Effects of periodic saturation on K0 for a sandstone-mudstone particle mixture

Abstract

Sandstone-mudstone particle mixture (SMPM) is one of the main materials, which has been widely used for filling in and around reservoirs for water conservation projects. During the periodic rising and falling of the water level, the fill material for the embankments, dam, and other waterfront features will also undergo drainage-saturation cycles. The deformation and coefficient of lateral pressure at rest K₀ may be affected by periodic saturation. In this study, a device is modified for testing the K₀ for gravel-soil under periodic saturation. In order to investigate the effects of periodic saturation on K₀, a series of experiments were performed for SMPM under different vertical stress and saturation cycling. K₀^N values of SMPM containing 20% mudstone particles under periodic saturation were obtained. The results shows that the K₀^N initially increased, but eventually reached a stable value with the increasing number of periodic saturation cycles. The magnitude of the coefficient increment was also found to be related to the stress condition. K₀^N is a logarithmic function of the saturation cycling time. By calculating K₀^N with the proposed empirical formula, the deformation and stress distribution of the SMPM filler in waterfront engineering works can be calculated with greater precision.     

非均质裂隙渗流场研究中的水化学方法

采用水化学分析、氢氧同位素示踪和氯离子质量平衡法相结合的手段 ,对非洲博茨瓦纳的帕拉匹水源地的地下水资源进行分析。结果表明该水源地有 2层水化学类型不同的含水层 ,即茨瓦蓬和鲁村纳 2个含水层 ,而且地下水主要在裂隙网络中运动。氢氧同位素示踪说明茨瓦蓬含水层的地下水主要来源于未受强烈蒸发的大气降水补给 ,用氯离子质量平衡法计算大气降水补给每年约 17mm。     

Finite Element Analysis of soft Foundation Strengthening by Vacuum Loading from Lower Position

Strengthening soft foundation by vacuum loading from lower position is a new method of ac-celerating the consolidation of dredger fill.This paper presents the mechanism of soft foundation strength-ening by vacuum loading from lower position and evaluates the effectiveness of this method under variousboundary conditions by means of finite element method(FEM)on the basis of Biot's consolidationtheory.     

褐藻中岩藻聚糖和岩藻多糖的结构与功能的研究

褐藻中两种硫酸多糖——岩藻多糖和岩藻聚糖含量丰富。它们在结构上相似而不相同 ,都具有抗凝血、抗肿瘤、抗病毒、抑制补体激活、抑制精卵结合、吸收重金属等功能。着重介绍了岩藻聚糖和岩藻多糖在抗凝血、抗肿瘤、抑制补体激活方面的研究进展。     

白沙河平原地下水系统数值模拟

通过对白沙河平原区地下水形成条件及开采现状的分析，建立了该区不连续双层含水层的水文地质概念模型及数学模型，并利用１９８８年资料进行了模型校正。计算结果表明，由于超采严重，导致海水入侵在４～６月最重。计算所采用的ＭＯＤＦＬＯＷ软件为ＵＮＤＰ专家ＭｏｓｈｅＢｏｔｂｏｌ所推荐，为适应中国的季节性河道特点，对该软件进行了修正。     

VORTEX SHEDDING FROM A CIRCULAR CYLINDER IN OSCILLATORY FAR FLOW

By using a process of successive approximations, the Boundary-Layer equations are solved to determine the separation points of a circular cylinder in oscillatory flow under the conditions of vortex existing. Combining with the discrete vortex model, the separation points and the fluid force coefficients are calculated at different KC numbers and Re numbers, A modified Morison equation is used in calculating the inline forces, and good agreements are obtained between the calculated results and those from other's experiments.     

东海赤潮高发区水体光谱吸收特性分析

赤潮是海洋中一种复杂的生态异常现象。赤潮的爆发、不仅严重影响近海景观,破坏水产养殖,危害人体健康,还对海洋生态平衡造成破坏,给人类造成惨重经济损失。近年来,在我国的赤潮观测记录中,赤潮的年发生次数逐渐增加,且面积不断增大,因此,对赤潮的发生发展机理及预测治理研究是科学家刻不容缓的研究课题。 赤潮发生时,赤潮生物大量聚集,使水体颜色发生明显变化,进而赤潮水体的光谱特征发生变化,且存在差异,使利用水色遥感监测赤潮成为可能,还可以用来区分赤潮种类的不同。水体光谱的变化特性(包括吸收与散射特性)是水色赤潮遥感监测的基础,是水色遥感生物光学算法开发的重要组成部分。因此对赤潮水体进行光谱吸收特性的分析研究对于发展研究海区的水色遥感生物光学算法及赤潮遥感监测方法都有重要意义。     

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从CPT原子钟到光钟

简要介绍了新型CPT（Coherent population trapping，相干布局囚禁）原子频标及光频标的基本原理和研究进展。被动型CPT铷原子钟物理部分的目前体积可控制在100cm^3以内，功耗1W左右，其稳定度为4×10^-11τ^-1/2（τ为测量取样的时间间隔）。CPT原理的铯原子频标的物理部分体积减小到1cm^3，功率减小到30mW，稳定度为6×10^-10τ^-1/2，成为当今体积最小、功耗最低的原子钟。随着飞秒激光梳状发生器技术的发展，已将传统的谐波光频链的体积从几间实验室缩小到1．2×1．0m^2的光学平台上，它与光频测量技术的结合，使微波频标与光频标联系起来，建立了光钟，它的稳定性可以从现在的10^-16的水平提高到10^-18乃至10^-22水平，成为当前最精密的时间计量仪器。     

Environmental flow assessment in a lake-marsh system with reverse seasonal hydrological patterns

Environmental flow (e-flow) assessment is essential for the ecological protection and restoration of lake-marsh systems. Previous studies on e-flow assessment for lake-marsh systems focused on lake-marsh systems with natural seasonal hydrological patterns (i.e., low water level in winter and high water level in summer). However, they have not considered lake-marsh systems with reverse seasonal hydrological patterns (i.e., high water level in winter and low water level in summer). The reverse seasonal hydrological patterns impose seriously negative impacts on waterbirds, because the hydrological patterns could lead to limited plant germination in spring and massive plant death in summer, leaving few plants available as food for waterbirds in winter, and could consequently reduce the sheltering and forageable areas for waterbirds. This study took Hongze Lake Wetland National Nature Reserve in China as the study area. Based on the habitat requirements of waterbirds, the sheltering and forageable areas for waterbirds under different water-depth and aquatic plant distribution scenarios were calculated. By exploring the impacts of reverse seasonal hydrological processes on waterbird habitats, we determined the necessary e-flows for lake-marsh systems with reverse seasonal hydrological patterns to meet the needs of waterbird habitat. The results showed that the water level of Hongze Lake should be controlled to 13.0–13.1 m in March, 12.5–12.6 m in July, and 12.9–13.0 m in October, which can meet the needs of waterbirds for both shelter and foraging.