Quantitative Zoning Assessment of Crustal Stability Along the Yunnan-Tibet Railway Line,Western China

The planned Yunnan-Tibet railway goes through the northwest of Yunnan Province and the southeast of the Tibet Autonomous Region. Because of its location near the collision belt of the Eurasian and Indian plates, complex engineering geological conditions and difficult engineering geological problems are encountered. The study is aimed at making the zoning assessment of crustal stability along the railway line so as to provide a better base for its construction, especially its line selection. For this purpose, the following seven influencing factors of crustal stability were selected and quantified by grading and scoring： active fault, seismic activity, geo-stress field, geo-strain field, geothermal field, geo-hazard, and lithologic character. Of these factors, the active fault, seismic activity and geo-hazard are the three most prominent factors influencing the railway construction. Along the railway line there are 1731703 calculation units to be divided. The zoning assessment calculation was completed by ArcGIS-based information fusion method. The assessment results aid railway line selection and show that there are 10 stable sectors, 28 relatively stable sectors, 23 relatively unstable sectors, and 20 unstable sectors along the Yunnan-Tibet railway line.

Railway Construction in Tibet

Authored by Li Ping and Li Xinhu, the book actually is the result of research into “schemes of construction of railways in Yunnan and Tibet.” The book centers around research into the scheme of construction of the YunnanTibet Railway, conducting comprehensive studies involving political, economic, technological, social and State security fields.

ALL TUNNELS ON LHASA-NYINGCHI RAILWAY COMPLETE

Construction on the last two(Mainling Tunnel and Zagar Tunnel)of the 47 tunnels pertaining to a railway linking Lhasa and Nyingchi in Tibet Autonomous Region has been completed on April 7.Lhasa-Nyingchi Railway is a section of Sichuan-Tibet Railway,which is the first electrified railway in Tibet with a total length of 435 km and a designated speed of 160 km per hour.It is expected to be completed by the end of 2020,and start operation in 2021.

EXPERIENCE THE RAILWAY FROM LHASA TO NYINGCHI

On June 25,2021,Tibet's first ectric railway,the Lhasa-Nyingchi Railway,was officially put into operation.This is the third railway to be opened in the Tibet Autonomous Region after the Qinghai-Tibet Railway and the Lhasa-Shigatse Railway.

Scientific problems and research proposals for Sichuan–Tibet railway tunnel construction

The Sichuan–Tibet railway construction has received significant attention from both China and abroad.The new section from Ya’an to Nyingchi is about 1018.6 km long,including 69 tunnels with a total length of 841.7 km.The longest tunnel(Yigong tunnel)is 42.4 km long.The successful construction of the Sichuan–Tibet railway depends largely on tunnel construction.Due to the complex conditions,tunnel construction for the Sichuan–Tibet railway poses great challenges to the research community.This paper aims to illustrate the necessity of interdisciplinary and joint research to solve problems associated with tunnel construction that will be encountered in the immediate future and facilitate the communication and exchange of ideas between disciplines.To this end,based on a systematic analysis of the available data related to Sichuan–Tibet railway tunnels,six major aspects of the geology,environment,and engineering conditions are identified.Next,based on the engineering responses from the Sichuan–Tibet railway tunnels,potential technical problems and risk characteristics are predicted and evaluated.Further,six key scientific issues are identified and discussed based on a coupled multi-layer analysis of essential tunnel engineering issues.Finally,research directions,technical ideas,and research methods that should be carried out for this project are proposed.

Refined Evaluation of Satellite Precipitation Products against Rain Gauge Observations along the Sichuan–Tibet Railway

Being constructed in southwestern China, the Sichuan–Tibet Railway(STR) travels across the eastern Tibetan Plateau where there is the most complex terrain and changeable weather in the world. Due to sparse ground-based observations over the Tibetan Plateau, precipitation products retrieved by remote sensing are more widely used;however,satellite-based precipitation products(SPPs) have not yet been strictly and systematically evaluated along the STR.This study aims to evaluate the performance of six SPPs by a series of metrics with available ground observations along the STR during 1998–2020. The six SPPs include the datasets derived from the Tropical Rainfall Measuring Mission(TRMM), Climate Prediction Center morphing technique(CMORPH), Global Precipitation Measurement(GPM), Global Satellite Mapping of Precipitation(GSMaP), Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks(PERSIANN), and Fengyun-2 satellites precipitation estimate(FY2PRE). The results indicate that most of the SPPs can capture the precipitation characteristics on multiple timescales(monthly,daily, hourly, and diurnal cycle) as shown by the evaluated metrics. The probability density functions of the daily and hourly precipitation are also well represented by the SPPs, and 30 mm day^(-1) and 16 mm h^(-1) are identified as the daily and hourly thresholds of extreme precipitation events along the STR. The best SPP varies at different timescales:GPM and GSMaP are suitable for the monthly and daily scale, and FY2PRE and GPM are suited to the hourly scale.In general, GPM is relatively optimum on multiple timescales, and PERSIANN gives the worst performance. In addition, the SPPs perform worse at higher altitudes and for more intense precipitation. Overall, the results from this study are expected to provide essential reference for using the SPPs in meteorological services and disaster prevention in the STR construction and its future operation.

News in Brief

Bullet Train Debuts on New Railway in Tibet The first electrified railway in the Tibet Autonomous Region opened on June 25,linking the regional capital Lhasa with the city of Nyingchi,as Fuxing bullet trains enter official operation on the plateau region.With a length of 435 km and a designed speed of 160 km per hour,the new railway is a single-line electrified railway.It is the first time that a Fuxing bullet train,which was independently developed by China,is transporting passengers in Tibet.