Dam Stability Analysis

Simulated failure sequence of a 27 m high, 22 m wide concrete dam section (Barrett Chute hydroelectric generating station, Ontario, Canada) founded on layered rock mass containing downstream dipping bedding planes.

The assessment of the structural stability of gravity dams is an important part of the overall process on ensuring the safety of both new and existing structures. Typically, concrete gravity dams must be designed to prevent several structural failure mechanisms, including horizontal sliding, overturning, and overstressing of the dam or foundation material.

Conventionally, sliding and overturning instability are assessed with limit equilibrium methods (LEM) to arrive at a factor of safety while overstressing is assessed using simple analytical methods (i.e., Gravity method) or continuum numerical methods (i.e., finite element or finite difference method). Although the use of these methods is well established, they are subject to some important limitations. In particular, each failure mechanism must be considered separately, the failure geometry is restricted, internal stress and deformations are neglected, and the specification of discontinuity shear strength can be challenging.

Irazu simulations can be employed as an alternative to the above mentioned conventional analysis methods. Using this approach the stress distribution, fracture development, and downstream dam displacement can be characterized within one single model. Furthermore, several characteristics of the rock mass fabric, including joints and bedding planes, and the roughness of the concrete-rock interface can be explicitly incorporated into models to assess how these features may influence the stability of the dam. Using an adaptive boundary algorithm, the numerical technique is able to follow the propagation of the pressurized fluid within interconnected, newly-formed and pre-existing fractures.

Further Reading:

  • Tatone BSA, Lisjak A, Mahabadi OK and Grasselli G (2010). "Evaluation of the combined finite-discrete element method for the assessment of gravity dam stability". In Proceedings of the Canadian Dam Association Conference. Niagara Falls, ON, Canada. 2-7 October, 2010.
Simulation highlights
  • Elastic models including isotropic and transversely isotropic
  • Isotropic and anisotropic strength models
  • Discrete Fracture Network (DFN) capability with frictional or cohesive discontinuities
  • Actual foundation profile can be included without the need to assume the mode of failure a priori
  • Hydrostatic fluid pressure with crack adaptive boundaries
  • Seismic loading
  • Simulation of progressive asperity damage through intact rock or concrete