15.3 Conditions from Inception to the Date of Analysis …
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• Engineering studies have determined the berms (raises) are non-erodable by
extreme meteorological conditions or even by a breach of the tailings pipeline.
• Supervision of the dam is of good quality in terms of both frequency and the skills
of the supervisor.
• Minor geometric divergences have been noted between the plans and the actual
structures and minor intermittent seepage is monitored at one location at the toe
of the starter berm.
• There are no known errors or omissions in this project, which has been third-party
reviewed by competent independent reviewers.
Geotechnical Investigations and testing:
• There are only a few boreholes along the dam layout (fewer than 1/100 m); they
are generally short (the engineers argue the rock is of a sound nature and no
weaknesses are expected), barely penetrating into the assumed bedrock.
• No continuous sampling was performed.
• Penetrometers, vane tests and cone tests were numerous but poorly distributed due
to limitations of access.
• Soil classification tests were performed in a reasonable number and at a reasonable
frequency.
• Geomechanical tests were numerous but poorly distributed.
• A limited number of residual strength, oedometer and triaxial tests were performed.
Analyses and documentation:
• The project is deemed to be of good quality by a competent engineering firm and
a skilled team.
• The “as built” plans display some imperfections and variations.
• The alteration plans have also some approximations.
Stability analyses:
• As shown in Table 15.4, effective, undrained and pseudostatic stability analyses
were performed by the engineers.
• No settlement analyses were performed.
• Liquefaction was dismissed by the engineers. Without proof we consider this as a
likely event due to dam’s construction and the material underlying the raises.
• Internal erosion analysis was estimated by engineers as not being a problem. We
consider again this as a likelihood, given surface observations.
Operations and monitoring:
• Pore pressure is measured with over twenty vibrating wire piezometers.
• Four inclinometers are regularly read (although they are too short in our opinion).
• There is an active and competent Independent Geotechnical Review Board (IGRB).
• There is an annual inspection run by a reputable third party.
229
• Engineering studies have determined the berms (raises) are non-erodable by
extreme meteorological conditions or even by a breach of the tailings pipeline.
• Supervision of the dam is of good quality in terms of both frequency and the skills
of the supervisor.
• Minor geometric divergences have been noted between the plans and the actual
structures and minor intermittent seepage is monitored at one location at the toe
of the starter berm.
• There are no known errors or omissions in this project, which has been third-party
reviewed by competent independent reviewers.
Geotechnical Investigations and testing:
• There are only a few boreholes along the dam layout (fewer than 1/100 m); they
are generally short (the engineers argue the rock is of a sound nature and no
weaknesses are expected), barely penetrating into the assumed bedrock.
• No continuous sampling was performed.
• Penetrometers, vane tests and cone tests were numerous but poorly distributed due
to limitations of access.
• Soil classification tests were performed in a reasonable number and at a reasonable
frequency.
• Geomechanical tests were numerous but poorly distributed.
• A limited number of residual strength, oedometer and triaxial tests were performed.
Analyses and documentation:
• The project is deemed to be of good quality by a competent engineering firm and
a skilled team.
• The “as built” plans display some imperfections and variations.
• The alteration plans have also some approximations.
Stability analyses:
• As shown in Table 15.4, effective, undrained and pseudostatic stability analyses
were performed by the engineers.
• No settlement analyses were performed.
• Liquefaction was dismissed by the engineers. Without proof we consider this as a
likely event due to dam’s construction and the material underlying the raises.
• Internal erosion analysis was estimated by engineers as not being a problem. We
consider again this as a likelihood, given surface observations.
Operations and monitoring:
• Pore pressure is measured with over twenty vibrating wire piezometers.
• Four inclinometers are regularly read (although they are too short in our opinion).
• There is an active and competent Independent Geotechnical Review Board (IGRB).
• There is an annual inspection run by a reputable third party.