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15 Risk-Informed Decision Making
Geotechnical Investigations and testing:
• There are only a few boreholes along the dam layout (fewer than 1/100 m); they
were at least as deep as the structure is high.
• No continuous sampling was performed, but fifteen trenches were dug, although
poorly distributed along and across the layout.
• 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 limited and poorly distributed.
• A very 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 significant imperfections and variations.
• the alteration plans also have some significant approximations.
Stability analyses:
• As shown in Table 15.4, effective drawdown and pseudostatic stability analyses
were performed by the engineers.
• No settlement analyses were performed.
• Liquefaction was dismissed by the engineers and we agreed.
• Internal erosion analysis was estimated by engineers as not being a problem.
Operations and monitoring:
• Pore pressure is measured with six vibrating wire piezometers.
• Deformations are monitored by topographic observations.
• There is no active Independent Geotechnical Review Board (IGRB).
• There is an annual inspection ran by a reputable third party.
Maintenance and repairs:
• No repairs are carried out when damages are identified during the inspection.
15.3.3 Dam 3
Construction:
• As described above, the raises are upstream, made of compacted crushed rock, on
tailings.
15 Risk-Informed Decision Making
Geotechnical Investigations and testing:
• There are only a few boreholes along the dam layout (fewer than 1/100 m); they
were at least as deep as the structure is high.
• No continuous sampling was performed, but fifteen trenches were dug, although
poorly distributed along and across the layout.
• 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 limited and poorly distributed.
• A very 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 significant imperfections and variations.
• the alteration plans also have some significant approximations.
Stability analyses:
• As shown in Table 15.4, effective drawdown and pseudostatic stability analyses
were performed by the engineers.
• No settlement analyses were performed.
• Liquefaction was dismissed by the engineers and we agreed.
• Internal erosion analysis was estimated by engineers as not being a problem.
Operations and monitoring:
• Pore pressure is measured with six vibrating wire piezometers.
• Deformations are monitored by topographic observations.
• There is no active Independent Geotechnical Review Board (IGRB).
• There is an annual inspection ran by a reputable third party.
Maintenance and repairs:
• No repairs are carried out when damages are identified during the inspection.
15.3.3 Dam 3
Construction:
• As described above, the raises are upstream, made of compacted crushed rock, on
tailings.