Monitoring a Dam Under Construction

A hydroelectric dam under construction in Serbia required monitoring of several environmental and structural properties to ensure its long-term strength and stability. Therefore the damís construction engineers put forth a proposal for a large number of geotechnical sensors to be installed and used during construction. These sensors included vibrating wire piezometers, joint meters, fill extensometers, and strain gauges.

Each sensor needed to interface with a universal data logger as part of a long-term logging solution. Additionally, the engineers specified that their desired monitoring solution needed to have a large number of vibrating wire sensor inputs, compatibility with a SCADA system, and potential for expansion.

dataTaker-DT85gTechnicians chose the dataTaker DT85G from CAS Dataloggers because of its compatibility with vibrating wire sensors, its large number of inputs, and its versatile communications capabilities. The dataTaker can monitor a wide variety of geotechnical data logging applications including slope stability, subsidence, dam wall monitoring, tunnel and mining excavation, ground water, tunnel wall monitoring and site assessment.

Ideal for all geotechnical data logging applications, the DT85G model has 16 analog channels capable of measuring up to 16 vibrating wire strain gauges with thermistors or 48 vibrating wire strain gauges without thermistors. Channel count can be expanded simply by connecting dataTaker Channel Expansion Modules (CEM20s). In this example, two DT85G data loggers are each paired with three CEM20 channel expansion modules allowing for a total of 146 vibrating wire sensors to be intelligently distributed throughout the dam structure. The dataTaker system can be further expanded to connect up to 640 vibrating wire sensors.

Vibrating wire sensors were chosen due to their ability to provide highly accurate measurements that are not affected by the electrical resistance of long lengths of cable. Connected to the dataTakers, these sensors now provide information about the damís stress, fissuring, foundation deformation, uplift, displacement, and seepage flow.

Data storage and retrieval can be achieved via USB memory stick, FTP, cell phone, Modbus for SCADA, Ethernet or Web. Here a SCADA system is used to query the sensor data from the†loggers. There are two methods by which this can be done: either Modbus RTU via RS-485 or Modbus TCP/IP via Ethernet, the latter being the protocol behind the internet, which potentially allows for monitoring worldwide.

The hydroelectric dam now uses the pair of dataTaker data loggers as a key part of this advanced sensor instrumentation to continually monitor its structural stability. The low-cost, low-power dataTaker DT85G is extremely versatile and easy to configure for communications, data capture and data analysis.

The dataTakerís high channel count and built-in support for major vibrating wire sensors provides the ideal data acquisition and monitoring solution for engineers working in the geotechnical environment.

 

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