水平水库大坝监测系统探讨和监测效果分析

为综合评判服役期内水平水库大坝的安全状况,从坝体表面变形、坝体横缝变形、坝肩接触缝发生变形、坝基渗压、坝体孔隙水压,以及坝体温度等多方面研究并剖析了该水库枢纽项目监测系统,将获取的大坝实测信息进行了综合整理、分析和研判。结果表明:服役期内该大坝能够正常安全运行;在监测位置的各个方向对于测点的高程、渗流量、坝体位移、横缝、垂直位移,以及渗压等各个方面得到的监测数据是精细全面的;可通过实测数据协助找出大坝变形规律,及时发现异常现象或工程隐患;可为指导大坝运行安全管理工作、充分发挥工程效益提供一定参考。

Experimental Analysis of Sediment Deposition Due to the Effect of an Upstream Reservoir Backwater

The phenomenon of aggradation due to sediment accumulation upstream reservoirs had been studied in this research. For this purpose, groups of experiments were conducted in a laboratory with 25 m long, 0.80 m wide and 0.70 m deep channel. A block was built at the end of the channel to work as a dam to impound water. The channel was supplied with drainage pipes on both sides to release water out in a manner similar to what happens in reservoirs. The bed of the channel was filled with sand of 0.80 mm median sieve diameter and 0.72 geometric standard deviation. The slope was 0.0093 for all experiments. Two sizes of sand were used representing the sediment. The median diameter and geometric standard deviation of the first were 0.365 mm and 0.46 mm, respectively. The second sample had 0.65 mm median diameter and 0.67 standard deviation. A total of 70 experiments were conducted in two groups to examine effects of sediment transport rate, particle size of sediment and flow velocity on aggradation characteristics. The results showed that there was a strong linear direct relationship between aggradation elements （length and depth） with the rate of sediment transport. Groups of dimensionless parameters affecting the aggradation characteristics were used to develop empirical equations to predict the length, maximum depth of aggradation and predict transient bed profile. The results of empirical approach were compared with the measurement data and previous numerical method. The results indicated that the percentage error was 19% to 31% for length of aggradation and -21% to 26% for maximum depth of aggradation. The results also showed that the sediment materials were deposited closer to the body of the dam when the released water from the dam is higher than the inflow.

Research on Seismicity and Source Parameters of Small Earthquakes in the Zipingpu Reservoir before the Wenchuan M_S 8. 0 Earthquake

Based on the digital seismic waveform data observed from regional and reservoir seismic networks,the seismicity and source parameters in the Zipingpu reservoir area from January 1,2000 to May 11,2008 before the Wenchuan MS8.0 earthquake are studied. The analysis shows a continuous activity of small earthquakes before the Wenchuan MS8. 0 earthquake. The level of seismic activity was from ML2.0 to ML3.0 in recent years. The impoundment of Zipingpu reservoir started in September 2005 and the obvious increment of seismic activities occurred in February 2008,but according to the analysis of the longer time series,the frequency and intensity of seismic activities do not exceed its range,which means it is still a fluctuation of regional seismic activities or tectonic activity. At the same time,we also studied the spatio-temporal distribution and the change of apparent stress difference in the source region before the great earthquake,and the results show that the apparent stress values of small earthquakes are generally higher than fitted values of apparent stress in the reservoir area in the nearly three months before the Wenchuan MS8.0 earthquake. It can be seen from the spatial distribution of apparent stress difference,that the epicenter of the earthquake is located at a low stress distribution area,and the relatively high apparent stress difference is at the east of the epicenter. Apparent stress increment occurred in local areas.

Inundation Calculation of the Coastal Narrow Plain Strip Impacted by Upstream Reservoir Flood Discharge in Rainy and Extreme Flood Conditions

In the context of current climate change, an abnormality of flooding is a common form of disaster in Vietnam. Hanh Stream reservoir has occurred great flood in 1986, 2010. In the future, the risk of flooding is possible to happen again. In view of management of the risk of natural disasters： large flooding situation downstream is one of the most dangerous risks for the reservoir. Due to downstream of Hanh Stream reservoir is a narrow coastal plains, quick infrastructure development, especially interwoven road and railway systems, so that flood drainage ability will be affected greatly. The consciousness of risks that may be occurred in the future in order to propose preventive measures and proactive response to minimize damages always is the requirement for all projects. The hydrodynamic calculation, flooding maps, emergency plan to prevent flooding downstream of Hanh Stream reservoir is also needed. The article is raised the issue of requirements to calculate coastal narrow delta strip flooding in the Central of Vietnam when impacted by the upstream reservoir of flood discharge in terms of extreme heavy rain and flooding and presented computational methods of Mike software package for case flooded plain of Cam Ranh Bay in downstream reservoirs of Hanh Stream, Khanh Hoa Province, Vietnam.

Assessment of Salinity Intrusion in the Red River under the Effect of Climate Change

This paper focuses on analysis of salinity distribution along Red River and its main branches to determine and limit effects of salinity intrusion under variable scenarios for outlet discharge from upstream reservoirs and the tidal magnitude under global climate change effects. The effect of outlet discharge from upstream reservoirs, which generates flow in droughty months, is considered as upstream input condition for salinity intrusion. The sea level rising phenomenon is represented by scenarios according to prediction of the Intergovernmental Panel on Climate Change （IPCC）. The lateral flow and the rainfall in dry season are neglected in the process of simulation. MIKE 11, ID river model software by DHI （Danish Hydraulic Institute）, is used to simulate the processes of salt water intrusion from the river mouths to the upstream of the river in consideration the effect of the Sea Level Rise phenomenon and the operation of existing reservoirs and those under construction. The results indicate that salinity intrusion length from river mouth depends on the estuary characteristics, discharges from upper reservoirs and tidal phases （low and high tides）. With the safe salinity concentration for agriculture and livestock is 4 psu, the study shows that the length of intruded salt in Red River is about 40km from the river mouth, in otherwise, the effect of salinity intrusion in Thai Binh river is negligible. The Sea Level Rise phenomenon has inconsiderable affects on salinity intrusion processes in Red River System. The influence of outlet discharges from upstream reservoirs has also negligible affects on prevent salinity intrusion from the sea. According to the results of the study, reasonable water resources utilization and appropriate reservoir operation approaches in the drought will be studied to protect the crop and aquaculture from salinity intrusion.

Model of water-sediment regulation in Yellow River and its effect

Water-sediment regulation of the Yellow River is to regulate and control the flow and sediment transport relationship of the lower reaches through reservoirs on the main streams and tributaries to create balance between water and sediment so that sediment transport capacity of the downstream channels can be maximized,shrinking of channels be contained,and medium flood channel be restored and maintained.Many years' research by the Yellow River Conservancy Commission(YRCC) reveals the water and sediment transport relationship that will prevent sedimentation at the downstream river channels.Based on this relationship and coming sediment and water conditions in the Yellow River basin,the YRCC,with maximized use of reservoirs on the main streams and tributaries,has developed three models of water-sediment regulation:single Xiaolangdi Reservoir-dominated regulation,space scale water-sediment match,and mainstream reservoirs joint operation.Ten water-sediment regulations based on these three models have resulted in an average drop of 1.5 m in the main channel of the downstream 800 km river and an increase of carrying capacity from 1800 to 4000 m3/s.Besides,the wetland ecosystems of estuarine delta has also been improved and restored significantly.