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Coquitlam 大坝建于 1913 年,坝高 30 m,为吹填土石坝。大坝位于加拿大 BC 省高地震危险带。风险人口数以万计。根据现行标准,大坝的抗震能力不符合要求,坝体冲填土和某些部位地基土松散,容易液化。在中度至重度的地震情况下,大坝将会遭受严重的损坏,并有可能溃决。提高大坝的抗震能力很有必要。选择最高设计地震为里氏7.5 级地震,地震地面水平峰值加速度 0.66g。在设计中,还需要对以下一些提高抗震能力的设计方案进行评估,包括结构修复、大坝重建、限制水库运行及退役。在综合考虑技术、社会、环境和经济因素的基础上,选择了兴建一座新的下游堤坝以提高其抗震能力,减少 Coquitlam 大坝的地震风险。新建坝包括一座土质心墙堆石堤坝和一个位于左坝肩的混凝土过渡带。新建堤坝大部分是建在具有承载力的淤泥土上,而混凝土过渡带则完全建在基岩上。由于现场和施工条件的限制,座落在现有大坝下游坝壳部分的新建堤坝上游坡的下部一小部分为沿原河道的液化砂砾石冲积层。先进的地震稳定性和变形分析结果表明,由于有足够的超高、厚厚的反滤体以及过渡带,大坝所产生的变形是可以接受的。为了控制基础渗流和出逸坡降,设计采用了塑性混凝土防渗墙、帷幕灌浆以及在下游增设一套减压井相结合的方案。为了监测新建坝的性态,在施工期和运行期的仪器监测设计中采用了基于破坏模式的方法。主要介绍了 Coquitlam新建堤坝的设计,包括大坝安全监测系统的设计。
Built in 1913, the dam of Coquitlam is 30 m high and serves as a dredging earth dam. The dam is located in the high seismic hazard zone of BC, Canada. Tens of thousands of people at risk. According to the current standards, the seismic capacity of the dam does not meet the requirements, the dam body fill soil and some parts of the foundation soil loose, easy to liquefaction. In moderate to severe earthquakes, the dam will suffer serious damage and may break. It is necessary to improve the dam’s seismic capacity. The highest designed earthquake is the Richter 7.5 earthquake, and the earth’s peak horizontal acceleration is 0.66g. In the design, some of the following design proposals for improving the seismic capacity will also need to be evaluated, including structural restoration, dam reconstruction, reservoir operation and decommissioning. Based on technical, social, environmental and economic considerations, a new downstream embankment was chosen to improve its seismic capacity and reduce the seismic risk of the Coquitlam Dam. The new dam consists of an earth core wall rockfill dam and a concrete transition zone on the left abutment. Most of the new dams are built on load-bearing silt, while the concrete transition zone is completely built on bedrock. Due to site and construction constraints, a small part of the lower part of the upstream dyke of the newly built dams located in the dam shell of the existing dam is a liquefied gravel alluvium along the original channel. Advanced seismic stability and deformation analysis results show that due to the sufficient ultra-high, thick filter body and the transition zone, the dam deformation is acceptable. In order to control the foundation seepage and outflow slope descending, a plastic concrete cutoff wall, curtain grouting and a combination of relief wells were added in the downstream. In order to monitor the behavior of a new dam, a damage-mode-based approach was used in the instrumentation design during construction and operation. It mainly introduces the design of the new dam of Coquitlam, including the design of dam safety monitoring system.