对滇藏铁路三江段工程地质问题的深化认识

IN-DEPTH DISCUSSIONS ON THE ENGINEERING GEOLOGICAL PROBLEMS ALONG SANJIANG SECTOR OF YUNNAN—TIBET RAILWAY LINE

滇藏铁路三江段东起云南省丽江城,西至西藏自治区八宿县城,是铁路建设最艰难的地段,特别是工程地质问题纷繁复杂。通过作者近几年来的工作,取得了对该区基础地质问题的一些新认识,据此从根本上来认识铁路可能存在的工程地质问题。三江地区广泛分布的地层岩性是古生界灰岩和中生界砂质泥岩,灰岩往往呈岛状被中生界砂质泥岩所围陷,以及燕山晚期岩浆岩。地震与活动断裂关系不密切,调查中未见区域性大断裂迹象。综合分析三江段存在的深层次铁路工程地质问题有:灰岩区岩溶引起的工程地质问题、碎屑岩区易溶盐析出引起的工程地质问题、坐滑体内工程地质问题、地震引起的工程地质问题、高地温区工程地质问题和劈理化带引起的工程地质问题,各类工程地质问题之间相互联系。工程地质问题严重的地段有玉龙县拉市海至香格里拉县虎跳镇街段、德钦县白马雪山段、德钦县梅里雪山段和八宿县冷曲段,对这些地段的工程地质问题应开展深入研究并采取工程对策。

The sector along the Yunnan—Tibet railway line,from Lijiang city in Yunnan province on the east and to Basu county in Tibet Autonomous region in the west is named as Sanjiang sector,where Sanjing means three rivers： Nujiang River,Lancangjiang River and Jinshajiang River.It has been confirmed that the Sanjiang sector is the most difficult sector for the railway construction.Especially there are complex engineering geological problems.On the basis of the authors＇ recent studies,some new understandings on the basic geology of the region are put forward in the paper.Recognitions on the possible railway engineering geological problems are fundamentallypointed out.The strata or rocks distributed extensively in Sanjiang region are Paleozoic limestone.It likes islands surrounded by Mesozoic sandy mudstone.Then the late Yanshan period magmatite was developed there.The connection between earthquake and active fault was not very close.There were no obvious regional fault signs.It is comprehensively realized that there were many deep-level railway engineering geological problems in Sanjiang sector.The problems are caused by karstification in limestone areas,by soluble salts precipitation in clastic rocks areas,by earthquake,and/or by cleavable zone.Some problems are in drop-style slide rock masses and/or,in high geothermal temperature areas.Each type of the problems are correlated.The sub-sectors with serious problems are the sector from Lashi lake in Yulong county to Hutiao town street in Sangrila county,the Baima Snow Mountain sector in Deqin county,the Meili Snow Mountain sector in Deqin county,and the Lengqu sector in Basu county.These subsectors should be deeply investigated and treated with adequate countermeasures.