【作者】 刘旭东；

【导师】 王正中；

【作者基本信息】 西北农林科技大学 ， 水工结构工程， 2010， 硕士

【摘要】 在我国东北永久性冻土地区和华北、西北季节性冻土地区,混凝土衬砌防渗渠道冻胀破坏分布广泛且损害严重,不但影响渠道的正常使用、浪费宝贵的水资源,而且缩短防渗渠道的使用寿命、增加工程修复次数和管理费用,严重地制约着工程效益的发挥。所以,如何防治混凝土衬砌渠道冻胀破坏已经成为一个非常现实的工程问题。针对混凝土衬砌渠道冻胀破坏,本文对渠道冻胀影响因素进行了探讨和研究,在此基础上对混凝土衬砌渠道抗冻胀技术措施进行了归类总结;针对设置不同纵缝措施、混凝土衬砌“适变断面”渠道和双层薄膜防渗衬砌渠道,本文利用有限元软件ADINA对其进行数值模拟,分别研究了三种抗冻胀技术措施的抗冻胀机理及削减冻胀效果。全文获得主要结论如下:(1)渠基土质、温度条件、水分条件及受力条件是影响渠道冻胀的四个主要因素。在此基础上,将混凝土衬砌渠道抗冻胀技术措施归类总结,可以有效地指导抗冻胀技术措施在实际工程中的应用。(2)抗冻胀综合措施就是对渠道冻胀影响因素中的两个或者两个以上因素进行改善,以达到更好的抗冻胀效果,其基本原理为:改善渠基土质+改善水分条件+改善温度条件+改善受力条件。该原理能够为现有抗冻胀措施的改进以及新型抗冻胀综合措施的开发提供科学的指导。(3)应用ADINA软件进行渠道冻胀数值模拟,其结果能够反映混凝土衬砌渠道冻胀变形及受力规律,且简洁通用,可用于渠道抗冻胀设计。通过对比分析表明:合理设置纵缝不仅能降低最大冻胀量61%,最大法向冻胀力45%,最大切向冻胀力32%,而且可使冻胀分布更加均匀,显著削减混凝土衬砌渠道的冻胀破坏;削减冻胀的显著性依次是1/3坡高处设纵缝、坡脚处设纵缝、不设纵缝;但针对坡板较短、底板较宽情况,在坡脚及底板中心处都设纵缝效果最好,降低最大冻胀量67%,最大法向冻胀力59%,最大切向冻胀力45%。(4)对比普通渠道,“适变断面”渠道抗冻胀效果明显,其衬砌板受力状态得到显著改善,且冻胀变形分布更加均匀,是一种较为理想的渠道抗冻胀技术措施。纵向伸缩缝周向压缩值总计为9.7㎝,相邻衬砌板间法向错位值总计为1.3㎝,揭示了混凝土衬砌“适变断面”渠道利用纵缝吸收衬砌板周向位移并释放法向冻胀变形来降低冻胀力、冻胀量并使其分布均匀化的抗冻胀机理。边坡系数i能够影响“适变断面”渠道的抗冻胀性能;当边坡系数i处在1:1.7～1:1.4之间时,渠道冻胀变形分布更为均匀,抗冻胀效果更好。(5)双层薄膜防渗衬砌渠道抗冻胀效果显著,不仅衬砌板自身受力状态得到显著改善,而且冻胀变形、冻胀力分布更加均匀。双层薄膜防渗衬砌渠道切向冻结力阴坡、渠底、阳坡极值及均方差降低幅度均大于法向冻胀力降低幅度,揭示了该种渠道通过削弱冻结约束来改善衬砌板冻胀受力及使冻胀量分布均匀的抗冻胀机理。弧底梯形作为双层薄膜防渗衬砌渠道适用断面,当渠坡板与弧底板发生较大冻胀错位时,由于冻结约束削弱、双层薄膜界面摩擦力不足,渠坡板可能发生滑动失稳。因此,在实际工程中应对弧底板和渠坡板之间的伸缩缝加强管理,或采用整体现浇式结构,以防止滑动失稳情况的发生。更多还原

【Abstract】 In the area of permanently frozen soil in Northeast China and the seasonal in North China and Northwest, there exists massive and serious frost heaving damage of concrete lining canal. The damage leading to low project benefit has not only disturbed regular work and wasted precious water, but also decreased project service life and increased reparative frequency and management cost. Therefore, how to prevent the damage has became an actual project problem.In order to prevent frost heaving damage of concrete lining canal, this paper has explored influencing ingredients of canal frost heaving and furtherly provided a detailed classification and summary on anti-frost heave technical measures of concrete lining canal. Then, finite element software ADINA has been applied to simulate setting different longitudinal joints, self-adjusting lining canal and lining canal with double films and respectively studyed their mechanism and effect of anti-frost heave. Main conclusions gained can be expressed as follow:(1) On the basis of the fact that main influencing ingredients of canal frost heaving include soil, water, temperature and stress conditions, the paper provided a detailed classification and summary on anti-frost heave technical measures of concrete lining canal in order to guide application of these measures in actual projects effectively.(2) Comprehensive measure of anti-frost heave can be interpreted as the one that improves two or more influencing ingredients for the sake of achieving better anti-frost heave effect. Its basic principle is: to improve soil condition + to improve the water + to improve the temperature + to improve the stress, which could provide scientific guidance for improvement and invention of anti-frost heave technical measures.(3) Computer simulation of canal frost heaving with the application of ADINA can demonstrate rules of heaving deformation and frost heaving force distribution, so as to be used in anti-frost heave design of canal owing to its simplicity and generality. Comparative analysis indicated that: setting joints reasonably not only could reduce maximum heaving quantity 61%, maximum normal frost heaving force 45% and the tangential 32%, but also weaken frost heaving damage remarkably due to more uniform distribution of frost heaving force; listed descending order of the significance of anti-frost heave is: setting joints in the 1/3 slope, in the toe of slope and not; whereas for canals of shorter slope plate and wider base plate, setting joints both in the toe of slope and center of base plate can get the best effect, reducing maximum heaving quantity 67%, maximum normal force 59% and the tangential 45%.(4) Compared with the common, self-adjusting lining canal can achieve an excellent anti-frost heave effect, through making frost heaving distribution more uniform to reform stress states remarkably. The fact that total normal dislocation value between lining plates is 1.3㎝ and total circumferential compression value of longitudinal elastic joints 9.7㎝demonstrates anti-frost heave mechanism of self-adjusting lining canal which makes full use of the joints to release normal deformation and absorb the circumferential. Best anti-frost heave effect of self-adjusting lining canal can be achieved when setting slope ratio i between 1:1.7 and 1:1.4.(5) As a convincing anti-frost heave technical measure,lining canal with double films can not only reform stress states of lining plates remarkably, but also make frost heaving distribution and force more uniform. For mean square deviation and extremum of shady slope, bottom and sunny slope, the fact that their decreasing amplitude of tangential adfreezing force exceeds that of normal frost heaving force demonstrates anti-frost heave mechanism of lining canal with double films which can make frost heaving distribution uniform and reform stress states through weakening the constraint. Suitable section of lining canal with double films comes down to the trapezoidal with arc-bottom. For that section, sliding instability of plate on slope becomes to emerge due to weakening adfreezing constraint and decreasing interfacial friction between two films when serious dislocation between arc-bottom plate and that on slope occurs. According to that, joints between arc-bottom plate and that on slope should be managed elaborately or integral structure applied to avoid sliding instability in the actual project.更多还原