垃圾填埋场砂土衬垫中膨润土添加剂的防渗能力

大部分垃圾填埋场选有低洼、底部由砂组成的地带,开发利用砂土作为填埋场防渗衬垫具有十分重要的意义。本文介绍了砂土中渗和膨润土添加２剂对砂土衬垫防渗性能改善的研究方法及研究结果。     

Rainfall‐runoff analysis based on competing linear impulse responses: decomposition of rainfall‐runoff processes

Many recent studies have successfully used neural networks for non‐linear rainfall‐runoff modelling. Due to fundamental limitation of linear structures, approaches employing linear models have been generally considered inferior to the neural network approaches in this area. However, the authors believe that with an appropriate extension, the concept of linear impulse responses can be a viable tool since it enables one to understand underlying dynamics of rainfall‐runoff processes. In this paper, the use of competing impulse responses for rainfall‐runoff analysis is proposed. The proposed method is based on the switch over of competing linear impulse‐responses, each of which satisfies the constraints of non‐negativity and uni‐modality. The computational analyses performed for the rainfall‐runoff data in the Seolma‐Chun experimental basin, Korea showed that the proposed method can yield promising results. Considering the basin characteristics as well as the results from this study, it may be concluded that three impulse responses are enough for rainfall‐runoff analysis. Copyright © 2007 John Wiley & Sons, Ltd.     

Composite landfill liner design with Ankara clay, Turkey

This study presents an overview of the geotechnical properties of the clayey soils, referred to as Ankara clay, at two sites of the Ankara region in an attempt to design a landfill profile composed of a high density polyethylene (HDPE) geomembrane/clay composite liner through the Hydrologic Evaluation of Landfill Performance (HELP) model and the Water Balance Method. The geotechnical properties of the landfill layers along with the water balance factors (i.e., evapotranspiration, precipitation, temperature, etc.) were assessed to determine the height of the water-saturated zone in the refuse above the composite liner for landfill design. The cumulative expected leakage rates through the composite liner constructed with compacted Ankara clay were related quantitatively to the cumulative average leachate head. The results of this investigation show that the leakage rates through the composite liner are within tolerable limits.     

水化后GCL中膨润土的微观结构研究

近年来土工织物膨润土垫（GCL）被越来越多地应用到各种防渗工程之中,而水化后GCL中膨润土的微观结构会对GCL的长期防渗性能和力学性能产生影响。采用压汞试验,对水化后GCL中膨润土的微观结构进行定量分析,研究了液体对微观结构的影响,并通过化学分析来揭示液体产生影响的机制。结果表明,(1) 采用垃圾渗滤液水化后的膨润土孔隙体积密度最大,大孔径孔隙所占比例最高;(2) 出现上述规律的原因可以归结为两个方面,一是由于渗滤液中阳离子浓度最高而使得蒙脱石表面双电层厚度最小,二是更加频繁的离子交换作用使得蒙脱石表面大直径离子比例最高。     

基于EIV模型的稳健估计

EIV（error-in-variables）模型同时考虑观测向量和系数矩阵的误差,自提出以来便得到广泛应用。目前针对EIV模型的整体最小二乘解法（TLS）假设观测值仅含有偶然误差,当观测值存在粗差时其解并不是最优的。文中通过选定合适的权函数,结合加权整体最小二乘迭代算法,导出基于EIV模型的稳健整体最小二乘迭代解法（RTLS）。线性拟合实验表明,文中方法能对粗差进行定位,且估计量受粗差影响较小,具有稳健性。     

基于最小二乘拟合模型和PCA变换的影像融合

针对传统的PCA变换融合法,利用高空间分辨率影像与多光谱影像的线性相关特性,提出了一种基于最小二乘模型和PCA变换的影像融合方法,采用偏差指数、相关系数和信息熵三个指标,对融合结果进行了定量评价。试验结果表明,在提高了多光谱影像空间分辨率的同时,更好地保留了多光谱影像的光谱信息。     

Multi-dimensional chemo-osmotic consolidation of clays

A model of chemo-osmotic consolidation of clays in multi-dimensional domains is presented, with volumetric strains induced by both changes in the chemistry and osmotically driven pore water flow considered. Three fully coupled governing equations considering force equilibrium, pore water transport and chemical transport are presented and solved using the transient finite element method. The proposed approach is verified via consideration of chemo-osmotic consolidation of a compacted clay landfill liner and then applied to investigation of a hypothetical case with a local leachate leak in the compacted clay liner. An assessment of the impact of the two-dimensional nature of the system is made. The consolidation process is found to be dominated by osmotic consolidation in the early stages and subsequently by chemical consolidation. It is found that the surface settlement and the leachate concentration in the compacted clay liner may be highly overestimated by a one-dimensional analysis. Moreover, the peak negative excess pore pressure predicted by the two-dimensional solution remains in a shallow region under the leak while in the one-dimensional solution it moves progressively downwards.     

Development of a technique for modelling clay liner desiccation

This paper presents a model for the analysis of clay liner desiccation in a landfill barrier system due to temperature effects. The model incorporates consideration of fully coupled heat‐moisture‐air flow, a non‐linear constitutive relationship, the dependence of void ratio and volumetric water content on stress, capillary pressure and temperature, and the effect of mechanical deformation on all governing equations. Mass conservative numerical schemes are proposed to improve the accuracy of the finite element solution to the governing equations. The application of the model is then demonstrated by examining three test problems, including isothermal infiltration, heat conduction and non‐isothermal water and heat transport. Comparisons are made with results from literature, and good agreement is observed. Copyright © 2003 John Wiley & Sons, Ltd.     

膨润土改性黄土衬里防渗性能室内测试与预测

试验测定了膨润土改性黄土试样的渗透系数,研究膨润土改性黄土用作废弃物填埋场衬里的可行性,为天然黏土匮乏地区防渗材料本土化提供依据。选取两种代表性黄土,即黏性较大的兰州黄土(LH)和砂性较大的榆林黄土(YH),分别向其中添加不同比例的两种膨润土后击实成样,利用柔性壁渗透仪测定改性黄土的渗透系数,分析了改性黄土渗透系数随膨润土添加率增大的变化规律,确定了满足衬里防渗要求的膨润土添加率。利用扫描电镜照片统计了改性黄土的孔隙特征参数,发现添加膨润土后黄土中原有的大孔隙被充填或分隔成更多的中、小孔隙,有效阻滞了渗流液体通过,从微观结构的角度揭示了改性黄土渗透性降低的实质。依据实测数据建立了膨润土改性黄土的渗透回归模型,据此可以预测不同添加量的膨润土改性黄土的渗透系数。     

考虑界面软化特性的垃圾填埋场斜坡上土工膜内力分析

为分析垃圾填埋场斜坡上防渗系统中的土工膜在上覆垃圾堆体重力作用下产生的拉应力,考虑土工膜-黏土界面的应变软化特性,通过建立土工膜受力的平衡方程获得了土工膜拉应力的解析解。与传统方法相比,该方法可分析土工膜-黏土界面不同位置所处的3种应力状态：弹性状态、软化状态及残余状态,从而使得垃圾填埋场斜坡上土工膜的受力分析更为合理。参数分析显示,当软化阶段的强度损失及残余位移与峰值位移的差值较小时,土工膜-黏土界面的峰值强度对土工膜最大拉应力的影响较小,而其残余强度是主要控制因素;而当土工膜-黏土界面的软化特征较明显时,则峰值强度和残余位移的影响也更为明显。另外,土工膜上覆堆体高度、斜坡坡度及土工膜锚固长度对土工膜拉应力也有较大影响。