川藏铁路季节性粗颗粒冻土边坡水热过程模拟
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摘要
以川藏铁路东段的季节性粗颗粒冻土边坡为研究对象,通过建立一个考虑积雪、渗流和年循环气温作用下的带相变的瞬态水热耦合的饱和-非饱和的多孔多相介质数值计算模型,结合野外实测,分析季节性粗颗粒冻土边坡的温度场、水分场的分布特征、冻结深度及其影响因素。研究结果表明:积雪消融入渗改变季节性粗颗粒冻土的水分场,地表可形成最大0.8 m的暂态饱和区。水分场的动态变化提高了热传递速度,增强了冻结能力,边坡冻结深度增大60%,冻结速率增大30%,融化速率增大200%。地下水热对流作用抑制土体冻结,加速土体融化,其中坡脚地下水出露边坡的冻融深度为地下水深埋边坡的63%,冻结速率为79%,融化速率增大1倍。川藏铁路新都桥地区季节性粗颗粒冻土边坡的冻结深度为1.0 m,最大可达到1.9 m。边坡不同位置的冻结深度不同,在坡肩处最高,坡脚处最低;进入融化期后,因冻结深度小及地下水热流作用,坡脚处最先融化。
This article based on the seasonal coarse-grained frozen soil slope in the eastern section of the Sichuan-Tibet Railway, a transient hydrothermal coupled saturated-unsaturated porous multiphase media numerical model with phase transition was established. This model considered snow cover, seepage and annual cycle temperatures. The temperature field of seasonal coarse-grained frozen soil slope, moisture distribution characteristics, freezing depth and its influencing factors were analyzed combing with field measurements. The results show that the removal and infiltration of snow may change the moisture field of seasonal coarse-grained frozen soil. The surface can form a transient saturation area of up to 0.8 m. The dynamic changes of the moisture field cause the increase of heat transfer rates, the enhancement of freezing ability. It also causes slope freeze depth increasing by 60%, the freezing rate by 30% and the melting rate by 200%. The soil freezing speed is suppressed by the boundary of the groundwater convection. The frozen-thawing depth of the outcrop slope at the slope foot is63% of the deep-buried slope of the groundwater, the freezing rate is 79% and the melting rate is increased by 1 time. The freezing depth of seasonal coarse-grained frozen soil slope in the Xinduqiao area of the Sichuan-Tibet railway is 1.0 m, and the maximum reachable is 1.9 m. The different depths of freezing in different positions of the slope are highest at the shoulders and lowest at the foot. After entering the melting period, due to the small depth of freezing and the effect of groundwater heat flow, the first step of melting is at the foot of the slope.
This article based on the seasonal coarse-grained frozen soil slope in the eastern section of the Sichuan-Tibet Railway, a transient hydrothermal coupled saturated-unsaturated porous multiphase media numerical model with phase transition was established. This model considered snow cover, seepage and annual cycle temperatures. The temperature field of seasonal coarse-grained frozen soil slope, moisture distribution characteristics, freezing depth and its influencing factors were analyzed combing with field measurements. The results show that the removal and infiltration of snow may change the moisture field of seasonal coarse-grained frozen soil. The surface can form a transient saturation area of up to 0.8 m. The dynamic changes of the moisture field cause the increase of heat transfer rates, the enhancement of freezing ability. It also causes slope freeze depth increasing by 60%, the freezing rate by 30% and the melting rate by 200%. The soil freezing speed is suppressed by the boundary of the groundwater convection. The frozen-thawing depth of the outcrop slope at the slope foot is63% of the deep-buried slope of the groundwater, the freezing rate is 79% and the melting rate is increased by 1 time. The freezing depth of seasonal coarse-grained frozen soil slope in the Xinduqiao area of the Sichuan-Tibet railway is 1.0 m, and the maximum reachable is 1.9 m. The different depths of freezing in different positions of the slope are highest at the shoulders and lowest at the foot. After entering the melting period, due to the small depth of freezing and the effect of groundwater heat flow, the first step of melting is at the foot of the slope.
引文
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[2]张玉芝,杜彦良,孙宝臣.季节性冻土地区高速铁路路基地温分布规律研究[J].岩石力学与工程学报,2014,33(6):1286-1296.ZHANG Yuzhi,DU Yanliang,SUN Baochen.Temperature distribution in roadbed of high-speed railway in seasonally frozen regions[J].Chinese Journal of Rock Mechanics and Engineering,2014(12):2546-2553.
[3]张媛,董建华,董旭光,等.季节性冻土区土钉边坡支护结构冻融反应分析[J].岩土力学,2017,38(2):574-582.ZHANG Yuan,DONG Jianhua,DONG Xuguang,et al.Analysis of freezing and thawing of slope improved by soil nailing structure in seasonal frozen soil region[J].Rock and Soil Mechanics,2017,38(2):574-582.
[4]习阿幸,刘志辉,卢文君.干旱区季节性冻土冻融状况及对融雪径流的影响[J].水土保持研究,2016,23(2):333-339.XI Axing,LIU Zhihui,LU Wenjun.Processes of seasonal frozen soil frezing-thawing and impact on snowmelt runoff in arid area[J].Research of Soil and Water Conservation,2016,23(2):333-339.
[5]吴青柏,蒋观利,蒲毅彬.青藏高原天然气水合物的形成与多年冻土的关系[J].地质通报,2006,25(2):29-33.WU Qingbai,JIANG Guanli,PU Yibin.Relationship between permafrost and gas hydrates on Qinghai-Tibet Plateau[J].Geologial Bulletin of China,2006,25(2):29-33.
[6]Black P,Tice A.Comparison of soil freezing curve and soil water curve data for windsor sandy loam[J].Water Resources Research,1989,25(10):2205-2210.
[7]Aubertin M,Mbonimpa M,Bussière B,et al.A model to predict the water retention curve from basic geotechnical properties[J].Canadian Geotechnical Journal,2003,40(6):1104-1122.
[8]Fredlund D G,XING Anqing.Equations for the soil-water characteristic curve[J].Canadian Geotechnical Journal,1994(31):521-532.
[9]Johansen O.Thermal conductivity of soils[D].Trondheim,Norway.(CRREL Draft Translation,637,1977),ADA044002.
[10]Anderson D M,Tice A R.The unfrozen interfacial phase in frozen soil water systems,physical aspects of soil water and salt in ecosystems[J].In Ecological Studies Springer Verlag,Berlin,1973(4):107-124.
[11]陈凯.融雪水在雪层中的冻融过程及侧渗出流研究[D].乌鲁木齐:新疆大学,2012.CHEN Kai.Research on freeze-thaw process and side flow of snowmelt in the snow[D].Urumuqi:Xinjiang University,2012.
[12]赵永峰,谢强,王子江,等.川藏铁路季节性冻土区粗颗粒土边坡温度场特征[J].铁道建筑,2017(5):95-99.ZHAO Yongfeng,XIE Qiang,WANG Zijiang,et al.Characteristics of temperature field of coarse-grained soil slope in seasonal frozen soil region along Sichuan-Tibet Railway[J].Railway Engineering,2017(5):95-99.