复杂地基重力坝深层抗滑稳定非线性有限元分析

重力坝的深层抗滑稳定是保证大坝安全的一个重要条件。针对《混凝土重力坝设计规范》(DL5 10 8—1999)中关于复杂地基重力坝的稳定性需进行有限元分析的新规定,笔者结合某重力坝稳定问题实例,用非线性有限元方法进行了分析计算,并与刚体极限平衡法及结构可靠度分析方法的成果进行了对比。对有限元法的适用性,岩体侧面阻滑力的影响及抗滑稳定安全度的表达方法等问题进行了探讨     

基于最大Lyapunov指数分析的尾矿坝浸润线控制混沌方法

为了改善尾矿坝浸润线状况，提出了一种控制混沌方法。该方法对时间序列叠加一个周期振动，通过最大Lyapunov指数分析，来判别叠加前后系统混沌特性的变化，进而实现控制混沌。应用这种方法，分析了银山铅锌矿尾矿坝浸润线实测数据。结果表明，叠加周期振动可以降低最大Lyapunov指数。最大Lyapunov指数的降低程度与振动周期成负相关，与振幅成正相关。采用控制混沌方法，即对尾矿排放、库水位调节、排渗、不同尾矿库的使用等措施进行周期性控制，可以提高尾矿坝安全度，实现尾矿坝科学管理。中还以防洪高度为例，具体分析了尾矿坝工程中的控制混沌，表明该方法在应用上是可行的。     

基于无人机摄影测量的尾矿坝边坡表面变形监测

为弥补传统基于GPS/GNSS的单点监测方式无法反映尾矿坝整体变形的局限性,提出1种结合坝坡现有位移监测系统的无人机尾矿坝边坡表面变形监测方法.利用单镜头轻小型多旋翼无人机和计算机视觉技术对尾矿坝的空间三维地理信息进行数据采集与重建;基于设置在坝坡表面的位移人工监测点(水泥桩)对多期尾矿坝点云数据进行配准;通过对不同时...     

Evaluation of a System to Automatically Sample Zooplankton From the Discharge of Dams1

ABSTRACT: Automatic plankton samplers installed at two dams on the Connecticut River Continuously monitored crustacean zooplankton from October 1977 through 1979 and allowed a significant reduction in man-hours involved in an extensive sampling program. Automatic samplers efficiently sampled most species and size classes of crustacean zooplankton in a similar, but not consistently identical manner as a commonly used towed-net plankton sampler. The smallest sized zooplankton were captured more efficiently than the largest. Mesh selection and sampler avoidance exerted different influences on automatic samplers and towed nets. Future use of the samplers and direct comparison of results to results obtained by other methods was supported.     

The International Environmental Expert Panel for Major Dam/Reservoir Projects: The Yellow River, China

The experience of the International Expert Panel on Environment for the Xiaolangdi dam/reservoir project in China (XEP) showed that the Panel meetings resulted in a marked improvement in project environmental performance by all parties participating in project implementation, with no parties exempt from the Panel's evaluations. Unfortunately the Loan Agreement authorizes use of the Panel only through the project stages of final design and construction, hence the 12th Panel meeting, which matched project construction completion, ended this series. The Panel has recommended that some meetings of the Panel be held during the project's operations stage in order to maintain continuing attention to environmental needs. The XEP experience showed that the XEP, in addition to monitoring project environmental performance, was very valuable for (i) training of Chinese staff involved in project implementation, and (ii) serving in the role as expert consultant for guiding the work of the Chinese participants. The XEP experience also showed the need for making a clear separation between evaluation, the overall resettlement program per se, and the environmental effects of the program. The Panel recommended that the Ministry of Water Resources and World Bank cooperate in sponsoring a book on The Environmental History of the Xiaolangdi Project, including both dam construction as well as resettlement problems, which would serve as a very valuable reference for guiding environmental planning for future dam projects in China (Ludwig, H.F. 1994–2000).     

DAM‐INDUCED MODIFICATIONS TO UPPER ALLEGHENY RIVER STREAMFLOW PATTERNS AND THEIR BIODIVERSITY IMPLICATIONS1

ABSTRACT: This study evaluates the streamflow characteristics of the upper Allegheny River during the periods preceding (1936 to 1965) and following (1966 to 1997) completion of the Kinzua Dam in northwestern Pennsylvania. Inter‐period trends in seasonal patterns of discharge and peak flow at three downstream sites are compared to those at two upstream sites to determine the influence of this large dam on surface water hydrology. Climatic records indicate that significant changes in annual total and seasonal precipitation occurred over the twentieth century. Increased runoff during the late summer through early winter led to increased discharge both upstream and downstream during these months, while slightly less early‐year rainfall produced minor reductions in spring flood peaks since 1966. The Kinzua Dam significantly enhanced these trends downstream, creating large reductions in peak flow, while greatly augmenting low flow during the growing season. This reduction in streamflow variability, coupled with other dam‐induced changes, has important biodiversity implications. The downstream riparian zone contains numerous threatened/endangered species, many of which are sensitive to the type of habitat modifications produced by the dam. Flood dynamics under the current post‐dam conditions are likely to compound the difficulties of maintaining their long‐term viability.     

A LAW AND ECONOMICS APPROACH TO RESOLVING RESERVOIR SEDIMENT MANAGEMENT CONFLICTS1

The loss of the world's reservoir capacity to sedimentation can be mitigated by altering dam operations to release sediment downstream. However, legal uncertainty regarding whether dam owners are liable for damages to surrounding landowners due to altered operations provides a significant disincentive for sustainable sediment management. Past work recommends that courts apply a “rule of reasonableness” in assessing liability: dam owners should be held liable for damages only if they act unreasonably in altering operations, and surrounding landowners should take reasonable measures to mitigate foreseeable damage. Based on past cases, judicial determinations of reasonable reservoir management and reasonable precautionary measures by landowners are generally highly speculative, controversial, and based on limited information. Courts can ease the future burden of making these difficult determinations with rulings that create economic incentives for parties to act reasonably. For example, courts might entitle landowners to be free from sediment related damages, and protect the entitlement with a liability rule. This gives dam owners an economic incentive to release sediment only if the benefits of doing so outweigh court ordered damages to landowners. Past judicial decisions are largely consistent with this legal regime.     

面板砂砾石坝异常状态渗流计算及稳定分析

运用非饱和土渗流与强度理论,把渗流计算的水力条件用于边坡稳定分析之中,对沟后面板砂砾石坝进行了渗流场分析与边坡稳定计算,得到一些新的结论,可补充以前相关的研究结果。计算结果表明:坝料填筑分离造成的渗透各向异性尽管使浸润线升高,但是由于水平排水能力的提高反而使坝体的孔隙水压力总体上降低,从而也就提高了边坡的抗滑稳定安全性;当顶部面板与坝体脱开并导致异常状态渗流时,坝体顶部有一饱和区并且渗流出逸点很高,但坝体中部仍未饱和,异常状态渗流增加的孔隙水压力有限,对坝坡的抗滑稳定影响也很小,因此,按照最高浸润线的位置确定孔隙水压力进行抗滑稳定计算会导致错误的结果;坝顶异常状态渗流增加的孔隙水压力并不会导致下游坝坡滑动失稳,而坝体顶部渗透破坏会导致局部坍塌,最终发生溃坝事故。     

思林水电站碾压混凝土坝的渗流分析

碾压混凝土重力坝的坝身及地基渗径是筑坝中的关键技术问题。文章是以思林水电站碾压混凝土重力坝为研究对象,以大型通用有限元软件ANSYS为平台,其核心是对坝基有相互作用的整体坝段数值模型的建立以及利用程序对典型坝段的渗流场进行二维有限元渗流计算分析,研究碾压混凝土坝渗透特性及其影响因素,并证明了这种分析方法的可行性。     

活性滤坝对城市内河中氮磷的削减效果

城市内河氮磷严重超标是当前水污染治理的重要难题。针对内河具有旱季水位低、水流速度慢、自净能力差等特点,提出采用活性滤坝削减氮磷,以铝基锁磷剂和沸石为活性滤坝基质滤料,实验室静态和动态实验研究了活性滤坝削减氮磷效果,讨论了基质滤料组合方式对削减氮磷效果影响,同时采用曲线方程拟合分析方法预测了活性滤坝吸附氮磷有效使用时间。静态实验结果表明,在控制进水氨氮15 mg·L⁻¹和正磷酸盐5 mg·L⁻¹情况下,实验历时20 d,活性滤坝对氨氮和正磷酸盐削减率分别为98.02%和100%,混合滤坝组削减氮磷效果最佳;动态实验结果表明,控制水中氨氮和正磷酸盐为8~15 mg·L⁻¹和2.5~5 mg·L⁻¹,流速为8.33 cm·h ⁻¹,实验历时37 d,完成氮和磷循环分别为11次和16次,拟合曲线方程预测混合滤坝组削减氨氮和正磷酸盐的有效使用时间分别为282 d和479 d。以上研究结果可为城市内河道修复提供技术参考。