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SANCOLD Conference 2017: The Study of Three-Dimensional Stability for a Complex Arch Dam Abutment

By RO Cassells and GD Roberts, ARQ Consulting Engineers, Pretoria, South Africa.

Abutment stability is obviously fundamental to the feasibility of an arch dam and an arch type structure will impose higher structural loads than any other dam type on its abutments. Consequently, an arch dam design must always include an evaluation of the stability of both abutments under the various important applicable loads. For a complex abutment rock mass, with various dominant joint sets, the importance of the abutment analyses increases and the abutment must consequently be defined as an appropriate series of rock wedges, the stability of each of which must independently and collectively be established.

In this paper, the authors describe a particular analysis relating to a complex abutment rock mass for a 275 m high double curvature arch dam. Subsequent to the analysis, rock mass relaxation related to the joint sets analysed resulted in a change in the abutment design and configuration. While the related issues are consequently only of academic interest, it is, however, considered of value to present the evaluation process followed as an example of an appropriate 3-dimensional discontinuum analysis of a jointed arch dam abutment rock mass of a super-high arch dam using a finite element analysis model.