【作者】 周春生；

【导师】 史海滨；

【作者基本信息】 内蒙古农业大学 ， 土壤学， 2011， 博士

【摘要】 随着水资源供需矛盾的加剧,节约利用水资源引起了各行业的高度重视,农业是用水大户,实施节水灌溉工程势在必行,其中渠道衬砌防渗工程以其施工简单、造价低等优点,得到了广泛的推广与应用。我国西北地区干旱、寒冷、盐渍化严重,渠道防渗材料的选择受到一定的限制,目前该地区渠道衬砌的主要材料为混凝土板,存在费用高、抗冻胀性能差、施工工期长、衬砌失效后固体废弃物污染环境等一系列突出问题,因此筛选新型防渗衬砌新材料是当前灌区面临的重要问题,其研究具有重要的实用价值及现实意义。本文通过室内实验和工程现场试验对复合土工膨润土垫(Geosynthetic Clay Liner)在寒旱盐渍化地区的防渗特性及相关机理进行如下研究:(1)测试GCL基本特性,结合研究区特点及GCL产地进行了试样筛选;(2)探讨了膨润土在不同电解质溶液中的膨胀特性、流变性、粘度、滤失量;(3)冻融循环及离子双因素耦合作用对膨润土特性及GCL防渗性能影响;(4)进行了高温、低温、高低温循环、紫外线照射、水泥砂浆浸泡、工程现场老化实验,分析GCL的力学性能变化;(5)用微观方法研究了膨润土的结构,通过微观结构参数(水力半径、形态指标、表面分维、孔隙率)分析膨润土结构变化。得到以下有价值的结论和成果:(1)膨润土的水化过程是分阶段进行的,电解质类型及浓度对膨润土特性有显著影响,膨润土自由膨胀体积、膨胀后的含水率、滤失量与水化液中离子浓度、化合价呈负相关,滤饼厚度、渗透系数则相反,呈正相关;水化液为黄河水时,悬浮体剪切应力增加,触变性降低。切应力的大小与膨润土颗粒分散度、细小颗粒含量呈正相关,与水化液电解质浓度呈负相关。(2)冻融循环改变膨润土颗粒结合方式,导致粘结性降低,分散性增强,自由膨胀体积、膨胀后的含水量、剪切应力增加,滤失量、滤饼厚度降低;水化液为蒸馏水、黄河水时,31次冻融循环后自由膨胀体积均值增加了17.8%、32.8%。含水率均值增加了9.3%、16.8%,EC值增加了32.7%、24.9%,剪切应力增加了38.0%、37.1%;滤失量均值降低了24.3%、23.4%;滤饼厚度降低了19.4%、15.4%。渗透系数约增加了1个数量级,但仍较小,仅为衬砌前渠床土壤渗透率的0.35%~0.72%。渗出过程中有膨润土颗粒滤出,滤出液EC值降低了55.3%、48.0%。(3) GCL应力-应变曲线呈“M”型,有两个屈服点,分四个阶段:下层织物弹性非线性变形阶段;下层织物极限断裂阶段;上层织物弹性非线性变形阶段以及极限断裂阶段。高温、低温、高-低温循环、温度-湿度耦合、紫外线照射、水泥砂浆浸泡均导致GCL的力学性能降低,影响较大的因素为高温和紫外线照射。工程现场试验表明,试验第1年力学性能降低幅度较大,随着泥沙淤积形成覆盖层,老化速度降低。(4)GCL应力-应变关系可用高斯双峰拟合得到的本构方程描述,经检验,有较好的相关性。其系数与不同老化因素呈指数、对数关系,使用年限预测结果表明,30年后其残余应力值可达到30%。(5) X荧光光谱分析结果表明:试样有良好的结晶度及层状结构,膨润土的主要成分为SiO2。黄河水水化冻融后金属氧化物的含量略有增加。膨润土SEM图像表明:电解质浓度及冻融循环影响膨润土孔隙分布、孔隙表面特征及孔隙的大小,可以通过膨润土微观结构的孔隙表面分维、孔隙率、水力半径和形态等微观结构参数描述。试样水力半径在33.18~372.11μm之间;孔隙率在6.21%~69.69%之间,表面分维在1.18~1.22之间,形态指标在0.05~0.52之间,孔隙主要以不规则板状孔隙结构为主。工程现场试验2年后膨润土孔隙率增加。(6)根据研究成果结合试验区特殊环境,提出了GCL在类似地区应用的工程措施。更多还原

【Abstract】 With the intensification of supply and demand of water resources, conservation of water resources were caused great importance by various industries.it has great potential to construction to water (seepage canal lining) for agricultural water users . In the northwest of China, the special conditions of drought, cold, salinity severely restricts the application of ordinary impermeable material in the area. At present, in the region the main material for channel lining is concrete slab. But it has high cost a, poor performance against frost, construction period long, solid waste after the refractory lining failure caused by environmental and other outstanding series of problems. it is an important issue facing the current irrigated area to filtrate new impervious lining materials.The following seepage properties and related mechanism was researched in the paper through the laboratory and field examination to GCL in cold, arid and saline areas: (1)The basic characteristics of GCL, fall together research region’s status and GCL’S producing area make sample selected; (2)The properties of bentonite in different electrolyte solution were researched including expansion properties, rheological characteristics, viscosity and filtration; (3)The effect of freezing and thawing cycle and ion double factors coupling on bentonite properties and GCL anti-seepage permeability; (4)Through the experiments of high temperature, low temperature, and high low temperature cycling, UV rays, soaking the cement mortar and construction site aging experiment, analyzed the changes of GCL’s mechanical properties;(5) The microstructure of bentonite was analyzed by microscopic methods, and micro-structural parameters (hydraulic radius, shape index, surface fractal dimension, porosity) reflected the structure’s changes of bentonite, to explain GCL impervious performance change mechanism .Through the above study, the valuable conclusions and results are as follows:(1) Bentonite hydration process is carried out in stages; the type and concentration of electrolyte solution have significant impaction on the properties of bentonite. Bentonite free expansion volume, post-expansion water content, filtration and the concentration of the ions in hydration fluid were negatively correlated. Filter cake thickness and permeability coefficient were positive correlation; Bentonite suspension body rheological research shows: system thixotropic loop was anti-clockwise and it was negative thixotropy; When hydration solution was Yellow River water, the suspension shear stress increased and thixotropy decreased. Shear stress of bentonite was positively correlated with particle size and dispersion, and it was negatively correlated with the hydration liquid electrolyte concentrations.(2) The freeze-thaw cycles changed the connection ways of bentonite particles, Led to adhesion and filtration decreased, and dispersion enhance, free swelling volume, post-expansion water content, shear stress increased; Filtration and the cake thickness decreases; When hydration solution was distilled water and the Yellow River water, the free expansion volume average respectively increased 17.8%, 32.8% after 31 freeze-thaw cycles. Moisture content increased 9.3%, 16.8%, EC value increased 32.7%, 24.9%, shear stress increased 38.0%, 37.1%; Filtration average had reduced 24.3%, 23.4%; Cake thickness decreased 19.4%, 15.4%. Permeability coefficient increased about 1 order of magnitude, but the permeability coefficient was still little. It was 0.35%~0.72% that before the canal lining of soil penetration. Bentonite particles filtered out in the process of exudation, and the filtrate EC value decreased 55.3%, 48.0%.(3) GCL stress - strain curve was "M" type, and it had two yield points in four phases: The lower stage of nonlinear deformation of elastic polyacrylamide; The lower limit of fracture stage polyacrylamide; upper polyester or polyethylene co-host of nonlinear elastic deformation stage; Polyester or polyethylene film limit fracture stage. High temperature, low temperature, high-low temperature cycling, coupling temperature and humidity, ultraviolet radiation, soaking cement could decrease mechanical properties of GCL, especially the factors of high temperature and ultraviolet radiation. Field experiments showed that the mechanical properties of the first year decreased obviously, and the aging rate decreased with the layer sediment covering.(4) GCL stress - strain relations could be obtained by fitting Gaussian peaks to the constitutive equation. the result had shown a good correlation. The coefficient had shown an exponential and logarithmic relationship with different aging factors. The service life prediction results showed that the value of the residual stress can reach 30% after 30 years.(5) The X fluorescence spectroscopy results showed that the samples had a good crystallinity and layered structure, and the main component of bentonite were SiO2. When hydration solution was the Yellow River water, the metal oxide content slightly increased with freezing and thawing cycles increased after freeze-thaw. Bentonite SEM images showed that the changes of hydration fluid and electrolyte concentration, freeze-thaw cycles had some influence on bentonite pore distribution. The pore surface characteristics and pore size. The microstructure parameters could be described by pore surface dimension, porosity, hydraulic radius and shape of bentonite microstructure. Hydraulic radius of the selected bentonite sample was between 33.18 and 372.11μm. Porosity was between 6.21% and 69.69%. The surface fractal dimension was between 1.18 and 1.22, morphological index was between 0.05 and 0.52, and pore was mainly irregular. Microstructure of bentonite showed that the gap will increase after 2 years’field experiments.(6) Combining with the research results and situation of test area, the measures of GCL engineering application were raised in the similar regions.更多还原