青藏铁路多年冻土隧道围岩季节活动层温度及响应的试验研究
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摘要
高原多年冻土区隧道的修建,将不可避免地影响到隧道背后多年冻结围岩的热稳定性,并形成季节融化与冻结的活动层。结合青藏铁路二期工程格尔木—拉萨段风火山隧道修建,选取11个断面对多年冻土隧道开挖直到贯通引起隧道冻结围岩体的热学响应规律进行深入的现场试验研究。现场试验结果表明:(1)隧道背后围岩地温随时间及深度呈线性变化趋势。(2)施工期间,因受人为热源影响,围岩冻融范围超过该地区天然冻土上限值。有些断面隧道背后围岩融化深度超过5m,远远超过该地区天然冻土上限值(1.36～2.11m)。分析结果表明,其围岩融化范围与多年冻土上限的比值,随着洞内温度与洞外温度比值呈现线性变化。(3)贯通后,良好的保温措施使得围岩冻融圈范围小于天然冻土上限,且其围岩融化范围与多年冻土上限的比值,随着围岩表面温度与隧道洞外温度比值也呈现线性变化。
The excavation of tunnel will affect the thermal stability of surrounding rock in permafrost region.Accordingly,an active layer close to the supporting system of tunnel is formed in the surrounding rock under seasonal thawing and freezing.Based on the excavation of Fenghuoshan Tunnel of Qinghai—Tibet Railway,a detailed experimental investigation is conducted.Some useful conclusions of the active layer's thermal regularity are achieved.First,an important fact of in-situ experiment is that temperature of frozen rock behind the liner varies with time and space linearly.Second,another interesting phenomenon is that thawing depth of surrounding rock surpasses the natural thawing depth of this region during construction period.For instance,some areas' thawing depths are found below 5 m,while the natural value of this region is only 1.36-2.11 m.Analytical result indicates that the temporary heat produced during excavation causes the additional thawing of frozen rock/soil behind liner,such as chamber blasting,machine operating,construction illuminating,and so on.According to the in-situ data,regression analysis shows that the ratio of thawing depth value during construction and its natural thawing value of this region vary with the ratio of atmospheric temperature inside to outside of the tunnel linearly.Finally,the achieved data illustrate that thawing depth is less than that of the region's natural value after tunnel excavation,which is deemed as a vital fact:the special insulating layer which is set between the primary support and the liner structure.Similarly,regression analysis shows that the ratio of thawing depth after excavation to its natural value changes with the ratio of atmospheric temperature inside to outside of the tunnel linearly,i.e.the atmospheric temperature in the tunnel refers to surface temperature of surrounding rock,where temperature monitoring units are installed on the surface of the primary support behind insulating layer.
The excavation of tunnel will affect the thermal stability of surrounding rock in permafrost region.Accordingly,an active layer close to the supporting system of tunnel is formed in the surrounding rock under seasonal thawing and freezing.Based on the excavation of Fenghuoshan Tunnel of Qinghai—Tibet Railway,a detailed experimental investigation is conducted.Some useful conclusions of the active layer's thermal regularity are achieved.First,an important fact of in-situ experiment is that temperature of frozen rock behind the liner varies with time and space linearly.Second,another interesting phenomenon is that thawing depth of surrounding rock surpasses the natural thawing depth of this region during construction period.For instance,some areas' thawing depths are found below 5 m,while the natural value of this region is only 1.36-2.11 m.Analytical result indicates that the temporary heat produced during excavation causes the additional thawing of frozen rock/soil behind liner,such as chamber blasting,machine operating,construction illuminating,and so on.According to the in-situ data,regression analysis shows that the ratio of thawing depth value during construction and its natural thawing value of this region vary with the ratio of atmospheric temperature inside to outside of the tunnel linearly.Finally,the achieved data illustrate that thawing depth is less than that of the region's natural value after tunnel excavation,which is deemed as a vital fact:the special insulating layer which is set between the primary support and the liner structure.Similarly,regression analysis shows that the ratio of thawing depth after excavation to its natural value changes with the ratio of atmospheric temperature inside to outside of the tunnel linearly,i.e.the atmospheric temperature in the tunnel refers to surface temperature of surrounding rock,where temperature monitoring units are installed on the surface of the primary support behind insulating layer.
引文
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[11]杨家松.高原隧道爆破施工技术探讨[J].现代隧道技术,2003,40(2):21-24.(YANG Jiasong.Discussion on blasting technique for plateau tunnel[J].Modern Tunnelling Technique,2003,40(2):21-24.(in Chinese))
[2]王大雁,朱元林,马巍,等.冻土超声波波速与冻土物理力学性质试验研究[J].岩石力学与工程学报,2003,22(11):1837-1840.(WANG Dayan,ZHU Yuanlin,MA Wei,et al.Testing study on relationship between ultrasonic wave velocities and physico-mechanical property of frozen soils[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(11):1837-1840.(in Chinese))
[3]张德华,王梦恕,谭忠盛,等.风火山隧道围岩胀对支护结构体系的影响[J].岩土工程学报,2003,25(5):571-573.(ZHANG Dehua,WANG Mengshu,TAN Zhongsheng,et al.Effect of frost freezing on tunnel supporting systems of Fenghuoshan Railway Tunnel[J].Chinese Journal of Geotechnical Engineering,2003,25(5):571-573.(in Chinese))
[4]HENRY K S.A review of the thermodynamics of frost heave[R]Technical Report ERDC/CRREL TR-00-16,2000.
[5]孙增奎,王连俊,白明洲,等.青藏铁路多年冻土路堤温度场的有限元分析[J].岩石力学与工程学报,2004,23(20):3454-3459.(SUN Zengkui,WANG Lianjun,BAI Mingzhou,et al.Finite element analysis of temperature field of Qinghai—Tibet Railway embankment on permafrost[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(20):3454-3459.(in Chinese))
[6]温智,盛煜,马巍,等.青藏高原北麓河地区原状多年冻土导热系数的试验研究[J].冰川冻土,2005,27(2):182-187.(WEN Zhi,SHENG Yu,MA Wei,et al.Experimental studies on thermal conductivity of undisturbed permafrost at Beiluhe testing site on the Qinghai—Tibet Plateau[J].Journal of Glaciology and Geocryology,2005,27(2):182-187.(in Chinese))
[7]王丽霞,凌贤长,徐学燕,等.多年冻土场地路基地震加速度反应谱特性研究[J].岩石力学与工程学报,2004,23(8):1330-1335.(WANG Lixia,LING Xianchang,XU Xueyan,et al.Study on response spectrum characteristics of earthquake acceleration for roadbed on permafrost site[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(8):1330-1335.(in Chinese))
[8]汪双杰,陈建兵,黄晓明.冻土路基护道地温特征研究[J].岩石力学与工程学报,2006,25(1):146-151.(WANG Shuangjie,CHEN Jianbing,HUANG Xiaoming.Study on ground temperature characteristics of embankment berm on permafrost[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(1):146-151.(in Chinese))
[9]徐斅祖，王家澄，张立新.冻土物理学[M].北京:科学出版社,2001.(XU Xiaozu,WANG Jiacheng,ZHANG Lixin.Physics of frozen soils[M].Beijing:Science Press,2001.(in Chinese))
[10]乜风鸣,刘艳.多年冻土及寒区铁路隧道衬砌开裂探讨[J].低温建筑技术,2002,(3):54-55.(NIE Fengming,LIU Yan.Discussion on the circumferential lining cracks of railway tunnel in permafrost area[J].Low Temperature Architecture Technology,2002,(3):54-55.(in Chinese))
[11]杨家松.高原隧道爆破施工技术探讨[J].现代隧道技术,2003,40(2):21-24.(YANG Jiasong.Discussion on blasting technique for plateau tunnel[J].Modern Tunnelling Technique,2003,40(2):21-24.(in Chinese))
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