Designing a dam monitoring system

Author:Craig Hewes

在2017年初，在美国加利福尼亚州的冬季风暴填补了冬季风暴，然后在加利福尼亚州加利福尼亚州的水库过度填充水库，导致疏散了加利福尼亚第二大人造湖奥罗维尔湖附近的数十万公民。

About 160 kilometres away, the Pardee and Camanche reservoirs also filled from the 2017 storms, reaching 103 per cent of capacity in March, but the dams were not overtopped, and releases were sustainable within the waterways.

Thanks to the installation of one of the nation’s most advanced automated GNSS-based dam monitoring systems at these two facilities, along with other instrumentation improvements, East Bay Municipal Utility District (EBMUD) had the technology in place to监控在这些大坝和堤防r波峰高度emotelywith improved temporal resolution. Having this type of data available is one more tool in an infrastructure owner’s tool belt for monitoring the condition and performance of critical facilities.

Designing for better data

Consulting with Sensemetrics, a firm specialising in networked sensor applications based in San Diego, USA., EBMUD designed and proposed a sophisticated monitoring system based on:

• 31 Leica GMX901+ GPS sensors
• Four Leica GM10 GNSS reference stations
• A radio network consisting of 900 MHz mesh radios
• 4 GHz repeaters and two radio towers
• Leica GNSS Spider and GeoMoS software solutions.

The use of Geosystems receivers is important, according to Cory Baldwin, president of Sensemetrics:“The GMX901+s are purpose-built for remote monitoring applications, with non-exposed, built-in antennas,“ 他说。“它们是我在这里的首选，因为其他供应商实际上没有一个很好的选择来监视这种环境。透明

GNSS参考站接收器中有三个是太阳能动力的，一个由120V AC进料提供动力。所有这些都牢固地固定在安装在混凝土基座上的Leica AR20天线附近的内部围墙内。The network is largely autonomous, needing only occasional attention. Data flow is through 900 MHz and 2.4 GHz spread spectrum radios into an existing microwave telemetry link to EBMUD’s business intranet at its Oakland headquarters, where a server runs the Spider and GeoMos software necessary to process the GNSS data and results. The results are then presented through software customised by Sensemetrics.

Five of the GMX901+ sensors as well as four seismographs are installed on the Pardee Dam connected via fiberoptic cable directly to the microwave business intranet. Theseinstruments continuously monitor dam movement and report remotely. Two of the GM10 reference stations were installed near and on either side of Pardee Dam and are connected to the fiberoptic line by 2.4 GHz radio connections.

Downstream from Pardee Dam, the Camanche Reservoir site consists of one large earth-filled dam and six dikes. The Camanche Reservoir is primarily used to control releases to downstream agencies and maintain flows for the salmon. Twenty-six GMX901+ sensors are installed around the reservoir, and these also monitor and report continuously.

A complete picture of infrastructure performance

The State of California Division of Safety of Dams (DSOD) requires semi-annual monitoring surveys. The new system provides准确的信息更快，，，，减少员工在监视上花费的时间，并且有能力tied into state-wide emergency and seismic monitoring systems当他们出现时。经过将近两年的服务后，DSOD监视要求得到了更完整的整体性能。

“EBMUD’s infrastructure is spread out over a vast area and covers multiple counties,”says Baldwin.“尤其是，帕迪和卡曼奇站点距离主要办公室几个小时了，半年度调查（先前进行）花了一周多的时间才能完成。这个新系统或多或少地提供了更准确的数据，当然，还可以减少工作人员在此任务上的时间。这是一个很大的进步，它的表现超出了预期。”

Baldwin says one important design goal was interconnectivity with existing and future monitoring systems. The potential to自动化并改善对地震事件的紧急响应is a major advantage of monitoring networks.

EBMUD now has立即更多调查信息at its fingertips regarding structure performance than at any previous moment in the district’s history. By being proactive and automating monitoring systems, EBMUD has greatly improved dam safety monitoring.

“ Pardee Dam的GPS系统现在为我们提供了由于混凝土结构的热膨胀和收缩而导致的季节变形的完整图片，”EBMUD调查主管Steven J. Martin说。“借助GPS监控系统的Camanche水库部分，我们能够满足DSOD监视要求，而无需长时间的调查人员出门，并在接近实时远程检查任何可能的变形。”

自动化大坝监测行动

A recent example of the benefits of automating a survey monitoring scheme comes from another EBMUD automated dam monitoring project on San Pablo Dam in California, USA. In 2008 and 2009, the dam underwent a seismic improvement to buttress the toe of the dam to bedrock using a cement deep soil mixing process. Increased monitoring requirements from the DSOD, while working on an active dam, were met via an Automated Motorised Total Station System (AMTS), which has been running several times a day since that project was completed in 2009. EBMUD also has a program to visually inspect dams and reservoirs immediately after an earthquake to check for cracking or other visible damage as a quick ground truth.

在2018年1月在以伯克利为中心的海沃德故障上发生了4.4级地震后，距离圣巴勃罗大坝站点不到8公里，EBMUD GEOTECHNICAL ENGINERSERS能够登录到AMTS自动化监控系统到审查大坝上是否有任何实际动作或跌倒，，，，and they confirmed that there was no significant movement. This ability to have information immediately and at their fingertips has proven to be a huge asset in managing dam safety at EBMUD.