岩土力学参数随机场的离散研究

基于岩土力学参数随机场并不一定是平稳弱变异高斯随机场这一事实,应用地质统计学原理并结合随机有限元中三种较常用的随机场离散方法对岩土力学参数随机场的离散作了探讨。由于所提方法是通过对随机场作空间变异性分析来获得随机场的空间结构特征而不是假定随机场为平稳弱变异高斯随机场,因此离散结果更切合实际     

Modelling ultrafine/nano particle dispersion in two differential mobility analyzers (M-DMA and L-DMA)

In the present work, the dispersion of ultrafine/nano particles in two differential mobility analyzers (DMA) namely, a medium DMA (M-DMA) and a long DMA (L-DMA) is numerically analyzed using the Lagrangian tracking method. Simplified geometries of the two DMA’s (M-DMA and L-DMA) that are truly representative of a wide class of DMAs have been considered for the present analysis. The exact profiles of velocity and electric field are used for conducting the present investigation. The Langevin equation is numerically solved to track the particles inside the DMAs. The Brownian force has been modelled as a Gaussian white noise random process. The effect of Brownian force on the dispersion of ultrafine/nano particles is clearly evident from the present investigation. The performance evaluation of both the DMAs have been carried out by comparing the transfer functions obtained using the present methodology with the widely accepted transfer functions of Knutson & Whitby and Stolzenburg. The numerical results obtained using the present methodology compare quite well with the experimental data available. It is also shown that DMAs with smaller effective electrode lengths have higher collection efficiencies for real nano-sized particles.     

Interactions between selected PAHs and the microbial community in rhizosphere of a paddy soil

This study investigated the interaction of three polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene (NAP), phenanthrene (PHN), and pyrene (PYR), with the microbial community in the rhizosphere of a paddy soil and the influence of the rice (Oryza sativa) rhizosphere on the microbial community structure. A range of initial NAP, PHN and PYR levels in soil (50-200, 18-72, and 6.6-26.6 mg kg^− 1, respectively) were prepared and the soil samples were then aged for 4 months (to yield PAH concentrations at 1.02-1.42, 1.32-4.77, and 2.98-18.5 mg kg^− 1, respectively) before the soil samples were planted with rice seedlings. The microbial phospholipid-fatty-acid (PLFA) patterns in PAH-contaminated soils were analyzed to elucidate the changes of the microbial biomass and community composition. Results indicated that at the applied concentrations the PAHs were not toxic to rice seedlings, as evidenced by no growth inhibition during the 8-week planting period. However, the microbial biomass, as revealed by PLFAs, decreased significantly with increasing PAH concentration in both rhizospheric and non-rhizospheric soils. The PAHs in soils were obviously toxic to microorganisms, and the toxicity of PHN was greater than PYR due likely to the higher PHN bioavailability. Total PLFAs in rhizospheric soils were profoundly higher than those in non-rhizospheric soils, suggesting that the inhibitive effect of PAHs on microbial activities was alleviated by the rice roots. The principal component analysis (PCA) of the PLFA signatures revealed pronounced changes in PLFA pattern in rhizospheric and non-rhizospheric soils with or without spiked PAHs. Using the PLFA patterns as a biomarker, it was found that Gram-positive bacteria were more sensitive to PAHs than Gram-negative bacteria, and the rhizosphere of rice roots stimulated the growth of aerobic bacteria.     

非均质岩石材料宏细观力学参数的关系研究

利用基于岩石矿物种类及其含量提出的岩石矿物细胞元随机性参数赋值方法,针对两矿物细胞元混合的非均质岩石模型进行参数赋值,通过数值试验研究了非均质岩石材料矿物细胞元含量及其力学参数对岩石宏观力学参数的影响;根据数值试验结果,探讨了岩石材料矿物细胞元弹性模量与宏观模量之间的函数关系。研究结果表明,岩石宏观弹性模量与矿物细胞元弹性模量、矿物细胞元含量都具有十分显著的线性相关关系,即基于岩石矿物种类及其含量的矿物细胞元随机性参数赋值方法建立的岩石有限元模型宏细观力学参数之间呈显著的线性关系;宏观力学参数可用细观力学参数的数学期望值即加权平均值来表示。     

Sr transfer factors between different levels in the trophic chain in two dams of Douro river (Portugal)

The study of Sr transfer in the trophic chain, was undertaken in the dams of Miranda do Douro and Régua belonging respectively to the upper and middle streams of Douro river.

This study was carried out during 17 months, between January 1985 and May 1986, and Sr was measured in water, phytoplankton (seston) zooplankton, specimens belonging to two benthic families (Chironomidae and Tubificidae) and in representatives of four species of fish of Cyprinidae family: Chondrostoma polylepis—boce; Cyprinus carpio—carp; Carassius auratus—goldfish; Barbus bocagei—barbel.

The results obtained showed the existence of strong seasonal variation in the levels of Sr in water and in the different levels of the food chain.

The minimum values in water correspond to the rainy seasons, when the flow is higher, identifying a clear dilution effect. In fish, where these variation are slighter, the amount of Sr is proportional to the size of the body (constant concentration), possibly because the greatest part of this element is found on skeleton pieces (bones and scales).

All the studied organisms present high Sr concentration factors from the water. However, taking into account annual averages, a great accumulation of Sr in the food chain, from the plankton to the fish itself, is not found, meaning that no important phenomena of biomagnification to Sr concentrations between prey and predator exist. The higher transfer factors (TFs) from benthic animals to fish are only due to the absence of skeleton in those animals. An estimation of TFs from benthic animals to the soft edible parts of fish show that no biomagnification exists.

The determination of TFs between food-chain levels during the different seasons, together with other physico-chemical, biological and hydrological data presented, is essential to the development of protective measures against radioactive threats.     

玄武岩残积土的电阻率与直剪强度关系

西南地区的玄武岩残积土具有结构性强、孔隙比大、塑性指数高等不良工程特征,其原位地基承载力较高,但遇水后强度降幅较大。依托在建的贵州省毕节一威宁高速公路工程,运用现场原位测试、室内试验和理论分析等手段,测试了玄武岩残积土的电阻率和工程特性指标,讨论了以玄武岩残积土电学特性评价其工程特性的可行性,最后通过对比现场高密度电阻率法的实测结果,证实了以玄武岩残积土的电阻率评价其工程特性是可行的。     

静力触探参数与地基土物理力学指标(天津地区)相关分析研究

通过静力触探参数与天津地区地基土物理力学指标的相关分析研究，得出一套实用的经验公式，并在实践中加以应用。     

土体应力应变关系的影响因素分析

土体与岩体作为岩土工程研究的重点对象广泛受到关注,地球表面的岩体经过不断的风化形成土体。土体作为一种三相介质,其应力应变关系非常的复杂,它的关系受到很多因素的影响。为了保障工程的顺利实施,土体的应力应变关系的研究一直备受重视。在总结分析现有研究的基础上,对影响土体本构关系的因素进行了归纳总结,其结果表明土体的结构性、应力条件是影响土体应力应变关系的主要因素。     

混凝土粗糙面形貌特征参数与节理粗糙度系数关系研究

裂缝面粗糙程度是描述其表面形貌的重要参数。基于三维扫描技术获取混凝土裂缝面的坐标点云数据,等间隔选取各裂缝面11条轮廓线,计算各轮廓线粗糙轮廓指数Rp、形貌线伸长指数δ和粗糙角i等特征参数,研究采样间隔SI对二维节理粗糙度系数JRC的影响;建立JRC与二维特征参数Rp、δ、i之间的函数关系、三维JRC3D与三维特征参数之间的关系。结果表明：JRC与SI呈二次函数关系,当SI为0.2 ～ 1.2mm时,随SI减小,JRC增大;JRC与Rp、δ分别呈二次函数和对数关系;JRC与二维特征参数中的粗糙角iZ2呈正相关关系。建议Rp作为二维节理粗糙度系数表征指标。JRC3D与三维特征参数的最大构造深度Rz相关性最好,拟合公式平方根R2为0.9109。提出的表征公式与已有成果最大平均相对误差MRE、平均绝对误差MAE和均方根误差RMSE分别为1.790%、0.316mm和0.408mm。说明提出的表征公式是合理的,适用于混凝土裂缝面粗糙度估算。     

Interaction between shallow foundations in tamped (punched) trenches and heaving soil

Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 14–16, July–August, 1989.     

Relationship between polished stone value (PSV) and Nordic abrasion value (A N) of volcanic rocks

Bulletin of Engineering Geology and the Environment - A set of 39 different volcanic rocks was studied for performance as crushed stone for road surfacing (wearing course) aggregates using two...     

岩体分级BQ与RMR的关系及其力学参数估计

在国标《工程岩体分级标准》（GB50218—94）岩体质量分级的基础上,提出了岩体基本质量指标BQ的简化计算方法。根据规范中建议的岩体物理力学参数取值范围,编制了各参数与BQ关系曲线图,通过非线性拟合分析,建立了各物理力学参数与BQ之间关系的经验公式。基于内摩擦角等效原则,通过比较已有的分别用RMR和BQ表达的岩体内摩擦角经验公式,推导出1个BQ和RMR之间的关系方程。同样基于变形模量等效原则,通过比较已有的分别用RMR和BQ表达的岩体变形模量经验公式,推导出4个BQ和RMR之间的关系方程。这5个关系方程与实测结果进行了比较分析,得到了上限线和下限线方程;由内摩擦角等效获得的关系方程趋势较好,取上限线和下限线的中间线对其进行修正,得到了本文建议的RMR和BQ之间的关系方程。     

盐渍土强度参数与含盐量、含水量关系初探

在室内试验条件下,以青海格尔木市郊土样为样品,研究了盐渍土抗剪力学性质的变化。试验结果表明,加入不同盐类和含量的氯盐及硫酸盐,土体粘聚力c和内摩擦角φ均与含盐量同含水量的比值m存在良好的线性关系。当m〈1.54时,加入的氯盐和硫酸盐所得c,φ值差异较大;当m〉1.54时,差异较小。经分析可以认为,盐渍土强度参数c,φ值的变化,主要是由土体中易溶盐相态变化所致。     

Effect of lime,cement and Sarooj (artificial pozzolan) on the swelling potential of an expansive soil from Oman

In this study, Al-Khod (town in northern Oman) expansive soil was stabilized using lime, cement, combinations of lime and cement, Sarooj (artificial pozzolan) and heat treatment. Initially, the chemical and physical properties of the untreated soil were determined. Then the soil was mixed with lime, cement and Sarooj (produced from Bilad Seet, a town in northern Oman) at 3%, 6% and 9% by dry weight of soil. Fixed percentages of lime (3% and 5%), plus different percentages of cement were also mixed with the soil. The physical results of the treated samples were determined. The untreated soil values were used as control points for comparison purposes. It was found that with the addition of 6% lime, both the swell percent and swell pressure reduced to zero. Heat treatment reduced swelling potential to zero. The use of lime showed superior results when compared with the other stabilizers.     

Atmospheric deposition and migration of artificial radionuclides in Alpine soils (Val Piora, Switzerland) compared to the distribution of selected major and trace elements

Artificial radionuclides (¹³⁷Cs, ⁹⁰Sr, Pu, and ²⁴¹Am) are present in soils because of Nuclear Weapon Tests and accidents in nuclear facilities. Their distribution in soil depth varies according to soil characteristics, their own chemical properties, and their deposition history. For this project, we studied the atmospheric deposition of ¹³⁷Cs, ⁹⁰Sr, Pu, ²⁴¹Am, ²¹⁰Pb, and stable Pb. We compared the distribution of these elements in soil profiles from different soil types from an alpine Valley (Val Piora, Switzerland) with the distribution of selected major and trace elements in the same soils. Our goals were to explain the distribution of the radioisotopes as a function of soil parameters and to identify stable elements with analogous behaviors. We found that Pu and ²⁴¹Am are relatively immobile and accumulate in the topsoil. In all soils, ⁹⁰Sr is more mobile and shows some accumulations at depth into Fe-Al rich horizons. This behavior is also observed for Cu and Zn, indicating that these elements may be used as chemical analogues for the migration of ⁹⁰Sr into the soil.     

Relationship between Dehalococcoides DNA in ground water and rates of reductive dechlorination at field scale

Certain strains of Dehalococcoides bacteria can dechlorinate chlorinated ethylenes to harmless products. This study was conducted to determine if there is a valid association between the density of Dehalococcoides DNA in ground water and the observed rates of reductive dechlorination at field scale. Dehalococcoides DNA in water from monitoring wells was determined using the quantitative real time polymerase chain reaction (q-PCR) with DNA primer set specific for Dehalococcoides organisms. Dechlorination rate constants were extracted from field data using the BIOCHLOR software. Of the six conventional plumes surveyed, "generally useful" rates of dechlorination (greater than or equal to 0.3 per year) of cis-dichloroethylene (cis-DCE) and vinyl chloride (VC) along the flow path were observed at three sites where Dehalococcoides DNA was detected, and little attenuation of cis-DCE and VC occurred at two sites where Dehalococcoides DNA was not detected. At the two sites where there was no net direction of ground water flow, the relationship between the density of Dehalococcoides DNA in ground water and the trend in concentrations of chlorinated ethylenes over time in monitoring wells was not so consistent as that observed for the conventional plumes. A comparison of our study to a field study performed by Lendvay and his coworker indicated that monitoring wells did not efficiently sample the Dehalococcoides organisms in the aquifer.     

当代公共空间中看与被看的关系研究——室内篇

该文阐述了“室内公共空间”的内涵及其形式与“看与被看”的内在联系,并且通过分析“看与被看”的当代发展趋势对于作为室内公共空间的大型商业广场的发展走向加以把握,最后以正大广场为例,围绕大型商业广场如何能真正走向积极“室内公共空间”进行分析探讨。     

Partitioning of hydrophobic organic chemicals (HOC) into anionic and cationic surfactant-modified sorbents

Surfactant-modified sorbents have been proposed for the removal of organic compounds from aqueous solution. In the present study, one cationic (HDTMA) and three anionic (DOWFAX-8390, STEOL-CS330, and Aerosol-OT) surfactants were tested for their sorptive behavior onto different sorbents (alumina, zeolite, and Canadian River Alluvium). These surfactant-modified materials were then used to sorb a range of hydrophobic organic chemicals (HOCs) of varying properties (benzene, toluene, ethylbenzene, 1,2-dichlorobenzene, naphthalene, and phenanthrene), and their sorption capacity and affinity (organic-carbon-normalized sorption coefficient, K(oc)) were quantified. The HDTMA-zeolite system proved to be the most stable surfactant-modified sorbent studied because of the limited surfactant desorption. Both anionic and cationic surfactants resulted in modified sorbents with higher sorption capacity and affinity than the unmodified Canadian River Alluvium containing only natural organic matter. The affinities of the surfactant-modified sorbents (K(oc)) for most HOCs are lower than octanol/water partition coefficient (K(ow)) normalized to the organic carbon content (f(oc)) and the density of octanol (K(oc) octanol); naphthalene and phenanthrene are the exceptions to this rule.