Strength Sensitivity of Marine Ariake Clays

Natural Ariake clays are characterized by high sensitivity. In this study, the mechanism and the factors controlling undrained shear strengths of both undisturbed and remolded Ariake clays are discussed. A series of unconfined compressive tests were performed on undisturbed samples of natural Ariake clays. The remolded undrained shear strength is predicted using a quantitative expression derived from extensive data of remolded undrained shear strength for a number of soils compiled from resources in the literature. The sensitivity of natural Ariake clays derived from the ratio of half of unconfined compressive strength for undisturbed samples to remolded undrained shear strength is found to be affected by both natural water content and normalized water content that is defined as the ratio of natural water content to liquid limit. The smaller the natural water content, the higher the sensitivity is at the same normalized water content. At the same natural water content, the larger the normalized water content, the higher the sensitivity is.     

粘性流体在光滑横管外壁形成液膜的机理研究

采用低雷诺数小流量模型 ,对轴向有外加恒定速度气体流动的粘性流体在水平管外形成的液膜的流速及膜厚分布进行分析和计算。计算中针对本文所研究对象的情况 ,对柱坐标系下的液膜和气膜连续方程和 Navier- Stokes方程均进行无量纲处理 ,忽略高阶小量 ,从而抓住影响问题的主要方面 ,进行计算得到了附壁膜流速表达式和膜厚的数值解。     

Suppression of Wave-Excited Vibration of Offshore Platform by Use of Tuned Liquid Dampers

This paper describes experimenlal and theoretical investigations of Tuned Liquid Damper (TLD) characteristics tor suppressing the wave-excited structural vibration. The structural model lor the experiments is scaled according to a full size offshore platform by matching their dynamic properties. Rectangular TLDs of different sizes with partially filled liquid are examined. By observing the performance and behavior of TLDs through laboratory experiments, the study investigates the influence of a number of parameters, including container size, container shape, frequency ratio, and incident wave characteristics. In an analytical study, a mathematical model that describes the nonlinear behavior of liquid in TLD and the interaction of TLD and structure is prerequisite. The validity of the model is evaluated and simulating results can reasonably match the corresponding experimental results.     

Numerical modeling of the elastoplastic damage behavior of dry and saturated concrete targets subjected to rigid projectile penetration

The objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts.     

Potential of time‐lapse photography for identifying saturation area dynamics on agricultural hillslopes

Mapping saturation areas during rainfall events is important for understanding the dynamics of overland flow. In this study, we evaluate the potential of high temporal resolution time‐lapse photography for mapping the dynamics of saturation areas (i.e., areas where water is visually ponding on the surface) on the hillslope scale during natural rainfall. We take 1 image per minute over a 100 × 15 m² depression area on an agricultural field in the Hydrological Open Air Laboratory, Austria. The images are georectified and classified by an automated procedure, using grey intensity as a threshold to identify saturation area. The optimum threshold T is obtained by comparing saturation areas from the automated analysis with the manual analysis of 149 images. T is found to be highly correlated with an image brightness characteristic defined as the greyscale image histogram mode M (Pearson correlation r = 0.91). We estimate T as T = M + C where C is a calibration parameter assumed to be constant during each event. The automated procedure estimates the total saturation area close to the manual analysis with mean normalized root mean square error of 9% and 21% if C is calibrated for each event and taken constant for all events, respectively. The spatial patterns of saturation are estimated with a geometric mean accuracy index of 94% as compared to the manual analysis of the same photos. The patterns are tested against field observations for one date as a preliminary demonstration, which yields a root mean square error of the shortest distance between the measured boundary points and the automatically classified boundary as 23 cm. The usefulness of the patterns is illustrated by exploring run‐off generation processes of an example event. Overall, the proposed classification method based on grey intensity is found to process images with highly varying brightnesses well. It is more efficient than the manual tracing for a large number of images, which allows the exploration of surface flow processes at high temporal resolution.     

鱼汁、海泥抽出液和人尿对小环藻生长的影响

在室内条件下,通过单因子实验和正交实验的方法,研究了鱼汁、海泥抽出液和人尿对小环藻(Cyclotella sp.)种群生长的影响。结果表明,350 mL的培养体积下,当鱼汁添加量为2~3 mL时,小环藻生长效果最好,相对生长率(K)较对照组升高了33.3%,平均倍增时间(G)降低了34.9%,但随着浓度升高,藻细胞开始出现死亡。海泥抽出液添加量为20 mL时,K值最大,较对照组增加35.6%,G值下降了25.15%。人尿添加量为10 mL时,K值最大,较对照组增加17.9%,G值下降了15.77%。统计分析表明,鱼汁、海泥抽出液和人尿对小环藻实验种群的生长均有极显著影响。海泥抽出液对小环藻影响大,其次是鱼汁和人尿。正交实验表明,在鱼汁、海泥抽出液和人尿的添加量分别为2.5、15.0和1.0 mL的组合实验组,小环藻的生长效果最好。     

Physically‐based modelling of double‐peak discharge responses at Slapton Wood catchment

Heavy winter rainfall produces double‐peak hydrographs at the Slapton Wood catchment, Devon, UK. The first peak is saturation‐excess overland flow in the hillslope hollows and the second (i.e. the delayed peak) is subsurface stormflow. The physically‐based spatially‐distributed model SHETRAN is used to try to improve the understanding of the processes that cause the double peaks. A three‐stage (multi‐scale) approach to calibration is used: (1) water balance validation for vertical one‐dimensional flow at arable, grassland and woodland plots; (2) two‐dimensional flow for cross‐sections cutting across the stream valley; and (3) three‐dimensional flow in the full catchment. The main data are for rainfall, stream discharge, evaporation, soil water potential and phreatic surface level. At each scale there was successful comparison with measured responses, using as far as possible parameter values from measurements. There was some calibration but all calibrated values at one scale were used at a larger scale. A large proportion of the subsurface runoff enters the stream from three dry valleys (hillslope hollows), and previous studies have suggested convergence of the water in the three large hollows as being the major mechanism for the production of the delayed peaks. The SHETRAN modelling suggests that the hillslopes that drain directly into the stream are also involved in producing the delayed discharges. The model shows how in the summer most of the catchment is hydraulically disconnected from the stream. In the autumn the catchment eventually ‘wets up’ and shallow subsurface flows are produced, with water deflected laterally along the soil‐bedrock interface producing the delayed peak in the stream hydrograph. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydro‐mechanical response of collapsible soils under different infiltration events

The behavior of a partially saturated soil during surface‐water infiltration is analyzed by means of an elasto‐plastic constitutive model formulated in terms of effective stress and extended to unsaturated conditions. The model is calibrated considering laboratory‐scale experimental results under suction‐controlled conditions. The wetting process in two collapsing soils, initially loaded at in situ stresses, is simulated by imposing two different boundary conditions: surface ponding and water flow. The stress paths resulting from the imbibition process are analyzed at different points inside the layer. Copyright © 2015 John Wiley & Sons, Ltd.     

超高效液相色谱-串联质谱法同时测定水体中37种典型抗生素

目前抗生素的环境检出受到人们的广泛关注,但能够同时测试地表水和地下水中七大类抗生素的方法仍较为缺乏。本文采用超高效液相色谱-串联三重四极杆质谱法(UPLC-MS/MS),建立了同时测定地表水和地下水中磺胺类、四环素类、大环内酯类、喹诺酮类、氯霉素类、β-内酰胺类和其他类共七大类37种抗生素的分析方法。该方法对水中抗生素有较好的富集作用及灵敏度,检出限为0.6～10.6ng/L,基质加标回收率大多为60%～130%。采用本方法测定了北京市永定河地表水、潮白河地表水及潮白河流域地下水中的抗生素。结果表明：永定河地表水中以磺胺类、喹诺酮类和大环内酯类为主,检出率分别为88.9%、55.6%和33.3%,其中氧氟沙星的最大值为111.9ng/L;潮白河地表水中磺胺类、喹诺酮类和氯霉素类抗生素的检出率均为100%,其中替米考星的浓度高达71.6ng/L;潮白河流域地下水中以磺胺类、喹诺酮类和β-内酰胺类抗生素为主,检出率分别为66.7%、55.6%和22.2%,磺胺嘧啶的最大值为69.3ng/L。污水处理厂附近样品中抗生素的检出率及浓度均明显高于其他点位。本研究建立的方法简单、快速、准确,为地表...