Designing a dam monitoring system

Author:克雷格·休斯

In early 2017, winter storms filled and then overfilled reservoirs in California, USA, leading to the evacuation of hundreds of thousands of citizens near Lake Oroville, California’s second largest manmade lake.

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 tomonitor crest elevations at these dams and dikes remotely随着时间分辨率的改善。在基础架构所有者的工具腰带中，拥有此类数据是一种用于监视关键设施的状况和性能的工具。

设计更好的数据

Ebmud与Sensemetrics咨询Sensemetrics，该公司专门从事位于美国圣地亚哥的网络传感器应用程序。

• 31 Leica GMX901+ GPS传感器
• Four Leica GM10 GNSS reference stations
• 由900 MHz网状收音机组成的无线电网络
• 4 GHz中继器和两个无线电塔
• Leica GNSS蜘蛛和Geomos软件解决方案。

Sensemetrics总裁Cory Baldwin表示，地理系统接收器的使用很重要：“The GMX901+s are purpose-built for remote monitoring applications, with non-exposed, built-in antennas,” he says. “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。”

Three of the GNSS reference station receivers are solar powered and one is powered by a 120v AC feed. All are securely fastened inside enclosures installed near the Leica AR20 antennas, which are mounted on concrete pedestals.该网络在很大程度上是自主的，只需要偶尔注意。数据流通过900 MHz和2.4 GHz扩展光谱传播到现有的微波遥测链接到其Oakland总部的EBMUD的业务Intranet，在该链接中，服务器在该服务器上运行了处理GNSS数据和结果所需的Spider和Geomos软件。然后通过Sensemetrics自定义的软件来显示结果。

GMX901+传感器中有五个以及四个地震仪安装在通过光纤电缆连接到微波业务Intranet的pardee坝上。这些仪器不断监视大坝的移动并远程报告。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.

Camanche Reservoir地点从Pardee大坝下游，由一个充满土壤的大水坝和六个堤防组成。Camanche水库主要用于控制下游机构的释放，并维持鲑鱼的流量。储层周围安装了26个GMX901+传感器，这些传感器还连续监视和报告。

基础设施性能的完整图片

The State of California Division of Safety of Dams (DSOD) requires semi-annual monitoring surveys. The new system providesaccurate information more rapidly,reduces staff time spent on monitoring, and is capable of being与全州紧急和地震监测系统有关当他们出现时。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的基础设施分布在广阔的地区，覆盖了多个县。”says Baldwin.“In particular, the Pardee and Camanche sites are several hours away from main offices, and the semi-annual surveys [conducted previously] took over a week to complete. This new system provides more accurate data, more or less constantly, and, of course, reduces the time survey crews spend on this task. It’s a big improvement, and it is performing beyond expectations.”

Baldwin says one important design goal was interconnectivity with existing and future monitoring systems. The potential toautomate and improve emergency responses to seismic eventsis a major advantage of monitoring networks.

Ebmud现在有more survey information immediately与该地区历史上的任何一刻相比，关于结构性能的指尖。通过积极主动和自动化监测系统，Ebmud大大改善了大坝安全监控。

“The GPS system at Pardee Dam now gives us a complete picture of the seasonal deformations due to thermal expansion and contraction of the concrete structure,”says Steven J. Martin, survey supervisor for EBMUD.“With the Camanche Reservoir portion of the GPS monitoring system, we are able to meet DSOD monitoring requirements without long trips out of town by the survey crew and to check for any possible deformations remotely in near real time.”

Automated dam monitoring in action

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.

After a 4.4 magnitude earthquake in January 2018 on the Hayward fault centred in Berkeley, less than 8 km from the San Pablo dam site, EBMUD geotechnical engineers were able to log in to the AMTS automated monitoring system toreview whether there had been any actual movement or slumping on the dam, 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.