The theme for this year’s event ‘Dams: a Critical Resource’, provides professionals in the dam industry an opportunity to learn from experts, exchange ideas and explore the critical role of dams in various aspects of todays society.
The importance of accounting for the compressibility of water in the seismic analysis of concrete dams
Sam Lalli (Senior Engineer – Dams and Hydropower, Francisco Lopez (Chief Technical Principal – Concrete Dams), Michael McKay (Associate Engineer – Dams and Hydropower), Stella Harrison (Engineer – Dams and Hydropower)
Finite Element Analysis of concrete dams is becoming increasingly more complex to better capture dam behaviour under static and seismic loading. One paramount aspect is the modelling of the dam-foundation-reservoir interaction during earthquakes. Hydrodynamic pressures can be estimated assuming that the water of the reservoir is an incompressible fluid or a compressible fluid. This paper presents a simple procedure for assessing the influence of water compressibility on the seismic response of a concrete gravity dam.
Impact of Element Size and Frequency Content of Input Earthquake on Dynamic Modelling of Embankment
Ryan Morrish (Engineer – Dams and Hydropower), Madhi Zoorabadi (Technical Principal – Geotechnics and Tunnels), Francisco Lopez (Chief Technical Principal – Concrete Dams)
The dynamic analysis of embankment dams subject to seismic events has evolved greatly over the years with the most common method being Finite Element Modelling (FEM). When using FEM, the selection of the element size has a dramatic effect on both the results of the analysis and the time required to process the model. This paper assesses the impact of different element sizes on the results of a FEM in order to determine the right balance between the results and processing times.
Extreme Floods: Reducing conservative estimates through revising non-linearity assumptions
Tim Rhodes (Technical Principal – Water Resources)
Extreme flood estimates constitute a key input to dam risk assessments, and they are subject to a high degree of uncertainty due to both a limited understanding of the meteorologic drivers and catchment runoff generation processes. Current estimation methods routinely apply an assumption of nonlinearity which results in increased peak flows. In essence, doubling rainfall results in more than double the runoff peak flow. There is little strong evidence to support the nonlinear assumption in the extreme flood range.
Advanced data-driven model-based estimates of dam breach parameters
Monte Azmi (Manager – Water Resources), Kyle Thomson (Technical Director – Forward Hydro)
While there is a general understanding of the most commonly considered physical and logical breaching mechanisms, reliable estimates of these parameters are challenging.
The research into newly developed data fusion-based models showed marked improvement over the existing empirical equations when compared against the developed historical datasets, exhibiting reduced uncertainty across all breach parameters.
To demonstrate the practical engineering implications of the findings, the proposed models’ outputs were applied to four real-world dam cases using a two-dimensional hydraulic model, specifically, the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) model.
Bendora Dam 20 Year Review – a Case Study Updating the Geological Model for a Project Without Intrusive Investigation
Helen Baxter-Crawford (Technical Principal Engineering Geologist), Kara Stariha (Associate Engineer – Geotechnics), Deryk Forster (Principal Engineering Geologist – Middle Third Geological)
Bendora Dam forms a critical component of the water supply network for the Canberra region, delivering approximately 4% percent of the territory’s storage capacity. In accordance with ANCOLD guidelines, Bendora Dam has been assessed as being a ‘High A’ Consequence Category dam for sunny day failure (SDF).
This case study demonstrates how cost-effective and rapidly acquirable remote sensing techniques, in conjunction with observational mapping, were combined to construct a three-dimensional model for the site that complements the historic data capture.