基于地统计学的伊犁-巩乃斯河谷渗透系数空间变异性研究

渗透系数的空间变异性研究是水文地质领域研究的热点问题之一,然而伊犁-巩乃斯河谷区渗透系数的变化规律尚不清楚,一定程度上制约了该地区地下水形成演化和资源评价的研究进程。运用地统计学理论和方法,进行了伊犁-巩乃斯河谷含水层渗透系数的空间变异性分析。结果表明:伊犁河谷西部平原区的潜水含水层的渗透系数服从Box-Cox变换的正态分布,承压水的渗透系数服从对数正态分布,变差函数均符合高斯模型;采用Kriging最优值理论进行了插值空间分析,潜水渗透系数插值结果表现为霍城县西部渗透系数偏高,伊宁县北部为渗透系数最小的区域,巩乃斯河谷地渗透系数较稳定;承压含水层渗透系数除察县附近外,总体呈现自东向西逐渐变小的特点;结合该区地形地貌和水文地质条件,划分了潜水和承压水的渗透系数分区,为地下水资源评价提供了关键水文地质参数。     

川中红层灌区地下水硝酸盐污染特征及影响因素

为探明川中红层灌区地下水硝酸盐污染特征及影响因素,选取简阳市内典型农业种植区,利用变异函数模型与Arc GIS地统计模块,分析了区内地下水硝酸盐污染空间变异特征,并通过因子分析识别其主要影响因素。研究表明:球状模型为本次插值分析的最优理论模型,块金值为0.067,基台值为0.736,块金效应0.091,研究区地下水硝酸盐分布的空间自相关性较强;区内大部分地区硝酸盐污染严重,约有91.8%的面积遭受硝酸盐污染,农业生产活动与包气带岩性特征加剧了地下水硝酸盐含量的升高;研究区中部金鸡河两侧地下水水力坡度较大,径流强烈,污染物不易富集,河流两侧硝酸盐含量明显较低;因子分析表明,地下水硝酸盐含量主要受地层岩性、地形地貌、p H值和人类活动等因素影响。     

基于球状模型参数的地下水水位空间变异特性及其演化规律分析

根据宁夏青铜峡灌区169眼观测井的20世纪90年代逐月地下水埋深观测资料,应用地质统计学方法,结合GIS技术,研究了灌区地下水水位的空间变异特性在年际和年内的演变规律.地下水埋深样本呈对数正态分布,利用球状模型拟合变异函数,通过研究球状模型参数中短轴变程与长轴变程的比值,发现样本存在不同程度的几何各向异性,但逐年趋于各向同性;各向异性程度的年内变化与灌溉过程有关,地下水埋深越浅,其各向异性程度越强.球状模型参数中的块金值与基台值的比值反映地下水埋深样本具有中等的空间相关性,其大小与灌溉活动关系密切,地下水埋深越浅,空间相关性越大,反之亦然.克里金插值结果表明,灌区地下水埋深总体上逐年增加,在年内变化上,顺着地下水自南向北的流向,地下水位随灌溉呈周期性涨落变化.     

托克托县潜水氮化物浓度空间分布及其成因

在区域自然地理和水文地质条件分析的基础上,对呼和浩特市托克托县潜水的pH值、氧化还原电位(Eh)、化学需氧量(CODMn)、氨氮、亚硝态氮、硝态氮6项指标的相关性进行了分析,结果表明:地下水中氨氮浓度与Eh值呈负相关关系,与CODMn浓度呈正相关关系。结合区域地下水流动系统特征,揭示了潜水中NH3-N,NO2-N,NO3-N的浓度空间分布特征及变化的原因:地下水的补、径、排特征控制着区域潜水的氧化还原环境,由补给区到排泄区氧化还原电位呈逐渐降低趋势;受地下水所处氧化还原环境影响,东南部地下水补给区潜水中硝态氮浓度普遍较高,氨氮浓度普遍较低,向西至大黑河沿岸硝态氮浓度逐渐降低,而氨氮浓度相对升高;牧业养殖废水和废物的无序排放是局部区域地下水中氮化物含量异常升高的主要原因。     

六岔河流域多水塘-沟渠系统中土壤养分空间变异特征研究

借助地理信息系统,利用地统计学中的半变量变异函数研究了巢湖北岸六岔河流域多水塘-沟渠系统中的土壤养分空间变异特征。研究结果表明：土壤中有机物 （OM） 、总氮 （TN）、总磷 （TP）、氨态氮 （NH4-N）、硝态氮NO3-N） 的空间变异函数理论模型均符合球状模型,总磷、氨态氮、有机物空间异质性中的结构性变异大于随机变异;总氮、硝态氮的结构性变异小于随机变异。有机物、总氮、总磷、氨态氮、硝态氮等空间自相关范围具有明显的差异性,变化范围为123.9~517.36m,呈现出氨态氮>硝态氮>总氮>有机物>总磷,变化范围相差4倍左右,上述差异主要与养分特性、土地利用以及多水塘-沟渠系统景观等因素关系密切。     

基于随机有限元法的圆形基础沉降最不利波动尺度分析

波动尺度(SOF)是表征土体空间变异性的重要参数,不同的波动尺度可以模拟土体参数的空间变异程度。基于随机有限元(RFEM)和蒙特卡罗模拟,假设弹性模量服从对数正态分布对土体实现非均质性建模,研究不同波动尺度下圆形基础的沉降变形规律。研究结果表明：中心沉降值符合对数正态分布,差异沉降值符合正态分布;随着波动尺度的增加,中心沉降和差异沉降均值基本不变,中心沉降标准偏差先增大最后趋于平缓,差异沉降标准偏差先增大后减少,在其峰值处平均绝对差异沉降达到最大,此时的波动尺度为最不利波动尺度,在勘察数据相对有限的情况下可以对基础沉降概率进行保守估计。     

土体强度的空间分布形式对单桩承载力的影响

土体参数可能服从不同类型的分布,而在考虑土性空间变异性的桩基础承载特性的研究中一般将随机变量假定为服从对数正态分布。以土体的不排水强度为随机变量,考虑不同的变异系数和相关距离,采用随机有限元法分别模拟了竖向和水平向荷载作用下单桩基础的承载性状,对比分析了土体不排水强度分别服从对数正态分布、Beta分布和Gamma分布条件下单桩的承载力均值和标准差。结果表明,土体强度的分布形式对单桩竖向承载力的均值没有影响,而服从对数正态分布的随机场中单桩水平承载力均值最大,服从Beta分布的随机场中单桩水平承载力均值最小;竖向荷载和水平荷载作用下Beta分布得到的承载力标准差均为最大。当地基土强度空间分布形式未知时,建议采用Beta分布确定单桩承载力。     

对数正态相关法

对数正态分布应用于某些水文变量频率分析中,較为簡单合理。因此本文概要地論述了对数正态相关法的特性,同时还討論了某些非綫性相关系数的性貭。一、回歸式 設随机变量X_1,X_2服从对数正态分布,随机变量X_3服从正态分布,X_1,X_2,X_3的数学期望为m_1,m_2,m_3;均方差为σ_1,σ_2,σ_3;离差系数为Cv_1,Cv_2,Cv_8。并设随机变量lnX_1,lnX_2的数学期望为α_1,     

结构可靠度方法在砌石重力坝设计中的应用(2)

前言 前文主要针对重力坝在荷载基本组合下的验算而论,按照设计规范规定,还要进行荷载特殊组合下的验算。荷载基本组合的荷载效应S和结构抗力R一般服从正态分布,即可直接用可靠度计算公式算出可靠指标β和结构的失效概率P_f,这是比较简便的。然而,有些荷载不宜当作正态分布的随机变景。例如坝体地震惯性力、地震动水压力、校核洪水流量的荷载、最大风压等一般认为服从极值l型分布,结构强度则仍按对数正态分布考虑,实验资料绘成的曲线     

东北地区降水量空间分布研究

以分辨率为1km降水量开源数为基础,运用GIS和地统计学空间分析方法,解析了东北地区降水量空间分布模式。结果表明,东北44地市的多年平均降水量介于248.2mm(锡林浩特)-1048.5mm(丹东)之间,区域内部降水量空间差异大。降水栅格像素值介于144-1304mm之间,空间均值为490.5mm,变异系数为31.21%。该地降水量空间分布符合高斯模型,其块金结构为0.10%,属于强烈空间自相关,在东西方向上呈指数函数自西向东增加,在南北方向呈U型分布。全区降水量丰度分属4种自然带,分布面积依次为干旱区(2.92%)湿润区(3.87%)半干旱区(23.345%)半湿润区(69.87%)。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.