Paper contribution

Towards a reliability-based monitoring system for uplift under concrete buttress dams

Johanna Dyberg Thonée; Maryam Zamzami; Johan Spross; Marie Westberg Wilde; Fredrik Johansson

Proceedings
EUROCK 2026
Pages
213-218
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

Uplift is one of the major forces acting on concrete dams and is inherently difficult to predict. In dam safety guidelines, uplift is typically evaluated deterministically, assuming simplified pressure distributions along the concrete–rock interface. For buttress dams, the concrete–rock contact area is smaller than that of gravity dams, but in the presence of persistent fracture planes in the rock foundation, the effective area over which uplift can act can be substantially larger. Due to the low self-weight of buttress dams, this poses a significant safety concern, as sliding stability has been shown to be sensitive to variations in uplift. To address these safety concerns, pore pressure monitoring with alarm thresholds and predefined countermeasures has been proposed in dam safety guidelines. However, there is limited guidance on how such alarm thresholds should be defined or implemented in practice. In this paper, we introduce a reliability-based framework in which alarm thresholds are derived from target probabilities of failure. The methodology is demonstrated for a concrete buttress monolith with characteristics similar to those of an existing dam in northern Sweden, where the probability of sliding failure is evaluated with uplift pressure represented by a random variable. The proposed framework enables the upper tail of the pore pressure distribution to be truncated at the alarm threshold, allowing stability requirements to be satisfied in re-evaluations of existing dams without structural measures while maintaining the required level of safety. Practical considerations when defining alarm thresholds are discussed, including how exceedance of an alarm threshold may reflect long-term changes in hydraulic behaviour caused by deterioration processes in the rock foundation and how to provide sufficient lead time for pre-defined countermeasures.

Contributors

Authors

  1. Johanna Dyberg Thonée KTH Royal Institute of Technology, Stockholm, Sweden ORCID 0009-0000-7988-2939
  2. Maryam Zamzami KTH Royal Institute of Technology, Stockholm, Sweden ORCID 0009-0003-9547-6529
  3. Johan Spross KTH Royal Institute of Technology, Stockholm, Sweden ORCID 0000-0001-5372-7519
  4. Marie Westberg Wilde KTH Royal Institute of Technology, Stockholm, Sweden; AFRY, Solna, Sweden ORCID 0000-0003-2584-1183
  5. Fredrik Johansson KTH Royal Institute of Technology, Stockholm, Sweden ORCID 0000-0002-8152-6092

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References

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