水入渗条件下边坡破坏离心模型试验研究

水的人渗能对土体强度产生较大的影响,它是造成边坡破坏的一个主要因素.不同含水量土质边坡的离心模型试验表明:边坡的破坏类型与其含水量大小有关,且主要存在两种破坏类型:一种是含水量较小时形成的拉裂缝破坏,另一种是含水量较大时形成的整体滑塌破坏;同时,含水量与边坡的最大稳定高度呈非线性关系.进一步的损伤力学分析表明,随着土体含水量的增加,损伤变量增大,并存在一个突变点;通过同离心模型试验结果比较,发现该突变点对应的含水量可作为两种破坏类型的判据.     

MODELING THE IMPACT OF MULTICOMPONENT VOCs ON GROUND WATER USING THE STEFAN‐MAXWELL EQUATION1

ABSTRACT: Computer programs that model the fate and transport of organic contaminants through porous media typically use Fick's first law to calculate vapor phase diffusion. Fick's first law, however, is limited to the case of a single, dilute species diffusing into a stagnant, high concentration, bulk vapor phase. When dealing with more than one diffusing species and at higher concentrations, the multicomponent coupling effects on vapor phase diffusion and advection of the various constituents become significant. VLEACH, a one‐dimensional finite difference model developed for the U.S. Environmental Protection Agency (USEPA), is typical of the models using Fick's first law to model vapor‐phase diffusion. The VLEACH model was modified to accommodate up to 10 components and to calculate the binary diffusion coefficients for each of the components based on molecular weight, molecular volume, temperature and pressure, and to address the coupling effects on multiple component vapor phase diffusion and its impact on ground water. The resulting model was renamed MC‐CHEMSOIL. At low vapor phase concentrations, MC‐CHEMSOIL predicts identical ground water impacts (dissolved phase loading) to those from VLEACH 2.2a. At higher vapor phase concentrations, however, the relative difference between the models exceeded 20 percent.     

New Metal Emission Patterns in Road Traffic Environments

The increased awareness of traffic as a major diffuse metal emission source emphasizes the need for more detailed information on the various traffic-related sources and how and where the metals are dispersed. In this study, metal emission patterns in the road traffic environment were examined from the perspective of different surrounding factors, e.g. the importance of intersections, deceleration, vehicle speed and traffic density. A total of 148 topsoil samples from 18 south Swedish roads were analysed (using GFAAS) for traffic-emitted metals, i.e. Cd, Cr, Cu, Ni, Pb, Sb and Zn. The roadside topsoil metal concentrations were used to examine correlations between metals and surrounding factors. The studied metals were divided into three groups corresponding to different emission sources: metals from decelerating activities (Cu, Sb and Zn), metals as historical residues from the combustion of petrol (Pb and Cd), and non-source-specific metals (Cr and Ni). It was found that Cu and Sb, despite their rather short history as traffic-emitted metals, have increased more than eightfold in roadside soils compared to background levels. The major source of road traffic related Cu and Sb is brake linings. The significant increase of Cu and Sb in roadside topsoil stresses the need for metal transport studies as well as effect studies of these metals. Metals emitted due to decelerating activities were not correlated to elevated concentrations near road junctions. Emission patterns of traffic-related metals alongside roads are crucial in order to be able to evaluate the optimal localization of storm water treatment ponds.     

地基弹性参数对于长型大截面地下结构横向自由振动的影响

自由振动分析是地下结构地震动力响应分析的基础.本文利用笔者先前得到的长型地下结构的自由振动方程,研究了地基弹性参数对地下结构自由振动的影响.由分析可以看出,随着地基弹性参数值的增加,结构中波速值总的趋势是增加,但是温克尔地基参数对结构中波速的影响远大于第二地基参数的影响;地下结构振动频率总的趋势是随着温克尔地基参数(k...     

考虑非饱和特性的黄土湿陷性与微观结构分析

利用扫描电子显微镜测试技术对3个场地16个土样的微观结构进行观测,并使用图像处理软件对微观图像进行处理、对土样孔隙的几何特征参数和分维数进行了提取,土样孔隙分布分维数为1.816~1.936。利用分形几何学原理建立非饱和土的孔隙分布函数,对天然湿度下黄土中水分分布进行分析,运用回归分析的方法对孔隙的分维数、非饱和孔隙孔隙率和湿陷性的关系进行了分析。结果表明:孔隙分维数越大,孔隙结构越复杂;天然湿度下处于非饱和状态的黄土孔隙孔径均大于40μm,黄土的湿陷系数随着孔隙分维数、非饱和孔隙孔隙率的增大而增大,非饱和孔隙是造成黄土湿陷的主要原因。     

云南粉土的动力特性试验研究

粉土是一种具有特殊工程性质的土,由粉土液化引起的工程震陷造成的危害极大。根据云南粉土的室内共振柱试验,得到了归一化处理后的G/Gm ax~γ/rγ和D~γ曲线,并运用修正后的双曲线模型进行了拟合分析。根据室内振动三轴试验,得出不同固结比和不同固结压力下的土的动强度与振动次数的试验曲线,发现动强度与破坏振次间符合较好的乘幂关系,动强度与固结比之间符合较好的二次抛物线关系;分析不同围压下孔压与破坏振次的试验曲线规律,发现可以用指数函数进行拟合。结果可供该类土的动力特性研究参考。     

风化煤组配改良剂结合水分管理对水稻根际土壤与稻米甲基汞含量的影响

采用以风化煤、碳酸钙与亚硒酸钠为主要原料组配的土壤改良剂,结合稻田水分管理(抽穗扬花期后保持80％田间持水量),通过盆栽试验和大田试验,研究改良剂和水分管理对稻田水稻土和水稻籽粒中甲基汞含量及水稻生产的影响.结果表明:①土壤改良剂结合稻田水分管理可以显著降低水稻根际土壤与水稻籽粒中甲基汞含量.在盆栽环境中,土壤改良剂+...     

城市地下空间开发中的弃土管理和处置对策

城市地下空间的大规模开发利用将产生大量弃土。简要分析了弃土对环境的影响,介绍了弃土管理和处置的现状以及存在的问题,提出了加强立法和管理、优化施工方法和技术、对弃土进行资源化利用、妥善处置已污染的弃土等对策。