Movement Surveillance & Monitoring

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"All structures move as the result of applied loads. Embankments settle and spread over time as the result of consolidation and secondary settlement of the dam and foundation from self weight. Embankments also deform due to external loads produced by reservoir water, rapid drawdown, earthquakes, undermining, swelling clays, and piping. Concrete structures deform due to internal loads such as pore pressure, cooling, and alkali aggregate reaction of concrete; and external loads caused by air and reservoir temperature, solar radiation, reservoir levels, uplift pressure, wind, earthquakes, undermining, ice, overflowing water, swelling clay, and foundation settlement."

"Dams, locks, levees, embankments, and other flood control structures are subject to external loads that cause deformation and permeation of the structure itself, as well as its foundations. Any indication of abnormal behavior may threaten the safety of the structure. Careful monitoring of the loads on a structure and its response to them can aid in determining abnormal behavior of that structure. In general, monitoring consists of both measurements and visual inspections... To facilitate the monitoring of structures, they should be permanently equipped with proper instrumentation and/or monitoring points per the goals of the observation, structure type and size, and site conditions."

Movements in response to such loads are normal and acceptable, provided they are within tolerable ranges and do not cause structural distress. Embankments are less brittle than concrete structures and can undergo larger movements without distress. As a result, measurements of surface movements of embankment dams are typically less precise than those for concrete structures. Sudden or unexpected direction, magnitude, or trend of surface movement could indicate developing problems. Internal movement measurements of both concrete and embankment dams and their foundations should be detailed and precise.

Types of Movement

• Settlement
• Rotation or Horizontal Movement
• Ground Motion (Seismicity)
• Seasonal Movements

Best Practices Resources

Engineering Guidelines for the Evaluation of Hydropower Projects: Chapter 9- Instrumentation and Monitoring (Federal Energy Regulatory Commission)

Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) (USACE)

Design Standards No. 13: Embankment Dams (Ch. 11: Instrumentation and Monitoring) (USBR)

Instrumentation for Concrete Structures (EM 1110-2-4300) (USACE)

Citations:

Revision ID: 7106
Revision Date: 07/11/2023