Gavan Hunter, David Jeffery and Chris Kelly
Laanecoorie Reservoir, located in central Victoria, passed 3 significant floods in late 2010 to early 2011; the last flood being the highest on record since 1909. Significant cracking and deformation of this 100 year old puddle core earthfill embankment occurred. A series of longitudinal cracks up to 25 mm in width opened up in the crest over a length of 70 m and crest settlements were up to 70 mm; very large for a dam of this age. A significant difference at Laanecoorie compared to other similar dams is that it experiences high tail water levels during major flooding.
Investigations into the embankment following the January 2011 flood encountered several defects
including a decomposed tree root hole (large void up to 90 mm) that almost fully penetrated the raised section of puddle core, permeable gravel layers within the puddle core and transverse cracks up to 2 mm wide. The encountered defects and performance of the embankment many years after construction highlighted the deterioration that can occur with aging of these older embankments and the issues associated with poor past practices in tree management adjacent to dam embankments.
Dam safety upgrade works were undertaken in 2013 to address the identified piping and stability risks.
The works included construction of a filter buttress, replacement of a length of the raised puddle core and construction of a buried gabion wall on the left abutment to provide protection against scour should the secondary spillway fail or overtop.
GMW implemented a series of actions during the flood events in accordance with the Dam Safety
Emergency Plan (DSEP) to address cracking and deformation. Once aware of the dam safety risks, interim actions were implemented including increased frequency of monitoring, together with set up and measurement of crack pins, and temporary survey markers on the embankment.
— OR —
Now showing 1-12 of 39 2978:
Dr Andy Hughes, Tom Wanner and Ben Jones
Hampstead Heath is one of London’s most popular open spaces, situated just 6 kilometres north of Trafalgar Square. ‘The Heath’ covers over 300 hectares and contains open countryside, an abundance of wildlife, sporting facilities and two chains of ornamental and fresh water swimming lakes, which date back to the 18th Century. The Heath is covered by its own Act of Parliament, of 1871, which protects its historic and environmental importance for the City of London.
In 2011 it was assessed that failure of one or more of the earthfill dams, that retain the ornamental and swimming lakes, could cause failure of downstream dams and subsequent release of floodwaters into the London Borough of Camden and the London Underground, with the potential for a high loss of life. As a result a study was carried out to better understand the scale of the works required to upgrade the dams to prevent their failure, and the associated environmental, social and political impacts.
This paper will present the ideas formulated to safely pass the design floods for ten dams within this sensitive environment, which include the installation of new spillways and/or the raising of dam crests, whilst taking in to account the site constraints and the age of the dams, some of which are up to 300 years old. The risk assessment carried out to quantify the overall risk of the dam failures will also be discussed including the breach inundation flood modelling of central London.
The paper will focus on the engineering and environmental constraints of the project in relation to the highly urbanised area, and the challenges faced when trying to accommodate the needs of many government and high profile stakeholder bodies, and pieces of legislation, in one of the most politically sensitive parts of the country
Suraj Neupane, Paul Southcott, and Tung Hoang
Conglomerate Dam has multiple cracks along the asbestos cement outlet conduits running through the embankment. The reservoir level has been maintained at 2m below the full supply level to reduce the amount of seepage, emerging on the downstream face, until the conduits are repaired and protect the embankment from slope instability and piping. Several methods were investigated under an options study to determine the most suitable internal lining method. Slip lining with polyethylene pipe was found to be the most suitable method in terms of technology as well as cost.
Francisco Lopez and Michael McKay
At 36 m high and completed in 1902, Barossa Dam is one of the first true concrete arch dams in the world. During the 1954 Darlington Earthquake the dam sustained some damage, in the form of several vertical cracks on both dam’s abutments. In 2013, GHD conducted a nonlinear time-history seismic assessment of Barossa Dam. The analyses, carried out using finite element techniques, included ground motion loading corresponding to Maximum Design Earthquakes (MDEs) with 1 in 10,000 Annual Exceedance Probability (AEP).
This paper will explain the purpose of the study, the material investigation phase, the methodology, model results, the anticipated seismic behaviour of the dam wall, as well as the predicted level of damage under the MDEs. The paper examines the dam construction practices of the beginning of the 20th century, and how such practices affected the material properties and the structural performance of Barossa Dam.
Paul Southcott, Tony Harman
This paper addresses structural behaviour of the Rowallan spillway walls and the learning that can be derived from this in the design of critical retaining walls in dams and how this can be applied both to remedial works and new work. The authors propose design criteria suitable for retaining walls in high hazard dams.
George Samios and Steve Gough
Following an extreme flood event late on Friday 22nd February 2013, water overtopped the dam crest leading to total collapse of the dam’s right embankment and a span of the nearby intake tower access bridge as well as the cutting of power to the dam gates. The dam’s left embankment was also severely damaged. Options considered for remediation of the dam include decommissioning or reinstatement and upgrading to NSW Dams Safety Committee requirements.