Dynamic response of mountain tunnel,bridge,and embankment along the Sichuan-Tibet transportation corridor to active fault based on model tests

The Sichuan-Tibet transportation corridor is prone to numerous active faults and frequent strong earthquakes.While extensive studies have individually explored the effect of active faults and strong earthquakes on different engineering structures,their combined effect remains unclear.This research employed multiple physical model tests to investigate the dynamic response of various engineering structures,including tunnels,bridges,and embankments,under the simultaneous influence of cumulative earthquakes and stick-slip misalignment of an active fault.The prototype selected for this study was the Kanding No.2 tunnel,which crosses the Yunongxi fault zone within the Sichuan-Tibet transportation corridor.The results demonstrated that the tunnel,bridge,and embankment exhibited amplification in response to the input seismic wave,with the amplification effect gradually decreasing as the input peak ground acceleration(PGA)increased.The PGAs of different engineering structures were weakened by the fault rupture zone.Nevertheless,the misalignment of the active fault may decrease the overall stiffness of the engineering structure,leading to more severe damage,with a small contribution from seismic vibration.Additionally,the seismic vibration effect might be enlarged with the height of the engineering structure,and the tunnel is supposed to have a smaller PGA and lower dynamic earth pressure compared to bridges and embankments in strong earthquake zones crossing active faults.The findings contribute valuable insights for evaluating the dynamic response of various engineering structures crossing an active fault and provide an experimental reference for secure engineering design in the challenging conditions of the Sichuan-Tibet transportation corridor.

Geological risk assessment of traffic engineering construction among 7.0-8.5 magnitude earthquake areas:Practice from the Sichuan-Tibet transport corridor in the eastern Tibetan Plateau

At least 13 active fault zones have developed in the Ya'an-Linzhi section of the Sichuan-Tibet transport corridor,and there have been undergone 17 MS≥7.0 earthquakes,the largest earthquake is 1950 Chayu MS 8.5 earthquake,which has very strong seismic activity.Therefore,carrying out engineering construction in the Sichuan-Tibet transport corridor is a huge challenge for geological technological personnel.To determining the spatial geometric distribution,activity of active faults and geological safety risk in the Sichuan-Tibet transport corridor.Based on remote sensing images,ground surveys,and chronological tests,as well as the deep geophysical and current GPS data,we investigated the geometry,segmentation,and paleoearthquake history of five major active fault zones in the Ya'an-Linzhi section of the Sichuan-Tibet transport corridor,namely the Xianshuihe,Litang,Batang,Jiali-Chayu and Lulang-Yigong.The five major fault zones are all Holocene active faults,which contain strike-slip components as well as thrust or normal fault components,and contain multiple branch faults.The Selaha-Kangding segment of the Xianshuihe fault zone,the Maoyaba and Litang segment of the Litang fault zone,the middle segment(Yigong-Tongmai-Bomi)of Jiali-Chayu fault zone and Lulang-Yigong fault zone have the risk of experiencing strong earthquakes in the future,with a high possibility of the occurrence of MS≥7.0 earthquakes.The Jinsha River and the Palong-Zangbu River,which is a high-risk area for geological hazard chain risk in the Ya'an-Linzhi section of the Sichuan-Tibet transport corridor.Construction and safe operation Ya'an-Linzhi section of the Sichuan-Tibet transport corridor,need strengthen analysis the current crustal deformation,stress distribution and fault activity patterns,clarify active faults relationship with large earthquakes,and determine the potential maximum magnitude,epicenters,and risk range.This study provides basic data for understanding the activity,seismicity,and tectonic deformation patterns of the regional faults in the Sichuan-Tibet transport corridor.

Potential seismic landslide hazard and engineering effect in the Ya’an-Linzhi section of the Sichuan-Tibet transportation corridor, China

The Sichuan-Tibet transportation corridor is located at the eastern margin of the Qinghai-Tibet Plateau,where the complex topography and geological conditions,developed geo-hazards have severely restricted the planning and construction of major projects.For the long-term prevention and early control of regional seismic landslides,based on analyzing seismic landslide characteristics,the Newmark model was used to carry out the potential seismic landslide hazard assessment with a 50-year beyond probability 10%.The results show that the high seismic landslide hazard is mainly distributed along large active tectonic belts and deep-cut river canyons,and are significantly affected by the active tectonics.The low seismic landslide hazard is mainly distributed in the flat terrain such as the Quaternary basins,broad river valleys,and plateau planation planes.The major east-west linear projects mainly pass through five areas with high seismic landslide hazard:Luding-Kangding section,Yajiang-Xinlong(Yalong river)section,Batang-Baiyu(Jinsha river)section,Basu(Nujiang river)section,and Bomi-Linzhi(eastern Himalaya syntaxis)section.The seismic action of the Bomi-Linzhi section can also induce high-risk geo-hazard chains such as the high-level glacial lake breaks and glacial debris flows.The early prevention of seismic landslides should be strengthened in the areas with high seismic landslide hazard.

Ecological vulnerability assessment of the Ya'an-Qamdo section along the southern route of the Sichuan-Tibet transportation corridor

Identifying the ecological vulnerability of the sensitive and fragile ecosystem of the Ya’anQamdo section along the southern route of the Sichuan-Tibet transport corridor is of paramount importance to reduce environmental damage resulting from infrastructure construction.This paper divided the Ya’an-Qamdo transport section into 22subzones according to their ecological environment characteristics.Based on the vulnerability evaluation model established by the fuzzy matter-element analysis method,the eight main assessment indicators of ecological vulnerability were windstorm,rainstorm,snowstorm,extreme temperature,extreme air pressure,geological hazard,natural conditions,and social resources.The rating and ranking of vulnerability in each subzone were based on the weight of the judgment indicators.Scientific processes were used to verify the rationality of both the indicators themselves and their weights.The results of this study show that subzone 9,located in the subalpine cold and humid forest and scrubland zone,is the most vulnerable,and subzone 1,located in the low-to mid-land warm and humid forest zone,is the least vulnerable.The conclusion of the study suggests that targeted measures of ecological protection should be formulated before development and construction of major transportation infrastructure.Construction should evade the most vulnerable areas,and in-depth research on ecological restoration should be carried out in low-to midvulnerability areas so that the ecological environment along the route can be protected effectively for sustainable economic and social development.

GIS-based spatial prediction of landslide using road factors and random forest for Sichuan-Tibet Highway

Accurate evaluation of landslide susceptibility is very important to ensure the safe operation of mountain highways.The Sichuan-Tibet Highway,which traverses the east of the Tibetan Plateau,frequently encounters natural hazards.Previous studies generally use statistical methods to analyze the hazards along the Sichuan-Tibet Highway.In this research,we present two road factors,namely aspect to road and road profile to increase the accuracy of landslide susceptibility mapping by considering the influence of landslide movement direction on road.First,the aspect to road,which represents the impact of different landslide movement directions on the highway,was extracted by combining road direction with mountain aspect.Then,the road profile,which reflects the subgrade structure between the road and surrounding mountains,was extracted according to the terrain data.Finally,the landslide susceptibility maps were produced based on the random forest(RF)method by using 473 landslides and 10 conditioning factors,including road factors(aspect to road,road profile)and primitive factors(slope,aspect,curvature,relief amplitude,peak ground acceleration,crustal movement velocity,faults,rainfall).The area under the receiver operating characteristic curve(AUC)and the Gini importance were used to evaluate the performance of proposed road factors.The AUC values on two groups that add road factors and only use primitive factors were 0.8517 and 0.8243,respectively.The Gini importance indicated that road profile(0.123)and aspect to road(0.116)have a significant contribution to landslides compared with the primitive factors.The results of multi-collinearity analysis and frequency ratio confirmed the suitability of the road factors for predicting hazards along the highway.

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.

Sichuan-Tibet Highway Brings Prosperity to Tibetans

SIXTY-EIGHT years ago, the Song of the Erlang Mountain was a smash hit all over China. It is an ode to the heroic builders of the highway between Sichuan and Tibet, which cuts through towering mountains and spans billowy rivers.

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.

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.

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.

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.

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.

明清之际川藏道的兴起及在中央和西藏地方中的连接作用

明清之际,川藏道逐渐兴起,并成为中央与西藏地方之间的重要连接纽带。除了中央政府的主动开拓,西藏地方也参与到了整个进程之中。自明中后期开始,大量藏族僧俗人员自川藏道前往内地朝贡,并将巨额茶叶、布匹、金银等物资带回西藏,这是“汉藏金桥”兴起的重要背景。当康区的白利土司阻断了川藏道时,以五世达赖喇嘛为首的西藏地方支持蒙古首领固始汗,攻灭了白利。清初,西藏地方与内地在川藏道东端打箭炉广泛开展贸易活动。康熙三十九年(1700)“西炉之役”与五十九年(1720)清军进藏驱逐准噶尔后,川藏道沿线多数地区逐渐纳入四川省管辖,清朝为保障道路畅通,以巨额茶叶与白银对西藏地方进行经济补贴。由川藏道的兴起及中央与西藏地方的互动,可以深刻理解该道成为双方连接纽带的原因,以及西藏地方牢固纳入中原政治体系的内在逻辑。

四川、西藏部分地区牦牛场球虫感染情况调查

【目的】调查四川省和西藏自治区部分地区牦牛球虫感染情况,为该地区牦牛球虫病的预防、控制提供理论参考。【方法】从四川省和西藏自治区部分地区8个牦牛场采集2~6、7~12和>12月龄牦牛的新鲜粪样共376份,采用饱和盐水漂浮法对粪便样品中球虫卵囊进行定性检查,采用麦克马斯特计数法统计球虫阳性粪样中每克粪便中的球虫卵囊数(OPG),了解不同牦牛场、不同月龄牦牛的球虫感染情况。【结果】8个牦牛场均检测出球虫感染,阳性样品共85份,平均感染率为22.6%(85/376),平均OPG为1643。共检出9种艾美耳属球虫,优势虫种为阿拉巴艾美耳球虫,感染率为37.6%(32/85),多呈混合感染。平均感染率最高的是2~6月龄牦牛,感染率为37.9%(11/29);其次是7~12月龄牦牛,感染率为31%(57/184);>12月龄牦牛的球虫感染率为10.4%(17/163)。【结论】四川和西藏部分地区牦牛场均存在不同程度的球虫感染,均以混合感染为主。牦牛球虫感染率、感染强度以及优势虫种在不同地区、不同年龄牦牛之间存在差异。

川藏铁路电力机车司机室空气品质控制研究

为了保证电力机车在川藏铁路运行过程中司机室内有良好的空气品质,通过调研雅安至林芝段沿线海拔、温度及隧道热害情况,分析人体对空气成分的耐受性,建立司机室空气品质仿真模型,研究了机车运行过程中司机室内O_(2)和CO_(2)质量比的动态变化特性。结果表明:该路段部分隧道存在热害及有毒有害气体问题;人体对空气成分的耐受性要求为司机室内CO_(2)质量百分比不应超过0.23%,以及O_(2)质量百分比应控制在21.5%~25.4%;司机室下方的O_(2)质量百分比高于司机头部上方,司机前方的O_(2)质量百分比较低。人员头部上方区域的O_(2)质量百分比大多都在19%以下,室内前端的CO_(2)质量百分比达到0.28%以上;机车以160 km/h的时速运行在热害及有毒气体隧道内关闭新风系统,而在其他路段将新风量从常规的25 m3/(h·人)增加到40 m^(3)/(h·人),可使司机室内O_(2)和CO_(2)质量百分比均满足室内环境要求;当车速一定时,随着新风量的提高,司机室内环境会有较好的改善;当新风量一定时,随着机车时速的增加,司机室内所需满足空气环境要求的新风量将会减少。研究结果可为川藏铁路机车设计提供参考依据。

基于红外相机对拟建川藏铁路(康定至巴塘段)沿线6种有蹄类动物活动节律研究

基于国家重大工程川藏线建设需求,为降低道路建设和运营对野生动物的影响,于2019年6月—2021年6月通过红外相机技术对拟建川藏铁路沿线(康定至巴塘段)6种有蹄类动物的活动节律进行了研究。结果表明:1)毛冠鹿(Elaphodus cephalophus)在6种有蹄类动物中相对丰富度最高,其次为中华鬣羚(Capricornis milneedwardsii),水鹿(Rusa unicolor),野猪(Sus scrofa),马麝(Moschus chrysogaster),中华斑羚(Naemorhedus griseus)。2)毛冠鹿与中华鬣羚的年活动格局具有较高的相似度,1—4月相对丰富度为全年最低,5—6月逐渐上升,7月达到全年最高峰,之后逐渐降低。3)毛冠鹿和马麝的日活动规律相似,均属双峰型,具明显晨昏习性;野猪和水鹿日活动模式呈单峰型,水鹿活动曲线呈U形,午间出现低谷,属于特殊的单峰模式;中华鬣羚和中华斑羚活动规律不明显。4)毛冠鹿和野猪在旱季和雨季的日活动节律具有明显的分化。5)水鹿和马麝是典型的夜行性动物,毛冠鹿和野猪是典型的昼行性动物,中华鬣羚和中华斑羚不具有明显的昼夜行性。

新时代“两路”精神的弘扬路径研究——纪念川藏、青藏公路建成通车70周年

“两路”精神是中国共产党人精神谱系的重要组成部分。新时代弘扬“两路”精神,不仅要注重史论结合,从内涵阐释、根源回溯和历史定位发轫,夯实传承弘扬基础,还要注重红绿相映,从国家文化公园、协同研究中心和实践教学基地建设着手,构建教育引导体系;既要注重文工交叉,从“两路”建设养护、进藏铁路修建及科技攻坚克难着力,实现文化涵育功能,又要注重文旅融合,从整合文化资源、创建品牌标识、完善支撑条件入手,助推红色经济发展。

近红外高光谱传感器在地震有关气体监测中的应用:以青藏高原东边界为例

为了促进高光谱技术在地震有关气体监测中的应用,本文选取对近地表信息敏感度较强的近红外高光谱传感器TROPOMI的二级产品数据,分析研究了青藏高原东北缘和川滇地区地震相关气体时空特征及其与构造和地震活动关系,评价了近红外传感器在地震有关气体监测中的应用效果和应用前景。结果表明:TROPOMI反演的研究区CH_(4)和CO气体在时间上呈现明显的季节变化,受气候变化、地貌、人类活动等影响;空间上在银川、渭河和四川盆地表现为高值,受地质背景、地形地貌和人类活动等因素影响。目前近红外高光谱传感器在时间分辨率和有效数据量上具有一定的局限性,但是相对于热红外高光谱传感器,近红外传感器可以较好地反映气体与近地表构造的关系。未来随着近红外高光谱传感器的应用和发展,近红外数据可以逐渐弥补热红外传感器数据对近地表信息敏感度低的不足,提高异常与地震关系的判断力。

318国道川藏线旅游景点空间分布特征及影响因素研究

景点是旅游系统中不可或缺的要素,厘清其空间分布特征及影响因素是优化旅游景点空间布局、促进区域旅游业发展的关键。本研究基于POI大数据,综合运用最邻近指数、变异系数、核密度分析、Getis-Ord Gi*热点分析、地理探测器探究318国道川藏线旅游景点的空间分布特征及影响因素,结果显示:(1)318国道川藏线旅游景点在空间分布上为典型的集聚分布。(2)318国道川藏线旅游景点整体呈现出“两中心高度集聚,其他区域零散分布”和“依山、聚盆”的分布态势,大多位于101~1000 m的低海拔区域和3000~5000 m的中高海拔区域,上山趋势明显。(3)318国道川藏线旅游景点冷热区域呈现出“东热西冷”的分布格局。(4)318国道川藏线旅游景点布局受GDP影响显著,受海拔影响最弱;双因子交互作用的影响力均高于单因子作用,并产生明显的双因子增强作用。基于上述研究结论,提出318国道川藏线旅游景点空间统筹优化建议,为促进道路沿线区域旅游提档升级发展提供借鉴。

重力异常改正在山区铁路工程控制网二等水准复测中的应用

川藏铁路高差起伏大,横断山区重力异常及其变化大,重力异常改正值远远大于测量误差,从不同水准路线进行环线闭合,必须进行水准面不平行改正、重力异常改正。通过工程案例可以看出,重力异常改正在二等水准网观测计算中至关重要。