Abstract
The Plavinas run-off river scheme in Latvia is founded on fine-grained deposits with artesian aquifers. These aquifers are drained with free flowing wells to assure the stability of the structures. In March 1979, one of these wells suddenly discharged high amounts of solids together with the drainage water. After a few days the water discharge stopped, the artesian pressures in the foundation increased and dirty water flew from the bottom of the tailrace channel area. Foundation failure could be mitigated by turning piezometers into free flowing relief wells. However, it was a critical situation for the powerhouse and caused significant permanent displacements of the concrete structures. A root-cause analysis was performed which is presented in this paper. It was found that caverns at the interface of alluvial and fine-grained deposits formed due to erosion of the fine fractions of the alluvium through the drainage wells. Such a cavern collapsed which caused the well blowout and the plugging of the drainage well resulting in increasing pore water pressures and local liquefaction of the powerhouse foundation.
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Notes
For concrete dams; for embankment dams the establishment of seepage paths through the structure are equally significant.
The nomenclature “underconsolidated” is used for soil zones where the pore water pressure exceeds the hydrostatic pressure, independent whether this pressure state is induced by loading of low permeable soils or by artesian aquifers.
At this stage one would argue for the installation of more effective filters. This was tried several times already during construction period with numerous different filter designs (see Zaretski and Karabayev 1998) and always led to significant reduced water discharge and hence ineffective drainage.
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Acknowledgments
The permission of AS Latvenergo to publish this paper is gratefully acknowledged. Linda Berga provided invaluable help in the translation of Latvian and Russian documents. Special thanks go to Dr. R. Peter Brenner for introducing me to the Plavinas site.
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Messerklinger, S. Erosion and Drainage Well Blowout in the Foundation of the Plavinas Powerhouse: Case History. Geotech Geol Eng 30, 1421–1433 (2012). https://doi.org/10.1007/s10706-012-9551-0
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DOI: https://doi.org/10.1007/s10706-012-9551-0