考虑冰盖生消和冰-结构-冻土协同作用的渠道弹性地基梁模型

冰-冻破坏是寒区冬季输水渠道结构破坏的主要原因,而目前尚缺乏准确的分析方法和评价准则。本文从冰盖生消过程中结冰初期、流冰期和封冻期3个阶段衬砌结构冰冻破坏机理出发,考虑在冰-结构-冻土协同作用下,基于弹性地基梁Winkler理论推导了衬砌结构的挠曲线微分方程,分别建立了3个阶段衬砌结构的冰冻破坏力学模型,并结合相应荷载组合和边界条件对模型求解获得了衬砌结构的挠度、内力和应力的解析表达。应用该模型对南水北调京石段某输水渠道进行冰冻破坏分析计算,结果表明:结冰初期、流冰期和封冻期3个阶段衬砌结构的法向冻胀位移最大值分别为10.62、13.89和5.05 cm,对应3个阶段衬砌结构的截面最大拉应力分别为3.63、 4.11和2.05 MPa,且破坏位置均在冻结区坡板的中下部,与现场监测渠道冰冻破坏分布规律吻合。据此,建议寒区冬季输水渠道控制运用中应尽量缩短结冰初期、流冰期时间,延长第3阶段稳定封冻期时间,同时应合理控制地下水位和冰盖厚度。研究结果可为寒区冬季输水渠道抗冰冻设计提供理论依据和分析方法。

Elastic foundation beam model of canal considering ice cover formation decaying and coupling effect between ice-structure-frozen soil

The ice-freeze damage is the main factor for the lining structure damage of water delivery canal in cold region in winter. However, there is still a lack of accurate analytical methods and evaluation crite-ria. In this paper, study started from the mechanism of frost failure of lining structure in the process of ice cover formation and extinction of three stages which is early ice-forming period, ice float period and ice freezing period. Considering ice-soil-structure coupling effect,based on Winkler theory of elastic founda-tion beam, a differential equation of deflection line of lining structure was derived. Then it established the mechanical models of frost failure of lining structures in three stages, and the analytical expressions of the deflection,internal force and stress of the lining structure were obtained by solving the model with the com-bination of corresponding loads and boundary conditions. The model is used to analyze and calculate the freezing damage of a water conveyance channel in Jing-Shi section of the South-to-North Water transfer project, the results shown that, the maximum normal frost heave displacement of lining structure were 10.62, 13.89 and 5.05cm respectively in three stages early, and the maximum tensile stresses on the sec-tions of the lining structure corresponding in the three stages were 3.63, 4.11 and 2.05MPa respectively. The location of the failure is in the middle and lower part of the slope slab in the freezing zone,which is consistent with the distribution law of the frozen failure of the monitoring canal on site. Accordingly, it is suggested that in the control of water conveyance canals in cold areas in winter,the early ice-forming peri-od and ice float period should be shortened as much as possible,and ice freezing period should be extend-ed. At the same time, the water table and the thickness of the ice cover should be reasonably controlled. The results can provide theoretical basis and analytical methods for anti-freezing design of water convey-ance canals in cold region in winter.