Posted November 24, 2021

Every good monitoring program consists of clear presentation of instrumentation data alongside other site metrics to present a cause-and-effect picture of how the site is performing.

The following are some tips to ensure that instrumentation data is presented in the most clear and concise manner.

Data Presentation

• Plots to assist data screening
  • lines of best fit to smooth out data (remove outliers)
• Plot data vs time for full data set
  • to assess data quality and show trends
• Plots showing observed vs predicted behavior
  • plotted regarding time and on same axis
• 
• Plots comparing measurements and observations
  • often form part of data interpretation
  • plotted regarding time and on same axis
  • e.g., fill placement, pond level, rainfall, and pore water pressure
• 
• Plots to examine cause and effect relationships
  • e.g., pore pressure increase and settlement as a function of fill placement
• 
• Determine the magnitude of change in the monitoring parameters required to validate performance of the structure
  • and verify that the proposed instruments can detect that magnitude of change
• Plot error bands on all data sets to assist in interpreting actual change in conditions vs possible sensor errors
• 
• Can the instruments you selected be sampled by the proposed system at the frequency required by your monitoring plan?

Data Interpretation

• Qualified personnel
• Follow a pre-determined procedure
• Do not delay interpretation
  • data collection, processing and interpretation influence each other
• Create plots with meaningful interpretation in mind
  • e.g., units from a MEMS IPI sensor can be displayed in:
    • Raw data digits
    • Acceleration in g
    • Tilt in radians
    • Tilt in degrees
    • Displacement in mm/m or in/ft
• First reaction is to reject unanticipated readings and/or blame the sensor, but data may be real (and be important)
• Consult with manufacturer to better understand performance of the instrument in question
• Ask “Can I think of a hypothesis that is consistent with the data”
  • check reading correctness to assess data validity
    • zero readings, gage factors, temperature corrections, barometric pressure, datalogger programs/power
  • check raw data
  • check installation records | difficulties encountered during install
  • site and environmental conditions
    • Construction, rainfall, headpond level

Compare Instrumentation data with design models

• Before reviewing data get a feel for what the values should be based on the design model and existing conditions
• How sensitive are model results to input parameters (parametric studies should be undertaken to show a range of expected results based on variation in soil type, water level, temperature etc.)
• Are there any localized conditions that could result in variations from the modelled section?
• 

VW Piezometer installation location and predicted water level | Reference: www.geostudio.com

Screen the data for expected site conditions vs. actual site conditions

• Before reviewing instrumentation data make sure the site conditions and change in those conditions with time is understood
• Construction data is often not synced to instrumentation data making it difficult to determine the loads the instruments are subjected to at the time of the readings
• There can be disconnects between the engineer(s) reviewing the instrumentation data and the designer/construction inspector
• 

Reference: www.klohn.com/blog/best-practices-for-tailings-dam-design

Reporting

• Conclusions, drawn from interpretations must be:
  • Reported and submitted
    • to those responsible for implementation of data on a regular schedule
• Final report to include
  • introduction, why are we monitoring
  • any design and construction information relative to monitoring program
  • summary of monitoring program plan
  • description of instruments and readouts and calibration procedures
  • plans and sections
  • surface and subsurface geotechnical data
  • procedures for data collection, processing, presentation, and interpretation
  • observed behavior with measured data and influencing factors and predicted behavior
  • conclusions, discussion, and remedial action
  • assessment of monitoring program along with suggested improvements

‹ Session 03 • Session 05 ›