垃圾填埋场土工合成材料的界面特性试验方法研究

拉拔、直剪、单剪试验常用于材料间界面特性研究,通过对垃圾填埋场中组成复合衬垫的土工膜、土工布和砂土、黏土界面分别进行了土工膜与砂土、土工膜与黏土、土工布与砂土、土工布与黏土的拉拔试验,土工布与砂土、土工膜与黏土的直剪试验及土工网–土工膜–黏土组合界面的单剪试验。研究结果表明:土工合成材料与土界面特性主要取决于土工合成材料的表面性质,直剪和单剪试验得到应力–位移曲线的初始斜率高于拉拔试验;法向应力由低向高变化时控制滑动面也发生了变化,界面特性受到防渗结构层中相邻材料的影响;在3种试验中拉拔试验得到的界面强度包线最高,单剪次之,直剪最低;单剪试验能较合理地模拟垃圾填埋场复合防渗结构的工作条件,建议利用单剪试验技术确定界面的强度参数,直剪试验也是可选择的试验方法。     

坝坡内置光纤土工膜的膜–土界面亲和性试验分析

光纤土工膜是具有破损定位功能的新型防渗材料。为了研究红土大坝中的光纤土工膜对坝坡稳定的影响,进行剪切强度试验和可调斜坡模型的抗滑试验,获得各种工况组合下膜–土界面的黏聚力、内摩擦角、滑动坡比、摩擦系数等数据。与纯粹红土组、红土内置复合土工膜组的数据进行比对分析,结果表明:光纤土工膜与红土的亲和性足以满足抗剪要求;光纤土工膜作为防渗体嵌入坝坡,在实际工程条件下的抗滑安全性能不低于传统土工膜,能够满足规范要求。     

复合土工膜对石油钻井井场防渗效果的试验研究

为研究复合土工膜在石油钻井工程中对井场的防渗效果,对井场中加入复合土工膜所形成的复合路面结构进行了防渗效果的现场观测及室内土样成份分析.试验结果表明复合土工膜完全起到了防渗漏的作用,为复合土工膜在同类工程中的应用提供了参考.     

土工膜与无砂混凝土垫层界面力学特性分析

在高面板堆石坝工程中,土工膜作为辅助性措施与面板联合防渗结构在工程中应用比较广泛,土工膜与相接触的垫层材料之间的接触剪切力学特性关系到坝体的稳定。本文首先对土工膜界面力学特性试验设备及其试验原理进行了详细的阐述;然后利用该仪器对面、膜联合防渗工程中两种土工膜与无砂透水混凝土垫层材料之间的接触剪切力学特性进行了试验研究,并对不同竖向荷载条件下接触剪切力学特性测试结果做了对比分析;最后通过数据处理并结合理论推导,得到了土工膜在接触剪切作用下的剪切应力-竖向应力关系式。     

复合土工膜应用于石油钻井井场工程中的耐腐蚀性试验研究

为研究复合土工膜应用于石油钻井井场防渗工程中的耐腐蚀性,对经过井场中的油污和废液浸泡的复合土工膜进行了浸泡前后的拉伸试验,试验结果表明复合土工膜具有优良的耐腐蚀性,其防渗能力不会因受到腐蚀而有所下降.为复合土工膜在同类工程中的应用提供了参考.     

探讨土工膜在水利防渗工程中的施工质量控制

土工膜具有优良的耐化学腐蚀性能,在水利防渗工程中应用广泛,是防渗加固的一种有效手段。文章结合水库工程案例,介绍了土工膜的作用机理和功能特性,详细阐述了土工膜在水利防渗工程中的施工方法和质量控制措施。实践表明,严格控制土工膜材料质量,加强现场施工技术管理,才能保证防渗施工质量,提高综合效益。     

复合土工膜在病险水库大坝防渗加固中的应用

复合土工膜是一种应用较为广泛的防渗材料,具有延展性成本低、施工简单及防渗性能好等特点。本文结合具体工程,介绍了复合土工膜在病险水库大坝防渗加固中的应用,并论述了复合土工膜施工技术及质量控制措施,为类似工程的应用提供了参考。     

基于测压管实测水位的王甫洲水利工程复合土工膜工作性态反馈

基于王甫洲水利工程近20 a的渗流监测资料,对复合土工膜的防渗工作性态进行反馈分析.首先对围堤土石坝整体渗流性态进行定性分析;然后选取典型断面建立测压管水位统计模型进行定量分析;接着采用正交设计-神经网络-数值计算相结合的方法,反演复合土工膜的渗透系数;最后对复合土工膜工作性态进行综合分析.研究表明,测压管实测水位仅在...     

沁河河口村水库防渗体设计

结合水库防渗体设计实例,介绍了防渗体的组成,对防渗材料即复合土工膜的设计、施工、质量控制进行了阐述,分析计算了复合土工膜稳定安全系数,得出相关结论,以期保证水库安全使用。     

防渗复合土工膜设计和施工

复合土工膜是水利工程中常用的防渗材料,结合某水库大坝加固工程介绍了复合土工膜设计、施工方面的技术要点。     

复合土工薄膜及其防渗设计

复合土工薄膜是以土工薄膜和土工织物在工厂通过挤压、液压或喷涂等工艺所制成的整体结构,它兼有薄膜防渗和织物排水的功能,起着薄膜加垫层的作用,并改善了薄膜的工程性能及简化施工程序,保证施工质量,是一种较为理想的防渗材料。文中针对复合土工薄膜用作斜墙铺盖防渗,从铺盖和透水地基界面的接触冲刷概念出发,导出了极限铺盖长度和渗流量的计算公式,经新疆桑株水库土坝坝面铺盖防渗工程实例计算比较,误差甚小,可供设计参考。文中根据薄膜理论建立了复合土工薄膜在其法向应力作用下的顶破强度计算公式和织物排水的公式,经云南恨虎水库堆石坝的校核,可合理选择复合土工薄膜。     

Evaluating barrier performance of geomembranes against 1,4-dioxane and bisphenol a in landfill leachates

Previous studies have shown that within a month benzene easily passes through geomembranes (PVC, LDPE, and HDPE geomembranes). This study uses diffusive permeation tests to clarify the barrier performance of geomembranes against bisphenol A and 1,4-dioxane, which have been detected in some Japanese waste leachates. Although dissolved bisphenol A can be adsorbed on the geomembranes, it does not pass through them during the testing period (at least 400 days are required for it to completely pass through 0.5-mm-thick PVC geomembranes). In addition, dissolved 1,4-dioxane is not adsorbed on any geomembranes and hardly passes through any of them (at least five years are required for it to completely pass through 0.5-mm-thick PVC geomembranes). Thus, geomembranes exhibit a good barrier performance against these two organic compounds, especially 1,4-dioxane.     

Tension in geomembranes on landfill slopes under static and earthquake loading—Centrifuge study

Geomembranes are some of the most commonly used geosynthetics in landfill liner systems. Geomembranes may experience harsh environmental conditions such as extreme temperatures or earthquake loading. Earthquake loading can be an extreme loading case for landfills located in seismic regions. This study, based on dynamic centrifuge testing, investigates the effects of simulated earthquake loading on the tension experienced by the geomembrane on a landfill slope. The landfill modelled in the dynamic centrifuge tests was a 7 m high municipal solid waste (MSW) landfill with a single geomembrane-clay liner system (45° side slope and 10 m slope length). Results show that moderate earthquake loading (base acceleration between 0.1 and 0.3 g) can result in a permanent increase in geomembrane tension of 5–25%.     

Destructive testing of geomembrane seams: Shear and peel testing of seam strength

An essential step to assure the proper long-term performance of a geomembrane liner that is in the process of being installed is 100% inspection of the seams to ensure their continuity. This step must be complemented with destructive testing of the seams to ensure their strength and integrity. At the present time, the principal destructive tests of seams involve strategic sampling and testing of the seams in accordance with standard ASTM methods for seam strength in shear and peel modes. This paper describes the seam testing of the different types of geomembranes and discusses specific tests that are used. Also discussed are the variables that are involved in the testing and the requirements that should be stated in the specifications in order to assure full understanding of the acceptance criteria and the requirements of quality control and quality assurance. The results of testing current geomembranes are presented. Finally, some limitations of destructive testing of seams are discussed.     

Addressing the special concerns of landfill closures: VLDPE and textured geomembranes

Landfill closures often require a somewhat different set of properties for synthetic liners than do landfill bottom liner installations. In particular, cap design usually presents the geotechnical engineer with greater concerns regarding long-term slope stability and accommodation of differential settlement. Friction between synthetic liners and materials contacting those liners, multiaxial elongation, and flexibility increase in importance. Since leachate does not contact the liners, chemical resistance becomes less important. Resistance to the components of landfill gas is, in most cases, all that is necessary.

As a result, synthetic liners with a textured surface to improve friction angles, and very low density polyethylene (VLDPE) geomembranes are becoming very attractive to geotechnical engineers. They provide considerable improvement in those areas which are important for cap installation. These materials, however, behave differently in standard index and performance testing of geomembranes, when compared with traditional polyethylene liners. These behaviors and differences are important for geotechnical engineers to understand. They are discussed in this paper.     

Field evaluation of geonet flow rate (transmissivity) under increasing load

This paper presents data from a full scale field test of a geonet placed between two geomembranes used as a leak detection system for a solid waste landfill. The cell under investigation is 1·54 ha in area, with the geonet covering 0·87 ha of the base of the cell. The remaining sideslope area was also covered by geonet, but did not contribute to the flow rate testing. Approximately 2300 liters of water were injected at three different times; i.e., at landfill waste heights corresponding to 12, 153 and 311 kPa normal stresses. The percentages of recovered water within a 15-h period were 93·9%, 89·6% and 81·2% respectively. The calculated transmissivity values reflected the increased normal stress as would have been anticipated, i.e., transmissivity values decreased from 45·2 to 43·5 to 40·0 × 10⁻⁴ m²/s, respectively. These decreases were anticipated due to the elastic intrusion of the geomembranes into the geonet under the gradually increasing normal stresses. The results indicate that geonets are viable drainage materials under actual full-scale field conditions and should certainly be considered as drainage replacements for natural granular soil drainage media.     

Influence of micro and macroroughness of geomembrane surfaces on soil-geomembrane and geotextile-geomembrane interface strength

The interface shear strength involving geosynthetics and other materials can be influenced by various parameters, such as the material type and the normal stress on the interface. Although several investigations have been conducted over the years on this topic, the large variation of interfaces that can be used has led researchers to develop other sources of information to improve design methods. This paper investigates how roughness parameters can influence the shear strength developed between different interfaces based on many inclined plane tests and microscopic analyses of the surface roughness. One smooth and three textured geomembranes were used to simulate a barrier layer and sand, and two nonwoven geotextiles were installed on them to simulate drainage or protective layers. A powerful optical apparatus provided fifteen bidimensional and tridimensional surface parameters for the two faces of the analyzed geomembranes. The results showed that the mean height of profile elements (R_c) and the core material volume (V_mc) parameters presented stronger correlations with the interface shear strength. The concept of interface roughness factor was introduced to estimate the interface friction between different materials based on the materials properties for interfaces with geotextiles.     

圆形构筑物周边土工膜沉降时的褶皱产生机理及分析模型

基于传统薄膜理论建立了下卧土体沉降作用下圆形构筑物周边土工膜受力变形的分析模型,发现在下卧土体沉降作用下圆形构筑物周边土工膜中将产生褶皱,并揭示了其产生机理。进一步通过引入"可变泊松比"概念并基于褶皱薄膜理论建立了褶皱区与张拉区土工膜受力变形的分析模型,分析了下卧土体沉降大小、上覆土压力、土工膜界面强度、圆形构筑物半径及土工膜抗拉刚度对土工膜褶皱程度与受力变形大小的影响。结果表明下卧土体沉降越大、圆形构筑物半径越小,则褶皱程度及土工膜最大应变越大。最后提出了工程上控制土工膜褶皱和最大应变与张力的几点工程措施。     

Sicherheitsverglasungen als Hybridbauteil

Security glazing as hybrid element. Hybrid elements play a more and more significant role in building construction. The systematic combination of different materials forming a composite element enables the engineer to adjust and optimise the desired structural properties for a specific application, which a single building material might not be able to cope with. When using glass in building construction, its combination with more ductile materials effectively contributes to broaden the range of applications beyond the limitations of the base materials involved. The material properties of security glazing units and especially their resistance against external attack can be significantly improved by using hybrid elements made of glass and polycarbonate. The composite panels are more slender and weigh less than conventional panes made of laminated safety glass. As part of the investigation on hybrid elements, experimental testing was carried to examine the composite panel's load capacity and residual strength. The test results provide a basis for the development of an analytical design approach of composite panels made of glass and polycarbonate. The investigation of hybrid building elements with glass forms a major part of the current research activities at the Institute of Building Construction at Technische Universität Dresden.     

Coextruded HDPE/VLDPE multilayer geomembranes

High density polyethylene (HDPE) geomembranes have been used extensively during the last decade and very low density (VLDPE) geomembranes have been introduced during the last few years. Both materials have properties that are desirable for particular applications. HDPE has excellent chemical resistance, UV resistance and high modulus. VLDPE is very flexible and is capable of much more elongation in field applications than HDPE.

A geomembrane made by the coextrusion of HDPE and VLDPE has several advantages over geomembranes made from either HDPE or VLDPE alone for many applications. These advantages are realized due to synergistic effects that occur between the two polymers, resulting in a product that incorporates desirable properties of the two materials and eliminates some of the less desirable ones. The Coextruded Multilayer Sheet (CEMS) addressed in this paper has better tensile strength, tear resistance, seam strength, chemical resistance, permeability and UV resistance than VLDPE and better puncture resistance, elongation and stress crack resistance than HDPE. Coextruded, multilayer geomembranes make available more options for the design engineer attempting to find the best product for a given application.