青藏工程走廊多年冻土场地地震安全性研究进展

Advances on Seismic Safety Study of the Permafrost Sites along QinghaiTibet Project Corridor

宽度不到10 km的青藏工程走廊穿越长约550 km的多年冻土区,承载了青藏铁路、青藏公路等重要生命线工程,同时,该地区强震多发,工程设施未来遭遇地震作用的风险较大。围绕青藏工程走廊多年冻土区这一特殊研究区域,从地震危险性分析和多年冻土场地地震动特征研究两方面对青藏工程走廊多年冻土区场地地震安全性研究现状进行回顾,并介绍最新研究进展。基于青藏工程走廊地震危险性对比分析结果,分别给出50年和100年超越概率63%、10%、2%的青藏工程走廊基岩地震动区划图,并转换得到50年超越概率10%的青藏工程走廊一般场地PGA区划图,与第五代中国地震动参数区划图相比,PGA=0.2g的范围有所扩大。场地反应分析结果表明,多年冻土场地地震动特征与冻土层温度及厚度、季节融化层厚度、冻土夹层厚度及其埋深有关。完全冻结场地地震动特征主要受冻土层温度和厚度影响,季节融化场地地震动特征主要受季节融化层厚度和多年冻土层厚度影响,多年冻土夹层场地地震动特征主要受冻土夹层厚度及埋深影响。研究结果可为青藏工程走廊内多年冻土区地震灾害风险区划、重大冻土工程地震安全性评价、寒区新建工程抗震设防及已有工程设施抗震加固等提供参考。

The Qinghai-Tibet Engineering Corridor(QTEC)with a width of less than 10 km passes through a permafrost region about 550 km long,carrying important lifeline projects such as the Qinghai-Tibet Railway and the Qinghai-Tibet Highway.At the same time,in this area,strong earthquakes are frequent,and the engineering facilities will face greater risk of earthquake damage in the future.Focusing on the particular study area of the permafrost region in the QTEC,the present state of seismic safety study on the permafrost site along QTEC is reviewed,and the latest research progress is introduced from the aspects of seismic hazard analysis and ground motion characteristics of permafrost sites.Based on the results of comparative analysis of the seismic hazards along QTEC,bedrock site PGA zonation maps of QTEC for 63%P.E,10%P.E,2%P.E in 50 a and 100 a are given,and then are converted to general site PGA zonation maps of QTEC for 10%P.E in 50 a.By comparing with the fifth-generation seismic ground motion parameters zonation map of China,the range of PGA=0.2 g extends.The results of the site seismic response analysis show that the seismic ground motion characteristics of the permafrost sites are related to the temperature and thickness of the frozen layer,the thickness of the seasonal thawing layer,and the thickness and buried depth of the frozen interlayer.The ground motion characteristics of the completely frozen site are mainly affected by the temperature and thickness of the frozen soil.The ground motion characteristics of the seasonal thawing site are mainly affected by the thickness of the seasonal thawing layer and the thickness of the permafrost layer.The ground motion characteristics of the site with frozen interlayer are mainly affected by the thickness and buried depth of the frozen interlayer.The research results can provide a reference for the seismic disaster risk assessment,seismic safety evaluation of major permafrost project,the seismic fortification of new projects and the seismic strengthening of existing engineering facilities in the permafrost region along QTEC.