John Prentice, Jim Barrett, Dr Martin Mallen-Cooper
Located in south-eastern Australia, the River Murray has provided almost a century of regulated water supply, bringing immense benefit to human welfare during this period. However a healthy river is recognised as being essential to its sustainable future. With this in mind, in March 2001 the Murray- Darling Basin Ministerial Council approved several actions including “a structural works program to provide passage for migratory fish, from the sea to Hume Dam”. The paper outlines progress to-date on this ambitious fishway construction program.
The program involves building fishways on twelve of the fourteen weirs on the river, and at the barrages. The criteria established, to enable passage for all native fish species known to regularly migrate, are detailed. The important lessons learned from earlier fishways, and confidence gained from the Torrumbarry Weir vertical-slot fishways constructed in the 1990’s, have been applied to the new designs. Part way through the program, important changes were made to the design criteria, and the reasons for doing so are described.The fishways constructed at the barrages near the Murray mouth, and their need to respond to estuarine and lake conditions, are recognised. In addition, Mildura and Euston Weirs vary from the other River Murray structures, and their special fish passage consideration is described.
In achieving a successful outcome to date, the important role of river managers, engineers and scientists working together with design consultants is acknowledged. A tri-State monitoring and assessment program has been established to enable the questions about the short and long term outcomes of the program to be answered. The beneficial results to date are detailed.
This paper outlines the steps and challenges involved in delivering this decade long program, scheduled for completion in 2011.
Keywords: Sustainable, fishways, fish passage, native fish, hydraulics, fish monitoring, Murray.
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Dr Azan Khan, Ahmad Nasir, Kumud Kandel, Jaya Kandasamy, Hadi Khabbaz, Mahub Ilahee
Cracking in the clay core of embankment dams is important to dam safety because it can cause seepage through transverse cracks and with excessive seepage cracks may begin to erode the soil on the sides of the crack. If there are no filters to control this erosion, the erosion may progress to form a pipe, eventually leading to breach of the dam. Recent climate change has resulted in long term drought conditions in various parts of Australia, especially west of the Dividing Range. The prolonged drought conditions can lead to the loss of moisture content in the clay core causing cracking of the core material. The current research is investigating a relationship between long term drought condition and loss of moisture content in the clay core. This paper presents the loss of moisture content in the clay core of three dams in Australia due to global warming. A rigorous finite element modelling has been conducted to capture the moisture content changes in a typical large clay core dam.
Keywords: clay core, dams, climate change, moisture content
Many earthen dams and embankments throughout the world are in need of remediation to address seepage or other issues and ensure structural integrity. Borehole drilling plays a vital role in facilitating implementation of remedial designs, both in the initial information gathering stage and the actual construction of a chosen remedy.
Within the past six to eight years Sonic drilling has become recognized within the geotechnical community as a viable method to meet overall project objectives and address site specific issues for a variety of projects. Key aspects of Sonics include: the ability to efficiently penetrate difficult subsurface conditions, provide a continuous core sample of unmatched quality, and minimize or eliminate risk to the structure from the drilling process. This paper focuses on the application of Sonic in support of a remedial effort at Wolf Creek Dam, including information on the background and overall objectives of the project, a brief explanation of the Sonic method, the scope of services required at the site, and the specific reasons for utilizing Sonic in this case.
Keywords: sonic drilling, grout curtain, Wolf Creek Dam, dam remediation
Thomas Vasconi, Glen Fergus
Abstract: This paper describes the design of an 80 m-high stepped chute spillway, in gabion material, that will be constructed on a tailings storage facility dam of a mine in South East Asia. This dam, constituted of two cells, will be raised progressively via a series of intermediate crest elevations as mining proceeds, and each lift will be equipped with an operational spillway. The design of such spillways was challenging since it had to integrate local topography configuration, dam design, water balance, wall raise sequence and structure interdependency parameters. The design included flood routing, spillway sizing, stepped spillway design, followed by hydraulic and civil/geotechnical computations. Challenging design aspects included optimizing the stepped spillway structure costs in light of the structure’s short service (estimated to be less than 5 years), and ensuring the stability component. The design incorporates an innovative solution which allows reduction in the rockfill quantity of up to 40% with associated cost benefits, and sustainability in terms of material usage. The lessons learnt in applying this innovative design are useful for other sites requiring adaptive construction and short service life spillways.
Keywords: tailings dam, stepped spillway, hydrology, hydraulics, mine water management, gabions.
In 2003, the Bureau of Meteorology revised the Probable Maximum Precipitation estimates and rainfall temporal patterns for Tinaroo Falls Dam using the Revised Generalised Tropical Storm Method. Based on the revised floods, the dam was assessed as having an ‘Extreme’ Flood Hazard Category rating. Subsequently a comprehensive risk assessment was undertaken in 2008 and this assessment recommended the dam be upgraded to pass the Fallback AFC which is the PMF event. The current spillway has a capacity for a flood with an AEP of 1 in 200. To achieve the AFC the concrete gravity Main Dam requires stabilising with post-tensioned anchors. The crest of the homogenous Saddle Dam needs to be raised by 300 mm and a filter and weighting zone needs to placed on the downstream face
Keywords: Tinaroo Falls Dam, mass concrete gravity dam, post-stressed anchors, Barron River, filter, weighting zone
Tariq I.H. Rahiman, Amanda Barrett, Greg Dryden, Mike Marley, Cecile Coll
In this study we present the engineering geology of complex Late Carboniferous to Early Permian silicic volcanic rocks underlying the Connors River dam site located on the Connors River, at Adopted Middle Thread Distance (AMTD) 97.7 km. The initial investigation of the site by SMEC in 1976 characterised the bedrock as simple laterally continuous layers of rhyolite and pyroclastic rocks. Engaged by SunWater Limited since October 2007, Golder Associates have utilised a range of modern investigative techniques to reveal a more intricate bedrock geological model.
Geological mapping, targeted vertical and angle geotechnical drilling and trenching reveal that the dam site foundation consists of complexly laid felsic crystalline volcanic flow deposits, volcaniclastic (pyroclastic) deposits, and mafic intrusives. Petrographical tests depict a broad range of rock types that includes rhyolite, rhyodacite, dacite, basalt, volcanic breccia, lapilli tuff and tuff. Surface structural mapping and downhole acoustic televiewer profiling reveal that defects of varying orientations have developed in the rocks mainly as a result of tectonism. The rock defects are predominantly open joints and faults, and minor bedding, flow bands, decomposed seams and veins. The permeability of the bedrock, which appears to be primarily controlled by rock defects, was assessed using the results of Lugeon tests.
Rock stratigraphy, mineralogy and texture combined with high resolution seismic tomographic imaging were used to delineate three main engineering rock units. Unit 1, the oldest, occurs on the right abutment and consists mainly of slightly weathered to fresh, high to very high strength dacites and rhyodacites. Unit 2 occupies the central area of the dam foundation and overlies Unit 1. It comprises weakly bedded, slightly weathered to fresh, high to very high strength volcaniclastic rocks. Unit 3, consisting of variably weathered, high to very high strength flow banded and autobrecciated rhyolite, is the youngest unit and it overlies and partially intrudes Unit 2. All three rock units are intruded by slightly weathered to fresh and very high strength basalt, either as dykes or sills. The rock mass properties of the rock units were evaluated based on rock strength tests and the geological strength index (GSI).
Keywords: engineering geology, dam foundation, volcanic rocks, Connors River, dam site