Numerical analysis of high‑speed railway slab tracks using calibrated and validated 3D time‑domain modelling

Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance frequency.In this paper,the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus.It is then compared to the performance of a ballasted track.First,slab and ballasted track models are developed to replicate the full-scale testing of track sections.Once the models are calibrated with the experimental results,the novel slab model is developed and compared against the calibrated slab track results.The slab and ballasted track models are then extended to create linear dynamic models,considering the track geodynamics,and simulating train passages at various speeds,for which the Ledsgard documented case was used to validate the models.Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil,considering the issues associated with critical speeds.Various train loading methods are discussed,and the most practical approach is retained and described.Moreover,correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards.It is found that considering the same ground condition,the slab track deflections are considerably smaller than those of the ballasted track at high speeds,while they show similar behaviour at low speeds.

New technologies for high-risk tunnel construction in GuiyangGuangzhou high-speed railway

Based on the construction of high risk tunnels in Guiguang-Guangzhou high-speed railway, several new technologies were developed for high-risk tunnel con- struction. First, an integrated advanced geological predic- tion was developed for tunneling in karst area. Then, a new system of ventilation by involving the dedusting technol- ogy was proposed and used in the field, which received a good air quality. Finally, a method to minimize the dis- tance between the working face and the invert installation was proposed by optimizing the invert installation and adopting the micro bench method. Applying the method to the project obtained an excellent result. The achievement obtained for this study would be able to provide a valuable reference to similar projects in the future.

The Influence of Sichuan-Tibet Railway on the Accessibility and Economic Development of City Propers along the Line: Taking Chengdu and Ya’an as Examples

The Chengdu-Ya’an section of Sichuan-Tibet Railway(STR),which has already started operation,is taken as an example.First,we apply the weighted average travel time and gravity model to analyze the accessibility of the site cities and the economic link intensity among them,with visualization by ArcGIS.Then,we use the difference-in-differences model with panel data of three cities from 2018 to 2019 to test the impact of the Chengdu-Ya’an section on regional urbanization along the route.The results show that the opening of the Chengdu-Ya’an section has significantly improved the accessibility and economic link of areas along the line and promoted regional economic development and urbanization.It is expected that the opening of the entire line of STR will have more significant impacts,which requires continuous research and attention in the future.

New Stage for Railway Reform and Development

1. Review of railway work in 1996 The year 1996 was an important year for China’s railways in facing a historic turning point—— committing itself to a programme of structural re-

New Railways in China

Beijing-Kowloon Railway The Beijing-Kowloon Railway (Beijing-Shenzhen linking up with Kowloon) runs from north Beijing, through Bazhou, Hengshui, Liaocheng, Heze, Shangqou, Fuyang, Macheng, Jiujiang, Nancheng, Xiangtang, Jian, Ganzhou, Longchuan to Shenzhen, linking up with Kowloon. It is 2, 538 km in length, consisting of a normal railway of 2, 370 km, a secondary railway of 77 km from Tianjin to Bazhou and another secondary railway of 91 km from Macheng to Wuhan. It runs through nine provinces and municipalities——Beijing, Tianjin, Hebei, Shangdong, Henan, Anhui, Hubei, Jiangxi and Guangdong. It will be built by the end of 1995, and begin trial operation in 1996. It has an

Systematic Research and Innovation Practice on New Concepts of Construction for Xiong'an Railway Station

As the first major transport infirastructure in Xiong'an New Area,Beijing-Xiong an Intercity Railway is an important step for China State Railway Group Co.A Ltd.to quickly implement the major strategic plan of CPC Central Committee and the State Council.for the establishment of Xiong'an New Area.Xiong'an Station with double-floor spacious waiting areas and the wonderfiul integration of overpass and station building is the first modern integrated transport hub of this kind in China.Based on the characteristics of Xiong'an Station and in the light of the relevant new theories,methods and technologies,systematic studies and innovative practices on the new concept of building up a"well-connected,filly-integrated,environmen-frindly,passenger-oriented,economically-efficient,uurally-rich,intelligent and convenient"passenger station are carried oul,which achieve good results of application and help accumulate valuable experiences for the construction of passenger stations of Chinese high-speed railways in the new era.

Ensure Rights and Interests of Passengers——On new rules of railway accident investigation and reporting

China has issued new regu- lations on the rescue and investigation of railway acci- dents, which came into forcein September 2007.

The West Railway Station:A New Goat to Beijing

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Dynamic behavior of new cutting subgrade structure of expensive soil under train loads coupling with service environment

Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.

Implementing New Requirements of Passenger Station Construction and Building Excellent Passenger Station

In line with the new concept of building up a“well-connected,fullyi integrated,environment-friendlypassenger-oriented,economically-efficient,culturally-rich,intelligent and convenient”railway station and the construction requirements of"elaborate,fine and exquisite construction of excellent passenger stations" put forward by China State Railway Group Co.Ltd.,design optimization and innovation are carried out in the construction of Nantongxi Railway Station and Pingtan Station in the aspects offunctional layout,decoration style,cultural enhancement,construction materials to be used,details treatment of the station buildings and the use of photoelectric technology,focusing on the consideration and research for furrther enhancing cultural confidence,deeply integrating into the regional features,inheriting historical context,innovating artistic expression,trying diversified integration,and exploring the use of science and technology in the contexl 0f the new era,and thus devoting to the construction of railway passenger stations in the new era which will meet the growing needs of the people for a better life.

Research on Management Innovation and Development for Railway Passenger Station Construction

Based on the general high-quality development requirements for railway construction in the new era,combined with the new concept of railway passenger stations of China State Railway Group Co.Ltd,namely"being well-connected,fully-integrated,environmeni-friendlypassenger-oriented,economically-efficient,culturally-rich,intelligent and convenient"and aiming at the construction of exemplary passenger station projects,this paper summarizes the construction experience in construction,decoration furnishing culture and art expression of railway passenger stations,proposes the working patterns of formulating the implementation plans of exemplary railway passenger station projects and the expert reviews in innovative way studies and forms 6 special-subject designs such as for colorshape,space,environment,art and culture,as wellas the specific design requirements for 13 key areas including waiting hall entrance and exit corridor;VIP room,etc.,and summarizes and puts forward the construction management system of railway passenger stations in the new era,so as to ensure the expected exemplary project quality of railway passenger stations.

Research on Practice of Excellent Railway Passenger Station Construction and High-quality Development

Taking the construction of excellent passenger stations in Beijing-Tianjin-AHebei region as the research object,the paper discusses the implementation of the new concept of building up“well-connected fully-integrated,envioment-friendlyy passenger-oriented,economically-eficient,culturally-rich intelligent and convenient”railway passenger stations It then strives to analyze the connotation of an excellent railway passenger station,the construction and management methods,and the innovation of the working mechanism in the new era.It offers thoughts and methods for promoting the highquality development in the practice of construction for innovative development of excellent passenger stations.

Path selection and mechanism innovation of improving railway energy efficiency–from foreign experience and Chinese practice

Purpose–Under the dual pressure of resources and environment,many countries have focused on the role of railways in promoting low-carbon development of integrated transportation and of even the whole society.This paper aims to provide a comprehensive study on methods to improve railway energy efficiency in other national railways and achievements made by China’s railways in the past practice,and then to propose ways in which in the future China’s railways could rationally select the path of improving energy efficiency regarding the needs of the nation’s ever-shifting development and carry out the re-engineering for mechanism innovation in energy conservation and emission reduction process.Design/methodology/approach–This paper first studies other national railways that have tried to promote the improvement of railway energy efficiency by the ways of technology,management and structural reconstruction to reduce energy consumption and carbon emissions.Among them,the effect of structural energy conservation and emission reduction has become more prominent.It has become the main energy conservation and emission reduction measure adopted by foreign railway sectors.The practice of energy conservation and emission reduction of railways in various countries has tended to shift from a technical level to a structural one.Findings–Key aspects in improving energy efficiency include re-optimization of energy structure,reinnovation of energy-saving technologies and optimization of transportation organization.Path selection includes continuing to promote electrified railway construction,increasing the use of new and renewable energy sources,and promoting the reform of railway transportation organizations.Originality/value–This paper provides further challenges and research directions in the proposed area and has referential value for the methodologies,approaches for practice in a Chinese context.To achieve the expected goals,relevant supporting policies and measures need to be formulated,including actively guiding integrated transportation toward railway-oriented development,promoting innovation in energy-saving and emission reduction mechanisms and strengthening policy incentives,focusing on improving the energy efficiency of railways through market behavior.At the same time,it is necessary to pay attention to new phenomena in the railway industry for track and analysis.

Viscoplastic solutions of time-dependent deformation for tunnels in swelling rock mass considering stress release

Excavation and control of tunneling responses in swelling soft-rock tunnels of Sichuan-Tibet railway under seepage conditions were studied.For this,a fractional viscoplastic(FVP)model for swelling soft rocks was established by introducing Abel dashpot and unsteady viscosity coefficient,considering additional swelling deformation and damage of rock caused by humidity effect.In view of the FVP model,the viscoplastic deformation solutions for rock mass surrounding tunnel under seepage conditions were derived and long-term mechanical responses of swelling rocks upon tunnel excavation were analyzed.Next,a stress release coefficient considering seepage and creep was proposed,based on which control responses considering stress release and failure mechanism of stress release measures were analyzed.The results showed that:(i)The one-dimensional(1D)FVP model has a good application for swelling rock and the three-dimensional(3D)FVP model could well describe the whole creep process of rock mass despite a much higher creep attenuation rate in the first stage of creep;and(ii)An appropriate stress release and deformation of surrounding rocks could effectively reduce the supporting resistance.However,upon a large stress release,the radius of plastic region could increase significantly,and the strength of the surrounding rock mass decreases greatly.The proposed solution could provide a theoretical framework for capturing the excavation and support responses for tunneling in swelling rock mass in consideration of time effect.

Analysis of the future trends of typical mountain glacier movements along the Sichuan-Tibet Railway based on ConvGRU network

The anomalous movements of glaciers cause disasters,such as debrisflows and landslides.It is very important to assess the glacier movements and their future trends.Glacier velocity refers to movement process.The current research aims to analyse past and current spatiotemporal changes in glacier velocity.No study has used neural network model to conduct a spatiotemporal prediction for glacier velocity.Therefore,this paper selected typical mountain glaciers G2 and G5 along the Sichuan-Tibet Railway as research objects and constructed the Convolutional Gate Recurrent Unit(ConvGRU)spatiotemporal prediction model based on 1988–2018 Landsat data to predict velocities in 2019–2028,and analysed the future trends of G2 and G5.The evaluation indexes met the model requirements to a large extent,quantitatively showing that the model has high accuracy and can successfully capture thefluctuation changes in time series data of glacier velocity.The mean deviations of G2 and G5 were 0.09 and-0.47 m/yr,respectively,reflecting the high reliability of the model applied to extraction of glacier velocity.The velocities of G2 and G5 showed a slow downtrend withfluctuations;that is,they will not cause damage to the construction and operation of the Sichuan-Tibet Railway in the short term.

Historical Changes and Future Projections of Extreme Temperature and Precipitation along the Sichuan-Tibet Railway

Based on multiresource high-resolution in situ and satellite merged observations along with model simulations from the Coordinated Regional Climate Downscaling Experiment(CORDEX),this study first investigated historical changes in extreme temperature and precipitation during the period of 1979-2018 in areas along the Sichuan-Tibet Railway,and then projected the future changes in the frequency and intensity of extreme temperature and precipitation under the RCP(Representative Concentration Pathway)4.5 and 8.5 scenarios.This paper is expected to enhance our understanding of the spatiotemporal variability in the extreme temperature and precipitation along the Sichuan-Tibet Railway,and to provide scientific basis to advance the Sichuan-Tibet Railway construction and operation.The results show that temperatures in the Sichuan-Tibet region display a noticeable warming trend in the past 40 years,and the increase of minimum temperature is significantly higher than that of maximum temperature in the northwest of the region.Significant increase of precipitation is found mainly over the northwest of the Tibetan Plateau.Except for Lhasa and its surrounding areas,precipitation over other areas along the Sichuan-Tibet Railway shows no significant change in the past 40 years,as indicated in five datasets;however,precipitation along the railway has shown a remarkable decrease in the past 20 years in the TRMM satellite dataset.The warm days and nights have clearly increased by 6 and 5 day decade1-for 1979-2019,while cold days and nights have markedly decreased by about 6.6 and 3.6 day decade-1,respectively.In the past 20 years,the areas with increased precipitation from very wet days and extremely wet days are mainly distributed to the north of the Sichuan-Tibet Railway,while in the areas along the railway itself,the very wet days and extremely wet days are decreasing.Under RCPs 4.5 and 8.5,the temperature in the Sichuan-Tibet region will increase significantly,and the frequency of extreme high(low)temperature events in the late 21 st century(2070-2099)will greatly increase(decrease)by about 50%-80%(10%)compared with occurrences in the late 20 th century(1970-1999).Meanwhile,the frequency of very wet days and extremely wet days in the Sichuan-Tibet region will increase by about 2%-19% and 2%-5%,respectively,and the areas along the Sichuan-Tibet Railway will be affected by more extreme high temperature and extreme precipitation events.

Risk warning technologies and emergency response mechanisms in Sichuan-Tibet Railway construction

Safety is one of the most critical themes in any large-scale railway construction project.Recognizing the importance of safety in railway engineering,practitioners and researchers have proposed various standards and procedures to ensure safety in construction activities.In this study,we first review four critical research areas of risk warning technologies and emergency response mechanisms in railway construction,namely,(i)risk identification methods of large-scale railway construction projects,(ii)risk management of large-scale railway construction,(iii)emergency response planning and management,and(iv)emergency response and rescue mechanisms.After reviewing the existing studies,we present four corresponding research areas and recommendations on the Sichuan-Tibet Railway construction.This study aims to inject new significant theoretical elements into the decision-making process and construction of this railway project in China.

Vertical temperature gradients of concrete box girder caused by solar radiation in Sichuan-Tibet railway

Spatial and temporal temperature variations are critical for concrete box girders,and non-uniform temperature distributions induced by solar radiation depend on the structural shapes and shadows cast on them.There have been many studies of temperature distributions and temperature gradients of concrete box girders,but few have considered a high altitude plateau climatic environment.In this study,the nonlinear temperature distributions of concrete box girders in the Sichuan-Tibet railway caused by solar radiation were investigated based on experimental analysis,real-time shadow-selection algorithm,and finite element method.Furthermore,a vertical temperature gradient model of the concrete box girders was obtained.The vertical temperature gradient values first rise,then decrease,and finally rise again from Chengdu to Lhasa,with samples forming a normal distribution.The recommended vertical temperature gradient value was 25℃with a confidence interval of 95%.This provides a reference for the design and maintenance of concrete box girders on the Sichuan-Tibet railway.

Reliability guarantee framework for the Sichuan-Tibet Railway

The Sichuan-Tibet Railway is facing extraordinary challenges in terms of construction,operation,and maintenance because of its extremely complicated natural environment and geological conditions.Consequently,countermeasures are necessary and urgent to ensure its safety and reliability in the whole life cycle.This study proposes a novel reliability framework to guarantee the ideal operation state of the Sichuan-Tibet Railway.Reliability application in many fields are summarized,including military equipment,rail locomotive,and railway engineering.Given the fact that the Sichuan-Tibet Railway is a complex giant system,Nine-Connotation was summarized(i.e.,safety,inherent reliability,testability,maintainability,supportability,environmental adaptability,predictability,resilience,and durability)under the goal of optimizing the operational efficiency.On the basis of the concept of the Nine-Connotation and the understanding of reliability transmission mechanism,the framework of reliability for the Sichuan-Tibet Railway was established,which can facilitate a comprehensive and real-time evaluation of all situations with a clear hierarchy.The proposed framework is composed of a resilience management system,an integrated technology system,and a dynamic reliability assessment system.The pathway for its application on railway construction was developed in this study.The proposed framework can assist in well-informed decisions for the construction,as well as the operation of the Sichuan-Tibet Railway.On the basis of a top-down design concept for the first time,this study emphasizes the railway's availability and validity to complete the assigned tasks as a whole,that is,operational efficiency.It also shows the reliability transmission and control mechanism of the railway's giant complex system,innovating and establishing the management principle of great safety and great reliability over the life cycle.

Deep learning based Doppler frequency offset estimation for 5G-NR downlink in HSR scenario

In the fifth-generation new radio(5G-NR) high-speed railway(HSR) downlink,a deep learning(DL) based Doppler frequency offset(DFO) estimation scheme is proposed by using the back propagation neural network(BPNN).The proposed method mainly includes pre-training,training,and estimation phases,where the pre-training and training belong to the off-line stage,and the estimation is the online stage.To reduce the performance loss caused by the random initialization,the pre-training method is employed to acquire a desirable initialization,which is used as the initial parameters of the training phase.Moreover,the initial DFO estimation is used as input along with the received pilots to further improve the estimation accuracy.Different from the training phase,the initial DFO estimation in pre-training phase is obtained by the data and pilot symbols.Simulation results show that the mean squared error(MSE) performance of the proposed method is better than those of the available algorithms,and it has acceptable computational complexity.