accumulation of ice crystals in subgrade soil, which grow upwards when freezing temperatures penetrate into the subgrade. This study establishes the allowable soil subgrade frost heave based on the roughness standard of asphalt pavement in China, and aims to balance the pavement design and frost heave resistance of subgrades in cold regions. We formulated a mechanical model of pavement supported by the boundary conditions of differential frost heave, based on the elastic layered system theory. The differential soil subgrade frost heave was modeled as a sinusoidal function, and the allowable frost heave and the roughness index were modeled as the displacement boundaries for the top and bottom of the pavement structure. Then the allowable frost heave was back-calculated according to the roughness standard. Numerical results show that the allowable frost heave depends on the pavement structure, material properties, the highway grade, and other factors. In order to ensure that the actual soil subgrade frost heave is lower than the allowable frost heave, pavement structures and materials need to be selected and designed carefully. The numerical method proposed here can be applied to establish the frost heave resistance of subgrade when the pavement structure and materials are determined.     

中国高铁站的溢出效应及其空间分异——基于夜间灯光数据的实证分析

高铁作为中国交通运输史上一次划时代的变革,对沿线地区的经济发展和区域空间格局产生了重大影响。准确度量高铁站溢出效应及其空间分异规律,对于布设高铁站点、规划高铁新城具有重要意义。本研究解译了2017年前开通的527个高铁站点（对应180个城市）周围地区2004—2017连续14年的夜间灯光数据,采用双重差分法测度了高铁站溢出效应,并解析其空间分异规律。研究发现：第一,在全国层面,中国高铁的投运使站点周围区域经济活动强度提升约4.7%,其中东部地区高铁站溢出效应更为显著。第二,同城高铁站及机场的存在会削弱高铁站的溢出效应,其中机场和高铁站的竞争关系在发达城市更为显著。第三,城市规模与高铁站溢出效应呈非线性关系,特大城市的高铁站溢出效应最为显著;城市第三产业的发展能够提升高铁站溢出效应。此外,与北京、上海、广州（北上广）三大都市的距离是影响高铁站溢出效应的重要因素,随着距离的增加高铁站溢出效应变得不显著甚至为负。上述结论可为高铁站选址、高铁新城规划建设提供重要参考。     

In-situ testing study on convection and temperature characteristics of a new crushed-rock slope embankment design in a permafrost region

For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section of the Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics. The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especially in cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new design of the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of the convection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushed rock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a better cooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditional crushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annual temperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat flux calculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated that the new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful in providing some references for improved engineering design and maintenance of roadbeds in permafrost regions.     

Probabilistic analysis of embankment slope stability in frozen ground regions based on random finite element method

Prediction on the coupled thermal-hydraulic fields of embankment and cutting slopes is essential to the assessment on evolution of melting zone and natural permafrost table, which is usually a key factor for permafrost embankment designin frozen ground regions. The prediction may be further complicated due to the inherent uncertainties of materialproperties. Hence, stochastic analyses should be conducted. Firstly, Karhunen-Loeve expansion is applied to attain the random fields for hydraulic and thermal conductions. Next, the mixed-form modified Richards equation for mass transfer (i.e., mass equation) and the heat transport equation for heat transient flow in a variably saturated frozen soil are combined into one equation with temperature unknown. Furthermore, the finite element formulation for the coupled thermal-hydraulic fields is derived. Based on the random fields, the stochastic finite element analyses on stability of embankment are carried out. Numerical results show that stochastic analyses of embankment stability may provide a more rational picture for the distribution of factors of safety (FOS), which is definitely useful forembankment design in frozen ground regions.     

高铁影响下成渝城市群旅游流网络的变化特征

运用社会网络分析法和GIS空间分析法,对高铁影响下成渝城市群旅游流网络的变化进行深入分析。结果表明：高铁影响下成渝城市群旅游流空间联系日益增强,“H”字型空间发展骨架凸显。高铁的开通加强了重庆主城和成都之间的旅游流互动,行政壁垒现象明显;成渝城市群旅游流在空间上呈现出以重庆主城、成都为核心的“轴-辐”空间组织模式,高铁进一步强化了两大核心的空间辐射能力;成渝城市群旅游流空间存在较为明显的层次性,高铁沿线地区旅游流联系更为密切,高铁增强了高铁沿线与非沿线地区之间的旅游流联系;高铁影响下成渝城市群旅游流空间差异呈扩大态势,高铁沿线旅游资源禀赋较好地区在旅游流网络中的重要性不断提升。     

中蒙俄高铁建设的影响机理及对策

中蒙俄高铁建设是促进中蒙俄交通基础设施互联互通、打造国际陆上交通走廊的重要举措,是中蒙俄经济走廊建设的重要突破口。科学合理地布局中蒙俄高铁线路、规避高铁建设面临的不利影响和风险,急需理清高铁建设的影响因子,揭示其作用机理和空间分布格局,制定针对性强的防控对策。本文分析了中蒙俄高铁建设的主要影响因子,阐明了各类因子对高铁建设的影响机理,通过构建一种综合集成的影响指数评估模型（IIIEM）,量化评估了不同地区各类影响因子的影响指数,揭示了其空间分布格局,并据此制定了消除影响的中蒙俄高铁东线和西线的线路布局建议方案。提出通过“高铁换资源、高铁换市场”等互利共赢创新合作模式,消除经济影响;加强沟通和技术展示,降低社会影响;通过设置缓冲区及高科技手段,规避生态风险;构建中蒙俄跨境地区三大生态风险跨国联合防控体系,加强政策对接,促进中蒙俄经济一体化等防控对策及保障措施。本研究将为中蒙俄高铁建设线路科学合理布局、风险防控提供科技支撑和决策参考。     

An evaluation of the economic,social, and ecological risks of China-Mongolia-Russia high-speed railway construction and policy suggestions

The construction of China-Mongolia-Russia high-speed railways is a strategic move to promote transportation infrastructure inter-connectivity between these countries, which will accelerate the implementation of the China-Mongolia-Russia Economic Corridor. However, well-planned China-Mongolia-Russia high-speed railways demand accurately identifying construction risks, scientifically evaluating risk levels, and mapping the spatial distribution of these risks. Therefore, this study established the integrated risk evaluation model (IREM) to scientifically evaluate the economic, social, and ecological risks of China-Mongolia-Russia high-speed railway construction and determine their magnitude and spatial distribution pattern. Based on this analysis, we propose designs for the east and west China-Mongolia-Russia high-speed railways and policy suggestions to mitigate construction risks. Suggestions include developing innovative cooperation of the "high-speed railway for resources and market", strengthening communication and technology dissemination, and applying innovative engineering techniques and setting buffers; establishing collaborative prevention and control systems to mitigate the three major ecological risks in the China, Mongolia, and Russia trans-border areas; and promoting economic integration by improving strategic coordination. In summary, this study provides scientific support for designing the China-Mongolia-Russia high-speed railways minimizing construction risks.     

京广沿线高铁站腹地的范围与结构研究

随着高铁网络建设全面展开,高铁这一新兴交通方式已在旅客运输中占据重要地位,极大地影响了人们对出行交通方式的选择.为研究高铁车站影响范围与结构,本文选取京广沿线14个高铁站为研究对象,引入“客流腹地”与“商务客流腹地”的概念,分别从总客流和商务客流的角度研究高铁站腹地的范围与结构,并结合相关理论深入探讨其影响因素.研究结果表明:京广沿线高铁站客流腹地的平均腹地半径约为151 km,大于其商务客流腹地(139 km);高铁站客流腹地范围大小与高铁站服务能力、乘客外部出行距离呈正相关,与乘客内部交通出行成本呈负相关;而高铁站商务客流腹地范围大小与高铁站服务能力、商务乘客外部出行距离呈正相关,与商务乘客内部交通出行成本呈负相关.高铁站客流腹地与商务客流腹地均具有明显的“核心—外围”结构,其中客流腹地的“核心—外围”结构与人口分布结构呈正相关,与乘客内部出行时间结构呈负相关,而商务客流腹地的“核心—外围”结构则与城市GDP结构呈正相关,与商务乘客内部出行时间结构呈负相关.     

基于高铁流的中国城市网络结构特征演变研究

高铁的网络化发展促进了资源要素的快速流动与重新整合,对城市关系产生了显著的影响,基于高铁流逐渐成为探索城市和区域空间结构的重要视角。论文使用2014—2019年高铁客运班次数据和社会网络分析法,对中国城市网络结构特征演变进行探讨。研究结果表明：① 伴随高铁线网的不断延伸和加密,城市网络整体上由东向西拓展,网络规模扩大、密度提升;② 节点功能和地位的时序变动重塑了网络的空间格局,改变了由少数东部城市主导的网络格局,呈现出多中心、均衡化的发展趋势;③ 从关联形态看,全国尺度上的复杂网络结构取代了区域尺度上的轴带式联系形态,整体上与“八纵八横”网络相对应;④ 城市网络的关联强度逐年提升,形成了4个联系层级,城市间的关系复杂而多样。     

高铁通车对中国城市创业投资网络的影响——基于跨城市创业投资事件的实证研究

为探究高铁通车对中国城市创业投资网络的影响,论文以2001—2017年间投资于中国大陆的41692件跨城市创业投资事件为样本,研究高铁通车对城市创业投资网络集聚力、辐射力和联系中介力的影响,并进一步探讨其作用机制。渐进双重差分模型(渐进DID模型)分析表明,高铁通车可以提高城市可达性,降低创业投资活动主体的综合交易成本,促进创新创业要素资源跨区流动,对创业投资网络集聚力、辐射力和联系中介力产生正向影响。中心城市的创业投资网络受高铁通车带来的正向影响更强。同时,高铁通车对创业投资网络最优作用范围依投资中心呈环形分布,投资中心辐射半径100~200 km的地区,创业投资网络集聚力、辐射力和联系中介力受高铁通车正向影响要明显强于100 km以内和200 km以外地区。此外,风险性低、回报稳定和市场化程度更高的扩张期和成熟期阶段的创业投资网络集聚力、辐射力和联系中介力受高铁通车影响较种子期和初创期阶段更为显著。