季冻区冬季输水渠道冻胀破坏机理及防冻胀破坏措施研究

As far, people generally think if the problem of the frost damage of the canal without water in winter would be solved, So would the canal with water in winter because the area with frost force acting on the lining of the canal with water in winter isn’t more than that without water, namely, only the part of the slope bed-soil above the water surface in the canal in winter is frozen upheaving while the whole of bed soil of the canal is frozen upheaving without water in winter. Therefore, a lot of research were focused on the damage theory of concrete lining and measures to prevent the canal without water in winter from lining frost damage, so did plenty of reported achievement. It doesn’t work for the canal without water in winter, but for the canal with water in winter. In the project, not only the relationships of internal force and deflection of the lining, quantitative value of deformation and temperature of the bed-soil in cross section of canal are studied by theoretical analysis and field investigation as well as model experimental study, but also the action way of frost heaving force on the lining is discovered. Moreover, the influence of the type, soil temperature and water contend of the bed-soil together with the surface parameters of the lining on the force of frost heaving was synthetically analyzed. The internal forces and its distribution law are quantitatively explored. At last, the failure mechanism of the concrete lining of the canal with water in winter is discovered and mechanical model of the concrete lining is established. Design method of the concrete lining and long-acting measures of anti-frost-heaving fracture of the concrete lining are provided. Those are scientific basis to solve the frost heaving damage of the concrete lining canal to make the canal safely delivery water in winter.

因为渠道冬季输水时仅渠水位以上边坡土体冻胀使受冻胀作用的衬砌面积较冬季停水时的小，所以人们一直认为解决了渠内无水时冻胀破坏问题，也就解决了防渗渠道的冻胀破坏问题。因而对寒区渠道冻胀破坏机理和防冻胀破坏措施所做的大量研究工作都是与冬季停水渠道有关，并已取得的丰硕成果。但实践证明这些成果应用于冬季停水渠道的成效显著，但对冬季输水渠效果不明显。所以，本项目通过理论分析、模型及现场试验、室内力学试验等方法研究冬季输水渠道横断面上衬砌层的内力、变形与基土温度及冻胀量耦合关系，探求冻胀力作用于衬砌层的方式；综合分析冻土类型、土体温度、含水量、水力参数、衬砌表面参数对冻胀力的影响，定量分析冻胀过程中衬砌层内力的分布规律；揭示冬季渠道冻胀破坏机理，建立衬砌层力学模型；寻求冬季输水渠抗冻胀破坏结构设计方法，提出适用于冬季输水渠道防冻胀破坏措施。本项目研究成果将为季节冻土区防渗渠安全可靠运行提供科学依据。

对冬季停水渠道的冻胀破坏已取得的成果及应用就使人们认为渠道的冻胀破坏问题已根本解决,但工程实例表明并非如此。本项目对人们较少研究的冬季过水渠道开展的主要工作有：1）现场调查和收集的冬季过水渠道相关的资料。2)在新疆某一电站引水渠上开展了运行工程渠道现场的试验研究，在掌握了渠道基土温度场的分布特点的基础上，从根本上对多年冬季运行渠道进行一些变参数的模型的试验研究。3）对渠道基土的冻胀变位和衬砌板变位及变形的相互关系、冻胀力的作用类型及数值展开理论研究。. 获得的重要成果有：1) 长期来看，既使采用工程实践检验效果较好的防冻胀破坏措施的渠道也发生衬砌层的冻胀破坏，而无防冻胀破坏保护的混凝土、浆砌石等刚性衬砌渠道的破坏现象或程度不比冬季停水的渠道少或轻，获得了冬季输水刚性衬砌渠道的冻胀破坏类型、破坏程度。2)地建立了冬季不同输水水位运行条件下的衬砌层的力学模型：不分缝的边坡衬砌板，在边坡下基土冻胀量相同的条件下，在多年冬季高水位运行条件下应视为水位面以上受拉弯作用于外伸悬臂、水位面以下受横向弯曲作用的外伸简支构件；在多年冬季低水位运行条件下应视为水位面以下受横向力作用、水位面以上受拉弯作用的外伸简支构件；而在中等水位运行条件下，应采用高、低水位两种力学模型。上述几个力学模型揭示了冬季输水渠道冻胀破坏的机理,给出了渠道衬砌板的冻胀力的类型。3)依据冬季输水渠道的冻胀破坏机理，明确了目前广泛采用的柔性卷材整体防渗的刚柔相济型防冻胀破坏的衬砌方案在渠基土冻结前含水量较高或“开敞体系下”冻结条件下水位面以上的衬砌层可能会出现的原因。并提出了恶劣条件下仍能有效的，高水位时满渠水运行的复合断面型式、渠基土局部换填封闭防渗及保温的，适用于冬季输水渠道的防冻胀破坏措施。.本项目研究成果为季节冻土区的本流域及跨流域调输水工程中设计出防冻胀破坏性能优良的明渠的提供理论基础，更全面地认识了渠道冻胀破坏机理的。