南水北调丹江口大坝加高工程施工技术

丹江口大坝加高工程,是南水北调中线工程的关键性、控制性、标志性的龙头工程。该工程规模大、难点多,其采用的新老混凝土结合技术、大体积混凝土及薄层混凝土拆除技术、水下金结埋件检测与修复技术、高水头下的帷幕灌浆技术等施工技术措施,可为老化和病害水工混凝土建筑物的修复和改造提供可供借鉴的经验。     

1923 Gleno Dam Break: Case Study and Numerical Modeling

On the morning of December 1, 1923, the Gleno Dam (located in the Central Italian Alps) suddenly collapsed a few days after the first complete reservoir filling. Nearly 4.5×106??m3 of water was released. The consequent inundation caused significant destruction along the downstream valley and a death toll of at least 356 lives. This failure is the only historical case of dam break caused by structural deficiencies that has occurred in Italy. As a result, it has deeply influenced the evolution of Italian regulations regarding dam design and hydraulic risk evaluation. However, in spite of its relevance, this event has never been characterized from a hydraulic standpoint. This paper reports the main information obtained from the analysis of a vast amount of historical documents regarding the Gleno Dam break to set up a case study useful for validating dam-break models in mountain settings. Moreover, it presents the main results of one-dimensional (1D) modeling of the dam break wave propagation accomplished with a first-order finite volume numerical scheme recently proposed in the literature for field applications. The overall effectiveness and reliability of the model are evaluated for this case characterized by very irregular topography. Finally, the practical relevance of several choices that the numerical reconstruction of this kind of event demands is tested.     

Earthquake Safety Evaluation of Gravity Dams Considering Aftershocks and Reduced Drainage Efficiency

This paper develops a methodology to perform seismic response analyses of concrete gravity dams considering aftershocks, and reduced drainage efficiency due to disruption of the drainage system. A database of earthquake records has been assembled to characterize main shocks and aftershocks. A drain finite difference hydraulic model considering laminar or turbulent two-dimensional flow in connecting cracks, geometrical distortions due to joint dilatancy while sliding, and misaligned drain segments is developed and validated. Coupled-hydromechanical analyses on the seismic response of a drained 90?m gravity dam are used to show the importance of cumulative displacements on the increase in uplift pressures, drain flow, and reduced sliding safety factors. Aftershock response is especially sensitive to the drainage system dimensions and model parameters, such as the foundation stiffness, and the number of potentially sliding joints. The proposed methodology forms the basis to develop displacement based performance criteria in stability evaluation of existing dams reevaluated for much higher ground motions intensities that they have been designed for many years ago.     

万家寨水利枢纽利用岩的开挖卸荷及对策

万家寨水利枢纽位于深切U型峡谷区，基坑开挖过程中，坝基及厂房利用岩的卸荷回弹与其地质背景和裸露时间密切相关，施工时根据其特征，采取了相应对策，并取得良好效果。     

隔河岩坝GPS自动化监测系统总控软件设计

介绍隔河岩大坝外部观测变形 GPS自动化安全监测系统总控管理软件的总体设计、结构和功能。     

清江水布垭工程施工通信系统

对清江水布垭工程施工通信方案设计的原则和通信系统的组成作了较为详细的介绍。     

湖南镇大坝安全监测系统回顾及改进

本文通过对湖南镇大坝安全监测系统回顾及其精度剖析，指出监测系统设计和监测设备中存在的问题，并有针对性地结合该大坝的特点，阐述了精度相对较低的项目如何对其观测方法、设备进行改进或改造，以提高观测精度。本文对其他混凝土大坝安全监测系统的设计和改造具有一定的参考价值。     

Explicit Schemes for Dam-Break Simulations

Dam-break problems involve the formation of shocks and rarefaction fans. The performance of 20 explicit numerical schemes used to solve the shallow water wave equations for simulating the dam-break problem is examined. Results from these schemes have been compared with analytical solutions to the dam-break problem with finite water depth and dry bed downstream of the dam. Most of the numerical schemes produce reasonable results for subcritical flows. Their performance for problems where there is a transition between subcritical and supercritical flows is mixed. Although many numerical schemes satisfy the Rankine-Hugoniot condition, some produce solutions which do not satisfy the entropy condition, producing nonphysical solutions. This was the case for the majority of first-order schemes examined. Numerical schemes which consider critical flow in the solution are guaranteed to produce entropy satisfying solutions. Second-order schemes avoid the generation of expansive shocks; however, some form of flux or slope limiter must be used to eliminate oscillations that are associated with these schemes. These limiters increase the complexity and the computational effort required, but they are generally more accurate than their first-order counterparts. The limiters employed by these second-order schemes will produce monotone or total variation diminishing solutions for scalar equations. Some limiters do not exhibit these properties when they are applied to the nonlinear shallow water wave equations. This comparative study shows that there are a variety of shock-capturing numerical schemes that are efficient, accurate, robust, and are suitable for solving the shallow water wave equations when discontinuities are encountered in the problem.     

山西省汾河二库枢纽工程建设简介

本文较系统地介绍汾河二库枢纽工程建设的基本情况，并就工程采用的新技术、新工艺、新设备、新材料以及工程建设的主要经济和教训作了简要分析和介绍。     

大坝加高试验温度应力仿真计算与原型监测对比分析

根据现场施工条件,对丹江口大坝2次加高试验进行了温度应力仿真计算,并对现场原型监测资料进行了分析,其计算结果与原型监测结果基本一致.通过对比分析后认为:施工期的温度应力不是控制因素,最大拉应力出现在试验块温度准稳定期,气温年变化是影响新老混凝土结合面应力状态的主要因素;新老混凝土结合面开度随年气温呈周期变化,并且任一时刻,结合面都是部分脱开部分接触.