The risk of internal erosion - assessment using the limit state method.

The risk of internal erosion - assessment using the limit state method

conference paper

Czech

In dam safety assessment the limit state method is gradually replacing the currently used traditional safety factor approach. The limit state method enables the more apposite expression of the uncertainty of individual factors entering the calculation. For example, Eurocode 7: Geotechnical design [13] strongly recommends the use of the limit state method for the assessment of geotechnical structures. The assessment of structural failures such as e.g. sliding is described in detail, including the limit state condition together with the appropriate partial load and resistance (reliability) factors. Conversely, the internal erosion criteria are formulated only vaguely, and the limit state conditions and reliability factors are not mentioned at all. In general, internal erosion phenomena are assessed by means of geometrical and/or hydraulic criteria, always starting (if possible) with geometrical conditions. This paper deals with hydraulic criteria only, assuming that geometrical criteria are not satisfied or cannot be used (e.g. in the case of external suffosion). In the paper the limit state conditions are formulated for selected internal erosion failure modes such as liquefaction/external suffosion, rupturing of the top stratum downstream of the dam (landward of the levee) and privileged seepage path development. The load, resistance and importance factors are discussed in the context of the requirements of Czech national technical standards.

In dam safety assessment the limit state method is gradually replacing the currently used traditional safety factor approach. The limit state method enables the more apposite expression of the uncertainty of individual factors entering the calculation. For example, Eurocode 7: Geotechnical design [13] strongly recommends the use of the limit state method for the assessment of geotechnical structures. The assessment of structural failures such as e.g. sliding is described in detail, including the limit state condition together with the appropriate partial load and resistance (reliability) factors. Conversely, the internal erosion criteria are formulated only vaguely, and the limit state conditions and reliability factors are not mentioned at all. In general, internal erosion phenomena are assessed by means of geometrical and/or hydraulic criteria, always starting (if possible) with geometrical conditions. This paper deals with hydraulic criteria only, assuming that geometrical criteria are not satisfied or cannot be used (e.g. in the case of external suffosion). In the paper the limit state conditions are formulated for selected internal erosion failure modes such as liquefaction/external suffosion, rupturing of the top stratum downstream of the dam (landward of the levee) and privileged seepage path development. The load, resistance and importance factors are discussed in the context of the requirements of Czech national technical standards.

dam,safety factor,external suffosion

dam,safety factor

ŘÍHA, J.

23. 5. 2010

VNCOLD -Vietnam National Committee on Large Dams&Water Resources Development

Hanoi, Vietnam

nemá

78-th Annual Meeting ICOLD, Hanoi, 23.-.26.5.2010. Proceedings-International Symposium "Dams&sustainable water resources development"

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