HDPE土工膜温度应力的试验研究

为了评价垃圾填埋场防渗系统中HDPE土工膜的温度应力,对短纤维无纺布和HDPE土工膜组成的防渗系统进行了模拟试验.试验结果表明,HDPE土工膜的温度应力随环境温度的变化而变化,当环境温度下降时将导致HDPE土工膜收缩产生温度应力.同时利用温度与HDPE土工膜弹性模量的关系对温度应力进行分析,计算结果与实测结果比较接近.     

复杂荷载作用下填埋场HDPE土工膜受拉计算

采用FLAC程序对典型荷载作用下城市垃圾填埋场HDPE土工膜的受力状况进行了计算分析。3种荷载条件包括:36 m高垃圾堆体自重荷载(分层填埋);下卧软弱黏土层不均匀沉降引起的荷载;地震引起的动力荷载。计算结果显示:①土工膜内的拉应力随着垃圾土分层填埋、基础不均匀沉降、地震荷载的作用而积累;②基础不均匀沉陷是影响衬垫层土工膜局部拉应力的主要因素;③中等强度水平的地震动输入(例如,峰值加速度为0.25g)可使覆盖层土工膜端部锚固位置拉应力超过极限拉应力。     

垃圾填埋场防渗衬垫特性的离心模型试验与数值分析研究

垃圾填埋场中垃圾体和防渗土工膜的受力变形特性是普遍关心的问题,在现场试验尚无法获得满意的监测结果时,利用离心模型试验和有限元数值分析进行探讨性研究也是可以尝试的途径。通过离心模型试验研究和有限元计算,模拟了垃圾填埋场中填埋垃圾大变形条件下土工防渗膜的变形性状,在模型比率80的条件下,可以找到相应的模型材料来模拟实际工程中的土工膜;选用的防渗膜模拟材料和木屑土能较好地模拟垃圾填埋场中材料;邓肯-张模型和Goodman接触面模型能模拟垃圾土和土工膜以及界面的工作状态;土工膜中最大拉应力靠近坡肩,可达到极限抗拉强度的1/1.5倍;考虑到HDPE膜的抗拉安全,最大设计坡长应加以控制。     

城市生活垃圾卫生填埋场的HDPE土工膜防渗技术

HDPE土工膜已成为城市生活垃圾卫生填埋场防渗系统的首选材料，介绍了HDPE土工膜的基本特性以及在垃圾填埋场应用中的设计和施工要点。     

热带地区城市垃圾填埋场防渗施工技术

以斯里兰卡科伦坡城市固体废弃物处理工程为依托,对垃圾填埋场防渗技术进行研究,并对膨润土垫和HDPE土工膜施工技术、施工存在的问题及控制要点进行阐述。工程应用表明,膨润土垫+HDPE土工膜+压实防渗黏土的复合防渗衬垫系统防渗效果良好。     

土工膜穿刺性能的试验研究

垃圾填埋场底部和坡面都设置了防渗系统,阻止渗滤液流入地下,采用几种不同端部角度的贯入棒进行土工膜穿刺性能试验,研究了基础强度、土工膜种类和无纺布铺设与否对土工膜耐穿刺性能的影响。     

苏州市危险废物填埋场防渗工程简介

介绍了苏州危险废物填埋场防渗工程的组成和构造设计,对填埋库的防渗系统尤其是采用带嵌钉的HDPE土工膜施工工艺作了重点阐述.     

垃圾填埋场工程防渗技术的设计与施工

浙江省仙居县生活垃圾填埋场工程设计选用的主要防渗材料包括天然黏土和人工合成土工膜防渗衬层等。介绍了该工程主库区、封场覆盖、调蓄池、渗沥液导排系统和垃圾挡坝工程的防渗结构设计,以及GCL土工聚合黏土衬垫与HDPE土工膜的关键施工技术。     

垃圾填埋场边坡上土工膜的受力分析

在垃圾填埋场中,土工膜可以隔离垃圾体与周围环境,避免地下水受到污染。在土工膜上填埋垃圾和土层,沿其长度方向将有剪应力作用,使得土工膜发生变形,内部产生拉力,为保证土工膜的安全使用,需要对土工膜的拉力进行分析。将土工膜与黏土界面的剪应力–位移关系曲线分为弹性、软化和残余强度3阶段,采用三阶段弹塑性模型来描述土工膜与黏土界面的剪切变形特性,推导出了界面处于弹性、软化和残余强度3阶段时土工膜位移–拉力的微分控制方程,由于3个阶段分界点的位置是未知的,利用迭代法求解土工膜的拉力,分析了填埋高度和坡度的变化对土工膜拉力的影响。     

HDPE土工膜柔性垂直防渗墙在污染治理项目中的应用

介绍了HDPE土工膜柔性垂直防渗墙的防渗原理与特点,结合四川江油某垃圾填埋场封场和云南某矿渣堆场污染治理的工程案例,重点阐述了HDPE土工膜柔性垂直防渗墙的应用优势、施工工艺流程和施工要点,指出需严格管控HDPE土工膜柔性垂直防渗墙产品系统和施工技术质量,从而保证防渗效果。     

Numerical study of strain development in high-density polyethylene geomembrane liner system in landfills using a new constitutive model for municipal solid waste

Tensile strain development in high-density polyethylene (HDPE) geomembrane (GMB) liner systems in landfills was numerically investigated. A new constitutive model for municipal solid waste (MSW) that incorporates both mechanical creep and biodegradation was employed in the analyses. The MSW constitutive model is a Cam-Clay type of plasticity model and was implemented in the finite difference computer program FLAC?. The influence of the friction angle of the liner system interfaces, the biodegradation of MSW, and the MSW filling rate on tensile strains were investigated. Several design alternatives to reduce the maximum tensile strain under both short- and long-term waste settlement were evaluated. Results of the analyses indicate that landfill geometry, interface friction angles, and short- and long-term waste settlement are key factors in the development of tensile strains. The results show that long-term waste settlement can induce additional tensile strains after waste placement is complete. Using a HDPE GMB with a friction angle on its upper interface that is lower than the friction angle on the underlying interface, increasing the number of benches, and reducing the slope inclination are shown to mitigate the maximum tensile strain caused by waste placement and waste settlement.     

Viscoplastic modelling of HDPE geomembrane local stresses and strains

The formulation, validation and application of a viscoplastic constitutive model for numerical analysis of HDPE geomembrane stresses and strains induced by overlying coarse gravel is presented. Model parameters were obtained from uniaxial tensile experiments conducted over a range of displacement rates. The model was implemented in geometrically-nonlinear finite-element-analysis and was able to match the force, displacement and strain measured from wide-width strip tensile experiments. The analysis also matched the geomembrane response measured from axisymmetric force-displacement experiments, where a 60-mm-diam. specimen, clamped around its perimeter, was subjected to loading normal to its plane from a steel probe machined to mimic the shape of a coarse gravel particle. The analysis matched: i) probe forces when loaded at a constant rate of displacement, ii) displacements when loaded with step function increments of probe force, iii) creep displacements under a constant probe force for 1000 h, and iv) decreases in probe force from stress relaxation when held at a constant displacement for 1000 h. The analysis was used to further validate the applicability of thin plate theory to calculate geomembrane strains from measured deformations and provide first estimates of stress that develop beneath a gravel particle.     

土工膜破坏原因分析及防治措施

为了防止雨水流入垃圾中形成的渗滤液等多种有害物质流入地下污染地下水以及周围环境,现代垃圾填埋场都设置了防渗系统.防渗系统一般由无纺布、防渗材料以及膨润土土工毯等组成,由于在热应力、拉应力以及穿刺等各种因素的作用下,可能导致防渗系统破坏而使有害物质流入地下.介绍了造成防渗系统破坏的原因及其防治措施.     

高放废物处置中的THM耦合理论及分析

 高放废物处置研究是非常重要和必要的，其处置形式的选择是处置安全的重要因素之一，相应处置结构的物理力学特性研究是决定高放废物处置形式的重要依据。在介绍高放废物处置形式的基础上，提出高放废物处置的相关研究课题，紧接着阐述高放废物处置中THM耦合理论，膨润土的土水特征曲线不仅相关于外部施加应力、蒸汽压力、水压力，而且也相关于温度；在考虑气体在压力作用下的传播、气体在水中的溶解和气体的凝固等影响下，建立气体和液体中的水量守恒方程；在考虑敏感热流和潜热流影响下，建立能量守恒方程；将所有的方程写成有限元和有限差分计算格式；最后编制一维计算程序。计算结果对在花岗岩体中决定高放废物储存洞室之间间距具有借鉴作用。     

基于风险降低的导电HDPE土工膜在防渗系统中应用

在对传统使用的HDPE土工膜防渗系统渗漏原因和风险进行分析的基础上,推荐了导电HDPE土工膜作为防渗系统中的升级新型材料;通过对导电HDPE土工膜优点及其应用情况的分析,凸显了导电HDPE土工膜在防渗系统中可以检测渗漏和降低风险的重要地位。     

Development of geomembrane strains in waste containment facility liners with waste settlement

The development of tensile strains in geomembrane liners due to loading and waste settlement in waste containment facilities is examined using a numerical model. Two different constitutive models are used to simulate the waste: (a) a modified Cam-Clay model and (b) a Mohr-Coulomb model. The numerical analyses indicate the role of the slope inclination on the maximum geomembrane liner strains for both short-term loading (immediately post closure) and long-term waste settlement. A geosynthetic reinforcement layer over the geomembrane liner is shown to reduce the maximum geomembrane liner strains, but the strain level of the geosynthetic reinforcement itself may become an engineering concern on steeper slopes (i.e., greater than 3H:1V) for cases and conditions examined in this paper. The paper considers some factors (e.g., slope inclination, use of a high stiffness geosynthetic over the geomembrane liner) and notes others (e.g., the designer selection of interface characteristics below and above the geomembrane, use of a slip layer above the geomembrane) that warrant consideration and further investigation to ensure good long-term performance of geomembrane liners in waste containment facilities.     

Assessment of HDPE geomembrane performance in a municipal waste landfill double liner system after eight years of service

In the late 1970s and early 1980s, environmental regulations were upgraded in a general national movement to effect secure management of our municipal and residual solid wastes. The new regulations required varying combinations of natural and/or synthetic barrier and drainage layers to prevent the unrestricted release of contaminants.

The acceptable barrier materials included synthetic flexible membrane liners (FMLs) of various types. One of those most commonly used has been high-density polyethylene (HDPE) geomembrane. HDPE has been selected because of its good chemical resistance characteristics, among others. Background compatibility testing has shown the HDPE geomembrane to be extremely resistant to the leachates that are generated by municipal and residual solid waste landfills. The background testing for design has generally been based on relatively short-term tests that are conducted under extreme conditions to ‘forecast’ service life.

Recently, a municipal solid waste landfill double liner system that was constructed in 1988 was exhumed. The HDPE geomembranes of this liner system had been exposed to varying degrees of leachate since 1989. Samples of the HDPE were extracted from the in-place liner system and were laboratory-tested for physical, mechanical and endurance properties. The selected suite of tests duplicated the test protocol conducted in 1988 as part of the liner system construction quality assurance (CQA) program.

The results of this testing show that the HDPE properties are still within the range of data generated by the original testing in 1988. No degradation in properties was indicated by this testing program. The HDPE had been exposed to the leachate, methane, and static and dynamic stresses for approximately 8 years. The results of this test program support the design selection of HDPE as the synthetic barrier component of this landfill liner system.     

冲击性顶板运动及其应力演化特征的3DEC 模拟研究

 采用三维离散元程序建立煤层综放开采模型，研究综放工作面推进过程中采场、采空区上覆顶板岩层的冲击性运动形式和分段性垮落形态，记录并且分析采场动态推进过程中，采动围岩中岩层块体垂直应力、水平应力的动态演化特征。研究结果表明，采空区基本顶的运动形式、来压周期、来压强度与直接顶的垮落厚度有关；支架后方的直接顶挤压成拱缓冲了基本顶的来压冲击强度，同时也改变了其来压步距。随着工作面向跟踪块体方向的推进，块体垂向应力、水平应力存在高低应力分区，并且不断地波动，岩层应力峰值位置随着岩层高度的增加稍向煤壁前方移动。     

垃圾填埋场土工合成材料界面摩擦特性的拉拔试验研究

土工合成材料与填料的界面特性是决定垃圾填埋场中衬垫系统与土工合成材料受力特性的重要因素。选择3种不同种类的土工合成材料,用砂土和黏土为填料,通过拉拔试验研究土工合成材料的界面特性。试验结果表明:界面的峰值剪切强度与峰值位移随着法向应力的增加而增加;土工合成材料与黏土之间的摩擦角较大;填料为砂土时,无纺布与填料间的摩擦角最大,EPDM次之,HDPE最小;当HDPE上下都铺无纺布时,界面的摩擦系数最小。