【作者】 李学军；

【导师】 费良军；

【作者基本信息】 西安理工大学 ， 水文学及水资源， 2008， 博士

【摘要】 渠道防渗是节水灌灌的重要技术措施之一。但是,我国季节性冻土分布约占国土面积的54%,在北方地区,一年近1/4时间地表及其附近存在季节性冻融,使渠道工程在冻融作用下发生冻胀破坏。因此,研究我国北方地区季节性冻融对防渗渠道的冻胀理论与技术成为重要课题。本文在查阅国内外大量相关文献的基础上,结合北方地区季节性冻融特点,采用室内试验与原型观测、理论分析与数值模拟相结合的技术路线,较系统地研究了季节性冻融作用下大型U形混凝土衬砌渠道渠基土壤水分运移特性和不同结构形式的大型弧形坡脚梯形防渗渠道的抗冻胀理论与关键技术,对防渗膜料的抗拉、变形、抗裂、抗渗及抗老化性能及土膜复合材料抗剪性能进行了试验研究,提出了膜料防渗渠道边坡稳定性计算方法,建立了渠道防渗经济效益模型。主要研究成果为：(1)通过一个完整季节性冻融循环作用下大型U形混凝土衬砌渠道的原型观测,获得了渠基不同部位和0-40 cm深度范围的水分运移特征,探讨了地下水深埋条件下大型U形混凝土衬砌渠道抗冻胀机理和渠基土壤水分运移机理,采用时间序列法对冻融期含水率变化进行了回归分析,用水分运动基本方程和热流运动基本方程建立了渠基冻融水热耦合运移数学模型,采用混合型Richards方程对冻结过程中渠基非饱和土壤水分运移进行了数值模拟,研究了大型U形混凝土衬砌渠道在季节性冻融作用下的冻深、地温、含水率、冻胀量、冻胀应力等参数之间的相互关系,建立了大型U形混凝土衬砌渠道冻深、冻胀量预测模型。使冻深、冻胀预测从纯经验方法向基于冻胀机理的方向发展,研究成果为大型U形混凝土衬砌渠道设计提供理论依据。(2)通过对大型弧形坡脚梯形防渗渠道的冻胀原型观测,较系统研究了大型弧形坡脚梯形渠道防渗抗冻胀理论,揭示了板膜复合防渗渠道的抗冻胀特点。试验提出了渠道衬砌材料和嵌缝材料最佳配合比,并对其性能进行了评价。针对北方寒冷地区特点,研究了混凝土预制板(8 cm、10 cm和П形)复合塑膜、现浇混凝土肋板复合塑膜、沥青混凝土预制板,混凝土预制板复合塑膜封闭土层(全断面封闭、半断面封闭和封闭渠底)共计4类8种结构形式的弧形坡脚梯形渠道的保温、冻深、变位等特性。通过对渠道板面冻结指数规律研究,提出了由气温冻结指数预测渠道板面冻结指数的计算公式和渠道板面冻结指数修正系数；通过对渠道冻深分布规律研究,提出了由渠道板面冻结指数预测渠道冻深的计算公式和渠道冻深修正系数；通过对渠道冻胀变位规律研究,提出了由冻深和土壤水分预测渠道变位的计算公式和渠道变位修正系数。研究成果为弧形坡脚梯形渠道防渗抗冻胀设计提供了理论依据。(3)在室内冻融和紫外线照射快速老化条件下,对防渗膜料的抗拉、变形、抗裂、抗渗及抗老化性能分别进行了试验研究；依据薄膜理论对膜料水压力作用下圆形、正方形、长方形边界时的变形、中心变位及应力应变抗裂模型进行了数学推导；利用膜料水压力鼓胀试验对变直径、变膜料圆形边界条件下的中心变位抗裂模型进行了验证。研究成果为膜料防渗或板膜复合防渗渠道设计和应用提供了理论依据。(4)利用直剪仪和三轴仪两种设备,对粘土、壤土和砂壤土在不同干密度、饱和与非饱和试样中铺设不同膜料并变换铺膜倾角时的土膜复合材料抗剪强度进行了试验,提出了土膜三轴抗剪强度的试验方法和直剪抗剪强度的折减系数及膜料防渗渠道边坡稳定性计算时土膜抗剪强度的理论值。(5)结合我国渠道膜料防渗土保护层的实际,研究了渠道边坡稳定性的影响因素；通过试验资料建立了渠道边坡稳定性安全系数与粘土和壤土干密度、粘聚力、内摩擦角、渠道水深、边坡系数及土保护层厚度之间的关系函数；提出了膜料防渗不同土质保护层渠道的不冲流速；研究了渠道边坡稳定控制时期、渗透水压力、最小安全系数、滑裂面位置及形式,提出了膜料防渗土保护层渠道边坡稳定性的计算方法。(6)依据经济学原理,分别在经济静态和动态条件下对混凝土衬砌渠道防渗性能随运行时间呈等差数列衰减、等比数列衰减及不随运行时间衰减时的防渗效益进行了较深入研究,建立了混凝土衬砌渠道防渗、维修或改建的判定原则及经济模型,并利用渠道渗漏观测成果进行了渠道防渗的必要性判定和经济效益分析,避免了渠道防渗的盲目性。更多还原

【Abstract】 Canal seepage control is one of the most important technologies in the water saving irrigation. But the distribution of the seasonal frozen soil in our country is about fifty-four percent, and in the northern area of China it exists on the soil surface or nearby place in almost a quarter of a year, thus some canals are destroyed by it. So the studies of theory and technology on the seasonal freezing and thawing for the seepage control canal in our northern area is becoming the most important subject.Based on prototype observation results of two large-arc canals, consulting abundant domestic and foreign interrelated data and using the technical routes which combine laboratory tests with prototype observation and theoretical analysis with numerical simulation, this dissertation systematically focused on the soil moisture movement on the base of U-shape canal with concrete lining in the process of seasonal freezing and thawing and the theory and technology of frost resistance of trapezoidal canal with arc foot lining with concrete and film, did some tests on the films characteristic of tensile, deformation, impermeability and crack resistance in aging time as well as the shear performance between soil and film, proposed the calculating method of side slopes of canal with film impervious and soil protective cover and established the model of effectiveness seepage under static and dynamic conditions. In the thesis, main results are as follows:(1) The frost-heaving mechanism of U-shape canal lining with concrete and soil moisture movement on canal base during seasonal freezing and thawing stage were studied on the temperature gradients theory. The characteristics of soil moisture movement within the depth of 40 cm of U-shape canal base were obtained by the prototype observation and the data of observation was analyzed using regression analysis according to time series. On this basis, a model of coupled heat-fluid transport was established by the soil moisture equation combined with heat movement equation in the cyclic process of freezing and thawing. The prediction model of frozen depth and frost-heaving deformation was derived with the amount of soil moisture movement, freezing temperature and observation value of frost depth. The test results show that the simulation and prediction curves were fitting with the prediction curves. The research supplies a theoretical basis for the design of U-shape canal lining with concrete.(2) By the prototype observation of large-trapezoidal canal with arc foot lining with the concrete prefabricated with film, the theory and technology of frost resistance of canal lining with concrete and film were studied 1) The optimization of mixing proportion of lining material and caulked material was presented that conformable local source, and the performance was studied in laboratory.2) Based on a fully consideration of the climate characteristics in north area, a section of large-trapezoidal canal with arc foot is designed with benefits to improve the non-uniformity of frost heave deformation, to prevent the occurrence of dislocation and crack, to replace the line after melting, to equalize the distribution velocity and convenience send transportation. The designed section is smaller in size and lower in cost than trapezoidal one. 3) In the structural form, the technology and the methods of avoiding, replacement and insulation had excluded, and 8 kinds of structural forms of 4 class had been designed. These are concrete prefabricated with (concrete prefabricated are consist of 8cm,10cm and∏-shape) concrete cast-in-place with film, bituminous concrete and concrete prefabricated with film of close soil layer (close soil layer are consist of the whole section, half a section closes and only bottom of canal) and, all the structural form were studied and evaluated.4) The research findings of soil temperature, soil moisture, water level, freezing depth, and amount of frost-having were given from large-arc canal.(3) The aging of crack resistance of film was studied by the use of freeze-thaw and the ultraviolet shine in laboratory. The results showed that the aging crack resistance of film was reduced to some extent in freeze-thaw and the ultraviolet shine. The mathematical model was established to describe the relation between stress and strain, breaking resistance and deformation high in freeze-thaw. Theoretical foundation has been studied and it was feasible for using as a guide for the design of the polyethylene in canal.(4) The shear strength of sample between film and soil was studied, which the soil was different classes or different density in saturated or unsaturated and, the film was changing in classes and angle, the instrument and the equipment were two kinds, one kind was tri-axial shear and the other one was direct shear. The new method and the steps of tests were proposed in shear performance between film and soil by using the result of two kinds of instrument and equipment. The reasonable parameters were provided for calculated stability of side slopes of canal with film impervious and soil protective cover.(5) Combined with the reality of prevention of seepage of our country’s large-scale canal, the influence of side slopes of canal with film impervious and soil protective cover were studied on water, temperature, wind speed, silt content, soil property, section form of canal and base, film classification, operation and management etc. The new calculated method of side slopes of canal with film impervious and soil protective cover was proposed. The control index of shear strength, coefficient of internal friction and safety factor were studied. The form and position of landside of side slopes of canal with film impervious and soil protective cover were analyzed.(6) According to principles of economy, the seepage control effectiveness of canal lining with concrete and film was studied under static and dynamic conditions, and the seepage control performance was geometric progression, arithmetic progression or no change with the time. The judge principles and economic models had been concluded in seepage control. With the examples of seepage observation for calculation, the economy of seepage control effectiveness of canal lining concrete with film has been discussed. It was avoided blindness of the seepage control of canals by necessity judgment of test.更多还原