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1.
磨刀门河口是珠江八大口门中输水输沙量最大的河口,口外拦门沙发育,其泄洪安全一直是磨刀门口门治理的头等大事。本文基于2003年洪季磨刀门河口拦门沙水域水文观测资料及近年典型洪枯季河床地形资料,分析了河口拦门沙排洪动力特征及拦门沙典型地貌单元对洪水的响应规律。研究结果表明:磨刀门拦门沙水域洪水季节水体分层明显,表现为浮力射流;外海高盐水被拦门沙阻挡,无法越过拦门沙向里侵入;拦门沙对洪水的壅水作用主要表现为低水位的壅高,灯笼山站与大横琴高潮位及低潮位水位差均和马口流量有较好的线性正相关关系。由于洪水季节磨刀门河口径流占显著优势,洪水成为拦门沙演变的主要动力,通过拦门沙典型地貌单元年际、年内演变特征分析发现,在洪水的冲决下拦门沙东、西汊得到较快发展,其中东汊的冲决效果更强烈,当洪水来临时东汊成为排洪的重要通道;洪水对交杯四沙冲刷作用较明显,特别是交杯四沙内侧南北向并岸沙堤易被洪水冲开;受洪水冲刷影响,拦门沙西汊前缘次一级分汊体系的雏形已经形成。  相似文献   

2.
珠江河口磨刀门口外拦门沙的形成,受径流、潮流、沿岸流、波浪影响,且河口的地形条件及泥沙运动也是拦门沙的重要影响因素。根据近40 a来实测地形资料,对磨刀门口外中心拦门沙、西侧拦门沙、东西两汊深槽的演变进行了分析,并对拦门沙区域的冲淤变化进行了讨论。分析结果表明珠江河口磨刀门口外拦门沙区东、西汊不断向海延伸、拓宽,大洪水对东、西汊的发育起到显著促进作用;东汊走向则有一定摆动,东汊发育具有显著的季节性特征,受波浪改造作用明显;中心拦门沙内外坡以冲刷为主,滩顶淤积加高,南北径缩短;西侧交杯沙在波浪作用下呈新月形发育,交杯四沙向陆并岸的过程中,易受到洪水冲决作用,在并岸的浅滩中冲出深槽。研究结果可为河口规划、整治提供参考。  相似文献   

3.
基于洪季磨刀门河口实测水沙观测资料和河床表层沉积物数据,通过对不同区域不同时刻悬沙浓度和粒度、沉积物粒径组成分析,运用因子分析和粒度谱等统计计算方法,重点研究近期洪季磨刀门河口及滨海水域悬沙与河床沙交换过程及其动力机制。结果表明:磨刀门河口拦门沙内河道及汊道口区域的动力以径流为主的涨落潮流流系,悬沙与河床沙交换过程较弱;拦门沙浅滩区域泥沙运动表现为"波浪掀沙,潮流输沙"特性,再悬浮泥沙平均量占实测悬沙浓度的32%;拦门沙外滨海水域悬沙组成受径流与潮汐相对强度影响显著,构成上大潮时以再悬浮泥沙为主,小潮时则以径流下泄悬沙沉积为主,而悬沙输运方向受到东南向波浪和沿岸流控制。  相似文献   

4.
珠江磨刀门河口拦门沙对排洪影响的初步研究   总被引:1,自引:1,他引:0  
建立了磨刀门河口二维水动力模型,在对现场实测资料验证良好的基础上,选取开挖中心拦门沙、东汊与西汊疏浚及导堤封堵东汊3个方案,比较了它们对排洪的影响,以探讨河口拦门沙的排洪效应问题。数值模拟表明,拦门沙开挖对磨刀门河口局部水动力特征的影响较小,拦门沙的开挖不能大幅增加洪水排泄的效率;修建导堤封堵东汊会加大挂定角至大井角的水面比降,造成更严重的壅水;东、西汊的浚深对排洪的影响也较小。拦门沙的存在看似对于泄洪有一定的阻碍作用,实际上河口及其拦门沙可以通过地貌形态的自动调整来与洪水径流作用相适应。  相似文献   

5.
丁晓英  喻丰华 《人民珠江》2011,32(4):3-5,27
利用近30年来的MSS、TM卫星影像,通过卫星遥感和G IS技术,对磨刀门的拦门沙浅滩演变进行研究,获得了磨刀门拦门沙的演变过程、发展趋势等情况,并探讨了磨刀门拦门沙变化的原因,为今后磨刀门口门浅滩的开发、治理、环境保护提供了重要信息。  相似文献   

6.
磨刀门拦门沙区域的泥沙沉积与口门治理   总被引:1,自引:0,他引:1  
珠江口磨刀门作为西江的主要出海口门,也是珠江三角洲重要的泄洪通道.应用实测资料和数学模型综合分析了磨刀门拦门沙区域的动力特点和泥沙搬运趋势,并提出了相应的治理措施.  相似文献   

7.
在对汕头港外拦门沙地区水流泥沙运动分析和汕头港外拦门沙整治措施的定床潮流模型试验的基础上,进行了在波浪和潮流共同作用下的动床模型试验。主要解决汕头港外拦门沙整治中的拦沙导流堤的走向、长度,并对各整治方案的航道淤积量做出定量预报。  相似文献   

8.
卢素兰  徐峰俊 《人民珠江》2012,33(Z1):69-72
珠江三角洲地区近年来咸潮灾害加重,磨刀门水道因其特殊的地理位置,咸情更备受关注。基于以往的研究成果,利用一、二维联解潮流、含氯度数学模型,模拟计算拦门沙发展变化对磨刀门水道咸潮入侵的影响;并在此基础上,开展了磨刀门水道防咸控咸的工程措施研究。  相似文献   

9.
河口拦门沙的存在与其上游地区的防洪、排涝、灌溉、生态环境,特别是通航等方面的关系甚为密切,与经济建设的发展关系重大。该文分析了珠江磨刀门拦门沙的演变及其主要影响因素,并对其治理提出对策,供有关部门研究参考。  相似文献   

10.
本文在分析黄河口拦门沙地区的流速、含沙量及泥沙粒径的基础上,总结出这些水动力因素防潮汐变化的规律.并结合河口地区滞流点的变化特点,初步探讨了拦门沙区的水动力特征与拦门沙演变模式之间的相互关系.  相似文献   

11.
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。  相似文献   

12.
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.  相似文献   

13.
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。  相似文献   

14.
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.  相似文献   

15.
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。  相似文献   

16.
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.  相似文献   

17.
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。  相似文献   

18.
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。  相似文献   

19.
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).  相似文献   

20.
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.  相似文献   

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