混合型缓冲回填材料非饱和水分扩散试验研究

设计了专门的浸水试验装置,测定了膨润土-石英砂混合物在非膨胀条件下吸水引起的水分分布及膨胀应力变化,研究了混合型缓冲回填材料非饱和水力学性质。试验结果表明,干密度约1.70 g/cmP3、掺砂率为30%的GMZ001膨润土-砂混合物的水分扩散系数与含水率的关系呈U型变化,即随着含水率增加,汽态水分扩散系数减小,液态水分扩散系数增大。根据理论推导建立非饱和导水率估算方程。计算发现,混合物的非饱和导水率随含水率的增大而增大。其中,汽态水分非饱和导水率先增大后略有减小,液态水非饱和导水率始终增大。试验发现,试样吸水后干密度趋于均匀化,试样内部不同位置的应力发展与水分迁移过程密切相关：渗入端的应力在入渗初期增长很快,随后减慢;渗出端的应力持续稳定增长;入渗96 h后,两端应力趋于一致。估算出的水分扩散系数及非饱和导水率,可用于评价混合型缓冲回填材料阻隔核素迁移安全性。     

Sequential indicator conditional simulation and indicator kriging applied to discrimination of dolomitization in GER 63-channel imaging spectrometer data

Laboratory reflectance spectra of synthetic mixtures of the carbonate minerals calcite and dolomite were measured in the visible and near-infrared wavelength region (0.4–2.5 m) using a high-spectral resolution laboratory spectrometer. The instrument measured reflectivity with an accuracy of 0.001 m, allowing detailed resolution of the carbonate spectrum. The spectra of calcite and dolomite could be characterized by the presence of a strong absorption band centered at 2.3465 m for pure calcite and at 2.3039 m for pure dolomite. Nine mixtures of intermediate composition were analyzed demonstrating that the position of the carbonate absorption band is semilinearly related to the calcite content of the sample. Theoretically, this model allows mapping of dolomitization from high-spectral resolution remotely sensed imagery, GER 63-channel imaging spectrometer data from southern Spain were used to attempt such a mapping. First, pixels of vegetation were removed. For the remaining pixels, the wavelength center of the carbonate absorption band was detected and converted to a category of calcite fraction. The percentage of calcite for the remaining pixels was estimated using direct indicator kriging (IK) and sequential conditional indicator simulation, assuming that the calcite content could be represented as a category variable (SCIS category variable) and as a continuous variable (SCIS continuous variable). Four realizations of an SCIS (category variable) showed that on the average, 60 percent of the data was simulated in the same class and over 90 percent of the data within one class difference. A comparison with field samples showed that IK estimates of calcite content were within 20 percent accurate. The SCIS (continuous variable) does not perform as well with differences between –45% and +26% calcite; however, simulation reproduces the spatial variability better.     

Eu(Ⅲ)溶液对膨润土-砂混合物渗透性能影响研究

在高放废物处置库长期运营过程中包封容器将发生破坏,核素会向外界迁移,缓冲回填材料的水力传导系数是评价处置库工程屏障性能的重要指标。采用柔性壁渗透仪,研究2.0×10-5 mol/L的Eu(III)溶液作为渗入液时膨润土-砂混合物的渗透特性。结果表明,膨润土-砂混合物的水力传导系数K=(2.07⁵.23)×10-10 cm/s;在05.23)×10-10 cm/s;在0⁵0%掺砂率范围内,膨润土-砂混合物吸水膨胀过程中渗透性能随掺砂率增大时没有明显的变化,能够满足高放废物处置库缓冲回填材料低渗透性的要求。使用有效黏土密度的概念,得到膨润土-砂混合物的体积膨胀率随初始有效黏土密度的增大呈指数增大的趋势;混合物水力传导系数的对数值与有效黏土密度存在良好的线性衰减关系;与蒸馏水相比,渗入液(ECDD)为2.0×10-5 mol/L的Eu(III)溶液时,膨润土-砂混合物的水力传导系数较小,可能是由于渗入液黏滞性的影响。     

几种图像去噪算法的对比分析

图像去噪作为一种重要的预处理手段,一直以来都是图像处理和计算机视觉领域的研究热点。去噪算法的难点在于去除噪声的同时尽可能保持原始信息的完整性。本文主要研究TV,BLS-GSM,NLM以及BM3D四种经典去噪算法的基本原理,并用模拟数据验证分析四种算法在图像去噪中的性能,实验证明,四种算法均能在保留图像细节的前提下很好的去除噪声,其中,BM3D算法在保证去噪质量的同时效率最高。     

Evolution of pore structure and hydraulic conductivity of randomly distributed soluble particle mixture

The plane strain behavior of particulate mixtures containing soluble particles was investigated by conducting both laboratory tests and numerical analysis. To perform the laboratory experiments, soluble mixtures were prepared using photoelastic disks and ice disks with diameters in the ratios (D_{ice disk}/D_{photoelastic disk}) of 0.5 and 0.7, and the evolution of the force chain and pore structure was monitored during the dissolution of the ice disks. Subsequently, numerical analysis was conducted by using the 2‐dimensional discrete element method for the soluble mixtures, and it was compared with the experimental results. Additionally, parametric studies were implemented by varying the particle size ratios between the soluble and non‐soluble particles and the volumetric fraction of the soluble particles. The results of the laboratory experiments and numerical analysis demonstrate that (1) after the dissolution of the soluble particles, the pore fabric of the specimens changed, resulting in a force chain changes, local void increases, and coordination number decreases; (2) the effects of soluble particles on the macro‐behaviors of the mixtures could be divided into 3 zones based on the particle size ratios between the soluble and non‐soluble particles and volumetric fraction of soluble particles. These zones were as follows: (Zone 1)—with a small total soluble volume, slight decrease in the in situ lateral pressure (K₀), and minor increase in the hydraulic conductivity (k); (Zone 2)—with a moderate soluble particle; the dissolution generated a honey‐comb particle structure; (Zone 3)—the total soluble volume was very large, and the high volumetric fraction of the dissolving particle collapsed the pore structure, decreasing in the in situ lateral pressure (K₀) but increasing the hydraulic conductivity (k). The horizontal stress returned to almost the original level, and the internal arching formation increased significantly with the hydraulic conductivity (k).     

掺砂率对膨润土与砂混合物膨胀特性的影响

膨润土与砂混合物的膨胀特性是评估核废料深层地质处置工程长期性能的重要指标。对比不同膨润土及其与砂混合物的膨胀试验结果可知,对纯膨润土及其低掺砂率混合物,浸水膨胀完成后蒙脱石孔隙比em与竖向应力?v在双对数坐标内呈惟一的线性关系,利用该线性关系可预测浸水完成后不同竖向应力下的体积变化量及不同初始状态对应的膨胀力;对高掺砂率混合物,在砂骨架形成之前,em-?v线性关系成立,随着竖向应力的增大,砂骨架形成,对应的em值脱离em-?v线性关系,混合物中掺砂率越大,脱离该线性关系时的竖向应力就越小。砂骨架形成前,砂颗粒被蒙脱石包围,外力由蒙脱石承担,最终变形量由试样中单位体积蒙脱石的含量决定;砂骨架形成后,竖向应力最终由砂骨架和蒙脱石共同承担。利用砂骨架孔隙比的概念可确定各种不同掺砂率混合物形成砂骨架时的应力起偏点。同时,还可确定混合物能够形成砂骨架的掺砂率范围。     

Cell bioassays for detection of aryl hydrocarbon (AhR) and estrogen receptor (ER) mediated activity in environmental samples

In vitro cell bioassays are useful techniques for the determination of receptor-mediated activities in environmental samples containing complex mixtures of contaminants. The cell bioassays determine contamination by pollutants that act through specific modes of action. This article presents strategies for the evaluation of aryl hydrocarbon receptor (hereafter referred as dioxin-like) or estrogen receptor mediated activities of potential endocrine disrupting compounds in complex environmental mixtures. Extracts from various types of environmental or food matrices can be tested by this technique to evaluate their 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents or estrogenic equivalents and to identify contaminated samples that need further investigation using resource-intensive instrumental analyses. Fractionation of sample extracts exhibiting significant activities, and subsequent reanalysis with the bioassays can identify important classes of contaminants that are responsible for the observed activity. Effect-directed chemical analysis is performed only for the active fractions to determine the responsible compounds. Potency-balance estimates of all major compounds contributing to the observed effects can be calculated to determine if all of the activity has been identified, and to assess the potential for interactions such as synergism or antagonism among contaminants present in the complex mixtures. The bioassay approach is an efficient (fast and cost effective) screening system to identify the samples of interest and to provide basic information for further analysis and risk evaluation.     

Calibration of modelled mixing patterns in loess grain-size distributions: an example from the north-eastern margin of the Tibetan Plateau, China

Genetically meaningful decomposition (unmixing) of sediment grain-size distributions is accomplished with the end-member modelling algorithm. Unmixing of the loess grain-size distributions of a Late Quaternary loess–palaeosol succession from the north-eastern Tibetan Plateau indicates that the loess is a mixture of three end-members representing very fine sandy, coarse silty and medium silty loess. The unmixing approach potentially enables the unravelling of sediment fluxes from multiple dust sources, opening the way to significant advances in palaeoclimatic reconstructions from loess grain-size distribution data. However, as laser-diffraction size analysis is a volume-based technique, the proportional contributions of the modelled end-members might deviate (significantly) from weight proportions. Hence, calibration of the end-member volume proportions to weight proportions must be established before one can calculate the source-specific dust fluxes. This paper reports the findings of a sediment-mixing experiment which enables calibration of the modelled mixing patterns established for the Tibetan loess–palaeosol succession.     

Effects of coarse-grained materials on properties of residual soil

Residual soils are generally characterised by a low coefficient of permeability and high shrinkage potential. Several soil improvement methods can be applied to overcome these problems, including mixing the residual soil with coarse-grained soils. In order to study the effects of varying coarse-grained materials on the hydraulic properties and shrinkage characteristics of residual soils, a local residual soil was mixed with different percentages of a gravelly sand and a medium sand. The hydraulic properties and shrinkage potential of the residual soil and the soil mixtures were investigated. The measurements showed that increasing the amount of coarse-grained materials increased the saturated permeability and reduced the shrinkage potential of the residual soil mixture. Increasing the amount of coarse-grained materials in the residual soil produced changes in several key parameters of soil-water characteristic curve (e.g., the slope, the air-entry value, the residual matric suction, and the residual volumetric water content), as well as the unsaturated permeabilities of the soil mixtures.     

Unmixing magnetic remanence curves without a priori knowledge

Many of the natural materials studied in rock and environmental magnetism contain a mixed assemblage of mineral grains with a variety of different origins. Mathematical decomposition of the bulk magnetic mineral assemblage into populations with different properties can therefore be a source of useful environmental information. Previous investigations have shown that such unmixing into component parts can provide insights concerning source materials, transport processes, diagenetic alteration, authigenic mineral growth and a number of other processes. A new approach will be presented that performs a linear unmixing of remanence data into coercivity based end-members using only a minimal number of assumptions. A non-negative matrix factorization (NMF) algorithm for unmixing remanence data into constituent end-members is described with case studies to demonstrate the utility of the approach. The shape of the end-members and their abundances obtained by NMF is based solely on the variation in the measured data set and there is no requirement for mathematical functions or type curves to represent individual components. Therefore, in contrast to previous approaches that aimed to unmix curves into components corresponding to individual minerals and domain states, NMF produces a genetically more meaningful decomposition showing how a data set can be represented as a linear sum of invariant parts. It has been found that the NMF algorithm performs well for both absolute and normalized remanence curves, with the capacity to process thousands of measured data points rapidly.