Mechanism of transverse-crack formation during river-ice breakup
-
摘要: 春季随着流量或水位增加,冰盖底部受水流上举力作用发生弯曲,首先在岸壁附近形成纵向冰缝,破坏冰盖与岸壁的冻结,导致冰盖体中间部分与岸壁脱落分离。采用弹性基础梁的理论及计算方法,通过对冰盖体弯矩及弯曲应力分析,针对平面弯曲和垂直弯曲两种弯曲形式导致冰盖体横向冰缝形成机理进行了研究,并提出了横向冰缝间距的计算表达式。计算结果得到了实测资料的验证。研究结果表明,横向冰缝间距与开河初期冰盖宽度、厚度、冰的抗弯强度及地貌特征有关。Abstract: During the river-ice breakup, the longitudinal cracks near banks are firstly formed due to the runoff increase, resulting in the detachment of central part of ice cover from both banks.Subsequently, as a result of horizontal bending or vertical bending of ice cover the transverse cracks will be further formed, and the continuous icE-cover is finally fractured into floes with cerain sizes.Based upon the theory and calculation method of elastic-foundation, the mechanism of transversE-crack formation is fully investigated.By means of studying on the bending moment and bending stresses of ice cover, the analytical expressions of the crack-spacing due to both horizontal bending and vertical bending are presented, and validated with the field measurements.The study indicates that the transversE-crack spacing depends on the icE-cover width, thickness, bending strength and topography.
-
Key words:
- mechanical ice-cover breakup /
- transverse crack /
- ice dam /
- mechanical principle /
- ice-cover
-
[1] 赵雪峰.开河期冰盖体断裂机理及开河判别准则研究[D].北京:清华大学.2008.(ZHAO XuE-feng.Study on mechanism of icE-cover breakup and criterion for onset of river-ice breakup[D].Beijing:Tsinghua University,2008.(in Chinese)) [2] 张磊.江河春季开河机理及冰坝形成和演变研究[D].北京:清华大学,2004.(ZHANG Lei.River-ice breakup mechanism and icE-dam formation and evolution[D].Beijing:Tsinghua University,2004.(in Chinese)) [3] GUO Qi-zhong.Applicability of criterion for onset of river ice breakup[J].Journal of Hydraulic Engineering,2002,128(11):1023-1026. [4] BELTAOS S.Threshold between mechanical and thermal breakup of river ice cover[J].Cold Regions Science and Technology,2003,37(1):1-13. [5] BELTAOS S.WavE-generated fractures in river ice covers[J].Cold Regions Science and Technology,2004,40(3):179-191. [6] 茅泽育,赵雪峰,王爱民,等.开河期冰盖纵向冰缝形成机理[J].水科学进展,2009,20(3):434-437.(MAO ZE-yu,ZHAO XuE-feng,WANG Ai-min,et al.The mechanism of longitudinal-crack formation during river-ice breakup[J].Advances in Water Science,2009,20(3):434-437.(in Chinese)) [7] 茅泽育,赵雪峰,王爱民,等.武开河的边壁阻力判别准则[J].冰川冻土,2008,30(3):508-513.(MAO ZE-yu,ZHAO XuE-feng,WANG Ai-min,et al.SidE-resistance criterion for onset of mechanical icE-cover breakup[J].Journal of Glaciology and Geocryology,2008,30(3):508-513.(in Chinese)) [8] BELTAOS S.Fracture and breakup of river ice cover[J].Canadian Journal of Civil Engineering,1990,17(2):171-183. [9] SANDERSON T J O.Ice mechanics:Risks to offshore structure[M].London:Graham and Trotman,1988. [10] BUTYAGIN I P.Strength of ice and ice cover:Nature research on the river of Siberia[R].Hanover:US Army Cold Regions and Engineering Laboratory,NH,1972. [11] ANDERSON J C.Liard and mackenzie river ice breakup[R].Ottawa:National Hydrology Research Institute,1982. [12] NUTTALL J B.Observations on breakup of river ice in north central Alberta[J].Canadian Geotechnical Journal,1970,7:457-463. [13] BELTAOS S.A conceptual model of river ice breakup[J].Canadian Journal of Civil Engineering,1984,11:516-529. [14] BILLFALK L.Breakup of solid ice covers due to rapid water level variations[R].Hanover:US Army Cold Regions Research and Engineering Laboratory,NH,1982. [15] BELTAOS S.Initial fracture patterns of river ice cover[R].Burlington:National Water Research Institute,1985. [16] HETENYI M.Beams on elastic foundation,Michigan[M].Ann Arbor:Cushing-Malloy INC,1955. -
点击查看大图
计量
- 文章访问数: 93
- HTML全文浏览量: 26
- PDF下载量: 490
- 被引次数: 0
下载:
