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Evaluating Unexpected Piezometer Trends in a Tailings Dam: Insights from Dissipation Testing

Session 4A

ABSTRACT

The monitoring of deformation and pore water pressure (PWP) within a tailings dam is crucial for ensuring structural integrity and operational safety. Unexpected trends are sometimes observed within monitoring instrumentation, and careful consideration of these trends is important as actions may range from ‘do nothing’ to ‘evacuate’. This paper presents and discusses unexpected trends in vibrating wire piezometer (VWP) readings within a heavily instrumented tailings dam during construction of a stabilisation solution. Observation of these unexpected trends resulted in a stoppage of works and prompted a detailed investigation to evaluate the validity of the VWP readings. The investigation included cone penetration testing (CPT), dissipation testing and installation of additional VWPs adjacent to those showing unexpected trends. The testing methodologies involved saturating the CPT pore pressure disc with both silicone oil and then glycerine after observing an unusual dissipation curve. The results at various locations showed differences based on the saturation fluid used. Findings using glycerine generally aligned with the expected trends and corroborated the data from the additional VWPs. This paper highlights and discusses the potential impact of saturation fluids in dissipation tests and the importance of assessing PWP trends and ensuring instrumentation accuracy for geotechnical monitoring.

AUTHORS

  1. Ricardo J. Dellamea, SRK Consulting
  2. Joe Rola, SRK Consulting
  3. Jonathon Eldridge, SRK Consulting
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